Activation cross-sections of proton induced reactions on natural Ni up to 65 MeV

Applied Radiation and Isotopes 92 (2014) 73–84

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Activation cross-sections of proton induced reactions on natural Ni up to 65 MeV N. Amjed a,b,n, F. Tárkányi b, A. Hermanne c, F. Ditrói b, S. Takács b, M. Hussain a a

Department of Physics, Government College University Lahore, Lahore 54000, Pakistan Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), 4026 Debrecen, Hungary c Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium b

H I G H L I G H T S








Production cross-sections of natNi(p,x)60,61Cu, 56,57Ni, 55,56,57,58Co reactions up to 65 MeV. Comparison of results with theoretical codes ALICE-IPPE, TALYS 1.4 and TENDL-2012 library. Calculation and comparison of physical yields with literature experiments. Thin layer activation (TLA) curves for57Ni and 57Co for industrial applications. The production rate for 55Co was compared for proton and deuteron induced reactions on Ni.

art ic l e i nf o

a b s t r a c t

Article history: Received 29 December 2013 Received in revised form 29 May 2014 Accepted 11 June 2014 Available online 20 June 2014

Production cross-sections of the natNi(p,x)60,61Cu, 56,57Ni, 55,56,57,58Co nuclear reactions were measured in five experiments up to 65 MeV by using a stacked foil activation technique. The results were compared with the available literature values, predictions of the nuclear reaction model codes ALICE-IPPE, TALYS1.4, and extracted data from the TENDL-2012 library. Spline fits were made on the basis of selected data, from which physical yields were calculated and compared with the literature values. The applicability of the natNi(p,x)57Ni, 57Co reactions for thin layer activation (TLA) was investigated. The production rate for 55 Co was compared for proton and deuteron induced reactions on Ni. & 2014 Elsevier Ltd. All rights reserved.

Keywords: Proton irradiation Natural nickel targets 60,61 Cu, 56,57Ni and 55,56,57,58Co excitation functions Spline fit Physical yields Thin layer activation

1. Introduction Nickel is one of the most frequently used structural materials (alloys, anti-corrosion), and its activation data are especially important when used in nuclear and space equipments working under intensive radiation. It was ranked among the high priority elements in the FENDL-3 work document “IFMIF deuteron and proton data needs” (Fischer, 2009). Nickel (especially in isotopically enriched form) plays an important role as target material for the production of medical radioisotopes (60,61,62,64Cu and 55,56,57,58 Co etc.) that are mostly produced via proton induced reactions. Therefore, activation cross-sections of proton induced n

Corresponding author at: Department of Physics, Government College University Lahore, Lahore 54000, Pakistan. E-mail address: [email protected] (N. Amjed). http://dx.doi.org/10.1016/j.apradiso.2014.06.008 0969-8043/& 2014 Elsevier Ltd. All rights reserved.

reactions on natural nickel find importance in the aforementioned applications as well as for testing the predictive power of conventional nuclear reaction theory. In a previous work we have investigated the activation crosssections of the deuteron induced nuclear reactions on nickel (covering different applications of the produced radioisotopes) (Amjed et al., 2013). In this work the activation cross-sections of residual nuclei in Niþ p collisions have been measured. Some of the following aims of the present investigation are closely connected to research projects coordinated by the IAEA.


To update the nuclear data for the “Nuclear Data Libraries for


Advanced Systems - Fusion Devices” IAEA FENDL-3 coordinated research program (Fischer, 2009) (all reaction products). To improve the IAEA database on thin layer activation (Thin Layer Activation-IAEA, 57Co product) (Takács, 2010).

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N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84


To perform further measurements and evaluation of data for





the natNi(p,x)56,57,58Co beam monitor reactions (Tárkányi et al., 2001) and for the production of the medically important radionuclides 55Co and 60,61Cu (Nichols and Capote, 2013). To check the predicting capability of the nuclear reaction model codes, particularly the widely used TALYS (Koning et al., 2012). The present-day EXFOR database contains numerous works, presenting mainly so called elemental and cumulative production cross sections of the proton-induced reaction products in natural nickel (see later). Due to the systematic work of Levkovskij (1991) and some other dedicated works, mainly related to medical isotope production (Qaim, 2011) and nuclear reaction theory studies, reaction cross sections (on separate target isotopes) for direct production of the relevant products are also available. In most cases the agreement between the different datasets is acceptable, but occasionally large disagreements still persist in some cases.

2. Experimental measurements and data evaluation The general characteristics and procedures for irradiation, activity assessment and data evaluation (including estimation of uncertainties) were similar to those in our previous work (Amjed et. al., 2013). The main experimental parameters for the present study are summarized in Table 1 while the methods used in data evaluation and the decay data are collected in Table 1 and Table 2.

3. Nuclear model calculations Many groups use the TALYS-based Nuclear Data Library (TENDL), which utilizes both default and adjusted TALYS calculations (a set of correcting parameters was obtained by fitting the original code results to selected experimental data and data from existing evaluations) (Koning et al., 2012). The TENDL library is

well developed for neutron induced reactions but not so developed for charged particles. To validate the measured cross-sections, we compared them with the results taken from TENDL-2012 library and with theoretical calculations based on TALYS 1.4 code (Koning et al., 2011) and the ALICE-IPPE code (Dityuk et al., 1998) The individual results of the reaction products of interest were weighted and summed according to the abundances of the isotopes of natural nickel (target). In case of cumulative formation, cumulative values were also included in the final results. For both theoretical models, TALYS 1.4 and ALICE-IPPE, we used only the default input parameter files.

4. Results and discussion The experimental cross-sections for each radionuclide obtained in this work together with their uncertainties are given in Tables 4–8. They are elemental cross-sections measured on natNi targets. For each radionuclide our measured cross-sections are compared with the published results obtained from other laboratories. Renormalized cross-sections on enriched 58Ni targets from literature are also presented in the figures, up to the threshold of reactions on 60Ni (see references there). Theoretical predictions calculated by TALYS 1.4, ALICE-IPPE (with default parameters) and calculated results taken from TENDL-2012 (library) are also presented for comparison. The list of contributing reactions with their Q-values and thresholds is given in Table 3. Our experimental results are shown in Figs. 1–8. When a reasonable amount of selected experimental data sets are available with corresponding estimated errors, a statistical fit over the data points can be performed to obtain the mean value of all the data. The spline fit method uses the technique of piece-wise approximation of experimental data by specifying important points (termed knots of the spline), applying individual interpolation in each interval between two knots, and matching these interpolations so that the first and second derivatives are continuous at the knots.

Table 1 Main experimental conditions and parameters Series no:

Experiment 1

Experiment 2

Accelerator

MGC-20E Cyclotron ATOMKI, DebrecenHungary 2012 17 MeV 16.8–4.2 MeV

CGR 560 Cyclotron of Vrije CGR 560 Cyclotron of Vrije CGR 560 Cyclotron of Vrije Universiteit Universiteit Brussels, Universiteit Brussels, Brussels, Belgium Belgium Belgium 2013 2013 2012 25 MeV 37 MeV 37 MeV 24.8–11.3 MeV 36.5–21 MeV 36.6–7.1 MeV

CYCLONE110 Cyclotron of Catholic University of Louvain, Louvain–la-– Neuve, Belgium 2012 65 MeV 63.6–47.1 MeV

Stacked foil nat Ni foils, 9.9 mm

Stacked foil nat Ni foils, 24.6 mm

Stacked foil nat Ni foils, 46.2 mm

19

19

19

Stacked foil (Ga 70 Ni 30) Alloy 13.35 mm on 12.5 mm Cu 20

Stacked foil (Ga 70 Ni 30) Alloy , 17.75 mm on 25 mm Au 18

0.5 h 177.42 nA nat Ti(p,x)48V reaction Tárkányi et al. (2001)

