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Evaluated activation cross sections of longer-lived radionuclides produced by deuteron induced reactions on natural nickel
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 260 (2007) 495–507 www.elsevier.com/locate/nimb
Evaluated activation cross sections of longer-lived radionuclides produced by deuteron induced reactions on natural nickel S. Taka´cs a
a,*
, F. Ta´rka´nyi a, B. Kira´ly a, A. Hermanne b, M. Sonck
b
Institute of Nuclear Research, Hungarian Academy of Sciences (Atomki), Debrecen H4026, Hungary b Cyclotron Department, Vrije Universiteit Brussel (VUB), Brussels B1090, Belgium Received 3 October 2006; received in revised form 20 November 2006 Available online 14 April 2007
Abstract Activation cross sections for deuteron induced nuclear reactions on natural nickel target were studied by using a standard stacked foil technique and gamma spectrometry up to 50 MeV deuteron bombarding energy. Reaction products with half life of at least half an hour were studied. Experimental elemental activation cross sections were determined for reactions on nickel resulting in 61,64Cu, 56,57Ni, 55,56,57,58,60,61 Co, 52,54,56Mn and 51Cr radionuclides and were compared with earlier measured data. Ó 2007 Elsevier B.V. All rights reserved. PACS: 25.45. z; 27.40.+z; 27.50.+e Keywords: Natural nickel target; Deuteron irradiation; Cyclotron; Excitation function; Cross section; Copper, nickel, cobalt, manganese and chromium radioisotopes
1. Introduction In our systematic study of charged particle induced nuclear reactions on metals we investigated the deuteron induced reactions on natural nickel targets. Nickel is an important structural and surface coating material which is used frequently in accelerator and nuclear technology. In an international project called IFMIF (International Fusion Materials Irradiation Facility) candidate materials for the future fusion reactor are tested using an accelerator-based D-Li neutron source [1]. Any intensity loss of the high intensity deuteron beams provided by the linear accelerator can cause activation of structural materials along the beam transport system. Nickel has physical characteristics of choice for nuclear technology but under deuteron bombardment considerable activation can occur, which can represent a radiation hazard during maintenance of irradiation units. On the other hand, some of the pro*
Corresponding author. Tel.: +36 52 509251; fax: +36 52 416181. E-mail address: [email protected] (S. Taka´cs).
0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.11.136
duced radionuclides can be useful for beam monitoring purposes or medical applications. It is therefore important to know the activation behaviour of nickel under deuteron bombardment. In this work, we investigated the natNi(d,x) reactions in which 61,64Cu, 56,57Ni,55,56,57,58,60,61Co, 52,54,56Mn and 51Cr isotopes are produced. Beside the reactions resulting in 61 Cu, often used for monitoring the parameters of the bombarding deuteron beam, we propose other reactions on this target material which are also suitable for beam monitoring. 2. Experimental 2.1. Irradiation and data measurement Several stacks of high purity natNi foils (15.5, 23.9 and 26.4 lm thick, Goodfellow, >99.5% Ni) were irradiated at the CGR-560 cyclotron of VUB, Brussels and at the Cyclone-110 cyclotron of Louvain-la-Neuve with incident deuteron beams of 20.4, 30 and 50 MeV. Irradiations were
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done in a target holder that served as a Faraday-cup for charge collection. Each stack contained aluminium and titanium high purity metallic foils for beam energy degradation and accurate assessment of the bombarding beam intensity and energy along the stacks and allowed a cross-check possibility of the measured cross sections. We used a standard experimental set-up and methods of data processing. By combining the results of the stacks the number of irradiated foils was sufficient to cover the whole energy range in almost uniform energy steps from the threshold of the (d,xn), (d,pxn), (d,axn), (d,2axn) and (d,2ap) reactions up to the maximum bombarding energy, as well as to generate overlapping energy regions between stacks. The incident beam energies were determined from the setting parameters of the accelerators and were adjusted if it was necessary using 27Al(d,x)22,24Na and nat Ti(d,x)48V monitor reactions in their respective energy regions. The reference monitor values were taken from [2]. The irradiated samples were measured without chemical separation by using HPGe detectors coupled to a PC analyser card/analysing software. The data acquisition began at least 1 h after the end of bombardment (EOB) depending on the irradiated stacks and was repeated several times to follow the decay of the investigated radionuclides. As the half life of the generated radionuclides varies from several minutes to years, not all the reactions were measured in optimal conditions. The counting distance was large for the first series of measurements to assure low dead times, to avoid pile-up effects and to minimize the required corrections for extended sample diameter (0.5 cm). Due to the high activity of the foils it was impossible to assess properly the isotopes with short half life (less than 30 min) and these were excluded from the investigation. The long-lived radionuclides were measured for more than 24 h duration at a distance of not less than 5 cm. The detection efficiency of the detector in a given geometry was determined by using standard calibrated sources. The activities of the various radionuclides produced in the nickel foils were calculated using the nuclear decay and spectroscopic data taken from an online nuclear decay database [3] and given in Table 1. Cumulative and independent elemental cross sections for the reactions were determined from the activities, target characteristics and deposited charge, using the well-known activation formula. 2.2. Data processing The beam current initially derived from a Faraday-cup measurement was corrected for the black current of the system and in the case of the 20 MeV irradiation increased by a few percent in accordance with the monitor reaction. The initial energy of the bombarding beam was determined from the cyclotron setups. The mean energy at the middle of each foil was deduced by calculating the energy degradation along the stack from the foil parameters and the stopping power data by using the polynomial approximation of Andersen and Ziegler [4]. The applied monitoring method-
Table 1 Decay data of 61,64Cu, 56,57Ni, 55,56,57,58,60,61Co, 52,54,56Mn and radionuclides used in the data evaluation, according to [3] Half life 61
Cu 64 Cu 56 Ni 57 Ni 55
Co Co 57 Co 56
58
Co Co
60
61
Co Mn 54 Mn 56 Mn 51 Cr 52
3.333 h 12.7 h 6.077 h 35.60 h 17.53 h 77.27 d 271.79 d 70.86 d 5.2714 y 1.650 h 5.591 d 312.3 d 2.5785 h 27.7025 d
Decay mode
Ec (keV)
EC, b+ EC, b+, b EC EC, b+
656.01 1345.84 158.38 127.164 1377.63
EC, b+ EC, b+ EC EC, b+ b b EC, b+ EC, b+, b b EC
931.3 846.77 122.0614 136.4743 810.775 1173.237 1332.501 67.412 935.538 834.848 846.771 320.0824
51
Cr
Ic (%) 10.77 0.473 98.8 16.7 81.7 75.0 100 85.60 10.68 99 99.9736 99.9856 85.0 94.5 99.976 98.9 10.0
ology, the whole excitation function of the used monitor reactions being measured and compared with the recommended one, allowed rather accurate determination of the mean beam energy at the middle of each target foil. The uncertainty in the primary beam energy was estimated to be ±0.3 MeV but due to straggling effect and foils thickness uncertainties increases gradually along the stack and reaches ±0.9 MeV at the end of a long stack. The estimation of uncertainties on cross section values was made as recommended in [5]. The following individual uncertainties are included in the propagated error: foil thickness or the number of target nuclei, including target non-uniformities (5%); incident particle intensity (4–6%); detection efficiency (3–7%) depending on the energy of the gamma-photon; determination of the peak areas, including statistical errors (1–9%); abundance of the gamma rays analysed (1–5%). Only the linearly contributing independent error sources were used the non-linear sources were omitted in the calculation. The uncertainties of time information (irradiation, cooling and measuring time and half life) were neglected since their contribution is not significant. The resulting total average uncertainties amount to 8–15%, obtained as square root of the sum of squares of the contributing sources. 3. Results and discussion The excitation curves obtained experimentally for each produced radionuclide are discussed in the following subsections comparing the results with values reported earlier. The experimental data are shown in Figs. 1–14 and their numerical values are presented in Tables 2–4. A Spline fit to the experimental points is also included in each graph. The reported cross sections are elemental cross sections measured on natural Ni target.
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nat
Ni(d,x)61Cu [7] Takács (1997) corr. [8] Zweit (1991) [9] Cogneau (1967) [10] Budzanowski (1962) [6] and This work [6] Pade fit Spline fit
100 Cross section (mb)
497
50
0 0
5
10
15
Fig. 1. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)61Cu in comparison with the data measured earlier.
12 nat
64
Ni(d,x) Cu
Cross section (mb)
10
8
6
[8] Zweit (1991)
4
This work Spline fit
2
0 0
5
10
15
Fig. 2. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
45
50
Ni(d,x)64Cu in comparison with the data measured earlier.
The 58,59,60,61,62,64,66Cu radionuclides can be produced in (d,xn) reactions on natural nickel in the investigated energy region. We determined excitation functions for the reactions resulting in the radionuclides 61,64Cu (Table 2). The half life of the 58,59,60,62,66Cu isotopes is too short to be assessed in the experimental conditions used. 61
40
nat
3.1. Production of copper radionuclides
3.2. Production of
35
Cu
The decay of the 61Cu radioisotope to 61Ni is followed by gamma radiation of 656 keV (Ic = 10.77%) that allows
easy measurement of the produced activity. Due to the short half life the statistical uncertainty on the collected peak area was around 3% for each spectrum. The extracted cross section data points from the stack irradiated at 20 MeV are somewhat lower than the results of earlier experiments indicating that the recommended cross section values, given in [2] as a Pade fit of selected experimental data, are overestimated in that energy region. The excitation function in the energy range studied essentially reflects a complex behaviour in accordance with the isotopic composition of the target material (Fig. 1). Our new Spline fit has a maximum at 7.4 MeV that corresponds to the contribution of the 60Ni(d,n) reaction. The curve exhibits some
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4.0 nat
Ni(d,x) 56 Ni
3.5
Cross section (mb)
3.0 2.5 2.0
[13] Cline (1971) This work Spline fit
1.5 1.0 0.5 0.0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 3. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)56Ni in comparison with the data measured earlier.
