Excitation functions of deuteron induced nuclear reactions on natTi up to 20 MeV for monitoring deuteron beams

~

Appl. Radiat. lsot. Vol. 48, No. 5, pp. 657 -665, 1997

Pergamon

PII:S0969-8043(97)00001-8

1997 ElsevierScience Ltd. All rights reserved Printed in Great Britain 0969-8043/97 $17.004- 0.00

Excitation Functions of Deuteron Induced Nuclear Reactions on natTi up to 20 M e V for Monitoring Deuteron Beams S. T A K A C S I, M. S O N C K 2'4, B. S C H O L T E N 3, A. H E R M A N N E

2

a n d F. T A R K , ~ N Y I *~ qnstitute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, H-4001, Hungary, :Vrije Universiteit Brussel, Cyclotron Department, Brussels, 1090, Belgium, qnstitut ffir Nuklearchemie, Forschungszentrum Jiilich GmbH, Jiilich, 52425, Germany and 4Aspirant of National Fund for Scientific Research (NFWO), Brussels, B-1000, Belgium (Received 4 October 1996)

Excitation functions were measured for nuclear reactions on natural Ti leading to the formation of the 43'44m'44g'46"47'485cand 48V isotopes up to 21 MeV deuteron energy using the stacked-foil technique. The

measured excitation functions, the calculated thick target yields and activity calibration functions for the thin layer activation technique have been compared with the earlier literature data. The investigation with respect to their potential application as monitor reactions showed that the reactions on "~"Ticould be recommended for monitoring deuteron beams, especially the ~"'Ti(d,x)4W reaction, in the energy range from 3 up to 20 MeV. However, to clear up the discrepancies in the literature and to compare the results with other monitor reactions, additional measurements are required, i l 1997 Elsevier Science Ltd

Introduction Systematic investigations of charged particle induced nuclear reactions on metals are in progress for evaluating their potential use as monitor reactions for determining the energy and intensity of the bombarding beam, and for obtaining reliable excitation functions for activation analytical studies and for optimization of the beam parameters in the thin layer activation technique (TLA) used for wear, corrosion or erosion measurement. The general philosophy of our systematic study is to try to use the same target material for monitoring all the light charged particle beams (p, d, 3He and ~). With a view to enhancing our knowledge of the necessary excitation functions we have compiled, critically evaluated and remeasured the absolute cross sections of some reactions induced by these particles (cf. Tfirkfinyi et al., 1991a, 1992; Kopeck~ et al., 1993; Takfics et al., 1994, 1995, 1996). Titanium has a broad range of applications as a construction material in different branches of industry and research. The physical and chemical properties and wide availability of titanium make it ideal as a target material for monitoring the beam performance. We have investigated the excitation functions of p-, ~- and 3He-particle induced reactions *To whom all correspondence should be addressed.

on n~Ti (Tfirkfinyi et al., 1992; KopeckS, et al., 1993). In this work we report the cross sections of deuteron induced reactions. A survey of the reactions available for monitoring low and medium energy deuteron beams showed that the status of the data is not satisfactory. Only a few of the deuteron induced reactions that can be used for monitoring purposes have been measured and the available data do not fulfil all the necessary requirements (cf. Schwerer and Okamoto, 1989). These standard reactions have to be well defined and their cross sections accurately known, it is also important to consider the energy range and the half-life of the product (cf. Hashizume, 1988), and this means that more than one standard is necessary to fulfil the requirements for different irradiation conditions (energy, irradiation time, intensity). The nominal errors of the measured cross sections ascribed by authors usually vary between 10 and 15%, but the data obtained by different authors at the same energy points differ (usually systematically) more significantly. Therefore, it is essential to set up recommended data sets for standard reactions with low uncertainty using critically compiled and evaluated experimental data. To improve the present situation on the available cross section data we decided to perform a series of experiments to complete the data base with reliable precision. 657

658

Facility MGC 20E Debrecen CV 28 Jiilich CGR 560 Brussels

S. Takfics et al.

Number of Ti foils 11 10 11 14 17

Table I. Target and irradiation parameters Foil thickness Primary deuteron (,am) energy (MeV) 21.6 9.7 20.0 13.6 12.1 16.8 21.6 20.8 50.0 21.8

