Parthasaradhi, K

Rao, A Lakshmana

Rao, J Rama

Rao, P V Ramana

English

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1.~i •• J. Phy •• 43, 298-299 (1969) Attenuation of low energy gamma rays In alloys By J. RAMA RAO, K. PARTHASARADHl, A. LAKsHMANA RAo ANOP. Y.RAMANARAo The Laboratories for Nuclear ReBearch, And"ra U"ivenity, Waltai., India, (Received February 8, 1968) With the increasing use of gamma active isotopes in industry, medicine and agriculture, It is becoming necessary to study the absorption of gamma rdlilatwn ill vanous materials. While the absorption in elements is widely studIed, very few attempts (e.g. Rama Rao et al (1961) seem to have been made to measure the attenuation of gamma rays in alloys and compounds. In the work by Rama Rao et al (1961) one of the present authors determined the total cross-sections for a few alloys and compounds at two gamma energies and compared dIe results with the predictions of an apporximate theory based on several assumptions. No further measurements, particu-larly, at lower photon energies, seem to have been reported so far. Fur-thermore, with the availabIlity of more accurate theoretical cross-sections it now becomes possible to make a meaningful comparison between theOry and experiment. Hence the present investigations are undertaken selecting two platinum-rhodium aUoys having the composition, Alloy A ; Pt 80% + Rh 20%; Alloy B: Pt 60% + Rh 40%, and gamma rays of energies 84, 1UO and 2dO keY proVIded by radioactive Isotopes Tm"', Om'" and Hg'" respectively. The isotopes of strength abo .. t 10 mC each, are obtained from the Ilhabha AtomiC Research Centre, Bombay, India. The total gamma ray cros~-sections tor the two alloy, are determined follOWing the same procedure as adopted earlier on a good geometry set up by Lakshmi-narayana ,t at (1901). The theoretical values of the cross-section for the two alloys at the three photon energies are computed makir.lg use of the theoretical sum rule and the total gamma ray cross-section in Pt and Kh taken irom the recently compiled data of Plechaty (1968). The experi-mental and the compiled values are given in table 1. It can be seen from table 1 that there is excellent agreement between the compiled and expenmental values at 280 keY. The agreement is not .0 good at IUO keY and there is definite deviation at 84 keY beyond the .scnbed errors. It may be also noted that the deviation is lIlore for alloy A wilich contains larger proportion of Pt. These two observations indicate that the dIscrepancy might be due to an overestimation of photoelectriC cross-section which forms a dominant part of the total cross-section for heavy elements and low energies. 198 1 TABLE 1. TOTAL GAMMA RAY caoss SBCnONS IN AllOYS BARNS Pia ATOM Alloy B Pt60%+ Rh40% 84 Experimental: 158O±80 1J60:1:58 Valu .. of Plecbaty: 178S±18 127HI3 100 Experimental: 1070:1:54 713:1:36 Valu .. 01 Ploch,ty: 1147:1:12 825H 280 Experimental: 97.5±1.9 72 7:1:1.5 ._ ~~ .. of PI,",h.tl"~~HI.:«! .. ___ 73.8:1:0.7 TABLE 2. ErncflvE ATOMIC NUMBI!1IS POI TOTAL GAMMA RAY INTERAnON Energy keY Alloy A Alloy B ----84-- 69.5:1:1.0 ----6J.±1.O-100 70.0:1:1.0 63.±1.0 . ____ ~ 69.:1:1.0 62.5:1;1.0 The effective Iotomic numbers for the two alloys at each energy are deduced from plots between the total atomic cross-section versus atomic number for elements at each energy, employing the earlier results of Ramana Rae e/ tJI (1969), Parthasaradhi e/ tJI (1969) in pres. and Rama Rao (Ph.D. Thesis, 196+). These value. are given in table 2. According to Hine (1952) the effective atomic number for total gamma ray interaction in alloys CaD DOt be represented by a single number and for each partial process the number has to be determined separately. However. from table 2 it may be noted that the number remains constant at these three energies. This may be due to the fact that the number for total interaction is mostly dominated by the number for photoe1ecttic process In the present region of energy since most of the cross-section contribu-tion to the totsl is due to that of photoelectric effect. Even though a little variation exists. it lies within the error limits of the present values. RaPBRINCES H,. O. J. mz, N ... I0 ...... 10, 9. LabhmtnaraYloa. V . .t ID .... an"", $. 1961, Pro .. Ph, •• Sot. L"""'. 71. 593. PIoohaty Eo L. 196B PhoIoIo C ..... S.",."., (Oolll1'ilatioo) Sc.entific I_formalion Sy.(em. Gr_up Law ..... Radiation Labroatory. Ram. Rao, I. Lllksllminarll1lna, V . .t I ....... d&, S. 1!163 J"",. oj Boi. Iodol. li ... . :108,587. Rama I\ao, I • .1964, PA. D. r,.".. RIIDt_ Blae, P. V. VilWftWlll'a Rao, V. Ram. ltao, T . .t Partb ... radhl, K. 1969, NfllJlJo O,tnIJ,W, 1 lU. hnIIaslrldbi. K., Rama Rio. J. ol it_till .10, P. V. 1969 Jvor. oj p,,*,. A J. U' 

Attenuation of Low Energy Gamma Rays in Alloys

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Attenuation of Low Energy Gamma Rays in Alloys

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