80 nat
57
Ni(d,x) Ni
Cross section (mb)
60
[7] Takács (1997) corr. [8] Zweit (1991) [9] Cogneau (1967) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) [16] Baron (1963) [17] Brinkman (1977) This work Spline fit
40
20
0 0
5
10
15
Fig. 4. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)57Ni in comparison with the data measured earlier.
structure around 16 and 30 MeV that reflects the contribution of the 61Ni(d,2n) and 62Ni(d,3n) reactions. Contribution from the 64Ni(d,5n) reaction (Ethreshold = 33.3 MeV) is energetically also possible but no significant cross section can be observed. Around the maximum of the excitation function the Spline fit follows the earlier measured data points rather than the three new experimental data points reflecting the statistical behaviour of the Spline method. A new dedicated experiment could solve this discrepancy. Results for this reaction were already published by our group earlier in [6] in comparison and cross-checking with other possible deuteron monitor reactions keeping the Pade fit given in [2] as a recommended data. Six earlier experiments were found in the literature [6–11]. One series of data in our publication [7] was norma-
lised in [6] (divided by 1.18). The shape of the excitation function published by Zweit et al. [8] and Cogneau et al. [9] is good but the data are too high around the maximum, the results of Budzanowski and Grotowski [10] and Coetzee and Peisach [11] are in agreement with our data. Data of [9] were not used for the Spline fit. 3.3. Production of
64
Cu
The radionuclide 64Cu (T1/2 = 12.7 h) is used both in internal therapy and in PET diagnostics. For production of 64Cu in no-carrier-added form various production routes on Ni and Zn targets were investigated. The 64Ni(d,2n) reaction is among the most efficient procedures. This reaction was investigated only by Zweit et al. [8] before. The 64Cu
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35 30 25 Cross section (mb)
nat
Ni(d,x)55Co
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) [16] Baron (1963) [17] Brinkman (1977) [18] Nakao (2004) This work Spline fit
20 15 10 5 0 0
5
10
15
Fig. 5. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)55Co in comparison with the data measured earlier.
160 nat
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) This work Spline fit
120 Cross section (mb)
56
Ni(d,x) Co
140
100 80 60 40 20 0 0
5
10
15
Fig. 6. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)56Co in comparison with the data measured earlier.
has a very weak Ec = 1345.8 keV (Ic = 0.473%) c-line that allows only limited accuracy of the measurement using natural nickel target and gamma spectrometry. Two reactions can contribute to the production of this isotope: 64Ni(d,2n) (Q = 4.68 MeV) and 62Ni(d,c) (Q = +11.8 MeV), but the latter reaction has a negligible contribution. Because of the importance of 64Cu from the point of view of medical application we discuss this reaction in comparison with other production routes in details in a separate article [12]. In Fig. 2 we present our new data and data of Zweit et al. [8] and a Spline fit of all data. 3.4. Production of nickel radionuclides In the investigated energy range production of the radionuclides 54,55,56,57,59,63,65Ni is energetically possible in
(d,pxn) reactions on natural nickel. We could only determine the excitation function for the reactions resulting in 56,57 Ni, Table 2, as the half life of 54,55Ni is too short, the 59,63 Ni have no gamma lines and 65Ni can only be produced by the (d,p) reaction with low cross section on low abundance 64Ni (less than 1%).
3.5. Production of
56
Ni
The strongest independent gamma line of 56Ni is Ec = 158.38 keV (Ic = 98.8%). The main contribution to the formation of 56Ni is from the 58Ni(d,p3n) (Q = 24.7 MeV) reaction. The (d,p5n) reaction on 60Ni has a high Q-value (Q = 45.08 MeV) and has no significant contribution in the investigated energy interval (Fig. 3). The
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500
700 nat
57
Ni(d,x) Co
600
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) This work Spline fit
Cross section (mb)
500 400 300 200 100 0 0
10
5
15
20
25
30
35
40
45
50
Deuteron energy (MeV) Fig. 7. Excitation functions for the reactions
nat
Ni(d,x)57Co in comparison with the data measured earlier.
400 nat
Ni(d,x) 58Co [7] Takács (1997) corr.
Cross section (mb)
300
[8] Zweit (1991) [13] Cline (1971) [19] Jung (1992) This work Spline fit
200
100
0 0
10
20
Fig. 8. Excitation function for the reaction
30 40 Deuteron energy (MeV)
57
60
nat
Ni(d,x)58Co in comparison with the data measured earlier.
formation of 56Ni can be considered by the decay of possible produced 56Cu. Only one data set was published before from 30 to 40 MeV by Cline [13] which, although somewhat lower, is in agreement with our data within experimental errors. The Spline fit was calculated using both data sets (Fig. 3). 3.6. Production of
50
Ni
The 57Ni radionuclide has a half life of T1/2 = 35.6 h and decays to the radioactive 57Co. The energy of the strongest gamma line is Ec = 1377.63 keV (Ic = 81.7%). The measured peak area was corrected for background signal due
to 214Bi (Ec = 1377.6 keV) although the contribution of the background to the total measured peak was almost negligible. Eight datasets were measured earlier, these are: [7–9,13–17] (Fig. 4). Out of them two sets of data [9,14] are too high or have a significant energy shift, the remaining data are in agreement up to 22 MeV. In the 22–25 MeV region data of Blann and Merkel [15] and Brinkman et al. [17] are about 35% higher than data of Cline [13] and our newly measured data. Above 25 MeV energy only data points measured in this work exist. The wide shape of the excitation function confirms that several reactions can take place and contribute to the production of 57Ni on natural nickel target. This reaction product
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501
100 nat
60
Ni(d,x) Co
Cross section (mb)
80
60
This work Spline fit
40
20
0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 9. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)60Co.
4 nat
61
Ni(d,x) Co
Cross section (mb)
3 This work Spline fit
2
1
0
0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 10. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)61Co.
can be used for beam monitoring above 25 MeV where the curve is rising steeply. The data of [9,14,17,15] above 22 MeV were excluded for performing the Spline fit because of their deviation as mentioned above.
tions for the reactions resulting in the 55,56,57,58,60,61Co radionuclides (Table 3). The results include all the (d,x) processes that directly or indirectly (through parent decay) result in cobalt radionuclides on natural nickel targets.
3.7. Production of cobalt radionuclides
3.8. Production of
Energetically the nuclides of cobalt from mass number 53 to 64 can be produced by deuteron bombardment of natural nickel target in the investigated energy region. Among them 53,54,62,63,64Co have too short half life to be assessed in this experiment. We determined excitation func-
The 55Co has relatively short half life T1/2 = 17.5 h. The intense Ec = 931 keV (Ic = 75%) gamma line gives an interference free determination possibility to measure its produced activity. The presented cross sections are elemental up to 34 MeV and cumulative above that energy
55
Co
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502
4.0 nat
52
Ni(d,x) Mn
3.5
Cross section (mb)
3.0 2.5 2.0
[13] Cline (1971) This work Spline fit
1.5 1.0 0.5 0.0
0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 11. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)52Mn in comparison with the data measured earlier.
35 nat
54
Ni(d,x) Mn
30
Cross section (mb)
25
20 [13] Cline (1971) This work Spline fit
15
10
5
0 0
5
10
15
20
25
30
35
40
45
50
Deuteron energy (MeV) Fig. 12. Excitation function for the reaction
nat
Ni(d,x)54Mn in comparison with the data measured earlier.
point, since 55Co is also produced by the decay of 55Ni at higher energies as can be seen in Fig. 5 as a rising tail of the excitation function above 40 MeV. Eight experiments were reported in literature before [7,8,13–18]. They are in relatively good agreement, except Blann’s data [15] which are higher about 50% than the others. Therefore in the Spline fit calculation this data set and the data of Cline [13], which are very much scattered, were not included. The reaction can be used also for monitoring purposes in the 15–35 MeV energy interval. The excitation function has a maximum of about 23 mbarn at 23 MeV.
3.9. Production of
56
Co
This radionuclide presents a special interest since it can be produced from several structural materials such as iron and nickel. It has a T1/2 = 77.27 d half life and several intensive gamma lines that provides easy determination of the produced activity. Although a significant part of the activity is produced through direct reactions, the reported cross sections are cumulative since 56Co is also formed by decay of the 56Ni radionuclide above 30 MeV. Some gamma lines present small interferences from decay of the shorter lived 56Mn for several hours after EOB. Five
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503
1.4 nat
56
Ni(d,x) Mn
1.2
Cross section (mb)
1.0 This work Spline fit
0.8
0.6
0.4
0.2
0.0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 13. Excitation function for the reaction
35
40
45
50
45
50
nat
Ni(d,x)56Mn.
16 nat
14
51
Ni(d,x) Cr
Cross section (mb)
12 10 8
This work Spline fit
6 4 2 0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 14. Excitation function for the reaction
datasets were published before [7,8,13–15]. As in the case of the reactions discussed above data of Blann and Merkel [15] are too high and data of Cline [13] are scattered and above 25 MeV only our new data exist (Fig. 6). Our new results are lower than the earlier published values below 20 MeV. In the Spline fit calculation [13,15] were not included. The excitation function has a local maximum of 43 mbarn at about 10 MeV that is followed by a slowly decreasing tail up to 30 MeV. In principle this reaction can be used for beam monitoring, although data are more scattered than data of the reaction mentioned above.
35
40
nat
Ni(d,x)51Cr.