Experimental Technique and Data Evaluation Excitation functions were m e a s u r e d via the activation m e t h o d using the well k n o w n stacked-foil technique. The experimental procedure, radioactivity measurements, data evaluation a n d error calculations were the same as, or similar to, those reported earlier in several publications from Jiilich (cf. Weinreich et al., 1980; Scholten et al., 1994), from Debrecen (cf. Tfirk~nyi et al., 1991a, 1991b; Takfics et al., 1994) a n d from Brussels (cf. H e r m a n n e et al., 1992, 1994). Here we give only the features relevant to the present measurements. High purity Ti foils were irradiated using the external beams of the cyclotrons in Debrecen ( M G C 20E), Jiilich (CV 28) a n d Brussels ( C G R 560). The composition o f the stacks a n d the irradiation parameters are summarized in Table 1. The stacks were irradiated in Faraday-cups equipped with a secondary electron suppressor. The n u m b e r of incident particles was determined from the integrated charge collected in the Faraday-cups. In some irradiation the b e a m was also m o n i t o r e d via the 27Al(d,x)24Na (Schwerer a n d O k a m o t o , 1989), placing high purity A1 foils in front o f the stacks. The high Q-value o f the 27Al(d,x)24Na reaction prevented us using this m o n i t o r reaction below 14 MeV. The F a r a d a y - c u p technique gave a value 10% lower

Average beam current (nA) 200 200 300 200 240

t h a n the value determined via the m o n i t o r reaction (the m o n i t o r values used are: Ed = 21 M e V a = 54 mb). F o r calculating the cross section data b e a m current measured by the F a r a d a y - c u p technique was accepted. The primary energies of the b o m b a r d i n g beams were determined by deflecting the charged particle b e a m in a calibrated magnetic field (Debrecen), by time o f flight (Brussels: cf. Sonck et al., 1996) a n d by measuring the distances between particle bunches in the b e a m (Jfilich: cf. Kormfiny, 1994). Beam current was kept c o n s t a n t t h r o u g h o u t all irradiations. High resolution g a m m a ray spectroscopy was used to determine the radioactivity of the irradiated samples without chemical separation. Each sample was measured several times to check the half-lives a n d to separate the c o n t r i b u t i o n s of the isomeric states. In the activity measurements the source to detector distances were always kept at more t h a n 10 cm to minimize the dead-time a n d the coincidence losses. Cross sections were calculated using the activation formula. The decay data used are listed in Table 2. The half-lives a n d g a m m a - r a y energies were taken from Browne a n d Firestone (1986), while the Q-values of the c o n t r i b u t i n g reactions were calculated from the nuclear masses given in the above reference. The reactions induced by secondary

Table 2. Decay data of the radionuclides investigated and a list of contributing processes Half-life Ey (keV) 17 (%) Contributing reactions 3.89 h 372.8 22.0 ~Ti(d,~n) 47Ti(d,~2n) **mSc 2.44 d 271.2 86.6 46Ti(d,cQ '~Ti(d,~n) 4STi(d,~2n) ~gSc 3.93 h 1157.0 99.9 ~Ti(d,a) 'TTi(d,~n) 4~Ti(d,~2n) 46Sc 83.83 d 889.3 100.0 4~Ti(d,2p) 47Ti(d,2pn) 4~Ti(d,~) 49Ti(d,an) 5°Ti(d,~2n) 47Sc 3.34 d 159.4 68 47Ti(d,2p) "STi(d,2pn) 49Ti(d,~) 5°Ti(d,o~n) 4SSc 1.82 d 1037.5 97.5 48Ti(d,2p) 49Ti(d,p2n) 5°Ti(d,~) 4sV 15.98 d 983.5 100.0 47Ti(d,n) 4*Ti(d,2n) 49Ti(d,3n) *For emission of d- and 3He-particles 2.2 and 7.7 MeV have to be added, correspondingly. Nuclide 43Sc

Irradiation time (h) 2 0.5 l I 1.5

Q-value (MeV) - 5.6 - 14.2 4.1 - 4.8 - 16.4 4.4 - 4.5 - 16.1 - 3.8 - 12.7" - 4.0 - 4.2 - 15.2 - 2.0 - 13.7* 6.5 - 4.5 - 5.4 - 13.6* 10.0 4.6 - 7.0 - 15.2

E x c i t a t i o n functions of d e u t e r o n induced nuclear reactions

659

Table 3. Measured cross sections of deuteron induced reactions on natural titianium Energy [MeV]