1h 132.26 nA nat Ti(p,x)48V reaction Tárkányi et al. (2001)

1h 126 nA nat Cu(p,x)62,65Zn reaction Tárkányi et al. (2001)

75min 88.4 nA nat Cu(p,x)62Zn reaction Tárkányi et al. (2001)

1h 104.17nA 27 Al(p,x)24Na reaction Tárkányi et al. (2001)

nat

nat

nat

nat

nat

HpGe 6 series

HpGe 4 series

HpGe 4 series

HpGe 5 series

HpGe 4 series

1.1–3 h, 3.5–7.3 h, 19.0–28.4 h, 30.0–125.0 h, 140.3–257.1 h, 277.4–621.5 h

5–11.3 h, 30.2–52.8 h, 683.5–724.6 h, 793.4–1015.8 h

5.4–13.2 h, 47.0–124.9 h, 148.5–289.3 h, 231.5–650 h

2.5–7.3 h, 22–37.8 h, 60.3–100.4 h, 286.7–434.8 h, 387.4–752.2 h

3.9–29.9 h, 21.4–25.4 h, 99.5–173.1 h, 943.6–1512.4 h

Irradiation year Primary energy Range of the proton energy (MeV) Method Target and thickness Number of target foils Irradiation time Beam current Monitor reaction, [recommended values] Monitor target and thickness Detector γ-Spectra measurements Cooling times

Ti, 12 mm

Ti, 10.9 mm

Experiment 3

Cu, 12.5 mm

Experiment 4

Cu, 12.5 mm

Experiment 5

Al, 26.96 mm

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

75

Table 2 Main parameters of data evaluation (with references). Gamma spectra evaluation

Genie (2000), Forgamma

Genie (2000) Software, Székely (1985)

Determination of beam intensity Decay data Reaction Q-values Determination of beam energy Uncertainty of energy

Faraday cup (preliminary) Fitted monitor reaction (final) NUDAT 2.6 Q-value calculator Anderson (preliminary) Fitted monitor reaction (final) Cumulative effects of possible uncertainties(nominal energy, targetthickness, energy straggling, correction to monitorreaction) Isotopic cross section Sum in quadrature of all individual contributions Beam-current (7%) Beam-loss corrections (max1.5%) Target thickness (1%) Detector efficiency (5–7%) Photo peak area determination andcounting statistics (1–20 %) Physical yield

Piel et al. (1992) NuDat2.6 data base QCalc, Q-value Calculator Andersen and Ziegler (1997), Tárkányi et al. (2001)

Cross sections Uncertainty of cross sections

Yield

Between the knots, the spline fit is presented by polynomials (each interval has its own polynomial) of the same degree (Oblozinsky et al., 2001). In this work, for each activation product a spline fit was made on the basis of our measured cross-sections and selected literature values. The experimental uncertainties were also taken into account during the approximation of the polynomial functions. 4.1. Radioisotopes of copper 4.1.1. Direct formation of 60Cu 60 Cu (T1/2 ¼ 23.7 min) is a short-lived radionuclide that is mainly produced through 60Ni(p, n)60Cu (Ethr ¼7.0 MeV) and 61Ni (p, 2n)60Cu (Ethr ¼15.0 MeV) reactions. Due to its short half-life it was only accessed in Experiment 1 (Ep ¼ 17 MeV). We were not able to access 60Cu in the higher energy irradiations due to the long cooling time required which was needed to avoid the increased radiation hazards in those experiments. The radionuclide 60Cu was identified by its most intense γ-line at 1332.5 keV (Iγ ¼88%). The measured production cross-sections for 60Cu are shown in Fig. 1 together with the literature values, results of theoretical calculations by ALICE-IPPE, TALYS 1.4 and results from the TENDL-2012 library. The status of natNi(p,x)60Cu reaction crosssections is rather weak so we also include the normalized crosssections of those experiments in which enriched 60Ni target was used. Our measured production cross-sections are in agreement with the literature measurements by Blosser and Handley (1955), Tanaka et al. (1972), Levkovskij (1991) and Singh et al. (2006). The cross sections reported by Levkovskij (1991) were decreased by 20%, in agreement with the new measurements for the natMo(p, x)96m,gTc monitor reaction by Takács et al. (2002). The literature values by Barrandon et al. (1975) are slightly higher due to the use of older decay data; therefore about 15% uncertainty on the crosssections was considered in those measurements. The measurements reported by Al-Saleh et al. (2007) are shifted towards higher energies. This energy shift cannot be compensated by a single normalization factor, due to the energy error propagation in the stack, so this experiment was not considered in the final fitting of the experimental data. Together with the present measurements, all literature values, except those by Al-Saleh et al. (2007), were taken into consideration while making the spline fit. Theoretical results taken from TENDL give about 5% higher cross-sections than our TALYS calculations but both results have similar shape as that of the experimental excitation function. The shape of the excitation function predicted by the ALICE-IPPE calculation is almost the same as that of the experiments but it predicts a maximum value about 30% higher than the experimental excitation function.

Guide to the expression of uncertainty in measurement (1995)

Bonardi (1987)

4.1.2. Direct formation of 61Cu Medically interesting 61Cu is a short-lived radionuclide (T1/ ¼3.333 h). It was accessed in Experiments 1, 2 and 3 but not in 2 Experiments 4 and 5 due to the long cooling time required in the latter experiments. For the activity measurement of 61Cu, the γline at 282.9 keV (Iγ ¼12.2%) was used. Mainly the target isotopes 61 Ni and 62Ni contribute to the production of 61Cu through the 61Ni (p,n)61Cu (Ethr ¼3.1 MeV) and 62Ni(p,2n)61Cu (Ethr ¼13.8 MeV) reactions respectively. As can be seen in Fig. 2 the first peak is due to the (p,n) reaction and the second one due to the contribution of the (p,2n) reaction. Our data are shown in Fig. 2 in comparison with earlier reported measurements, results of model calculations by ALICE-IPPE, TALYS 1.4 and with the results from TENDL-2012 library. Our measurements are in good agreement with the results by Michel et al. (1978), Michel and Brinkmann (1980), Titerenko et al. (2011), Blaser et al. (1951), Blosser and Handley (1955), Tanaka et al. (1972), Johnson et al. (1960), Tingwell et al. (1988), Antropov et al. (1992), Szelecsényi et al. (1993) and Singh et al. (2006). The measurements by Barrandon et al. (1975) and Tanaka et al. (1959) are higher than all other experiments. The reported values by Al-Saleh et al. (2007) are shifted towards higher energies. So except for the measurements by Barrandon et al. (1975), Tanaka et al. (1959) and Al-Saleh et al. (2007), all other experiments together with the present measurements were considered in the formation of spline fit. Theoretical results by ALICE-IPPE overestimate the cross-sections. The results of TALYS 1.4 and TENDL-2012 show the same shape of the excitation function as the experiments but in both cases a slight energy shift was observed over the whole excitation function.

4.2. Radioisotopes of nickel 4.2.1. Cumulative production of 56Ni 56 Ni (T1/2 ¼6.077 d) is a long-lived radionuclide mainly produced from the highest abundant stable target isotope 58Ni through a combination of 58Ni(p,t)56Ni (Ethr ¼14.2 MeV), 58Ni(p, nþd)56Ni (Ethr ¼20.6 MeV) and 58Ni(p,2n þp)56Ni (Ethr ¼22.8 MeV) reactions. It is also produced through a combination of 60Ni (p,2nþ t)56Ni (Ethr ¼34.9 MeV), 60Ni(p,3n þd)56Ni (Ethr ¼39.2 MeV) and 60Ni(p,4n þ p)56Ni (Ethr ¼41.3 MeV) reactions. 56Ni was assayed by using its most intense γ-line at 158.38 keV (Iγ ¼98.8%). In addition to the above mentioned direct formation routes, 56Ni may also be produced by the decay of the very short-lived 56Cu (T1/2 ¼ 78 ms) radionuclide, which is produced via the 58Ni(p,3n)56Cu (Ethr ¼39.1 MeV) reaction. Therefore our measured cross-sections

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N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

Table 3 Decay characteristics of the60,61Cu,

55,56,57,58

Co and

56,57

Ni and Q-values of reactions for their productions.