3.10. Production of
57
Co
The 57Co is a long-lived radioisotope with half life of T1/2 = 271.79 d. It has two strong gamma lines at energy of Ec = 122.06 keV (Ic = 85.6%) and Ec = 136.47 keV (Ic = 10.68%). The 57Co radionuclide can be produced in several direct reactions on natural nickel target and also generated as a daughter product of 57Ni. Cumulative activity measurements of the foils were started several days after EOB when 57Ni decayed completely. Five datasets were published before [7,8,13–15] Again, as in the case of the
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504
Table 2 Cross sections for deuteron induced reactions on natural nickel resulting in 61,64Cu and 56,57Ni radionuclides Energy (MeV)
r (mb) 61
4.2 ± 0.5 6.6 ± 0.4 8.5 ± 0.4 9.6 ± 0.5 10.1 ± 0.4 10.8 ± 0.4 10.9 ± 0.5 11.6 ± 0.4 12.0 ± 0.4 13.0 ± 0.4 13.1 ± 0.4 14.1 ± 0.4 14.3 ± 0.3 15.1 ± 0.4 15.6 ± 0.3 16.0 ± 0.3 16.9 ± 0.3 16.9 ± 0.3 17.8 ± 0.3 18.0 ± 0.5 18.1 ± 0.3 18.6 ± 0.3 19.3 ± 0.3 19.4 ± 0.3 20.2 ± 0.3 20.4 ± 0.3 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
Cu
45.3 ± 5.9 64.5 ± 8.4 56.3 ± 7.3 46.8 ± 5.6 46.0 ± 6.0 36.2 ± 4.3 43.3 ± 4.9 37.6 ± 4.9 30.0 ± 3.6 31.8 ± 4.1 26.7 ± 3.2 19.3 ± 2.3 27.5 ± 3.6 21.1 ± 2.5 24.3 ± 3.2 17.3 ± 2.1 22.0 ± 2.9 18.6 ± 2.2 15.7 ± 1.9 18.0 ± 2.1 19.8 ± 2.6 17.1 ± 2.0 18.1 ± 2.4 15.7 ± 1.9 12.4 ± 1.5 17.1 ± 2.2 14.3 ± 1.6 13.6 ± 1.6 14.3 ± 1.7 14.7 ± 1.7 15.4 ± 1.8 14.7 ± 1.7 13.5 ± 1.6 12.5 ± 1.5 12.7 ± 1.5 12.4 ± 1.5 11.1 ± 1.4 11.7 ± 1.4 10.8 ± 1.3 11.3 ± 1.4 8.7 ± 1.1 10.6 ± 1.3 10.2 ± 1.3 10.2 ± 1.3 9.2 ± 1.1
64
Cu
56
Ni
57
Ni
6.1 ± 0.7
0.13 ± 0.02
6.3 ± 0.8
0.42 ± 0.05 0.14 ± 0.05
7.1 ± 0.9
0.87 ± 0.10
7.6 ± 0.9 8.2 ± 1.0
1.4 ± 0.2 1.9 ± 0.2
7.0 ± 0.8
2.3 ± 0.3
8.0 ± 1.0
2.7 ± 0.3
6.9 ± 0.8 6.9 ± 0.8
3.4 ± 0.4 3.9 ± 0.5 3.7 ± 0.5
6.2 ± 0.7
4.8 ± 0.6
3.7 ± 0.4 3.5 ± 0.4
5.8 ± 0.7 7.5 ± 0.9 15.3 ± 1.8
0.27 ± 0.08 0.34 ± 0.10 0.39 ± 0.15 0.50 ± 0.12 1.05 ± 0.18 0.95 ± 0.25 0.97 ± 0.22 1.88 ± 0.28 1.92 ± 0.25 2.41 ± 0.32 2.49 ± 0.35 2.85 ± 0.40 3.13 ± 0.38 3.13 ± 0.38
38.7 ± 4.4 43.8 ± 5.0 55.6 ± 6.3 63.3 ± 7.3 61.1 ± 7.0 65.1 ± 7.4 64.6 ± 7.3 62.2 ± 7.1 62.3 ± 7.1 61.2 ± 6.9 59.4 ± 6.8 59.9 ± 6.8 61.1 ± 6.9 58.0 ± 6.6
reactions discussed above, data of Blann and Merkel [15] are higher above 20 MeV and data of Cline [13] are scattered and lower than the other reported data. Above 25 MeV only our new data exist (Fig. 7). From the Spline fit calculation [13,15] were excluded. The excitation curve slowly starts to rise at 10 MeV and is increasing steadily up to 20 MeV. Above 20 MeV a steep increase can be observed reaching a value of more than 500 mbarn at about 34 MeV. This reaction is probably the most appropriate for monitoring deuteron beam parameters, especially in the 20–50 MeV region.
3.11. Production of
58
Co
The 58Co has a metastable state (T1/2 = 9.04 h) that decays for 100% by IT to the ground state with emission of only a very low energy c-ray. The ground state has a gamma line with energy of Ec = 810.775 keV (Ic = 99%). In these conditions only cumulative production of the ground state could be assessed which required a few days of cooling time for total decay of the metastable state. Four cross sections sets were reported for this reaction earlier [7,8,13,19]. Data of Zweit et al. [8] are too low for this reaction, unlike for other reactions where their data are in agreement or a little higher than our data. It indicates that probably the applied cooling time was not long enough for total decay of the metastable state. Data of Cline [13] are scattered and lower than our data as is the case with the other reactions. Jung’s data seems to be shifted to higher energies, otherwise the amplitude and shape of the reported curve is in agreement with our data. It is clearly visible on Fig. 8 that the corrected data reported by our group earlier [7] represent the highest values and do not correspond perfectly to the newly measured data sets in which the data points from the low and high energy irradiations show a slight difference in amplitude although they are in agreement within errors. The Spline fit was calculated by excluding the data of Zweit et al. [8]. The reaction has low threshold energy and has the highest cross section values in the 10–25 MeV energy interval. This feature of the reaction makes it very suitable for use as monitor reaction. Because of the activation and decay characteristics of this process it is also favorable for use in wear measurements of machine parts or structural materials having nickel content. 3.12. Production of
60
Co
The radioisotope 60Co is long-lived (T1/2 = 5.2714 y). It has also a metastable state (T1/2 = 10.47 min) that decays by IT to the ground state (99.76%) and by b to 60Ni (0.24%). The two almost 100% abundant gamma lines emitted at Ec = 1173.237 keV and Ec = 1332.501 keV give a good possibility to measure the produced activity. Long measurements were required to decrease the statistical error to an acceptable 5% level. The excitation function starts to rise only above 25 MeV and is increasing steadily up to 80 mbarn in the investigated energy region (up to 50 MeV) (Fig. 9). As no data were found in the literature the Spline fit was calculated over the newly measured experimental cross section data points. 3.13. Production of
61
Co
Production of 61Co can take place on the heavier Ni low abundance nickel isotopes; therefore the elemental cross sections are relatively low. As the radionuclide 61 Co has only three gamma lines which all are interfering 61,62,64
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507 Table 3 Cross sections for deuteron induced reactions on natural nickel resulting in Energy (MeV)
9.6 ± 0.5 10.8 ± 0.4 10.9 ± 0.5 12.0 ± 0.4 13.1 ± 0.4 14.1 ± 0.4 15.1 ± 0.4 16.0 ± 0.3 16.9 ± 0.3 17.8 ± 0.3 18.0 ± 0.5 18.6 ± 0.3 19.4 ± 0.3 20.2 ± 0.3 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
Co
Co radionuclides
56
57
58
35.9 ± 4.3 33.0 ± 4.0 34.1 ± 4.2 30.2 ± 3.6 24.2 ± 2.9 20.0 ± 2.4 15.7 ± 1.9 14.4 ± 1.7 12.0 ± 1.4 10.9 ± 1.3 15.0 ± 2.1 8.7 ± 1.0 8.6 ± 1.0 7.6 ± 0.9 10.4 ± 2.1 7.3 ± 0.9 8.2 ± 1.1 10.4 ± 1.2 12.1 ± 2.1 13.5 ± 1.6 20.6 ± 2.4 26.6 ± 3.1 35.0 ± 4.0 45.6 ± 5.3 55.7 ± 6.3 66.1 ± 7.6 92.8 ± 10.6 99.3 ± 11.2 109.8 ± 12.5 112.9 ± 12.8 126.2 ± 14.4 127.9 ± 14.4 131.1 ± 14.8
1.3 ± 0.2 3.7 ± 0.4 5.2 ± 1.5 9.3 ± 1.1 14.6 ± 1.7 20.1 ± 2.4 23.3 ± 2.8 28.7 ± 3.4 39.0 ± 4.7 49.9 ± 6.0 47.5 ± 5.8 67.4 ± 8.1 85.2 ± 10.2 111.1 ± 13.3 245.3 ± 28.3 293.9 ± 33.0 354.0 ± 39.8 424.3 ± 47.7 441.3 ± 50.0 464.8 ± 52.2 505.0 ± 56.8 513.9 ± 57.8 515.4 ± 57.9 499.5 ± 56.2 497.3 ± 55.9 481.7 ± 54.2 455.9 ± 51.3 440.0 ± 49.5 422.7 ± 47.6 427.0 ± 48.1 411.7 ± 46.4 406.1 ± 45.6 402.9 ± 45.3
82.8 ± 9.9 130.4 ± 15.6 81.3 ± 9.5 151.2 ± 18.1 161.6 ± 19.4 187.8 ± 22.5 185.7 ± 22.3 197.6 ± 23.7 205.6 ± 24.7 213.5 ± 25.6 225.9 ± 25.7 205.6 ± 24.7 204.3 ± 24.5 190.2 ± 22.8 210.4 ± 24.3 184.3 ± 20.7 169.9 ± 19.2 144.6 ± 16.3 150.2 ± 17.3 135.3 ± 15.2 112.5 ± 12.7 106.6 ± 12.1 105.6 ± 11.9 105.0 ± 12.0 104.6 ± 11.8 108.1 ± 12.3 113.6 ± 12.9 113.4 ± 12.8 115.2 ± 13.1 117.6 ± 13.3 118.0 ± 13.4 118.8 ± 13.4 118.0 ± 13.3
Co
0.10 ± 0.01 0.57 ± 0.07 0.10 ± 0.05 2.3 ± 0.3 4.8 ± 0.6 7.4 ± 0.9 9.5 ± 1.1 11.6 ± 1.4 14.0 ± 1.7 16.1 ± 1.9 12.7 ± 1.4 17.7 ± 2.1 18.6 ± 2.2 20.1 ± 2.4 21.6 ± 2.4 20.4 ± 2.3 19.8 ± 2.3 16.2 ± 1.9 18.0 ± 2.0 15.2 ± 1.8 11.5 ± 1.3 10.3 ± 1.2 8.6 ± 1.0 8.6 ± 1.0 8.1 ± 1.0 8.0 ± 0.9 7.5 ± 0.9 7.1 ± 0.8 7.3 ± 0.9 7.4 ± 0.9 7.9 ± 0.9 9.0 ± 1.1 9.4 ± 1.1
Co
Table 4 Cross sections for deuteron induced reactions on natural nickel resulting in 52,54,56Mn and 51Cr radionuclides r (mb) 52
Mn
18.0 ± 0.5 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
55,56,57,58,60,61
r (mb) 55
Energy (MeV)
505
0.11 ± 0.06 1.5 ± 0.3 1.8 ± 0.3 2.0 ± 0.4 2.8 ± 0.4 2.7 ± 0.4 2.6 ± 0.4 2.2 ± 0.4 2.6 ± 0.5 1.9 ± 0.4 1.5 ± 0.3 1.5 ± 0.3
0.9 ± 0.3 0.8 ± 0.5 1.5 ± 0.6 1.6 ± 0.4 1.9 ± 0.4
54
Mn
56
Mn
2.6 ± 0.5 4.5 ± 1.0 9.5 ± 1.2
0.07 ± 0.03 0.04 ± 0.03 0.02 ± 0.03
15.3 ± 1.9 22.3 ± 2.9 26.3 ± 3.5 25.4 ± 3.3 29.2 ± 4.1 29.2 ± 3.5 29.1 ± 3.9 26.7 ± 3.9 26.1 ± 3.2 22.3 ± 3.3 23.7 ± 3.4 20.6 ± 3.3 21.4 ± 2.9 18.6 ± 2.5
0.04 ± 0.03 0.11 ± 0.04 0.18 ± 0.05 0.29 ± 0.06 0.41 ± 0.07 0.50 ± 0.09 0.53 ± 0.08 0.71 ± 0.10 0.75 ± 0.11 0.80 ± 0.12 0.97 ± 0.14 0.98 ± 0.17 1.09 ± 0.15 1.10 ± 0.14
51
Cr
3.6 ± 1.2 4.1 ± 1.1 6.4 ± 1.3 7.2 ± 1.8 7.0 ± 1.2 9.2 ± 1.9 10.7 ± 2.4 10.8 ± 1.5 11.7 ± 1.4 12.2 ± 2.1 9.2 ± 2.3 9.1 ± 1.5 9.1 ± 1.5
Co
60
Co
61
Co
1.6 ± 0.2
1.4 ± 0.2
14.9 ± 3.1 2.4 ± 4.5 12.6 ± 4.3 13.1 ± 3.2 14.1 ± 5.3 12.2 ± 6.1 28.0 ± 7.6 32.1 ± 9.3 32.5 ± 6.1 40.5 ± 9.7 48.0 ± 11.4 49.2 ± 7.5 68.3 ± 12.9 62.8 ± 12.5 70.8 ± 18.9 66.3 ± 10.8 78.8 ± 11.9
1.4 ± 0.5 1.6 ± 0.2 1.9 ± 0.2 1.6 ± 0.2 1.6 ± 0.2 1.8 ± 0.2 2.1 ± 0.3 2.5 ± 0.6 2.6 ± 0.4 2.7 ± 0.4 2.5 ± 0.3 2.8 ± 0.3 2.8 ± 0.3 2.9 ± 0.3 2.4 ± 0.3 2.9 ± 0.3 2.8 ± 0.3 3.2 ± 0.4 2.9 ± 0.4
with the 61Cu gamma lines since both radionuclides decay to 61Ni; special attention was paid to the assessment of this radioisotope. Contribution to the measured peak area from the simultaneously produced longer lived 61Cu was subtracted before the cross sections were calculated. No data were found in the literature, only our data points are available with relatively high uncertainties due to the low statistics and the applied process to separate the contribution of 61 Cu. In general the measured cross sections are low. As no experimental points below 10 MeV could be obtained, no information can be given around the threshold of this reaction (Fig. 10).