Cross section [mb] na~Ti(d,x)48V natTi(d,x)47Sc

2.95 ± 0.52 3 . 9 7 ± 0.47 4 . 8 4 ± 0.43 5.61 ± 0.39 5.88 ± 0.99 6.31 ± 0.35 6 . 4 4 ± 0.83 6.96_+ 0.69 6.97 ± 0.32 7 . 0 3 ± 1.38 7.46 ± 0.57 7 . 5 8 ± 0.29 8 . 1 6 ± 0.27 8.4(1± 1.25 8.72± 0.24 8.98±(I.43 9 . 2 4 ± 0.22 9.40±0.34 9 . 6 2 ± 1.14 9.75±0.20 9.81 ± 0.20 t(I.20± 0.19 1(I.59 ± 0.12 10.74± 1.(14 I 1.78 ± (I.94 I 1.81 ± 0.05 12.76 _+ 0.86 13.69 _+ 0.78 14.27 ± 0.78 14.48 ± 0.71 14.57 ± 0.71 14.69_+0.64 14.89 _+ 0.58 15.10±0.53 15.30 _+ 0.48 15.41 _+ 0.64 15.5(I_+ 0.44 15.70± 0.40 15.89±0.36 16.09 ± 0.33 16.17± 1.04 16.22 ± 0.58 16.28±0.30 16.52±0.94 16.85 ± 0.86 17.01 _+ 0.53 17.18 ± 0.78 17.51±0.71 17.76±0.48 17.83 ± 0.64 18.15±0.58 18.47±0.53 18.49 ± 0.44 18.78 ± 0.48 19.08 ± 0.44 19.21 ± 0.40 19.39 ± (I.40 19.68 ± 0.36 19.9(1±0.36 19.98 ± 0.33 20.27 ± 0.30 20.57 ± 0.33 20.86 ± 0.33 21.23±0.30 21.26 _+ 0.33

neutrons and/or

0.32 ± 0.04 2.1 ± 0 . 4 5.4±0.8 9.6 ± 1.3 12.7 ± 2.1 13.6 ± 1.7 16.5± 1.9 20.9±2.9 17.3 _+ 2.0 14.4_+ 1.6 22.9 _+ 2.0 21.2±2.5 25.4 ± 3.(1 23.7 ± 2.6 29.2±3.4 34.6 ± 1.7 32.9 ± 3.9 37.8 ± 3.1 30.2 ± 3.3 35.4 ± 4.4 39.6 ± 3.8 43.9 z 3.2 44.9 z 2.9 39.3 ± 4.2 45.0 ± 4.8 47.8 ± 2.5 46.4 ± 5.(I 47.3±5.1 39.5±5.2 38.3 ± 5.(I 39.7±4.3 39.2 ± 5. I 37.7 ± 4.q 39.4 ± 5.1 35.1 ± 4 . 8 38.0 ± 4.1 32.7 ± 4.4 35.9 ± 4.9 34.4±4.4 34.1 ± 4 . 1 34.4_+5.1 34.5 ± 3.7 32.9 ± 4.6 32.3 _+ 4.9 35.4 ± 4.6 32.0±3.4 32.4 ± 4.5 33.9±5.11 28.7±3.1 30.6 ± 4.4 31.1 ± 4 . 6 30.1 ± 4.8 28.5 ± 3.1 30.2±4.3 33.4 ± 4.8 29.8 ± 3.2 31.6 ± 4.5 30.3±4.5 27.6 ± 3.0 30.3 ± 4.8 28.5 ± 4.2 29.0 ± 3.1 36.7 ± 9.9 27.3 ± 3.0 26.2 ± 3.8

5.0± 0.6 0.042±0.005 15.5± 2.0 0.18±0.02 24.6± 3.1 0.37±0.05 25.7± 3.3 0.60 ±0.07 26.6 ± 4.4 0.75 ±0.12 25.6± 3.4 0 . 8 4 ± 0.1 26.6± 5.2 0.93 ± 0.1 24.9± 4.3 .1±0.1 23.5 _+ 3.0 .I±0.1 34.0±4.1 .0±0.1 26.6 ± 4.8 .6±0.2 23.0± 3.0 .4±0.2 28.7± 3.5 .6±0.2 4 2 . 4 ± 5.2 .5±0.2 52.4± 6.4 1.8±0.2 83.6± 11.3 2.0±0.2 84.9± 10.0 2.1±0.2 122± 19 2.3±0.2 90.4± 10.2 2.3±0.3 123± 15 2.3±0.3 2.4±0.4 152± 13 185± 13 2.5±0.3 2 0 9 ± 14 2.7±0.2 179± 20 2.8±0.3 238 ± 25 3.2±0.3 2 8 2 ± 10 3.2±0.2 2 9 8 ± 32 3.6±0.4 341 _+ 37 3.9±0.4 3 5 8 ± 4(1 4.7±0.5 362 ± 40 4.8±0.5 3 5 6 ± 38 4.4±0.5 365±41 4.8±0.5 3 6 6 ± 41 4.6±0.5 377±41 5.6±0.6 356 ± 40 4.5±0.5 3 6 5 ± 39 4.9±0.5 3 6 3 ± 41 4.9±0.5 3 8 4 ± 43 5.3±0.6 384±43 5.3±0.6 3 6 0 ± 38 4.6±0.5 377±45 5.4±0.6 373 ± 39 5.3±0.6 363±40 5.8±0.6 368±44 5.8±0.7 3 8 6 ± 44 5.6±0.6 3 8 0 ± 41 5.8±0.6 379 ± 45 5.8±0.6 390±44 5.8±0.6 382±40 6.8±0.7 376±42 5.3±0.6 370±41 5.9±0.7 404±44 6.9±0.8 389 ± 4 I 7.2±0.8 393 ± 44 6.8±0.7 389 ± 44 7.3±0.8 3 7 6 ± 40 7.7±0.8 399 ± 45 8.1±0.9 398 ± 44 8.0±0.9 381±41 8.5±0.9 3 8 8 ± 44 8.1_+0.9 3 5 2 ± 39 7.8_+0.8 365 _+ 38 9.2_+1.0 337 _+ 46 8.7±1.1 328±34 9.3±0.9 3 0 5 ± 36 8.4±0.9

