Measurements were made of the hydrogen and helium production cross sections for both natural elements and separated isotopes which are constituents of metal under consideration for the first wall of fusion reactors. (MOW

Alvar, K. R.

Barschall, H. H.

Grimes, S. M.

Haight, R. C.

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0 C o M t - n s n o s - - ^ C00-2719-5 ) Production of Hydrogen, Deuterium, and Helium by 15-MeV Neutrons This report was prepared as an account of work sponsored by Ihe United States Government Neither the United States nor the United States Department of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information apparatus, product or process disclosed, or represents that its use would not infringe privately owned nghts R.C. Haight, S.M. Grimes Lawrence Livermore Laboratory, Livermore, California 94550 and K.R. Alvar, H.H. Barschall University of Wisconsin, Madison, Wisconsin 53706 The lifetime of the first xvall of a fusion reactor is expected to be limited by radiation damage from 14-MeV neutrons. This radiation damage will be caused partly by hydrogen and helium produced in nuclear transmutations. We have measured the hydrogen and helium production cross sections for both natural elements and separated isotopes which are con-stituents of metals under consideration for the first wall of fusion reactors. In most previous measurements cross sections have been deduced from induced radioactivities. Since many of the reactions of interest do not produce radioactive nuclides, emitted protons, deuterons, and alpha particles were observed directly in the present measurements. A magnetic lens system focussed the charged particles that were produced by 15-MeV neutrons in a thin radiator, onto a detector about 2.5 in from the radiator. Fig. 1 shows the arrangement of the neutron source, the charged-particle DISTRIBUTION OF THIS DOCUMENT IS BNLD3IXEIF DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. r- 2 -transport system, and the detector. Charged particles emitted in different directions with respect to the incident neutrons were observed by moving the charged-particle transport system along its axis. Monatomic 400-keV deuterons bombarded a rotating titanium tritide 2 12 target producing about 3 x 10 neutrons/sec. A thin Si solid-state detector in coincidence with a thick Si detector served to identify the charged par-ticles and measure their energy. At each reaction angle the energy distributions were determined at nine different magnet settings to cover the entire charged-particle energy spectrum. From these measurements the charged-particle energy spectrum at one angle was deduced. Fig. 2 shows as an example the proton energy dis-tribution from Ni. Measurements at several angles were combined to yield energy distributions from which the reaction cross section could be deduced. Absolute cross sections were obtained by normalization to the neutron-proton or neutron-deuteron scattering cross section. Table 1 summarizes the results of all measurements of reaction 3-5 cross sections obtained to date, including some previously published data The uncertainties include both statistical and systematic errors. Some of the present results may be compared with mass-spectroscopic helium production determinations . The results of both types of measurements agree within the quoted uncertainties. FIGURE CAPTIONS Fig. 1. Experimental arrangement for observing charged particles produced by DT neutrons. A typical trajectory of a charged particle focussed by the magnetic quadrupole triplet is shown. The system is moved parallel to its axis for observations at different reaction angles. Fig. 2. Energy distribution of protons from Ni at 90° reaction angle. REFERENCES 1. K.R. Alvar, H.H. Barschall, R.R. Borchers, S.M. Grimes, and R.C. Haight, Nucl. Inst. Meth. 148, 303 (1978). 2. R. Booth and H.H. Barschall, Nucl. Inst. Meth. 99, 1 (1972). 3. S.M. Grimes, R.C. Haight, and J.D. Anderson, Nucl. Sci. Eng. , 62, 187 (1977). 4. S.M. Grimes, R.C. Haight, and J.D. Anderson, Phys. Rev. C YT_> 508 (1978). 5. R.C. Haight, S.M. Grimes, and J.D. Anderson, Nucl. Sci. Eng. 63, 200 (1977). 6. H. Farrar IV and D.W. Kneff, Trans. Am. Nucl. Soc. (June 1978). TABLE 1 Cross Sections for 15-MeV Neutrons (mib) Target Proton Production Deuteron Production Alpha Particle Production 27A1 400 ± 60 19 + 8 121 ± 25 46T. 670 ± 90 9 + 4 98 ± 18 48T. Ti 85 ± 16 7 + 3 28 ± 6 51v 91 ± 14 7 + 3 17 ± 3 50Cr 830 ±100 13 + 4 94 ± 15 52Cr 182 ± 25 8 + 3 38 ± 6 natCr 182 + 25 9 + 3 37 ± 6 54Fe 900 ±110 10 + 4 80 ± 13 56Fe • 190 ± 20 8 + 3 41 ± 7 nat„ Fe 220 ± 30 8 + 3 43 ± 7 NI 1000 ±120 14 + 6 106 ± 17 60M. Ni 330 ± 40 11 + 4 76 ± 12 Ni 800 ±100 13 + 5 97 ± 16 63r Cu 320 ± 50 9 + 4 56 ± 10 65„ Cu 44 ± 5 10 + 4 14 ± 3 93 51 ± 8 8 + 3 14 ± 3 304SS 260 ± 38 8 + 2 48 ± 7 316SS 260 ± 38 8 + 2 48 ± 7 QUADRUPOLES RTNS A o x b a • ~ i r—r »+ ^jxmfTm EZ3 RADIATOR LEAD VZZ& IRON KS3 BORATED POLYETHYLENE B HEAVY METtmiB DIRECTION OF MOTION OF SYSTEM I Or cm 0 DETECTOR ezzzza TO I A I i ^ 0 40 cm 12-10-i > (0 .Q E b 6 2 -— 1 • 9 © 9 ' 1 1 1 -— * 9 9 9 9 natNi(n,xp) 9 9 9 * 9 9 — 9 — 1 1 1 * * 1 1 * « 1 . « « » 2 6 8 10 12 14 E (MeV) 

Production of hydrogen, deuterium, and helium by 15-MeV neutrons

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Production of hydrogen, deuterium, and helium by 15-MeV neutrons

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