3.14. Production of manganese radionuclides In this section the processes resulting in the formation of manganese radionuclides are discussed. In the investigated energy interval practically production of all manganese radionuclides is energetically possible. Due to their half life and decay characteristics only the 52,54,56Mn could be measured (Table 4).
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
506
3.15. Production of
52
Mn
The radionuclide 52Mn has a ground state with T1/2 = 5.591 d half life and a metastable state with half life of T1/2 = 21.1 min, which decays only for 1.75% by IT mode to the ground state and by b+ and EC (98.25%) to 52 Cr. We assessed the 52Mn ground state after a few hours cooling time when the metastable state had completely decayed. The Ec = 935.5 keV gamma line (Ic = 94.5%) was used for measuring the activity of the produced 52 Mn. The excitation function shows a local minimum around 43 MeV and rises again due to the contribution of the reactions on the second most abundant 60Ni isotope (Fig. 11). We found one earlier dataset measured by Cline [13] on enriched 58Ni. While the reported curve in [13] has a similar shape, the data points are scattered and around the maximum the values are somewhat higher than our data (opposite to the reactions discussed above) even after correction for the used gamma intensity (data in [13] were calculated with Ic = 84%). In this case the Spline fit was calculated over our new data points only. 3.16. Production of
54
Mn
The half life of 54Mn is T1/2 = 312.3 d. Its only gamma line is very strong (Ec = 834.85 keV, Ic = 99.976%) what makes it relatively easy to assess this radionuclide. The excitation function starts to rise at 23 MeV and reaches its maximum of 28.8 mbarn at 38 MeV. Although several reaction channels are possible, in which emission of different combination of single and complex particles occur, the excitation curve has a simple one maximum shape in the investigated energy region. There is one data set measured by Cline [13] on enriched 58Ni. The reported curve has a similar shape, data points are scattered and they are somewhat lower than our data. Only our data were considered in calculating the Spline fit (Fig. 12). 3.17. Production of
56
Mn
The 56Mn radionuclide has a half life of T1/2 = 2.58 h and decays by b to 56Fe. As the simultaneously produced 56 Co with longer half life (T1/2 = 77.27 d) decays to the same nuclide 56Fe, which results in the same gamma lines, the assessment of the 56Mn required separation of the 56Co contribution. This was performed by taking two spectra with good statistics at different times: a first measurement shortly after EOB to determine the common activity of 56 Co and 56Mn and a second one after total decay of 56 Mn to determine the 56Co activity which is also influenced by the decay of 56Ni. The measured excitation function has a simple rising shape starting at 28 MeV. It is not clear if the first two low energy points have real higher value or if this is an artefact due to the uncertainty from the data separation process (Fig. 13). No other data are available in the literature.
3.18. Production of chromium radionuclides Production of several chromium isotopes is possible energetically in the investigated energy region. Due to the decay characteristics of the possibly produced radionuclides of chromium we were able to identify only the 51Cr. 3.19. Production of
51
Cr
The 51Cr has the longest half life among the radioactive chromium isotopes (T1/2 = 27.7 d). It decays to 51V and has only one gamma line (Ec = 320.08 keV, Ic = 10%). Assessment of this reaction product was possible only in the high energy part of the investigated energy region. The measured excitation function shows a single peak. The highest measured cross section is around 12 mbarn at 44.4 MeV. (Table 4.) No other measurements reported in literature were found. The Spline fit was calculated over our newly measured experimental cross sections (Fig. 14). 4. Conclusion Activation cross sections of deuteron induced reactions were measured on natural nickel up to 50 MeV. We determined elemental cross sections for the 61,64Cu, 56,57Ni, 55,56,57,58,60,61 Co, 52,54,56Mn and 51Cr radionuclides. Production of these longer lived radionuclides are important in the estimation of accumulated radioactivity in the structural materials of accelerator components and beam transport systems (activation by direct beam hit or beam loss during long-term operation). It is especially relevant for the ongoing IFMIF project (International Fusion Materials Irradiation Facility) which was established to study and test fusion materials by an accelerator-based D-Li high intensity neutron source. For the earlier established monitor reaction nat Ni(d,x)61Cu [6] we propose new evaluated cross section values and we also give reliable results for reaction products (57Ni, 56,57,58Co) that can be used for alternative beam monitoring purposes in the energy range from 10 to 50 MeV. The detailed results for the efficient production of 64Cu, an important radionuclide in PET imaging, by 64 Ni(d,2n) reaction will be presented separately. Thick target yields were calculated based on the Spline fitted excitation functions (see Fig. 15) for each investigated end product. From the point of view of accelerator exploitation such as the IFMIF facility it is obvious that the EOB activity is higher for the short lived radionuclides with high cross sections, but radiation burden from these radionuclides will be negligible after one or two days of cooling time. For most of the reaction products investigated here however the days long half-lives require a too long cooling time to wait for the decay of the products which is not favorable for maintenance personnel. As the long lived radionuclides will accumulate during long periods of irradiation, it is important to avoid unnecessary activation of structural materials
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
507
1000 61
Cu Co 57 Ni 55 Co 61
Integral yield (MBq/μAh)
100
56
Mn Co Co 56 Co 52 Mn 51 Cr 56 Ni 54 Mn 60 Co 58
10
57
1
0.1
0.01
0.001
0
10
20 30 Deuteron energy (MeV)
40
50
Fig. 15. Thick target yields calculated from the fitted excitation functions for the investigated processes.