due to the (d,xn) reactions beam

natTi(d,x)46Sc

collimators

and

the

0.007 ± 0.001 0.043±0.021 0.14±0.02 0.24 ± 0.03 0.31 ± 0.09 0.36 ± 0.05 0.46±0.13 0.69±0.19 0.56 ± 0.07 0.43±0.05 1.1 ± 0.2 0.7_+0.1 0.8 _+ 0.1 0.7 ± 0. I 0.9±0.1 1,2 ± 0. I 1.0 ± 0. I 1.2± (1.2 1.1±0.1 1.2 ± 0. I 1.3 ± (1.2 1.3 ± (1.2 1.4 ± 0.1 1.2 ± 0.1 1.5 ± 0.2 1.8 ± 0. I 1.7 ± 0.2 1.8±0.2 2.1±0.3 2.3 ± 0.3 2.0±0.2 2.5 ± (1.3 2.4±(I.3 2.5 ± (1.3 2.3±(I.3 2.4 ± 0.2 2.5 ± 0.3 2.7 ± 0.3 2.9±0.3 2.8±0.3 2.6±0.3 2.6 ± 0.3 2.9 ± 0.3 2.8 ± 0.4 3.1 + 0.4 3.1 +(/.3 3.2 ± (1.4 3.1 ± 0 . 4 3.8±0.4 3.3 ± 0.4 3.6±0.4 4,0 ± 0,5 4.4 ± 0.5 4.4±0.5 4.7 ± 0.5 4.9 ± 0.5 5.1 ± (1.6 5.3±0.6 5.7 ± 0.6 5.5 ± (1.6 5.4 ± (1.6 6.4 ± 0.7 5.4 ± 0.7 6.8 ± (1,7 5.8 ± 0.7

on the target break-up

of

deuterons also have to be taken into account, because secondary neutrons are always present. These neutrons can contribute to the formation

of the final

product via (n,p) and (n,np) reactions mainly on the ARt 48;5-D

natTi(d,x)48Sc natTi(d,x)44Sc nawTi(d,x)44msc 0.11 ±0.04 0.65_+0.19 1.2_+0.3 1.9 ± 0.4

most abundant

2.5 _+ (1.5 2.8 ± 0.5 3.3±0.4 3.0±0.5 3.4 ± 0.6 4.6 ± 0.5 3.9±0.7 4. l ± 0.7 5.5 ± 0.7 4.1 ± 0.7

6.1 ± 0.7 6 . 0 ± 0.7 5.5 ± 0.6 5.3±0.6 4.9±0.6 5.9 ± 0.6 5.3±0.6 5.4 ± 0.6 5.4±0.6 5.8 _+ 0.6 5.9±0.6 5.5 _+ 0.7 5.4 _+ 0.6 5.8 _+ 0.6 6.1_+0.7 5.7±0.6 5.1±0.8 5.3 ± 0.6 5.8 ± 0.6 5.2 ± 0.8 5.5 ± 0.8 5.9±0.7 5.7 ± 0.9 5.5_+0.8 6,3_+0.7 5.6 ± 0.9 5.6±0.9 6.1 ± 0.9 6.4 ± 0.8 6.1±0.9 5.9 ± 0.9 6.7 ± 0.8 6.4 ± 1.0 6 . 5 ± 1.1 7.0 ± 0.8 6.5 _+ 1.0 6.3 ± 1.0 7.1 _+ 0.8 6.3 ± 0.7