Radionuclide

Half-life

Decay mode (%)

Eg (keV)

Ig (%)

Contributing reaction

Q-value (MeV)

Eth (MeV)

60

23.7 min

EC(7)

826.04 1332.5 1791.6 282.96 656.01 477.2 931.1 1316.6 1408.5

21.7 88.0 45.4 12.2 10.8 20.2 75 7.1 16.9

60

6.9 14.7

7.0 15.0

3.0 13.6 –1.3 –21.1 –21.7 –29.5 –29.6 –33.1 –50.0 –30.6 –36.9 –39.1 –11.6 –19.5 –19.5 –30.1 –40.0 –47.7 –20.2 –22.5 –0.3 –8.1 –8.2 –18.7 –28.6 –35.2 –36.4 –47.0 –10.0 –12.2 –21.8 0.5 –10.1 –20.0 –26.6 –27.8 –38.4

3.1 13.8 1.4 21.5 22.1 30.0 30.1 33.6 50.8 31.2 37.5 39.7 11.8 19.8 19.9 30.5 40.6 48.5 20.6 22.8 0.3 8.2 8.3 19.0 29 35.7 37 47.7 10.2 12.4 22.2 0.0 10.3 20.3 27.0 28.3 39

–14.0 –20.2 –22.5 –34.4 –38.6 –40.6 –42.8 –10.0 –12.2 –24.1 –32.6 –31.9 –40.4 –21.8

14.2 20.6 22.8 34.9 39.2 41.3 43.6 10.2 12.4 24.5 33.6 32.5 41.1 22.2

Cu

61

Cu

3.333 h

β þ (93) EC(39) β þ (61) EC(26) β þ (76)

Ni (p, n)60Cu Ni (p, 2n)60Cu

61

61

55

Co

17.53 h

56

Co

77.236d

EC(80.3) β þ (19.7)

846.77 1037.84 1238.29 1360.21

99.94 14.05 66.46 4.28

Co

271.74d

EC

122.06 136.47 692.41

85.6 10.68 0.149

70.86 d

EC(85.1) β þ (14.9)

810.759

99.45

Ni

6.075d

EC

158.38 269.5 480.44 749.95 811.85

98.8 36.5 36.5 49.5 86

Ni

35.6 h

EC(56.4) β þ (43.6)

127.164 1046 1377.63

16.7 0.134 81.7

57

58m þ g

56

57

Co

are direct below 39 MeV and cumulative above this energy. Fig. 3 shows the results of our measurements, old literature data and comparison with theory (ALICE-IPPE, TALYS 1.4 and TENDL-2012). It can be seen from Fig. 3 that the practical threshold for the production of 56Ni is 16 MeV (indicating the contribution of cluster emission) and hence it was not accessed in Experiment 1 (17 MeV irradiation). Our measurements are in good agreement with literature values by Michel et al. (1978), Aleksandrov et al. (1987a, b), Furukawa et al. (1990), Bringas et al. (2005), Al-Saleh et al. (2007) and Khandaker et al. (2011). The literature values by Michel et al. (1997) has lower cross-sections after 44 MeV. Measurements reported by Haasbroek et al. (1977) are shifted towards higher energies and measurements by Aleksandrov et al. (1987a, b) show higher cross section values. Therefore those two measurements, i.e. Haasbroek et al. (1977) and Aleksandrov et al.

Ni (p, n)61Cu Ni (p, 2n)61Cu 58 Ni(p,α) 58 Ni(p,p þt) 60 Ni(p,2n þ α) 61 Ni(p,3n þ α) 58 Ni(p,2p2n) 60 Ni(p,2t) 60 Ni(p,4n þ 2p) 58 Ni(p,n þ t)55Ni-55Co 58 Ni(p,2n þ d)55Ni-55Co 58 Ni(p,3n þ p)55Ni-55Co 60 Ni(p,n þ α) 61 Ni(p,2n þ α) 58 Ni(p,n þ 2p) 62 Ni(p,3n þ α) 60 Ni(p,3n þ 2p) 61 Ni(p,4n þ 2p) 58 Ni(p,n þ d)56Ni-56Co 58Ni(p,2n þp)56Ni-56Co 60 Ni(p,α) 61 Ni(p,n þ α) 58 Ni(p,2p) 62 Ni(p,2n þ α) 60 Ni(p,2n þ 2p) 64 Ni(p,4n þ α) 61 Ni(p,3n þ 2p) 62 Ni(p,4n þ 2p) 58 Ni(p,d)57Ni-57Co 58 Ni(p,n þ p)57Ni-57Co 58 Ni(p,2n)57Cu-57Ni-57Co 61 Ni(p, α) 62 Ni(p,n þ α) 60 Ni(p,n þ 2p) 64 Ni(p,3n þ α) 61 Ni(p,2n þ 2p) 62 Ni(p,3n þ 2p) IT decay of58mCo 58 Ni(p,t) 58 Ni(p,n þ d) 58 Ni(p,2n þ p) 60 Ni(p,2n þ t) 60 Ni(p,3n þ d) 60 Ni(p,4n þ p) 58 Ni(p,3n)56Cu-56Ni 58 Ni(p,d) 58 Ni(p,np) 60 Ni(p, nþ t) 60 Ni(p,3n þ p) 61 Ni(p,2n þ t) 61 Ni(p,4n þ p) 58 Ni(p,2n)57Cu-57Ni 62

(1987a, b), were not considered in the formation of the spline fit. Between 16 and 26 MeV, all the theoretical model calculations fail to predict the correct behavior of the experimental excitation function. Above 26 MeV ALICE-IPPE overestimates the magnitude of the excitation function, whereas TALYS 1.4 and TENDL show good agreement with the experimental data, except in the peak region.

4.2.2. Cumulative formation of 57Ni The radionuclide 57Ni (T1/2 ¼35.6 h) is not only produced by the direct contribution of 58Ni(p,d) 57Ni (Ethr ¼ 10.2 MeV), 58Ni(p,np)57Ni (Ethr ¼12.4 MeV), 60Ni(p,nþt)57Ni (Ethr ¼ 24.5 MeV), 61Ni(p,2nþ t)57Ni (Ethr ¼32.5 MeV), 60Ni(p,3nþp)57Ni (Ethr ¼33.6 MeV) and 61Ni (p,4nþp)57Ni (Ethr ¼41.1 MeV) reactions but also produced by the

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

Table 4 Cross-sections (mb) for production of E (MeV)

16.8 70.02 16.3 70.1 15.8 70.1 15.3 70.2 14.8 70.3 14.2 70.4 13.7 70.4 13.1 70.5 12.5 70.5 11.9 70.6 11.2 70.6 10.5 70.7 9.8 70.7 9.1 70.8 8.3 70.8 7.4 70.9 6.5 70.9 5.4 71.0 4.2 71.1

57

Ni(p,x)55Co

Ni, and

nat

60,61

Cu by protons on

Ni(p,x)57Co

nat

326.9 7 36.7 279.17 31.3 243.87 27.4 177.17 19.9 117.3 7 13.2 86.5 7 9.71 50.9 7 5.72 29.5 7 3.32 17.8 7 2.01 13.8 7 1.6 11.5 7 1.3 9.8 7 1.1 7.4 7 0.8 4.4 7 0.5 2.5 7 0.3 0.9 7 0.1 0.2 7 0.04