by energetic deuteron beam by choosing proper materials and suitable designs. Acknowledgements We are pleased to acknowledge the co-operation and help in performing the irradiations of the teams of the Louvain-la-Neuve Cyclone-110, Brussels CGR-560 and the Debrecen MGC-20E cyclotron laboratories.This work was partly supported by the Fund for Scientific Research (FWO-Vlaanderen), the Hungarian Academy of Sciences and the OZR-VUB. References [1] IFMIF International team, IFMIF-KEP; International Fusion Materials Irradiation Facility Key Element Technology Phase Report, JAERI-Tech 2003-005, 2003. [2] F. Ta´rka´nyi, S. Taka´cs, K. Gul, A. Hermanne, M.G. Mustafa, M. Nortier, P. Oblozinsky, S.M. Qaim, B. Scholten, Yu.N. Shubin, Z. Youxiang, Beam Monitor Reactions in: IAEA-TECDOC-1211, IAEA, Vienna, 2001, p. 49,
[5] Guide to the Expression of Uncertainty in Measurement, International Organization for Standardization, Geneva, 1995 (ISBN 92-6710188-9). [6] S. Taka´cs, F. Szelecse´nyi, F. Ta´rka´nyi, M. Sonck, A. Hermanne, Yu.N. Shubin, A. Dityuk, M.G. Mustafa, Z. Youxiang, Nucl. Instr. and Meth. B 174 (2001) 235. [7] S. Taka´cs, M. Sonck, A. Azzam, A. Hermanne, F. Ta´rka´nyi, Radiochim. Acta 76 (1997) 15. [8] J. Zweit, A.M. Smith, S. Downey, H.L. Sharma, Appl. Radiat. Isotopes 42 (1991) 193. [9] M. Cogneau, L.J. Gilly, J. Cara, Nucl. Phys. A 99 (1967) 689. [10] A. Budzanowski, K. Grotowski, Phys. Lett. 2 (1962) 280. [11] P.P. Coetzee, M. Peisach, Radiochim. Acta 17 (1972) 1. [12] A. Hermanne, F. Ta´rka´nyi, S. Taka´cs, S.F. Kovalev, A. Ignatyuk, Nucl. Instr. and Meth. B, submitted for publication. [13] C.K. Cline, J. Nucl. Phys. A 174 (1971) 73. [14] Z. Fuying, T. Zhenlan, W. Zhenxia, Chinese J. Nucl. Phys. 5 (1983) 166. [15] M. Blann, G. Merkel, Phys. Rev. 131 (1963) 764. [16] N. Baron, B.L. Cohen, Phys. Rev. 129 (1963) 2636. [17] G.A. Brinkman, J. Helmer, L. Lindner, Radiochem. Radioanal. Lett. 28 (1977) 9. [18] M. Nakao, K. Ochiai, N. Kubota, N.S. Ishioka, T. Nishitani, in: Proceedings of the Symposium on Nuclear Data, Tokai, JAERI, Tokai, Japan, November 11–12, 2004, Electronic edition:
Nuclear Instruments and Methods in Physics Research B 260 (2007) 495–507 www.elsevier.com/locate/nimb
Evaluated activation cross sections of longer-lived radionuclides produced by deuteron induced reactions on natural nickel S. Taka´cs a
a,*
, F. Ta´rka´nyi a, B. Kira´ly a, A. Hermanne b, M. Sonck
b
Institute of Nuclear Research, Hungarian Academy of Sciences (Atomki), Debrecen H4026, Hungary b Cyclotron Department, Vrije Universiteit Brussel (VUB), Brussels B1090, Belgium Received 3 October 2006; received in revised form 20 November 2006 Available online 14 April 2007
Abstract Activation cross sections for deuteron induced nuclear reactions on natural nickel target were studied by using a standard stacked foil technique and gamma spectrometry up to 50 MeV deuteron bombarding energy. Reaction products with half life of at least half an hour were studied. Experimental elemental activation cross sections were determined for reactions on nickel resulting in 61,64Cu, 56,57Ni, 55,56,57,58,60,61 Co, 52,54,56Mn and 51Cr radionuclides and were compared with earlier measured data. Ó 2007 Elsevier B.V. All rights reserved. PACS: 25.45. z; 27.40.+z; 27.50.+e Keywords: Natural nickel target; Deuteron irradiation; Cyclotron; Excitation function; Cross section; Copper, nickel, cobalt, manganese and chromium radioisotopes
1. Introduction In our systematic study of charged particle induced nuclear reactions on metals we investigated the deuteron induced reactions on natural nickel targets. Nickel is an important structural and surface coating material which is used frequently in accelerator and nuclear technology. In an international project called IFMIF (International Fusion Materials Irradiation Facility) candidate materials for the future fusion reactor are tested using an accelerator-based D-Li neutron source [1]. Any intensity loss of the high intensity deuteron beams provided by the linear accelerator can cause activation of structural materials along the beam transport system. Nickel has physical characteristics of choice for nuclear technology but under deuteron bombardment considerable activation can occur, which can represent a radiation hazard during maintenance of irradiation units. On the other hand, some of the pro*
Corresponding author. Tel.: +36 52 509251; fax: +36 52 416181. E-mail address: [email protected] (S. Taka´cs).
0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.11.136
duced radionuclides can be useful for beam monitoring purposes or medical applications. It is therefore important to know the activation behaviour of nickel under deuteron bombardment. In this work, we investigated the natNi(d,x) reactions in which 61,64Cu, 56,57Ni,55,56,57,58,60,61Co, 52,54,56Mn and 51Cr isotopes are produced. Beside the reactions resulting in 61 Cu, often used for monitoring the parameters of the bombarding deuteron beam, we propose other reactions on this target material which are also suitable for beam monitoring. 2. Experimental 2.1. Irradiation and data measurement Several stacks of high purity natNi foils (15.5, 23.9 and 26.4 lm thick, Goodfellow, >99.5% Ni) were irradiated at the CGR-560 cyclotron of VUB, Brussels and at the Cyclone-110 cyclotron of Louvain-la-Neuve with incident deuteron beams of 20.4, 30 and 50 MeV. Irradiations were
496
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
done in a target holder that served as a Faraday-cup for charge collection. Each stack contained aluminium and titanium high purity metallic foils for beam energy degradation and accurate assessment of the bombarding beam intensity and energy along the stacks and allowed a cross-check possibility of the measured cross sections. We used a standard experimental set-up and methods of data processing. By combining the results of the stacks the number of irradiated foils was sufficient to cover the whole energy range in almost uniform energy steps from the threshold of the (d,xn), (d,pxn), (d,axn), (d,2axn) and (d,2ap) reactions up to the maximum bombarding energy, as well as to generate overlapping energy regions between stacks. The incident beam energies were determined from the setting parameters of the accelerators and were adjusted if it was necessary using 27Al(d,x)22,24Na and nat Ti(d,x)48V monitor reactions in their respective energy regions. The reference monitor values were taken from [2]. The irradiated samples were measured without chemical separation by using HPGe detectors coupled to a PC analyser card/analysing software. The data acquisition began at least 1 h after the end of bombardment (EOB) depending on the irradiated stacks and was repeated several times to follow the decay of the investigated radionuclides. As the half life of the generated radionuclides varies from several minutes to years, not all the reactions were measured in optimal conditions. The counting distance was large for the first series of measurements to assure low dead times, to avoid pile-up effects and to minimize the required corrections for extended sample diameter (0.5 cm). Due to the high activity of the foils it was impossible to assess properly the isotopes with short half life (less than 30 min) and these were excluded from the investigation. The long-lived radionuclides were measured for more than 24 h duration at a distance of not less than 5 cm. The detection efficiency of the detector in a given geometry was determined by using standard calibrated sources. The activities of the various radionuclides produced in the nickel foils were calculated using the nuclear decay and spectroscopic data taken from an online nuclear decay database [3] and given in Table 1. Cumulative and independent elemental cross sections for the reactions were determined from the activities, target characteristics and deposited charge, using the well-known activation formula. 2.2. Data processing The beam current initially derived from a Faraday-cup measurement was corrected for the black current of the system and in the case of the 20 MeV irradiation increased by a few percent in accordance with the monitor reaction. The initial energy of the bombarding beam was determined from the cyclotron setups. The mean energy at the middle of each foil was deduced by calculating the energy degradation along the stack from the foil parameters and the stopping power data by using the polynomial approximation of Andersen and Ziegler [4]. The applied monitoring method-
Table 1 Decay data of 61,64Cu, 56,57Ni, 55,56,57,58,60,61Co, 52,54,56Mn and radionuclides used in the data evaluation, according to [3] Half life 61
Cu 64 Cu 56 Ni 57 Ni 55
Co Co 57 Co 56
58
Co Co
60
61
Co Mn 54 Mn 56 Mn 51 Cr 52
3.333 h 12.7 h 6.077 h 35.60 h 17.53 h 77.27 d 271.79 d 70.86 d 5.2714 y 1.650 h 5.591 d 312.3 d 2.5785 h 27.7025 d
Decay mode
Ec (keV)
EC, b+ EC, b+, b EC EC, b+
656.01 1345.84 158.38 127.164 1377.63
EC, b+ EC, b+ EC EC, b+ b b EC, b+ EC, b+, b b EC
931.3 846.77 122.0614 136.4743 810.775 1173.237 1332.501 67.412 935.538 834.848 846.771 320.0824
51
Cr
Ic (%) 10.77 0.473 98.8 16.7 81.7 75.0 100 85.60 10.68 99 99.9736 99.9856 85.0 94.5 99.976 98.9 10.0
ology, the whole excitation function of the used monitor reactions being measured and compared with the recommended one, allowed rather accurate determination of the mean beam energy at the middle of each target foil. The uncertainty in the primary beam energy was estimated to be ±0.3 MeV but due to straggling effect and foils thickness uncertainties increases gradually along the stack and reaches ±0.9 MeV at the end of a long stack. The estimation of uncertainties on cross section values was made as recommended in [5]. The following individual uncertainties are included in the propagated error: foil thickness or the number of target nuclei, including target non-uniformities (5%); incident particle intensity (4–6%); detection efficiency (3–7%) depending on the energy of the gamma-photon; determination of the peak areas, including statistical errors (1–9%); abundance of the gamma rays analysed (1–5%). Only the linearly contributing independent error sources were used the non-linear sources were omitted in the calculation. The uncertainties of time information (irradiation, cooling and measuring time and half life) were neglected since their contribution is not significant. The resulting total average uncertainties amount to 8–15%, obtained as square root of the sum of squares of the contributing sources. 3. Results and discussion The excitation curves obtained experimentally for each produced radionuclide are discussed in the following subsections comparing the results with values reported earlier. The experimental data are shown in Figs. 1–14 and their numerical values are presented in Tables 2–4. A Spline fit to the experimental points is also included in each graph. The reported cross sections are elemental cross sections measured on natural Ni target.
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
nat
Ni(d,x)61Cu [7] Takács (1997) corr. [8] Zweit (1991) [9] Cogneau (1967) [10] Budzanowski (1962) [6] and This work [6] Pade fit Spline fit
100 Cross section (mb)
497
50
0 0
5
10
15
Fig. 1. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)61Cu in comparison with the data measured earlier.
12 nat
64
Ni(d,x) Cu
Cross section (mb)
10
8
6
[8] Zweit (1991)
4
This work Spline fit
2
0 0
5
10
15
Fig. 2. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
45
50
Ni(d,x)64Cu in comparison with the data measured earlier.
The 58,59,60,61,62,64,66Cu radionuclides can be produced in (d,xn) reactions on natural nickel in the investigated energy region. We determined excitation functions for the reactions resulting in the radionuclides 61,64Cu (Table 2). The half life of the 58,59,60,62,66Cu isotopes is too short to be assessed in the experimental conditions used. 61
40
nat
3.1. Production of copper radionuclides
3.2. Production of
35
Cu
The decay of the 61Cu radioisotope to 61Ni is followed by gamma radiation of 656 keV (Ic = 10.77%) that allows
easy measurement of the produced activity. Due to the short half life the statistical uncertainty on the collected peak area was around 3% for each spectrum. The extracted cross section data points from the stack irradiated at 20 MeV are somewhat lower than the results of earlier experiments indicating that the recommended cross section values, given in [2] as a Pade fit of selected experimental data, are overestimated in that energy region. The excitation function in the energy range studied essentially reflects a complex behaviour in accordance with the isotopic composition of the target material (Fig. 1). Our new Spline fit has a maximum at 7.4 MeV that corresponds to the contribution of the 60Ni(d,n) reaction. The curve exhibits some
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498
4.0 nat
Ni(d,x) 56 Ni
3.5
Cross section (mb)
3.0 2.5 2.0
[13] Cline (1971) This work Spline fit
1.5 1.0 0.5 0.0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 3. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)56Ni in comparison with the data measured earlier.