natTi(d,x)43Sc

0.0020 ± 0.0007 0.017±0.009 0.11±0.02 0.20 ± 0.03 0.25 ± 0.06 0.31 ± 0.04 0.35±0.07 0.45±0.08 0.44 ± 0.05 0.26±0.03 0.78 ± O. 11 0.59±0.07 0.73 ± 0.08 0.63 ± 0.07 0.87±0.10 0.97 ± O. 12 1.0 ± 0.1 1.1 ± 0.1 1.0_+ 0.1 1.2 _+ 0. I 1.1 _+ 0.2 1.3 _+ 0.2 1.4 ± 0.1 1.3 ± 0.1 0.026±0.0~ 1.5 ± 0.2 1.7 ± 0. I 0.14±0.02 1.8 ± 0.2 2.1 _+0.2 0.5±0.05 2.6±0.3 2.7 ± 0.3 1.0 ± 0.1 2.4±0.3 2.7 ± (1.3 2.7±0.3 2.7 ± 0.3 2.5±0.3 2.7 ± 0.3 1.7 ± 0.2 2.7 ± 0.3 2.9 ± 0.3 3.0±0.4 2.9±0.3 2.9±0.4 2.2 ± 0 . 2 2.8 ± 0.3 2.9 ± 0.3 2.9 ± 0.5 3.1 _+ 0.4 3.0±0.3 2.8±0.3 2.9 ± 0.3 3.1 ± 0 . 4 3.4±0.4 3.3±0.3 3.1 ± 0.4 3.1 ± 0 . 4 3.3 ± 0.4 3.9±0.4 3.4 ± 0.4 3.4±0.4 3.5 ± 0.4 4.3±0.5 3.5 ± 0.4 3.8 _+ 0.4 3.6±0.4 3.6 ± 0.4 4.7±0.5 3.7 ± 0.4 3.5 ± 0.4 3.7 ± 0.4 5.0±0.5 4.8±0.6 3.6 ± 0.5 4.7±0.5 3.7 ± 0.4 5.2±0.7 3.4 ± 0.4

48Ti. T h e e f f e c t o f s e c o n d a r y n e u t r o n s

can be noticed, mainly below or near the lowest thresholds of the contributing charged particle reactions, as a constant

tail towards

low deuteron

energies. After experiments on neutron activation of t h e s a m e t y p e o f foils, w e c o u l d c o n c l u d e t h a t t h e

660

S. Tak~cs et al,

uatTl(d,x)43Sc

I

natTl(d,x)445Sc

7

_ .

5

--

4

5

_e

4 3 . 2

• this work

• --

,"

this w o r k t h i s w o r k fit

- - t h i s work fit

1

0

. . . . O

'

'

'

'

'

5

'

0

'

10 Deuteron

15

energy

'

20

'

•

'

0

'

'

i

,

~

5

i

Deuteron

[MeV I

i

,

10

i

i

i

i

i

i

15 energy

,

20

[MeV]

Fig. 1. Cross sections for the formation of 4~Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

Fig. 3. Cross sections for the formations of ~Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

contribution of the (n,p) and (n,np) processes is small (and will be published separately). The total error in each cross section was calculated by combining the individual errors in quadrature: the estimated uncertainty of the target atoms (1%), the nuclear decay data (3%), the effect of the fluctuations in the beam intensity (1%), the errors on calibration of gamma-spectrometer (5%), the statistical error and error of peak fitting (1-10%), the uncertainty on the beam intensity (7%). The effective particle energy in each foil of the stack was calculated according to the work of Andersen and Ziegler (1977) and Williamson et al. (1966). For estimating the error of the energy scale the cumulative effect of the individual error sources (primary energy, foil thickness and uniformity and beam straggling effects) have been taken into account.

5.2%). Contributions from the direct processes are collected in Table 2). In the case of ~4Sc the isomeric state has a long enough half-life to separate it from the ground state, therefore, we calculated independent production cross sections for both the metastable and the ground state.

Results and Discussion The numerical values of the cross sections for the production of 43"44m'44g'46'47'48Scand 4sW nuclides are listed in Table 3 and plotted in Figs 1 - 7. The data were calculated for the natural isotopic composition of Ti (46Ti8.2%, 47Ti7.4%, 48Ti 73.8%, 49Ti 5.4%, S°Ti

Excitation Junctions

There are only a few earlier measurements on the deuteron induced reactions on titanium. Burgus et al. (1954) measured cross section values for the reactions n"'Ti(d,x)48V below 20 MeV, using chemical separation and absolute/~ +-counting and normalizing the obtained values to 100% isotopic abundance of 4~Ti. Anders and Meinke (1960) measured the absolute (d,7) cross section for the formation of 46Sc from titanium targets of natural isotopic composition. A more detailed investigation was done by Chen and Miller (1964). They measured individual cross sections for the production of 44"'Sc, 44gSc,46Sc, 47Vand 48V on isotopically enriched 46"4748"49"S°Ti samples using the scintillation gamma-ray counting technique and /3-proportional counters. Production cross sections of ~6Sc and 48V were measured by Jung (1987, 1992) at 9 and 14 MeV, in connection with the long-term 50

natTi(d,x)44msc

natTl(d,x)46S 40

_~3

~ 30 g

U 1

• -"" •

. """