24.47 2.7 24.47 2.7 25.7 7 2.9 24.17 2.7 23.2 7 2.6 19.9 7 2.2 18.2 7 2.1 16.0 7 1.8 15.0 7 1.7 13.2 7 1.5 10.2 7 1.2 11.4 7 1.6 6.0 7 0.7 2.8 7 0.3 0.7 7 0.1 0.2 7 0.1

Table 5 Cross-sections (mb) for production of

nat

Ni (Experiment 1)

55,56,57,58

Co,

56,57

Ni and

Ni(p,x)58Co

nat

1.0 7 0.12 0.9 7 0.12 1.17 0.13 1.0 7 0.12 17 0.13 1.0 7 0.12 1.0 7 0.12 1.0 7 0.11 1.0 7 0.11 0.9 7 0.11 0.8 7 0.09 0.8 7 0.10 0.7 7 0.08 0.6 7 0.07 0.4 7 0.05 0.3 7 0.04 0.2 7 0.03 0.2 7 0.03 0.2 7 0.03

61

Cu by protons on

nat

Ni(p,x)57Ni

35.073.9 25.4 72.9 17.5 72.0 10.0 71.1 5.5 70.6 1.9 70.2 0.3 70.1

nat

Ni(p,x)60Cu

39.17 4.5 48.47 5.6 59.4 7 7.0 66.97 7.9 79.9 7 9.6 83.2 7 9.4 87.0 7 9.9 82.7 7 9.5 87.9 7 10.1 79.9 7 9.3 79.4 7 9.4 74.4 7 9.0 44.8 7 6.8 43.4 7 6.3 7.2 7 3.5

nat

Ni(p,x)61Cu

6.1 70.8 4.5 70.5 3.9 70.5 3.3 70.4 2.9 70.4 2.6 70.3 3.0 70.3 3.5 70.4 4.0 70.5 4.7 70.5 5.0 70.6 5.5 70.6 5.5 70.6 5.2 70.6 4.6 70.5 4.1 70.5 3.5 70.4 1.9 70.2 0.6 70.1

Ni (Experiment 2).

Cross sections (mb) nat

24.8 70.02 24.2 70.1 23.6 70.2 22.9 70.3 22.2 70.4 21.6 70.5 20.9 70.6 20.1 70.7 19.4 70.8 18.6 70.8 17.8 70.9 17.0 70.9 16.2 71.0 15.3 71.1 14.4 71.2 13.4 71.2 12.4 71.3 11.3 71.4

Co,

Cross sections (mb) nat

E (MeV)

55,57,58

77

Ni(p,x)55Co

5.7 7 0.6 6.2 7 0.7 7.4 7 0.8 8.4 7 0.9 10.3 7 1.2 12.17 1.4 14.9 7 1.7 17.4 7 2.0 21.3 7 2.4 23.3 7 2.6 25.4 7 2.8 26.7 7 3.0 26.6 7 3.0 25.5 7 2.9 22.9 7 2.6 20.8 7 2.3 16.8 7 1.9 13.3 7 1.5

nat

Ni(p,x)56Co

13.8 7 1.6 12.3 7 1.4 10.4 7 1.2 8.8 7 1.0 7.0 7 0.8 5.17 0.6 3.3 7 0.4 1.8 7 0.2 0.8 7 0.1 0.4 7 0.04 0.17 0.01

nat

Ni(p,x)57Co

575.3 7 64.6 579.6 7 65.1 580.7 7 65.2 578.3 7 64.9 575.2 7 64.6 565.4 7 63.5 561.9 7 3.1 548.07 61.5 530.6 7 59.6 492.27 55.3 446.4 7 50.1 395.3 7 44.4 313.6 7 35.2 223.8 7 25.1 127.9 7 14.4 57.7 7 6.5 23.5 7 2.6 14.3 7 1.6

complete EC decay of the short-lived 57Cu (T1/2 ¼196.4 ms) radionuclide formed via the 58Ni(p,2n)57Cu (Ethr ¼22.2 MeV) reaction. Therefore the measured cross-sections are cumulative over the whole investigated energy range. The product 57Ni was identified by its strong γ-line with energy 1377.63 keV (Iγ ¼81.7%). Our data in comparison with the literature data and theory are given in Fig. 4. The database for this reaction is very broad. Our measurements are in agreement with the literature values reported by Michel et al. (1978), (1983), (1997), Michel and Brinkmann (1980), Furukawa et al. (1990), Tárkányi et al. (1989), (1991), Sonck et al. (1998), Szelecsényi et al. (2001), Takács et al. (2002), Al-Saleh et al. (2007), Alharbi et al. (2011), Khandaker et al. (2011), Cohen et al. (1955), Kaufman (1960), Tanaka et al. (1972) and Brinkman et al. (1997). The data by Levkovskij (1991) and those by Reimer and Qaim (1998) were reported for a highly enriched 58Ni target. They were normalized to nat Ni as target material. Further the cross sections reported by Levkovskij (1991) were decreased by 20%, (see above). Our data agree with the latter two data sets also. The literature values reported by Ewart and Blann (1964), Barrandon et al. (1975) and Zhuravlev et al.(1984) have lower cross-sections than all other experiments. The

nat

Ni(p,x)58Co

4.4 7 0.5 4.17 0.5 3.9 7 0.4 3.6 7 0.4 3.4 7 0.4 3.0 7 0.3 2.9 7 0.3 2.4 7 0.3 2.17 0.2 1.7 7 0.2 1.4 7 0.2 1.4 7 0.2 1.4 7 0.2 1.4 7 0.2 1.3 7 0.2 1.3 7 0.2 1.2 7 0.1 1.17 0.1

nat

Ni(p,x)56Ni 1.17 0.1 1.17 0.1 1.2 7 0.1 0.9 7 0.1 0.9 7 0.1 0.8 7 0.1 0.7 7 0.1 0.6 7 0.1 0.4 7 0.05 0.2 7 0.03 0.17 0.03 0.2 7 0.02 0.17 0.02 0.2 7 0.03 0.3 7 0.04 0.2 7 0.03 0.17 0.01 0.2 7 0.03

nat

Ni(p,x)57Ni

171.2 719.2 163.1 718.3 156.0 717.5 159.6 717.9 136.7 715.3 130.5 714.6 118.4 713.3 108.5 712.2 91.3 710.3 71.6 78.0 49.6 75.6 29.4 73.3 13.8 71.6 4.7 70.5 0.7 70.1

nat

Ni(p,x)61Cu

10.8 7 1.2 11.7 7 1.3 11.8 7 1.3 12.4 7 1.4 12.6 7 1.4 12.2 7 1.4 12.7 7 1.4 11.9 7 1.3 11.2 7 1.3 9.7 7 1.1 8.4 7 1.0 7.0 7 0.8 5.2 7 0.6 4.2 7 0.5 3.17 0.4 3.3 7 0.4 4.2 7 0.5

cross-sections reported by Haasbroek et al., 1977 are shifted towards higher energies and the results by Aleksandrov et al. (1987a, b) are higher than those given in other measurements. Therefore the latter three data sets were not included in the formation of spline fit. The theoretical prediction of ALICE-IPPE gives the similar shape of the excitation function as the experimental data but it gives more than two times higher cross-sections. Theoretical results of TALYS and TENDL are in fair agreement with experimental data up to 33 MeV but overestimate the cross-sections at higher energies. 4.3. Radioisotopes of cobalt 4.3.1. Production of 55Co 55 Co is a relatively shorter lived radionuclide with a half-life of 17.53 h. It can be assessed by its interference free gamma rays at 477, 931 and 1408 keV. The most abundant and interference free γ-line, 931 keV (Iγ ¼ 75%), provides a clear possibility of activity measurement. In our investigated energy region, the radionuclide 55Co is mainly formed by direct contributions of the 58Ni(p,α)55Co (Ethr ¼1.4 MeV), 58 Ni(p,pþt)55Co (Ethr ¼ 21.5 MeV), 60Ni(p,2nþ α)55Co (Ethr ¼22.1 MeV),

