Measurement of mass and linear attenuation coefficients of gammarays for various elements through aqueous solution of salts

Transcription

1 ndian Journal of Pure & Applied Physics Vol. 39 December 200 L pp. R Measurement of mass and linear attenuation coefficients of gammarays for various elements through aqueous solution of salts M T Tcli C S Mahajan & R Nathuram* Nuclear Research Laboratory Departmcnt of Physics Dr Habasaheb Ambedkar Marathwada University Aurangahad 43 1 oo..! *Radiation Standard and nstrumentation Division Bhabha Atomic Research Centre Mumbai 400 OR5 Received 21 May 200 ; accepted 6 August 200 Solution technique is developcd for the measurement of linear and mass attenuation coefficients of salts for gammarays and from them elemental attenuation coefficients arc estimated. mproved mixture rule (Radial Ph)\' & ehl'l/ 5:1 (1998) 593) is employed for the measurement for salts containing carbonates sulphates and chlorides etc. for variolls Gamma energies Mass attenuation coej'licients for many clements are estimated. Their results show excellent agreemenl with theory. 1 ntroduction With wide spread utilization of radiation and radioisotopes in medicine industry and basic sciences the problem of radiation protection has become important aspect while handling radiation sources and rad iation generating equipments. Selection of materials for radiation shielding and protection needs accurate assessment of interaction parameters. These parameters are of immense importance for photons being highly penetrating radiation as compared to particulate radiations. Although theoretical and experimental values for elements and solids are available in literature accurate values for inorganic salts used in several applications are scare. Katab & Hamidi have measured mass attenuation coefficients of organic compounds and estimated the coefficients for the elements H C and O. Gagandeep ef a{y and Singh et (/1.4 also have done work in gamma photon interaction with solutions of some compounds. A method of measuring attenuation coefficient of several inorganic salts in water phase using mixture rule has been developed and used by Teli ef 0[ The values arrived at have been compared theoreticallylj.14 and can be utilized in accurate dosimetric applications. t is inconvenient to use elements directly in pure form for measurement of gamma attenuation coefficients and it is difficult to obtain them in pure form too. The authors therefore use the elements in the form of their organic or inorganic compounds such as salts which are readily available also. Furthermore liquid or solution form is most suitable as its density being very low there is less possibi l ity of multiple scattering and so a longer column of absorber can be used which will reduce the error in the measurement of the length of the path traversed by the radiation. The authors use water-soluble salts for their experiments. They have made measurements for six gamma energies for the salts containing carbonates sulphates chlorides nitrates and oxides and from them estimated the gamma attenuation coefficients for the elements. Comparison of them with the values in Hubbell TableslJ.l shows good agreement. 2 Method The method of measurement of linear and mass attenuation coefficients of gamma-rays for salts by using their aqueous solutions has already been developed by Teli et au- and they have measured linear and mass attenuation coefficients of some salts also. The method is further improved by Teli 1 5 by considering the fact that volume of solution is not equal to the sum of the volumes of salt (solute) and of water (solvent) This improved method is employed in this work for measuring the mass attenuation coefficients of salts from their aqueous solution. Mixture rule is further employed for obtaining the mass attenuation coefficients of elements. Brief theory is given below to explain the technique.

2 TEll et of.: ATTENUATON COEFFCENTS OF GAMMA RAYS 817 Burette T(.:- Btttette Cap!... ;.;.;;..;;.A.....;..;;.;.';:';';O.. Glass Container ==;';:";':';;';':';':';';':'::..: - t -.to:.::.o.::..;.:::..:.:.:..;;.;.;.. t ==..." i Jf: i :}} l: :! - -:":':":':':'':":":..:.:.--.. Scintilation COlwter Fig. - Experimental set-up for measurement of the gamma ray absorption coefticienls 3 Theory When and 10 are the intensities of gamma radiation of energy E traversed through the container respectively with and without the absorber of height h then the linear (11) and mass (/l/p) attenuation coefficients are given from the exponential law viz: as... ( )