10

. this work - - t h i s w o r k fit

0 5

10 Deuteron

energy

15

20

[MeV]

Fig. 2. Cross sections for the formation of '4~Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

• thiswork ', ..... - - t h i s w o r k fit ,

'

~¢/

--'"

- - - C h e n . l i d M i l l e r , (1964)

5

10 Deuteron

15 energy

20

[MeV]

Fig. 4. Cross sections for the formation of 46Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

661

Excitation functions of deuteron induced nuclear reactions 10

450

'" •

9

,

natTi(d'x)47Sc

400

/

nltTi(d,x) 48V

/

_ ". t*

8 ~'7 --6

I

i 2so i 200

;a 3

•"

* this work - - t h i s work fit

,'"

°

~ t~ ?~:

I00

f

. this work - - t h i s work fit

*"

-----'~Bhu~ilW srekt °ufll~.,<1954, - - - Chen ind Miller,(1964)

50 5

10 Deuteron energy

15 [MeVI

20

5

10 Deuteron energy

15 IMeV]

20

Fig. 5. Cross sections for the formation of 47Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

Fig. 7. Cross sections for the formation of 4~V in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve•

activation of metals used for fusion reactor technology. The earlier experimental results are reproduced in Figs 1 - 7 in comparison with our data, which represent elemental cross sections including all contributing processes. Comparing the available data, the main conclusion is that cross sections measured earlier show considerable disagreement. The normalized data from the earlier works are in most cases lower than the cross sections determined by us in the whole energy region. "°'Ti(d,x)43Sc. No earlier experimental data were found in the literature. The production of 43Sc in the investigated energy region is attributed to the 4~Ti(d,c~n) process (see Table 2). °~'Ti(d,x)~Sc and "~'Ti(d,x)44gSc. Two experimental studes on 44mSc and 44gSc were found (cf. Anders and Meinke, 1960; Chen and Miller, 1964). The agreement between the single data point of Anders and Meinke (1960) for 44gSc and our measurement is good (see Fig. 3). The results of Chen and Miller (1964) converted to natural isotopic composition are systematically lower, as shown in Figs 2 and 3. No reason for this discrepancy was found. The contributing processes in the studied energy region

for producing 4~mScand ~gSc are the (d,~xn) reactions o n 46'47'48Ti isotopes. "°'Ti(d,x)46Sc. The excitation function for 46Sc measured in this work is shown in Fig. 4 in comparison with the converted data of Chen and Miller (1964). The magnitude of the contributing reactions can also be seen in Fig. 4 based on the converted data of Chen and Miller (1964). There is a significant disagreement between the results: the literature data being systematically lower than our experimental data. The only data point of Anders and Meinke (1960) cannot resolve the discrepancy as it is in the energy region where both curves are still in good agreement. 465c is mainly produced by the (d,~) reaction on the high abundance 48Ti. ""'Ti(d,x)4ZSc. In agreement with the contributing processes (see Table 2) the excitation fimction measured on natural titanium (see Fig. 5) is also complex. For production of 47Sc besides the represented channels the possible effect of the secondary neutrons also has to be taken into account. In the literature only the data by Chen and Miller (1964) on enriched targets are available. The data of Chen and Miller (1964), converted to natural titanium, are systematically higher except at the

100 65

natTi(d'x)4$Sc

/

.D

~

-~4 I

.~ 0.0l i 0"=|

i

3

0.1

//1~-.,I ".

47Se\ ~//' ~\ ~ Cl O.O001 ~

•

~ 2 • .

4%

'

• this work

o.oooo,

.

.

. 5

.

Vikllovaet iI. (1983) Guvermlmn|nil Kr~er (19~9)

;. , 5

10 Deuteron energy

10 Deuteron energy

15 {MeV]

20

Fig. 6. Cross sections for the formation of 4~Sc in the interaction of deuterons with titanium of natural isotopic composition and eye-guide curve.

46Sc

.

0 0

", / 4~C /

15

20

[MeV]

Fig. 8. Calculated thick target yields of 435C,44mSC,4495C, 465C, 47Sc, 48Sc and 4sV in the interactions of deuterons with natural titanium as a function of the incident deuteron energy. Comparison of the calculated thick target yield with the experimental data in the literature for 4W.