78

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

Table 6 Cross-sections (mb) for production of E (MeV)

Ni(p,x)55Co

Ni, and

61

Cu by protons on

nat

nat

nat

182.5 720.5 182.8 720.5 164.2 718.4 151.6 717.0 140.7 715.8 129.1 714.5 110.6 712.4 94.8 710.6 79.3 78.9 67.4 77.6 49.2 75.5 36.3 74.1 27.5 73.1 19.3 72.2 15.1 71.7 12.4 71.4 9.9 71.1 7.5 70.8 5.1 70.6

240.5 727.0 267.7 730.1 274.7 730.9 278.0 731.3 311.3 735.0 345.2 738.8 340.6 738.3 371.7 741.8 405.7 745.6 454.0 751.0 458.5 751.5 463.6 752.1 525.0 758.9 521.0 758.5 539.9 760.6 567.0 763.6 557.9 762.6 545.2 761.2 535.2 760.1

55,56,57,58

Co and

56,57

Ni(p,x)57Co

Niby protons on

nat

58

nat

Ni(p,x)58Co

nat

74.2 710.3 72.6 710.0 62.6 78.7 62.8 78.7 49.1 76.9 45.5 76.3 41.5 76.3 35.0 75.4 23.8 73.7 20.1 73.1 15.6 72.4 14.2 72.2 8.3 71.3 6.6 71.0 7.5 71.2 5.5 70.9 5.4 70.8 4.7 70.7 4.7 70.7

Ni(p,x)56Ni

nat

9.3 7 1.1 8.8 7 1.0 8.17 0.9 7.3 7 0.8 6.6 7 0.7 5.8 7 0.7 5.17 0.6 4.4 7 0.5 3.8 7 0.4 3.17 0.3 2.4 7 0.3 1.8 7 0.2 1.5 7 0.2 1.2 7 0.1 1.0 7 0.1 0.9 7 0.1 0.8 7 0.1 0.7 7 0.1 0.6 7 0.1

Ni(p,x)57Ni

103.0 7 11.6 109.0 7 12.3 109.0 7 12.3 115.3 7 13.0 122.8 7 13.8 129.17 14.5 134.6 7 15.2 144.9 7 16.3 150.7 7 17.0 162.6 7 18.3 165.17 18.6 171.4 7 19.3 180.6 7 20.3 174.6 7 19.6 175.5 7 19.7 166.67 18.7 158.4 7 17.8 148.6 7 16.7 140.2 7 15.8

nat

Ni(p,x)61Cu

2.2 70.3 3.2 70.4 2.3 70.3 2.8 70.4 3.3 70.4 4.1 70.5 3.8 70.5 4.0 70.5 4.9 70.5 5.6 70.6 6.2 70.7 6.9 70.7 8.4 70.9 8.4 70.9 10.1 71.0 10.7 71.1 11.4 71.2 11.9 71.2 12.0 71.2

Ni (Experiment 4)

Ni(p,x)55Co

3.5 7 0.4 3.6 7 0.4 2.7 7 0.3 2.9 7 0.3 2.7 7 0.3 2.17 2.1 3.2 7 0.4 2.8 7 0.3 3.9 7 0.5 5.6 7 0.6 6.5 7 0.7 10.3 7 1.2 16.2 7 1.8 21.3 7 2.4 20.6 7 2.3 20.7 7 2.4 17.2 7 1.9 10.17 1.2 7.6 7 0.9 2.6 7 0.3

nat

Ni(p,x)56Co

nat

Ni(p,x)5757Co

193.7 7 21.8 182.5 7 20.5 157.4 7 17.7 147.7 7 16.6 107.8 7 12.1 86.6 7 9.7 62.7 7 7.1 34.8 7 3.9 21.2 7 2.4 14.4 7 1.6 9.9 7 1.1 4.8 7 0.6 2.0 7 0.2 0.2 7 0.03

250.4 728.1 269.7 730.3 273.7 730.7 319.3 735.9 315.8 735.5 366.8 741.2 438.5 749.2 470.2752.8 511.8 757.5 591.7 766.4 537.4 760.3 545.7 761.3 529.6 759.5 462.4 751.9 330.6737.1 208.4 723.4 63.3 77.1 14.3 71.6 9.7 71.1 4.8 70.5

Ni(p,3nþ α)55Co (Ethr ¼30.0 MeV), 60Ni(p,2t)55Co (Ethr ¼33.6 MeV), Ni(p,2p2n)55Co (Ethr ¼ 30.1 MeV) and 60Ni(p,4nþ 2p)55Co (Ethr ¼ 50.8 MeV) reactions. The presented data are direct elemental cross-sections up to 31 MeV and cumulative at higher energies, due to the contribution from the decay of 55Ni produced via the 58Ni(p,n þ t)55Ni (Ethr ¼31.2 MeV) 58Ni(p,2n þ d)55Ni(Ethr ¼ 37.5 MeV) and 58Ni (p,3n þp)55Ni(Ethr ¼39.8 MeV) reactions. Fig. 5 shows our results in comparison to literature data and values from theoretical model calculations. The excitation function shows clearly the contribution from the most abundant target isotope of nickel (58Ni): the first and second peaks in Fig. 5 are essentially due to major contributions of the (p,α) and (p,2p2n) reactions on 58Ni target, respectively. Our measurements are in good agreement with the literature values reported by Michel et al. (1978), (1997), Michel and Brinkmann (1980), Tárkányi et al. (1991), Sonck et al. (1996), Al-Saleh et al. (2007), Khandaker et al. (2011), Kaufman (1960), 61

Ni (Experiment 3).

Cross sections (mb) nat

36.7 7 0.03 35.5 7 0.1 34.3 7 0.2 33.17 0.3 31.8 7 0.4 30.5 7 0.4 29.2 7 0.5 27.8 7 0.6 26.3 7 0.7 24.8 7 0.8 23.2 7 0.9 21.5 7 1.1 19.7 7 1.2 18.0 7 1.3 16.5 7 1.4 14.8 7 1.5 13.0 7 1.6 11.0 7 1.8 9.2 7 1.9 7.7 7 2.0

56,57

Ni(p,x)56Co

4.0 70.4 3.7 70.4 3.3 70.4 3.2 70.4 3.0 70.3 3.0 70.3 3.0 70.3 2.9 70.3 3.0 70.3 3.1 70.3 3.3 70.4 3.5 70.4 3.9 70.4 4.3 70.5 5.0 70.6 5.8 70.6 6.9 70.8 8.6 71.0 10.9 71.2

Table 7 Cross-sections (mb) for production of E (MeV)

Co,

Cross sections (mb) nat

36.5 7 0.02 35.6 7 0.1 34.8 7 0.2 33.9 7 0.3 33.17 0.4 32.2 7 0.5 31.5 7 0.6 30.7 7 0.6 30.0 7 0.7 29.2 7 0.8 28.3 7 0.9 27.5 7 1.0 26.7 7 1.0 25.8 7 1.1 24.9 7 1.2 24.0 7 1.3 23.0 7 1.4 22.17 1.5 21.0 7 1.6