80 nat
57
Ni(d,x) Ni
Cross section (mb)
60
[7] Takács (1997) corr. [8] Zweit (1991) [9] Cogneau (1967) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) [16] Baron (1963) [17] Brinkman (1977) This work Spline fit
40
20
0 0
5
10
15
Fig. 4. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)57Ni in comparison with the data measured earlier.
structure around 16 and 30 MeV that reflects the contribution of the 61Ni(d,2n) and 62Ni(d,3n) reactions. Contribution from the 64Ni(d,5n) reaction (Ethreshold = 33.3 MeV) is energetically also possible but no significant cross section can be observed. Around the maximum of the excitation function the Spline fit follows the earlier measured data points rather than the three new experimental data points reflecting the statistical behaviour of the Spline method. A new dedicated experiment could solve this discrepancy. Results for this reaction were already published by our group earlier in [6] in comparison and cross-checking with other possible deuteron monitor reactions keeping the Pade fit given in [2] as a recommended data. Six earlier experiments were found in the literature [6–11]. One series of data in our publication [7] was norma-
lised in [6] (divided by 1.18). The shape of the excitation function published by Zweit et al. [8] and Cogneau et al. [9] is good but the data are too high around the maximum, the results of Budzanowski and Grotowski [10] and Coetzee and Peisach [11] are in agreement with our data. Data of [9] were not used for the Spline fit. 3.3. Production of
64
Cu
The radionuclide 64Cu (T1/2 = 12.7 h) is used both in internal therapy and in PET diagnostics. For production of 64Cu in no-carrier-added form various production routes on Ni and Zn targets were investigated. The 64Ni(d,2n) reaction is among the most efficient procedures. This reaction was investigated only by Zweit et al. [8] before. The 64Cu
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
499
35 30 25 Cross section (mb)
nat
Ni(d,x)55Co
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) [16] Baron (1963) [17] Brinkman (1977) [18] Nakao (2004) This work Spline fit
20 15 10 5 0 0
5
10
15
Fig. 5. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)55Co in comparison with the data measured earlier.
160 nat
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) This work Spline fit
120 Cross section (mb)
56
Ni(d,x) Co
140
100 80 60 40 20 0 0
5
10
15
Fig. 6. Excitation function for the reaction
20 25 30 Deuteron energy (MeV)
35
40
45
50
nat
Ni(d,x)56Co in comparison with the data measured earlier.
has a very weak Ec = 1345.8 keV (Ic = 0.473%) c-line that allows only limited accuracy of the measurement using natural nickel target and gamma spectrometry. Two reactions can contribute to the production of this isotope: 64Ni(d,2n) (Q = 4.68 MeV) and 62Ni(d,c) (Q = +11.8 MeV), but the latter reaction has a negligible contribution. Because of the importance of 64Cu from the point of view of medical application we discuss this reaction in comparison with other production routes in details in a separate article [12]. In Fig. 2 we present our new data and data of Zweit et al. [8] and a Spline fit of all data. 3.4. Production of nickel radionuclides In the investigated energy range production of the radionuclides 54,55,56,57,59,63,65Ni is energetically possible in
(d,pxn) reactions on natural nickel. We could only determine the excitation function for the reactions resulting in 56,57 Ni, Table 2, as the half life of 54,55Ni is too short, the 59,63 Ni have no gamma lines and 65Ni can only be produced by the (d,p) reaction with low cross section on low abundance 64Ni (less than 1%).
3.5. Production of
56
Ni
The strongest independent gamma line of 56Ni is Ec = 158.38 keV (Ic = 98.8%). The main contribution to the formation of 56Ni is from the 58Ni(d,p3n) (Q = 24.7 MeV) reaction. The (d,p5n) reaction on 60Ni has a high Q-value (Q = 45.08 MeV) and has no significant contribution in the investigated energy interval (Fig. 3). The
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
500
700 nat
57
Ni(d,x) Co
600
[7] Takács (1997) corr. [8] Zweit (1991) [13] Cline (1971) [14] Fuying (1983) [15] Blann (1963) This work Spline fit
Cross section (mb)
500 400 300 200 100 0 0
10
5
15
20
25
30
35
40
45
50
Deuteron energy (MeV) Fig. 7. Excitation functions for the reactions
nat
Ni(d,x)57Co in comparison with the data measured earlier.
400 nat
Ni(d,x) 58Co [7] Takács (1997) corr.
Cross section (mb)
300
[8] Zweit (1991) [13] Cline (1971) [19] Jung (1992) This work Spline fit
200
100
0 0
10
20
Fig. 8. Excitation function for the reaction
30 40 Deuteron energy (MeV)
57
60
nat
Ni(d,x)58Co in comparison with the data measured earlier.
formation of 56Ni can be considered by the decay of possible produced 56Cu. Only one data set was published before from 30 to 40 MeV by Cline [13] which, although somewhat lower, is in agreement with our data within experimental errors. The Spline fit was calculated using both data sets (Fig. 3). 3.6. Production of
50
Ni
The 57Ni radionuclide has a half life of T1/2 = 35.6 h and decays to the radioactive 57Co. The energy of the strongest gamma line is Ec = 1377.63 keV (Ic = 81.7%). The measured peak area was corrected for background signal due
to 214Bi (Ec = 1377.6 keV) although the contribution of the background to the total measured peak was almost negligible. Eight datasets were measured earlier, these are: [7–9,13–17] (Fig. 4). Out of them two sets of data [9,14] are too high or have a significant energy shift, the remaining data are in agreement up to 22 MeV. In the 22–25 MeV region data of Blann and Merkel [15] and Brinkman et al. [17] are about 35% higher than data of Cline [13] and our newly measured data. Above 25 MeV energy only data points measured in this work exist. The wide shape of the excitation function confirms that several reactions can take place and contribute to the production of 57Ni on natural nickel target. This reaction product
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
501
100 nat
60
Ni(d,x) Co
Cross section (mb)
80
60
This work Spline fit
40
20
0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 9. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)60Co.
4 nat
61
Ni(d,x) Co
Cross section (mb)
3 This work Spline fit
2
1
0
0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 10. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)61Co.
can be used for beam monitoring above 25 MeV where the curve is rising steeply. The data of [9,14,17,15] above 22 MeV were excluded for performing the Spline fit because of their deviation as mentioned above.
tions for the reactions resulting in the 55,56,57,58,60,61Co radionuclides (Table 3). The results include all the (d,x) processes that directly or indirectly (through parent decay) result in cobalt radionuclides on natural nickel targets.
3.7. Production of cobalt radionuclides
3.8. Production of
Energetically the nuclides of cobalt from mass number 53 to 64 can be produced by deuteron bombardment of natural nickel target in the investigated energy region. Among them 53,54,62,63,64Co have too short half life to be assessed in this experiment. We determined excitation func-
The 55Co has relatively short half life T1/2 = 17.5 h. The intense Ec = 931 keV (Ic = 75%) gamma line gives an interference free determination possibility to measure its produced activity. The presented cross sections are elemental up to 34 MeV and cumulative above that energy
55
Co
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
502
4.0 nat
52
Ni(d,x) Mn
3.5
Cross section (mb)
3.0 2.5 2.0
[13] Cline (1971) This work Spline fit
1.5 1.0 0.5 0.0
0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 11. Excitation function for the reaction
35
40
45
50
nat
Ni(d,x)52Mn in comparison with the data measured earlier.
35 nat
54
Ni(d,x) Mn
30
Cross section (mb)
25
20 [13] Cline (1971) This work Spline fit
15
10
5
0 0
5
10
15
20
25
30
35
40
45
50
Deuteron energy (MeV) Fig. 12. Excitation function for the reaction
nat
Ni(d,x)54Mn in comparison with the data measured earlier.
point, since 55Co is also produced by the decay of 55Ni at higher energies as can be seen in Fig. 5 as a rising tail of the excitation function above 40 MeV. Eight experiments were reported in literature before [7,8,13–18]. They are in relatively good agreement, except Blann’s data [15] which are higher about 50% than the others. Therefore in the Spline fit calculation this data set and the data of Cline [13], which are very much scattered, were not included. The reaction can be used also for monitoring purposes in the 15–35 MeV energy interval. The excitation function has a maximum of about 23 mbarn at 23 MeV.
3.9. Production of
56
Co
This radionuclide presents a special interest since it can be produced from several structural materials such as iron and nickel. It has a T1/2 = 77.27 d half life and several intensive gamma lines that provides easy determination of the produced activity. Although a significant part of the activity is produced through direct reactions, the reported cross sections are cumulative since 56Co is also formed by decay of the 56Ni radionuclide above 30 MeV. Some gamma lines present small interferences from decay of the shorter lived 56Mn for several hours after EOB. Five
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
503
1.4 nat
56
Ni(d,x) Mn
1.2
Cross section (mb)
1.0 This work Spline fit
0.8
0.6
0.4
0.2
0.0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 13. Excitation function for the reaction
35
40
45
50
45
50
nat
Ni(d,x)56Mn.
16 nat
14
51
Ni(d,x) Cr
Cross section (mb)
12 10 8
This work Spline fit
6 4 2 0 0
5
10
15
20 25 30 Deuteron energy (MeV)
Fig. 14. Excitation function for the reaction
datasets were published before [7,8,13–15]. As in the case of the reactions discussed above data of Blann and Merkel [15] are too high and data of Cline [13] are scattered and above 25 MeV only our new data exist (Fig. 6). Our new results are lower than the earlier published values below 20 MeV. In the Spline fit calculation [13,15] were not included. The excitation function has a local maximum of 43 mbarn at about 10 MeV that is followed by a slowly decreasing tail up to 30 MeV. In principle this reaction can be used for beam monitoring, although data are more scattered than data of the reaction mentioned above.
35
40
nat
Ni(d,x)51Cr.