662

S. Tak~icset al.

energies below 7 MeV where the 49Ti(d,0047Sc-process is dominant. "'Ti(d,x)4SSc. So far, the production of 48Sc by deuteron induced reactions on Ti has not been considered in the literature. The data obtained in this work (see Fig. 6) describe effective cross sections on natural titanium. Secondary neutrons also can contribute to the production of 48Sc via the 48Ti(n,p)48Sc reaction, but in the complex excitation function it is difficult to observe. Taking into account the thickness of the used stacks and the energy range covered the estimated effect of the neutrons is small. Since the cross section data obtained from different stacks having overlapping energy regions are in good agreement, we can assume that the contribution of neutron induced reactions is not significant, since this depends predominantly on the experimental conditions. "'Ti(d,x)48V. The excitation function for the production of 4SV is given in Fig. 7. Below 8 MeV the contributing reaction is (d,n) on 47Ti; above 8 MeV the dominating process is (d,2n) on "STi. The shapes of the excitation functions obtained by different authors (see Fig. 7) are similar, but the absolute values of the earlier measurements of Burgus et al. (1954) and Chen and Miller (1964) are lower than the results presented in this work. At Eo = 15 MeV the difference is about 30%. Deduced quantities and applications Thick target yields. For deuteron induced reactions on natural titanium only very few direct yield measurements were published. Gruverman and Kruger (1959) obtained 2.77 MBq/pAh at 15 MeV deuteron energy and Aten and Halberstadt (1959) published a value of 12.95 MBq/#Ah at 30 MeV for production of 48V. Dmitriev et al. (1970) presented experimental thick target yields as a function of the bombarding energy up to 21.5 MeV. Vakilova et al. (1983) measured the integral yields of 48V from 4 up to 12 MeV in 1 MeV steps. Dmitriev (1986) and Konstantinov and Krasnov (1971) presented compilation work based on the excitation functions obtained by other authors. We notice that in his compilation Dmitriev (1986) did not use his own direct experimental yield values measured earlier Dmitriev et al. (1970). The integral yields for the production of 43'44m'44g'46'47'48Sc and 48V are presented in Fig. 8. To test the excitation functions obtained and to clear the disagreements we compared our calculated integral yield of 48V with the direct yield measurements using thick targets reported in the literature. The comparison in Fig. 8 shows that our calculated yield data and the latest experimental yield of Vakilova et al. (1983) are in agreement, and are significantly higher than the other yields measured earlier. No reasons and effects were found to explain the situation.

12 "~

~

10

"'~A

V-48 this work

-* , • --o

~ •" ••.~..~ ~ "'~

Konstantinov (1997) V 4 8 Herkett (1975) V-48KonstantinovandKrssnov(1971) S¢-46 this work S¢-46 Lllcroix et al. (1996)

8 a

6

.~

4

c-46 H e r k e r t (1975) "''".

"'h,

0

100

200

300

400

500

600

700

Depth Imieron]

Fig. 9. Measured and calculated calibration curves for "~tTi(d,x)4SVand °"'Ti(d,x)46Screactions. From the point of view of routine production the 47Sc and 48V should be investigated. 47Sc is used in radiotherapy (cf. Pietrelli et al., 1992) and as a marker in metabolic studies (cf. Rossof et al., 1965; Wagner, 1995). The application of 4W was proposed for biological studies (Wagner, 1968), for the activation analysis of steel (Vinogradova et al., 1969) and as calibration source for PET cameras (cf. Hichwa et al., 1995). For the production of 4W several routes have been suggested (for recent compilations see Iljinov et al., 1991, 1994, Semenov et al., 1995) based on processes like 48Ti(p,n)4SV (for a review see Kopeck2~ et al., 1993; Michel et al., 1978; Michel and Brinkmann, 1980), 48Ti(d,2n)48V (cf. Gryschowski et al., 1985), 48Ti(0~,x)4SV, 48Ti(3He,x)48V (cf. Weinreich et al., 1980; Lahiri et al., 1996), 5~V(p,x)48V(cf. Michel et al., 1979, 1985), 5~V(d,p4n)48V (cf. Qaim and Probst, 1984). Out of the suggested routes for production of carrier free 48V at low and middle energy cyclotrons the "~Ti(p,x)48V and the recently investigated ~tTi(d,x)48V processes have the highest production yields. For the production of aTSc the following routes have been reported (for compilation see Iljinov et al., 1991; Iljinov et al., 1994; Semenov et al., 1995): 48Ti(7,p)47Sc, (cf. Yagi and Kondo, 1977), 4STi(p,2p)47Sc (for reviews see KopeckS, et al., 1993; Pietrelli et al., 1992; Michel et al., 1978; Michel and Brinkmann, 1980), 48Ti(~,x)47Sc, 4~Ti(3He,x)47Sc (cf. Weinreich et al., 1980; Lahiri et al., 1996), 51V(p,x)475c (cf. Michel et al., 1979, 1985), 5~V(d,x)nTSc (cf. Qaim and Probst, 1984). The production yields are not satisfactory for low energy cyclotrons. At middle energy cyclotrons the proton and the recently investigated deuteron induced production routes are preferred. Calibration curves for thin layer activation technique ( T L A ) . In TLA technique the loss of material owing