55,56,57,58

nat

Ni(p,x)58Co

83.9 7 9.2 74.17 8.2 63.0 7 6.9 51.6 7 5.7 36.5 7 4.0 24.97 2.7 12.5 7 1.4 9.3 7 1.0 8.3 7 0.4 5.7 7 0.5 5.0 7 0.6 4.3 7 0.5 3.7 7 0.4 2.0 7 0.2 2.0 7 0.2 1.7 7 0.2 1.6 7 0.2 1.5 7 0.2 1.4 7 0.2 1.3 7 0.1

nat

Ni(p,x)56Ni

9.6 7 1.1 8.9 7 1.0 7.7 7 0.9 6.6 7 0.7 4.8 7 0.5 4.0 7 0.5 3.17 0.4 1.8 7 0.2 1.2 7 0.1 1.17 0.1 1.2 7 0.1 0.7 7 0.1

nat

Ni(p,x)57Ni

93.17 10.5 100.6 7 11.3 94.9 7 10.7 112.17 12.6 117.6 7 13.2 126.7 7 14.2 151.17 17.0 152.3 7 17.1 170.9 7 19.2 173.6 7 19.5 142.0 7 16.0 134.17 15.1 117.17 13.2 84.6 7 9.5 43.0 7 4.8 14.4 7 1.6 0.2 7 0.04

Ewart and Blann (1964), Tanaka et al. (1972) and Brinkman et al. (1977). Similar to 57Ni mentioned above, the data for 55Co reported by Levkovskij (1991) and Reimer and Qaim (1998) using enriched 58 Ni were normalized to natNi. Furthermore, the cross sections reported by Levkovskij (1991) were decreased by 20%, (see above). The reported values by Barrandon et al. (1975) are lower than all other experiments whereas the measurements by Haasbroek et al. (1977) are shifted towards higher energies. Therefore the latter two old measurements were not used in the formation of spline fit. ALICE-IPPE predicts well first peak of the excitation function but overestimates the cross-section for the second peak of the excitation function. TALYS curve predicts well the magnitude of the excitation function but the predicted cross-sections for first peak are slightly lower than the majority of the experiments. TENDL is fairly in agreement with the experimental data but it slightly overestimates the first peak in the rising part after 13 MeV and slightly underestimates the remaining half after 20 MeV.

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

Table 8 Cross-sections (mb) for production of E (MeV)

55,56,57,58

Cross sections (mb) nat Ni(p,x)55Co

63.6 7 0.03 62.8 7 0.1 61.9 7 0.2 61.0 7 0.3 60.1 7 0.5 59.2 7 0.6 58.2 7 0.7 57.3 7 0.8 56.4 7 0.9 55.4 7 1.0 54.4 7 1.1 53.4 7 1.2 52.4 7 1.4 51.4 7 1.5 50.3 7 1.6 49.3 7 1.7 48.2 7 1.9 47.1 7 2.0

56,57

Co and

38.6 7 4.7 47.6 7 7.6 46.4 7 7.2 33.47 11.7 29.4 7 7.2 46.6 7 5.7 29.4 7 9.5 37.7 7 10.1 37.17 10.8 44.17 5.1 30.5 7 9.6 40.0 7 4.7 37.17 4.5 40.0 7 9.3 39.6 7 7.9

nat

Ni by protons on

Ni(p,x)56Co

Ni (Experiment 5).

nat

107.8 7 12.1 123.9 7 13.9 128.7 7 14.4 123.0 7 13.8 115.7 7 13.0 125.9 7 14.1 133.67 15.0 130.8 7 14.7 127.2 7 14.3 130.9 7 14.7 132.17 14.8 129.0 7 14.5 132.6 7 14.9 134.6 7 15.1 134.0 7 15.0 143.5 7 16.1 161.7 7 18.2 173.6 7 19.5

35.17 4.4 28.17 3.2

nat

79

Ni(p,x)57Co

nat

194.2 7 21.8 226.5 7 25.4 235.87 26.5 228.7 7 25.7 216.3 7 24.3 236.6 7 26.6 251.2 7 28.2 245.27 27.5 238.5 7 26.8 242.07 27.2 241.4 7 27.1 231.7 7 26.0 231.4 7 26.0 225.4 7 25.3 216.0 7 24.2 220.6 7 24.8 232.3 7 26.1 234.3 7 26.3

Ni(p,x)58Co

nat

36.3 74.1 41.3 74.6 42.9 74.8 41.7 74.7 39.6 74.4 43.1 74.8 46.0 77.1 44.8 75.0 45.0 75.1 45.1 75.1 46.6 75.2 44.7 75.0 46.3 75.2 46.2 75.2 46.2 75.2 48.9 75.5 55.1 76.2 58.0 76.5

140

14

120

12

100

10

Ni(p,x)56Ni

nat

9.17 1.1 7.0 7 0.8 10.3 7 1.2 8.8 7 1.0 8.3 7 1.0 9.7 7 1.1 9.9 7 1.1 10.0 7 1.2 9.3 7 1.1 10.9 7 1.2 9.4 7 1.1 11.0 7 1.2 10.8 7 1.2 9.5 7 1.1 10.0 7 1.1 10.8 7 1.2 11.6 7 1.3 11.3 7 1.3

63.17 7.2 73.9 7 8.4 73.4 7 8.4 73.17 8.4 69.5 7 8.0 76.3 7 8.6 81.2 7 9.3 81.17 9.3 74.5 7 8.6 73.9 7 8.3 74.2 7 8.5 71.5 7 8.0 67.2 7 7.6 67.8 7 7.8 65.17 7.4 70.77 8.1 71.7 7 8.1 73.8 7 8.3

nat

Cross-section (mb)

Cross-section (mb)

nat

80

60

Ni(p,x) Cu

60

40

Ni(p,x)57Ni

56

Ni(p,x) Ni

8

6

4

2

20

0

0 5

10

15

20

25

30

35

10

15

20

25

30

35

Proton energy (MeV) Fig. 1. Excitation function of former results and spline fit.

40

45

50

55

60

65

70

75

Proton energy (MeV)

nat

Ni(p,x)60Cu reaction in comparison with theory,

Fig. 3. Excitation function of former results and spline fit.

22

nat

Ni(p,x)56Ni reaction in comparison with theory,

350

20

300

18

nat

Ni(p,x)57Ni

250 Cross-section (mb)

Cross-section (mb)

16

nat

61 Ni(p,x) Cu

14 12 10 8

200

150

100

6 4

50 2

0

0 0

10

20

30

40

50

0

15

Proton energy (MeV) Fig. 2. Excitation function of former results and spline fit.

nat

Ni(p,x)61Cu reaction in comparison with theory,

30

45

60

75

Proton energy (MeV) Fig. 4. Excitation function of former results and spline fit.

nat

Ni(p,x)57Ni reaction in comparison with theory,

80

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

70

100

65

90

60 55

80

45

Cross-section (mb)

Cross-section (mb)

50

40 35 30 25 20

70 60 50 40

15

30

10

20

5

10

0 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

Proton energy (MeV) Fig. 5. Excitation function of former results and spline fit.

nat

0 0

Ni(p,x)55Co reaction in comparison with theory,

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

Proton energy (MeV) Fig. 8. Excitation function of natNi(p,x)58m þ gCo reaction in comparison with theory, former results and with spline fit.