3 NDAN J PURE & APPL PHYS VOL 39DECEMBER Theoretical.3.: :2.a Experinental : J2!l S... u c.. ::t. 2.:2 2 1.a Atoxnic Number eo (Z) Fig. 2 - M ass attenuation coefficient versus atomic number for elements at gamma energy M e V. The continuous l i ne is the l4 theoretical curve from Hubbel l & Sel tzer. Experimental values are shown by points ( Theoretical Experimental o s" JWC.'" " ; 0. 1 "' ".-. bo --. N._ :2 S ::t a "' eo 40 a Atomic Number (Z) Fig 3 - Mass attenuation coefficient versus atomic number for elements in the gamma energy MeV. The continuous l4 lines are the theoretical curves from H u bbel l & Seltzer Experimental values are shown by points For the container of the absorber i n cyl i ndrical... ( 2) = m/nrh where is the inner radius of the container and absorber mass of height h i n the container. and E. p form of inner cross-section nr p d d(ph) [ (!!l ) l n 1 l = _ n ph (!!l ) Eg. (3) then simplifies to:... (3) n r is the

4 TELl et al.:atenuaton COEFFCENTS OF GAMMA RAYS 819 Table - Measured values of gamma mass attenuation coefficients (Wp) cm 2 /gm of various salts and compounds for six ganuna energies from to 1.33 MeV and comparison of them with Hubbell Tables 14 Figures are given upto 5 decimals for exhibiting deviation Salt Gamma energy (MeV) Acetone Expt Theo % devi Ethanol Expt Theo %devi propanol Expt Theo %devi NN-di-methyl Expt acetamide. Theo %devi Carbon tetra- Expt chloride Theo %devi Lithium carbonate Expt Theo %devi Sodium carbonate Expt Theo %devi Potassium Expt carbonate Theo %devi Ammonium Expt sulphate Theo %devi Sodium sulphate Expt Theo %devi Copper sulphate Expt Theo %devi Zinc sulphate Expt Theo %devi Magneisum Expt chloride Theo %devi Alumnium Expt chloride Theo %devi Calcium chloride Expt Theo %devi (Contd)

5 820 NDAN J PURE & APPL PHYS VOL 39 DECEMBER Salt Table 1 Gamma energy (MeV)... (Contd) Cobaltus chloride Expt Theo %devi Nickel chloride Expt Theo %devi Strontuim chloride Expt Theo %devi Barium chloride Expt Theo %devi Stannous chloride Expt Theo %devi Caesium chloride Expt Theo %devi Mercurius chloride Expt Theo %devi Titanium dioxide Expt Theo %devi Chromic oxide Expt Theo %devi Zirconium dioxide Expt Theo %devi Neodium oxide Expt Theo %devi Samarium oxide Expt Theo %devi Dysporsium oxide Expt R Theo %devi Bismuth nitrate Expt Theo %devi Silver nitrate Expt Theo %devi Boric acid Expt Theo %devi Ammonium meta- Expt vanadium Theo %devi Cadmium acetate Expt Theo %devi

6 TELl et al.:a TTENUA non COEFFCENTS OF GAMMA RAYS 821 Table 2 - Measured values of gamma mass attenuation coefficients (lip) cm 2 /gm of various elements for six gamma energies from to 1.33 Me V and comparison of them with Hubbell Tables 14. Figures are given up to 5 decimals for exhibiting deviation Element Gamma energy (MeV) Hydrogen Expt () Theo %devi Lithium Expt (3) Theo %devi Boron Expt (4) Theo %devi Carbon Expt (6) Theo %devi Nitrogen Expt (7) Theo %devi Oxygen Expt (8) Theo %devi Sodium Expt (11) Theo %devi Magnesium Expt (12) Theo %devi Aluminium Expt (13) Theo %devi Sulphur Expt (16) Theo %devi Chlorine Expt (17) Theo %devi Potassium Expt (19) Theo %devi Calcium Expt (20) Theo %devi Titanium Expt (22) Theo %devi Vanadium Expt (23) Theo %devi Chromium Expt (24) Theo %devi Contd...

7 822 NDAN J PURE & APPL PHYS VOL 39 DECEMBER 2(0) Table 2... (Contd) Element Gamma energy (MeV) ron Expt (26) Thoo %devi Cobalt Expt (27) Thoo %devi Nickel Expt (28) Thoo %devi Copper Expt (29) Thoo %devi Zinc Expt (30) Theo %devi Strontium Expt (38) Theo %devi Zirconium Expt (40) Thoo %devi Silver Expt (47) Thoo %devi Cadmium Expt (48) Theo %devi Tin Expt (50) Theo %devi Dl' Antimony Expt (5 1) Theo %devi Cesium Expt (55) Theo %devi Barium Expt (56) Theo %devi Neodymium Expt (60) Theo %devi Samarium Expt (62) Theo %devi Dysporsium Expt (66) Theo %devi Mercury Expt «;? (80) Thoo %devi Bismuth Expt (83) Theo %devi