to wear, corrosion or erosion is characterized by detecting the changes in radioactivity from the activated surface layer. It is possible to monitor the radioactivity of the separated particles or to detect the remnant radioactivity on the surface using well known calibration curves. The high precision calibration curves are usually determined in separate,

Excitation functions of deuteron induced nuclear reactions time consuming experiments. To establish these functions we have proposed a new method based on well measured excitation functions. The calculated calibration curves are normalized and checked experimentally only at a few energy (depth) points (cf. Tak~,cs et al., 1994). In Fig. 9 we have compared the calibration curves calculated from the excitation functions presented in this work with the published calibration curves obtained by direct measurement (cf. Herkert, 1975; Konstantinov and Krasnov, 1971; Lacroix et al., 1996: Konstantinov, 1997) of the radioactivity as a function of the removed layer thickness. For comparison a normalization was necessary, To calculate the exact distribution of the produced radioactivity as a function of depth an accurate knowledge of the incident energy, the excitation function and relationship between the range and the energy of the charged particle in the investigated material is required, as it is well known from the basic principles of the surface activation. In practice these data are only available with some uncertainties. The range-energy relationship can be calculated only for materials with well known compositions and densities. Therefore, the calculated rangemnergy relationship has to be fitted experimentally at several points determined in a separate experiment (cf. Takfics et al., 1994). To fit the calculated depth distribution of the induced radioactivity (calibration curve) with the experimental calibration curves, obtained on materials with a composition not exactly known, one should use the density as a fitting parameter in the energy range calculation. Figure 9 shows the experimentally determined calibration curves for 4~Sc and ~V reported in the literature in comparison with calculated curves using the excitation functions presented in this work. The agreement of the measured data and calculated curves is good, which gives additional support to the higher trends of our excitation functions and a verification of the use of the excitation functions for calculating the calibration curves for TLA. Us'e ~[ excitation Junctions to monitor deuteron beams. Investigating the obtained excitation functions as potential candidates to monitor bombarding beams the following conclusions can be made. From the reactions investigated taking into account the absolute values and the trends of the obtained cross section data, the decay data of the product nuclei and the possible influence of neutron activation, the ....Ti(d,x)~V process could be considered as a good candidate to monitor deuteron beams in the energy range from 3 up to 20 MeV. The existing data, however, are contradictory. Only very few previous experiments were made, and often low resolution detection techniques were used. The conflicting results of the independent yield measurements further complicate the critical evaluation. New independent, rigorously performed measurements are necessary to check the reliability of the data

663

and to clear up the discrepancies. It is worthwhile extending the energy range above 20 MeV and performing intercomparisons in all energy regions with other proposed monitor reactions, like n"tFe(d,x)56"SVCo, "a~Cu(d,x)65Zn (Takfies et al., 1997a), ""'Ni(d,x)5657Co (Takfics et al., 1997b), °"W(d,x)5~Cr and °"'Al(d,x)-'-~Na (Schwerer and Okamoto, 1989).

Conclusions The present work gives a detailed study of the excitation functions of deuteron induced reactions on natural titanium in the low energy range. The values of the obtained cross section data are, in most cases, systematically higher than the earlier results. The trends of the excitation functions, the deduced thick target yields and the calibration curves for activation technique are in good agreement with the earlier experimental data. The deuteron induced reactions on natural titanium could be effectively used in different activation techniques. The ""~Ti(d,x)48V reaction is a good candidate for monitoring deuteron beams but, because of the systematic disagreements in the absolute values of the cross sections reported by different authors, additional intercomparisons are necessary above 12 MeV.

Acknowledgements--The authors thank the crews of the Debrecen MGC 20E, Jiilich CV-28 and Brussels CGR 560 cyclotrons for performing the irradiations. The authors also wish to thank Dr S. M. Qaim for helpful discussions and critical comments. This work was done in the frame of a Co-ordinated Research Project 'Development of Reference Charged Particle Cross Section Data Base for Medical Radioisotope Production' organized and partly supported by the International Atomic Energy Agency, Vienna, Austria, and in collaboration between the National Fund for Scientific Research, Belgium and the Hungarian Academy of Sciences, Hungary.

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