270 240

Cross-section (mb)

210 180 150 120 90 60 30 0 15

20

25

30

35

40

45

50

55

60

65

70

75

Proton energy (MeV) Fig. 6. Excitation function of former results and spline fit

nat

Ni(p,x)56Co reaction in comparison with theory,

650 600 nat

550

Ni(p,x)57Co

Cross-section (mb)

500 450 400

4.3.2. Cumulative formation of 56Co The long-lived radionuclide 56Co (T1/2 ¼ 77.27 d) is not only produced by several direct reaction, e.g. 58Ni(p,nþ 2p)56Co (Ethr ¼ 19.9 MeV), 60Ni(p,nþ α)56Co (Ethr ¼11.8 MeV), 61Ni(p,2nþ α)56Co (Ethr ¼ 19.8 MeV), 62Ni(p,3nþ α)56Co (Ethr ¼30.5 MeV), 60Ni(p,3nþ 2p)56Co (Ethr ¼40.6 MeV) and 61Ni(p,4nþ2p)56Co (Ethr ¼48.5 MeV) reactions, but also above 20 MeV from an EC decay of the comparatively short-lived 56Ni (T1/2 ¼6.077 d) radionuclide, via 58Ni(p, nþd)56Co (Ethr ¼20.6 MeV) 58Ni(p,2nþp)56Co (Ethr ¼ 22.8 MeV) reactions. Therefore, the production cross-sections of 56Co are cumulative above 20 MeV. The radionuclide 56Co can be identified by two intense γ-lines; 846.77 keV (Iγ ¼100%) and 1238.28 keV (Iγ ¼67.6%). In all our experiments, to measure the 56Co cross-section, the cooling time was selected (about one month after the irradiation) carefully to get the 100% contribution from 56Ni decay. The measured production crosssections for 56Co are shown in Fig. 6 together with literature values, results of theoretical calculations by ALICE-IPPE, TALYS 1.4 and TENDL2012 library. It can be seen that the cross-sections for 56Co production below 17 MeV are small; therefore it was not accessed in Experiment 1. Our results are in excellent agreement with the earlier measurements by Michel et al. (1978), (1997), Tárkányi et al. (1991), Al-Saleh et al. (2007), Titarenko et al. (2011) and Khandaker et al. (2011). Literature values reported by Haasbroek et al. (1977) are shifted towards higher energies whereas the reported data by Aleksandrov et al. (1987a, b) are not consistent with other experiments; therefore those two results were not considered in the final spline fit. All the theoretical results predict well the shape and magnitude of the excitation function, except in the peak energy region where the considerable discrepancy can be observed.

350 300 250 200 150 100 50 0 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

Proton energy (MeV) Fig. 7. Excitation function of former results and spline fit.

nat

Ni(p,x)57Co reaction in comparison with theory,

4.3.3. Cumulative production of 57Co The long-lived radionuclide 57Co (T1/2 ¼271.79 d) has two strong and independent low energy γ-lines (122.1 and 136.5 keV) that make its identification easy. 57Co can be produced from all the stable isotopes of Ni mainly through the direct contribution of 60Ni(p,α)57Co (Ethr ¼ 0.3 MeV), 61Ni(p,n þ α)57Co (Ethr ¼ 8.2 MeV), 58Ni(p,2p)57Co (Ethr ¼ 8.3 MeV), 62Ni(p,2n þ α)57Co 60 64 (Ethr ¼ 19 MeV), Ni(p,2n þ2p)57Co (Ethr ¼29 MeV), Ni 57 61 57 (p,4nþ α) Co (Ethr ¼35.7 MeV), Ni(p,3n þ 2p) Co (Ethr ¼ 37 MeV) and 62Ni(p,4n þ2p)57Co (Ethr ¼47.7 MeV) reactions. 57 Co can also be produced indirectly by the 100% positron decay of the short-lived radionuclide 57Ni (T1/2 ¼ 35.6 h). The measured cross-

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

sections are hence cumulative. In all our experiments, to measure the 57 Co cross-section, the cooling time was selected carefully to get the 100% contribution from 57Ni decay. Our data are given in Fig. 7 in comparison to literature data and results of theoretical model calculations. Our measured cumulative cross-sections are in good agreement with the experiments reported by Jung (1991) and cumulative values reported by Michel et al. (1997). Cumulative theoretical excitation functions by ALICE-IPPE, TALYS and TENDL2012 are also in excellent agreement with our values. In this figure we have also given the theoretical excitation functions for the direct formation of 57Co, which show that the reported results by Michel et al. (1978), (1997), Michel and Brinkmann (1980), Tárkányi et al. (1991), Al-Saleh et al. (2007), Titarenko et al. (2011) and Khandaker et al. (2011) either refer to the direct route or the selected cooling time was not long enough to include the 100% contribution of 57Ni decay. The results reported by Haasbroek et al. (1977) are shifted towards higher energies and measurements by Aleksandrov et al. (1987a, b) are not consistent with other experiments. We only used cumulative measurements by Michel et al. (1997) and reported values by Jung (1991) together with our results in the formation of spline fit. ALICE-IPPE excellently reproduces the cumulative experimental excitation function up to 43 MeV but underestimates at higher energies. Results of TALYS and TENDL-2012 are also in excellent agreement except in the region from 37 to 47 MeV where they slightly overestimate the experimental excitation function.

4.3.4. Cumulative production of 58(m þ g)Co The radionuclide 58Co has two states, a long-lived ground state 58g Co (T1/2 ¼70.86 d) and a relatively short-lived metastable state 58m Co (T1/2 ¼9.15 h, IT decay¼100%). Production cross-sections of the metastable state could not be assessed in our experiment because of its single, very weak, γ-line at 25 keV. Therefore the measured cross-sections for 58Co also include the full contribution from the decay of its shorter lived metastable state and our reported cross-sections are cumulative. The production of these states is mainly via 61Ni(p,α)58Co (Ethr ¼0.0 MeV), 62Ni(p, nþ α)58Co (Ethr ¼ 10.3 MeV), 60Ni(p,n þ 2p)58Co (Ethr ¼20.3 MeV), 64 Ni(p,3n þ α)58Co (Ethr ¼27 MeV), 61Ni(p,2n þ2p)58Co (Ethr ¼28.3 MeV), and 62Ni(p,3n þ2p)58Co (Ethr ¼39 MeV) reactions. The 58Co is identified by using its only single characteristic strong γ-ray of 810.77 keV (Iγ ¼99%). However, above 25 MeV this γ-line is overlapped by the characteristic γ-ray of 811.85 keV (Iγ ¼86%) of 56Ni. Therefore, the peak area of 56Ni was subtracted to avoid its contribution. Our measured cross-sections for 58m þ gCo, earlier experimental measurements and theoretical results are presented

81

in Fig. 8. Our data are in excellent agreement with Michel et al. (1978), (1983), (1997), Michel and Brinkmann (1980), Al-Saleh et al. (2007) and Khandaker et al. (2011). The data by Sudar et al. (1993) were reported for enriched 61Ni target. They were normalized to natNi as target material (up to the threshold of 62Ni target). Again the data by Haasbroek et al. (1977) are shifted towards higher energies and data by Aleksandrov et al. (1987a, b) are scattered and not consistent with other experiments. Therefore except for data by Haasbroek et al. (1977) and Aleksandrov et al. (1987a, b), all experiments, including our measurements, were used in the final spline fit. Theoretical results predict well the shape of the excitation function but all the results underestimate in the peak region of the experimental excitation function. 4.4. Integral yields The integral yield of each measured activation product was calculated using the fitted cross-sections and the continuously varying stopping power of natNi over the energy range from the incident beam energy down to the threshold, taking into account that the whole energy is absorbed in the target (Tárkányi et al., 2001). Our deduced physical yields (Bonardi, 1987) are shown in Figs. 9 and 10 as a function of the energy in comparison to literature experimental values reported by Dmitriev and Molin (1981), Spellerberg et al. (1998) and Landini and Osso (2001). Spellerberg et al. (1998) have reported the yields for 55Co and 57Co for highly enriched 58Ni target. They were normalized to the natNi as target material. It can be seen that our calculated integral yields are in good agreement with the reported values by Dmitriev and Molin (1981), Spellerberg et al. (1998) and Landini and Osso (2001) except for the 57 Ni value. Experimental yield values for 57Co are seem to be lower than our calculated values; because they were measured for direct formation route whereas we have calculated for cumulative crosssections. It should therefore be mentioned that our calculated integral yields can be confidently used for the optimization of production yield of the corresponding radionuclide.