3.10. Production of
57
Co
The 57Co is a long-lived radioisotope with half life of T1/2 = 271.79 d. It has two strong gamma lines at energy of Ec = 122.06 keV (Ic = 85.6%) and Ec = 136.47 keV (Ic = 10.68%). The 57Co radionuclide can be produced in several direct reactions on natural nickel target and also generated as a daughter product of 57Ni. Cumulative activity measurements of the foils were started several days after EOB when 57Ni decayed completely. Five datasets were published before [7,8,13–15] Again, as in the case of the
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
504
Table 2 Cross sections for deuteron induced reactions on natural nickel resulting in 61,64Cu and 56,57Ni radionuclides Energy (MeV)
r (mb) 61
4.2 ± 0.5 6.6 ± 0.4 8.5 ± 0.4 9.6 ± 0.5 10.1 ± 0.4 10.8 ± 0.4 10.9 ± 0.5 11.6 ± 0.4 12.0 ± 0.4 13.0 ± 0.4 13.1 ± 0.4 14.1 ± 0.4 14.3 ± 0.3 15.1 ± 0.4 15.6 ± 0.3 16.0 ± 0.3 16.9 ± 0.3 16.9 ± 0.3 17.8 ± 0.3 18.0 ± 0.5 18.1 ± 0.3 18.6 ± 0.3 19.3 ± 0.3 19.4 ± 0.3 20.2 ± 0.3 20.4 ± 0.3 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
Cu
45.3 ± 5.9 64.5 ± 8.4 56.3 ± 7.3 46.8 ± 5.6 46.0 ± 6.0 36.2 ± 4.3 43.3 ± 4.9 37.6 ± 4.9 30.0 ± 3.6 31.8 ± 4.1 26.7 ± 3.2 19.3 ± 2.3 27.5 ± 3.6 21.1 ± 2.5 24.3 ± 3.2 17.3 ± 2.1 22.0 ± 2.9 18.6 ± 2.2 15.7 ± 1.9 18.0 ± 2.1 19.8 ± 2.6 17.1 ± 2.0 18.1 ± 2.4 15.7 ± 1.9 12.4 ± 1.5 17.1 ± 2.2 14.3 ± 1.6 13.6 ± 1.6 14.3 ± 1.7 14.7 ± 1.7 15.4 ± 1.8 14.7 ± 1.7 13.5 ± 1.6 12.5 ± 1.5 12.7 ± 1.5 12.4 ± 1.5 11.1 ± 1.4 11.7 ± 1.4 10.8 ± 1.3 11.3 ± 1.4 8.7 ± 1.1 10.6 ± 1.3 10.2 ± 1.3 10.2 ± 1.3 9.2 ± 1.1
64
Cu
56
Ni
57
Ni
6.1 ± 0.7
0.13 ± 0.02
6.3 ± 0.8
0.42 ± 0.05 0.14 ± 0.05
7.1 ± 0.9
0.87 ± 0.10
7.6 ± 0.9 8.2 ± 1.0
1.4 ± 0.2 1.9 ± 0.2
7.0 ± 0.8
2.3 ± 0.3
8.0 ± 1.0
2.7 ± 0.3
6.9 ± 0.8 6.9 ± 0.8
3.4 ± 0.4 3.9 ± 0.5 3.7 ± 0.5
6.2 ± 0.7
4.8 ± 0.6
3.7 ± 0.4 3.5 ± 0.4
5.8 ± 0.7 7.5 ± 0.9 15.3 ± 1.8
0.27 ± 0.08 0.34 ± 0.10 0.39 ± 0.15 0.50 ± 0.12 1.05 ± 0.18 0.95 ± 0.25 0.97 ± 0.22 1.88 ± 0.28 1.92 ± 0.25 2.41 ± 0.32 2.49 ± 0.35 2.85 ± 0.40 3.13 ± 0.38 3.13 ± 0.38
38.7 ± 4.4 43.8 ± 5.0 55.6 ± 6.3 63.3 ± 7.3 61.1 ± 7.0 65.1 ± 7.4 64.6 ± 7.3 62.2 ± 7.1 62.3 ± 7.1 61.2 ± 6.9 59.4 ± 6.8 59.9 ± 6.8 61.1 ± 6.9 58.0 ± 6.6
reactions discussed above, data of Blann and Merkel [15] are higher above 20 MeV and data of Cline [13] are scattered and lower than the other reported data. Above 25 MeV only our new data exist (Fig. 7). From the Spline fit calculation [13,15] were excluded. The excitation curve slowly starts to rise at 10 MeV and is increasing steadily up to 20 MeV. Above 20 MeV a steep increase can be observed reaching a value of more than 500 mbarn at about 34 MeV. This reaction is probably the most appropriate for monitoring deuteron beam parameters, especially in the 20–50 MeV region.
3.11. Production of
58
Co
The 58Co has a metastable state (T1/2 = 9.04 h) that decays for 100% by IT to the ground state with emission of only a very low energy c-ray. The ground state has a gamma line with energy of Ec = 810.775 keV (Ic = 99%). In these conditions only cumulative production of the ground state could be assessed which required a few days of cooling time for total decay of the metastable state. Four cross sections sets were reported for this reaction earlier [7,8,13,19]. Data of Zweit et al. [8] are too low for this reaction, unlike for other reactions where their data are in agreement or a little higher than our data. It indicates that probably the applied cooling time was not long enough for total decay of the metastable state. Data of Cline [13] are scattered and lower than our data as is the case with the other reactions. Jung’s data seems to be shifted to higher energies, otherwise the amplitude and shape of the reported curve is in agreement with our data. It is clearly visible on Fig. 8 that the corrected data reported by our group earlier [7] represent the highest values and do not correspond perfectly to the newly measured data sets in which the data points from the low and high energy irradiations show a slight difference in amplitude although they are in agreement within errors. The Spline fit was calculated by excluding the data of Zweit et al. [8]. The reaction has low threshold energy and has the highest cross section values in the 10–25 MeV energy interval. This feature of the reaction makes it very suitable for use as monitor reaction. Because of the activation and decay characteristics of this process it is also favorable for use in wear measurements of machine parts or structural materials having nickel content. 3.12. Production of
60
Co
The radioisotope 60Co is long-lived (T1/2 = 5.2714 y). It has also a metastable state (T1/2 = 10.47 min) that decays by IT to the ground state (99.76%) and by b to 60Ni (0.24%). The two almost 100% abundant gamma lines emitted at Ec = 1173.237 keV and Ec = 1332.501 keV give a good possibility to measure the produced activity. Long measurements were required to decrease the statistical error to an acceptable 5% level. The excitation function starts to rise only above 25 MeV and is increasing steadily up to 80 mbarn in the investigated energy region (up to 50 MeV) (Fig. 9). As no data were found in the literature the Spline fit was calculated over the newly measured experimental cross section data points. 3.13. Production of
61
Co
Production of 61Co can take place on the heavier Ni low abundance nickel isotopes; therefore the elemental cross sections are relatively low. As the radionuclide 61 Co has only three gamma lines which all are interfering 61,62,64
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507 Table 3 Cross sections for deuteron induced reactions on natural nickel resulting in Energy (MeV)
9.6 ± 0.5 10.8 ± 0.4 10.9 ± 0.5 12.0 ± 0.4 13.1 ± 0.4 14.1 ± 0.4 15.1 ± 0.4 16.0 ± 0.3 16.9 ± 0.3 17.8 ± 0.3 18.0 ± 0.5 18.6 ± 0.3 19.4 ± 0.3 20.2 ± 0.3 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
Co
Co radionuclides
56
57
58
35.9 ± 4.3 33.0 ± 4.0 34.1 ± 4.2 30.2 ± 3.6 24.2 ± 2.9 20.0 ± 2.4 15.7 ± 1.9 14.4 ± 1.7 12.0 ± 1.4 10.9 ± 1.3 15.0 ± 2.1 8.7 ± 1.0 8.6 ± 1.0 7.6 ± 0.9 10.4 ± 2.1 7.3 ± 0.9 8.2 ± 1.1 10.4 ± 1.2 12.1 ± 2.1 13.5 ± 1.6 20.6 ± 2.4 26.6 ± 3.1 35.0 ± 4.0 45.6 ± 5.3 55.7 ± 6.3 66.1 ± 7.6 92.8 ± 10.6 99.3 ± 11.2 109.8 ± 12.5 112.9 ± 12.8 126.2 ± 14.4 127.9 ± 14.4 131.1 ± 14.8
1.3 ± 0.2 3.7 ± 0.4 5.2 ± 1.5 9.3 ± 1.1 14.6 ± 1.7 20.1 ± 2.4 23.3 ± 2.8 28.7 ± 3.4 39.0 ± 4.7 49.9 ± 6.0 47.5 ± 5.8 67.4 ± 8.1 85.2 ± 10.2 111.1 ± 13.3 245.3 ± 28.3 293.9 ± 33.0 354.0 ± 39.8 424.3 ± 47.7 441.3 ± 50.0 464.8 ± 52.2 505.0 ± 56.8 513.9 ± 57.8 515.4 ± 57.9 499.5 ± 56.2 497.3 ± 55.9 481.7 ± 54.2 455.9 ± 51.3 440.0 ± 49.5 422.7 ± 47.6 427.0 ± 48.1 411.7 ± 46.4 406.1 ± 45.6 402.9 ± 45.3
82.8 ± 9.9 130.4 ± 15.6 81.3 ± 9.5 151.2 ± 18.1 161.6 ± 19.4 187.8 ± 22.5 185.7 ± 22.3 197.6 ± 23.7 205.6 ± 24.7 213.5 ± 25.6 225.9 ± 25.7 205.6 ± 24.7 204.3 ± 24.5 190.2 ± 22.8 210.4 ± 24.3 184.3 ± 20.7 169.9 ± 19.2 144.6 ± 16.3 150.2 ± 17.3 135.3 ± 15.2 112.5 ± 12.7 106.6 ± 12.1 105.6 ± 11.9 105.0 ± 12.0 104.6 ± 11.8 108.1 ± 12.3 113.6 ± 12.9 113.4 ± 12.8 115.2 ± 13.1 117.6 ± 13.3 118.0 ± 13.4 118.8 ± 13.4 118.0 ± 13.3
Co
0.10 ± 0.01 0.57 ± 0.07 0.10 ± 0.05 2.3 ± 0.3 4.8 ± 0.6 7.4 ± 0.9 9.5 ± 1.1 11.6 ± 1.4 14.0 ± 1.7 16.1 ± 1.9 12.7 ± 1.4 17.7 ± 2.1 18.6 ± 2.2 20.1 ± 2.4 21.6 ± 2.4 20.4 ± 2.3 19.8 ± 2.3 16.2 ± 1.9 18.0 ± 2.0 15.2 ± 1.8 11.5 ± 1.3 10.3 ± 1.2 8.6 ± 1.0 8.6 ± 1.0 8.1 ± 1.0 8.0 ± 0.9 7.5 ± 0.9 7.1 ± 0.8 7.3 ± 0.9 7.4 ± 0.9 7.9 ± 0.9 9.0 ± 1.1 9.4 ± 1.1
Co
Table 4 Cross sections for deuteron induced reactions on natural nickel resulting in 52,54,56Mn and 51Cr radionuclides r (mb) 52
Mn
18.0 ± 0.5 23.3 ± 0.4 24.9 ± 0.9 26.2 ± 0.8 28.3 ± 0.8 29.2 ± 0.4 29.5 ± 0.7 32.4 ± 0.7 33.7 ± 0.7 35.1 ± 0.6 36.6 ± 0.6 37.8 ± 0.6 38.6 ± 0.5 41.7 ± 0.5 42.5 ± 0.5 43.9 ± 0.4 44.4 ± 0.4 46.5 ± 0.4 47.5 ± 0.4 48.5 ± 0.4
55,56,57,58,60,61
r (mb) 55
Energy (MeV)
505
0.11 ± 0.06 1.5 ± 0.3 1.8 ± 0.3 2.0 ± 0.4 2.8 ± 0.4 2.7 ± 0.4 2.6 ± 0.4 2.2 ± 0.4 2.6 ± 0.5 1.9 ± 0.4 1.5 ± 0.3 1.5 ± 0.3
0.9 ± 0.3 0.8 ± 0.5 1.5 ± 0.6 1.6 ± 0.4 1.9 ± 0.4
54
Mn
56
Mn
2.6 ± 0.5 4.5 ± 1.0 9.5 ± 1.2
0.07 ± 0.03 0.04 ± 0.03 0.02 ± 0.03
15.3 ± 1.9 22.3 ± 2.9 26.3 ± 3.5 25.4 ± 3.3 29.2 ± 4.1 29.2 ± 3.5 29.1 ± 3.9 26.7 ± 3.9 26.1 ± 3.2 22.3 ± 3.3 23.7 ± 3.4 20.6 ± 3.3 21.4 ± 2.9 18.6 ± 2.5
0.04 ± 0.03 0.11 ± 0.04 0.18 ± 0.05 0.29 ± 0.06 0.41 ± 0.07 0.50 ± 0.09 0.53 ± 0.08 0.71 ± 0.10 0.75 ± 0.11 0.80 ± 0.12 0.97 ± 0.14 0.98 ± 0.17 1.09 ± 0.15 1.10 ± 0.14