5. Applications 5.1. Thin layer activation of nickel Presently in the IAEA database (Takács, 2010) for TLA (1977) (cf. IAEA-TECDOC-924) only two reactions are listed for Ni targets: 15

7000

600

12 6000

500

5000 400

9

4000 300 3000

6

200 2000 100

3

1000

0

0 0

10

20

30

40

50

60

70

Proton energy (MeV) Fig. 9. Thick target yields of 60,61Co, 55Co and 57Ni radionuclides calculated from the spline fit, in comparison with literature values.

0 0

10

20

30

40

50

60

70

Proton energy (MeV) Fig. 10. Thick target yields of 56,57,58Co and 56Ni radionuclides calculated from the spline fit, in comparison with literature values.

82

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

nat Ni(p,x)57Ni and natNi(d,x)56Co. In this work we present the specific activity-depth distribution curves (TLA curves) for 57Co and 57Ni. TLA curves are shown in Figs. 11 and 12 for EOB (End of Bombardment) and after 3 d cooling time. 57Ni shows very high specific activity and long range, but it is a less convenient choice due to its short half-life (35.6 h) and the need for high energy irradiation. A better choice could be 57Co because of its long range and sufficiently long half-life (271.79 d), which is suitable for nuclear wear measurements.

5.2. Production of 55Co via proton and deuteron beam on (integral yield comparison)

nat

300 250 200 150 100 50 0 600

Fig. 11. TLA activity distribution curves for for 1 h with a 1 mA beam current.

57

800

1000

5 4

2

350

400

6

3

400

200

7

Ni

The radionuclide 55Co (T1/2 ¼17.53 h) is a relatively short-lived positron emitter, which is potentially useful for several diagnostic studies, through Positron Emission Tomography (PET) and therefore it is one of the radionuclides selected for study in the IAEA CRP (Nichols and Capote, 2013). It can be produced by irradiating nickel targets using proton and deuteron beams, both from natural nickel or highly enriched 58Ni targets. In Section 4.3.1 of this work we determined fitted crosssections for the production of 55Co with proton induced reactions on natNi up to 65 MeV. In our previous work (Amjed et. al, 2013) we presented the recommended data for production of the same radionuclide on the same targets up to 50 MeV deuterons. In Fig. 13 we compare the rate of production of 55Co for both production routes using the above mentioned fitted cross-sections. It can be seen (Fig. 13) that the production rate for deuteron induced reactions on natNi approaches that of protons at about 36 MeV but the proton induced reaction shows a higher production rate than deuteron over the whole energy range. The major contribution in case of deuteron induced reaction is from 58Ni(d, nα)55Co (Ethr ¼4.6 MeV), 60Ni(d,3nα)55Co (Ethr ¼ 24.2 MeV), 61Ni 62 (d,4nα)55Co (Ethr ¼ 29.6 MeV) and Ni(d,5nα)55Co (Ethr ¼48.6 MeV) reactions. The two risings parts of the natNiþp curve (Fig. 13) are due to the major contribution of the 58Ni(p, α)55Co (Ethr ¼1.4 MeV) and 58Ni (p,2n2p)55Co (Ethr ¼ 30.1 MeV) reactions, respectively. The indirect contributions from decay of 55 Ni produced through 58Ni(p,nt)55Ni (Ethr ¼31.1 MeV) and 58Ni (p,2nd)55Ni (Ethr ¼ 37.5 MeV) have lower importance in the second rising part of the natNiþp curve where the major contribution is due to opening of the (p,2n2p) channel on 58Ni. Our reported production rates can be normalized for enriched 58 Ni targets up to the thresholds of reactions on 60Ni (22.1 MeV

0

8

1200

Ni irradiated with 27.7 MeV protons

1 0 0

200

400

600

Fig. 12. TLA activity distribution curves for for 1 h with a 1 mA beam current.

800

1000

57

Co irradiated with 23.9 MeV protons

100 nat nat

55

Ni(p,x) Co 55

Ni(d,x) Co

80

60

40

20

0 5

10

15

20

25

30

35

40

45

50

55

Particle energy (MeV) Fig. 13. Integral yield comparison of

55

Co via proton and deuteron beam on

nat

Ni.

and 24.2 MeV for proton and deuteron, respectively). Therefore the given data can also be used for the optimization of these production routes. Production of chemically pure 55Co requires a separation from the bulk Ni target material and from the Ni, Cu and Fe activation products. For production of 55Co with high radionuclidic purity, in proton irradiation enriched 58Ni targets should be used (cf. Reimer and Qaim, 1998) to avoid formation of 58Co, and to decrease the 57 Co content. In proton irradiations, production of 56Co can be avoided by using incident energy limited to 15 MeV (below the practical threshold of the 58Ni(p,x)56Co and 58Ni(p,pn)57Ni (decaying during irradiation to 57Co) reactions) but this results in large reduction of yield. Anyhow the direct formation of 57Co by 58Ni(p,2p)57Co will always be present. The relative contamination will be 2% at EOB (not taken into account any decay of 55Co during chemistry). At 30 MeV incident energy and for 100% enriched 58Ni targets the yield for 55Co would be about 48 MBq/μAh (with our extrapolated data), the contamination from 57Co and 56Co will be 0.38 MBq/μAh and 0.6 MBq/μAh, respectively. This yield value at 30 MeV is comparable with the yield value of 49MBq//μAh, reported by Reimer and Qaim (1998).

N. Amjed et al. / Applied Radiation and Isotopes 92 (2014) 73–84

6. Conclusion In the present work, excitation functions were experimentally measured for the proton-induced reactions on natNi, in five experiments, up to 65 MeV. Elemental cross-sections for the formation of the 60,61Cu, 56,57Ni and 55,56,57,58Co radionuclides were determined. All cross-sections were obtained relative to measured excitation functions of monitor reactions, for which recommended values are published in IAEA TECDOC-1211. Our measurements confirm the earlier results and increase the reliability of the database. For all isotopes, the yield curves have also been calculated and compared with the available literature data to provide a quick guide for users in the field of isotope production. We made a comparative study of proton and deuteron induced reactions on the nickel target for production rate of 55Co and concluded that proton induced reactions have better production rates but with limited purity. We reported on the application of the reaction natNi(p,x)57Co for TLA and wear measurements. Since our fitted cross-sections for the natNi(p,x)57Ni reaction are not significantly different from already reported cross-sections in the IAEA database, also the new TLA curve for 57Ni is nearly identical to the existing curve in the IAEA-TLA database. But comparatively 57Co, being a longer lived radionuclide, could be a better choice for TLA. We used two theoretical nuclear model predictions, ALICE-IPPE and TALYS 1.4 to check the reliability of our reported crosssections and literature data. We also compared the results of TALYS 1.4 model calculations, in two different ways (default and adjusted as TENDL-2012) with the experimental data to evaluate the capability and further improvement in the power to calculate proton-induced reactions. We can state that the description of the upgraded TALYS code is satisfactory but ALICE-IPPE still needs improvements to enhance the quantitative prediction of experimental cross-sections.

Acknowledgments The first author would like to express his gratitude to the Institute for Nuclear Research of Hungarian Academy of Science (ATOMKI) for imparting the research training. He thanks the Higher Education Commission of Pakistan (HEC) for the financial assistance under International Research Support Initiative Programme (IRSIP). He is also grateful to Prof. Dr. S.M. Qaim for his critical comments on the manuscript. The work was done in the frame of the IAEA CRP on nuclear data for charged-particle monitor reactions and medical isotopes production.

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