51
Cr
3.6 ± 1.2 4.1 ± 1.1 6.4 ± 1.3 7.2 ± 1.8 7.0 ± 1.2 9.2 ± 1.9 10.7 ± 2.4 10.8 ± 1.5 11.7 ± 1.4 12.2 ± 2.1 9.2 ± 2.3 9.1 ± 1.5 9.1 ± 1.5
Co
60
Co
61
Co
1.6 ± 0.2
1.4 ± 0.2
14.9 ± 3.1 2.4 ± 4.5 12.6 ± 4.3 13.1 ± 3.2 14.1 ± 5.3 12.2 ± 6.1 28.0 ± 7.6 32.1 ± 9.3 32.5 ± 6.1 40.5 ± 9.7 48.0 ± 11.4 49.2 ± 7.5 68.3 ± 12.9 62.8 ± 12.5 70.8 ± 18.9 66.3 ± 10.8 78.8 ± 11.9
1.4 ± 0.5 1.6 ± 0.2 1.9 ± 0.2 1.6 ± 0.2 1.6 ± 0.2 1.8 ± 0.2 2.1 ± 0.3 2.5 ± 0.6 2.6 ± 0.4 2.7 ± 0.4 2.5 ± 0.3 2.8 ± 0.3 2.8 ± 0.3 2.9 ± 0.3 2.4 ± 0.3 2.9 ± 0.3 2.8 ± 0.3 3.2 ± 0.4 2.9 ± 0.4
with the 61Cu gamma lines since both radionuclides decay to 61Ni; special attention was paid to the assessment of this radioisotope. Contribution to the measured peak area from the simultaneously produced longer lived 61Cu was subtracted before the cross sections were calculated. No data were found in the literature, only our data points are available with relatively high uncertainties due to the low statistics and the applied process to separate the contribution of 61 Cu. In general the measured cross sections are low. As no experimental points below 10 MeV could be obtained, no information can be given around the threshold of this reaction (Fig. 10).
3.14. Production of manganese radionuclides In this section the processes resulting in the formation of manganese radionuclides are discussed. In the investigated energy interval practically production of all manganese radionuclides is energetically possible. Due to their half life and decay characteristics only the 52,54,56Mn could be measured (Table 4).
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506
3.15. Production of
52
Mn
The radionuclide 52Mn has a ground state with T1/2 = 5.591 d half life and a metastable state with half life of T1/2 = 21.1 min, which decays only for 1.75% by IT mode to the ground state and by b+ and EC (98.25%) to 52 Cr. We assessed the 52Mn ground state after a few hours cooling time when the metastable state had completely decayed. The Ec = 935.5 keV gamma line (Ic = 94.5%) was used for measuring the activity of the produced 52 Mn. The excitation function shows a local minimum around 43 MeV and rises again due to the contribution of the reactions on the second most abundant 60Ni isotope (Fig. 11). We found one earlier dataset measured by Cline [13] on enriched 58Ni. While the reported curve in [13] has a similar shape, the data points are scattered and around the maximum the values are somewhat higher than our data (opposite to the reactions discussed above) even after correction for the used gamma intensity (data in [13] were calculated with Ic = 84%). In this case the Spline fit was calculated over our new data points only. 3.16. Production of
54
Mn
The half life of 54Mn is T1/2 = 312.3 d. Its only gamma line is very strong (Ec = 834.85 keV, Ic = 99.976%) what makes it relatively easy to assess this radionuclide. The excitation function starts to rise at 23 MeV and reaches its maximum of 28.8 mbarn at 38 MeV. Although several reaction channels are possible, in which emission of different combination of single and complex particles occur, the excitation curve has a simple one maximum shape in the investigated energy region. There is one data set measured by Cline [13] on enriched 58Ni. The reported curve has a similar shape, data points are scattered and they are somewhat lower than our data. Only our data were considered in calculating the Spline fit (Fig. 12). 3.17. Production of
56
Mn
The 56Mn radionuclide has a half life of T1/2 = 2.58 h and decays by b to 56Fe. As the simultaneously produced 56 Co with longer half life (T1/2 = 77.27 d) decays to the same nuclide 56Fe, which results in the same gamma lines, the assessment of the 56Mn required separation of the 56Co contribution. This was performed by taking two spectra with good statistics at different times: a first measurement shortly after EOB to determine the common activity of 56 Co and 56Mn and a second one after total decay of 56 Mn to determine the 56Co activity which is also influenced by the decay of 56Ni. The measured excitation function has a simple rising shape starting at 28 MeV. It is not clear if the first two low energy points have real higher value or if this is an artefact due to the uncertainty from the data separation process (Fig. 13). No other data are available in the literature.
3.18. Production of chromium radionuclides Production of several chromium isotopes is possible energetically in the investigated energy region. Due to the decay characteristics of the possibly produced radionuclides of chromium we were able to identify only the 51Cr. 3.19. Production of
51
Cr
The 51Cr has the longest half life among the radioactive chromium isotopes (T1/2 = 27.7 d). It decays to 51V and has only one gamma line (Ec = 320.08 keV, Ic = 10%). Assessment of this reaction product was possible only in the high energy part of the investigated energy region. The measured excitation function shows a single peak. The highest measured cross section is around 12 mbarn at 44.4 MeV. (Table 4.) No other measurements reported in literature were found. The Spline fit was calculated over our newly measured experimental cross sections (Fig. 14). 4. Conclusion Activation cross sections of deuteron induced reactions were measured on natural nickel up to 50 MeV. We determined elemental cross sections for the 61,64Cu, 56,57Ni, 55,56,57,58,60,61 Co, 52,54,56Mn and 51Cr radionuclides. Production of these longer lived radionuclides are important in the estimation of accumulated radioactivity in the structural materials of accelerator components and beam transport systems (activation by direct beam hit or beam loss during long-term operation). It is especially relevant for the ongoing IFMIF project (International Fusion Materials Irradiation Facility) which was established to study and test fusion materials by an accelerator-based D-Li high intensity neutron source. For the earlier established monitor reaction nat Ni(d,x)61Cu [6] we propose new evaluated cross section values and we also give reliable results for reaction products (57Ni, 56,57,58Co) that can be used for alternative beam monitoring purposes in the energy range from 10 to 50 MeV. The detailed results for the efficient production of 64Cu, an important radionuclide in PET imaging, by 64 Ni(d,2n) reaction will be presented separately. Thick target yields were calculated based on the Spline fitted excitation functions (see Fig. 15) for each investigated end product. From the point of view of accelerator exploitation such as the IFMIF facility it is obvious that the EOB activity is higher for the short lived radionuclides with high cross sections, but radiation burden from these radionuclides will be negligible after one or two days of cooling time. For most of the reaction products investigated here however the days long half-lives require a too long cooling time to wait for the decay of the products which is not favorable for maintenance personnel. As the long lived radionuclides will accumulate during long periods of irradiation, it is important to avoid unnecessary activation of structural materials
S. Taka´cs et al. / Nucl. Instr. and Meth. in Phys. Res. B 260 (2007) 495–507
507
1000 61
Cu Co 57 Ni 55 Co 61
Integral yield (MBq/μAh)
100
56
Mn Co Co 56 Co 52 Mn 51 Cr 56 Ni 54 Mn 60 Co 58
10
57
1
0.1
0.01
0.001
0
10
20 30 Deuteron energy (MeV)
40
50
Fig. 15. Thick target yields calculated from the fitted excitation functions for the investigated processes.
by energetic deuteron beam by choosing proper materials and suitable designs. Acknowledgements We are pleased to acknowledge the co-operation and help in performing the irradiations of the teams of the Louvain-la-Neuve Cyclone-110, Brussels CGR-560 and the Debrecen MGC-20E cyclotron laboratories.This work was partly supported by the Fund for Scientific Research (FWO-Vlaanderen), the Hungarian Academy of Sciences and the OZR-VUB. References [1] IFMIF International team, IFMIF-KEP; International Fusion Materials Irradiation Facility Key Element Technology Phase Report, JAERI-Tech 2003-005, 2003. [2] F. Ta´rka´nyi, S. Taka´cs, K. Gul, A. Hermanne, M.G. Mustafa, M. Nortier, P. Oblozinsky, S.M. Qaim, B. Scholten, Yu.N. Shubin, Z. Youxiang, Beam Monitor Reactions in: IAEA-TECDOC-1211, IAEA, Vienna, 2001, p. 49,
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