8 TELl et al.: ATTENUATON COEFFCENTS OF GAMMA RAYS 823 Jl 2 d. m- 2. '. ' -=1fr. -[n(lo ll)]=-n(lo ) p. dm m... (4) n the formulae (2) to (4) derivatives involve slopes of the curves of n (lell) against m or h. The graphs being ideally straight lines the slopes can replaced by the right hand sides of the respective equations. This avoids the use of the graphs. When the absorber consists of a mixture of various elements with mass weight factors m/m m/m etc the ()1p) of the mixture or compound is given by the Jll following mixture rule:. Jl = L!!!il...(5) P m p Using p = m/v this reduces to: Jlv = LJliV....(6) For a solution of binary compounds m = m l + m2 and Eq. (5) reduces to: be... (7) This represents a straight line for the plot of p versus (m/m). The intercept on the p axis gives ( P) while the slope gives [( P)2-( P)]. From these ( P) and (J1P)2 are determined. Similarly if v = V + V2 in Eq. (6) then for linear attenuation coefficient also we get a straight line equation:... (8) This determines Jl and 112 for the. members. of the solution mixture. For water solution however v. + Vw does not coincide with the solution volume and so Eq. (8) cannot be directly applied6 17 n this case the authors re-scale the linear attenuation coefficient as Teli15 V Jl' = Jl- v' =V1 +v2 v'... (9) where V is the volume of the solution and l is its experimentally measured value by using Eq. (2). Dividing Eq. (6) by v ' we again get a straight line now for l ' as: Jl' == Jl. + (P 2 - Jl.) [ :: ]... ( 1 0) Here Jl' is computed from Eq. (9) by using experimental Jl. The plot of Jl' against (vz/v') now leads to the accurate determination of Jl and 11 2 i.e. of Jl. (for salt) and Jlw (for water). 4 Experimental Technique The authors measured the mass attenuation coefficients of the compounds by performing vertical narrow beam geometry (Fig. 1). The diameter of the collimator is 1.18 cm. A cylindrical glass container of internal diameter 2.9 cm was placed below the source at a distance of 12.3 cm and 9.0 cm above the detector. To prevent the evaporation of the chemicals the burette was directly connected to the glass container. The burette and the glass container are sealed and interconnected through 1.2 mm diameter polyethylene tube to bypass the air. The sodium odide detector [0.75" x 2") was connected to PC based 8k-MCA (4k-MCA was also used in another set-up). n their calculations the intensities (counts) 1 and 1 0 are replaced in Eqs (2) to (4) by the gross area under the photo-peak in the accumulated gamma spectrum for 1800 sec. Using Eq. (7) the authors measured (J1p) for 33 salts containing (a) carbonates of lithium potassium sodium and barium (b) sulphates of ammonia sodium ferric copper and zinc (c) chlorides of aluminium calcium cobalt nickel strontium stannous caesium and mercurius (d) nitrates of silver and bismuth (e) micro fined oxides of titanium chromium zirconium neodium samarium and dysporsium and boric acid ammonium metavanadium cadmium acetate dihydrate etc. Six standard gamma sources COS? (0. 123) Na22 ( ) Cs1J7 (0.662) and C06C1 ( ) MeV are used. The results are shown. in the Table 1. For the measurement of the mass attenuation coefficients of the elements the authors first aimed to estimate the attenuation coefficients for the basic elements H C and O. For this purpose the authors measured the attenuation coefficients of acetone ethanol and -propanol and solved the three

9 NDAN J PURE & APPL PHYS VOL 39DECEMBER simultaneous equations given by their mixture rule various and thus obtained the mass attenuation coefficients Compton effect and pair production to the total processes such as photoelectric effect for the elements hydrogen carbon and oxygen. absorption cross section for low energy gamma Similar type of measurements for the elements H C radiation. The measured mass and linear attenuation and coefficients of salts are useful for dosimetry purpose 0 has been done by Kateb & Himid but the authors' results show better accuracy Teli et Next they measured the mass a(1. attenuation coefficient for carbon tetrachloride and using the mixture rule obtained the coefficients for chlorine while those of the pure elements are important from theoretical points of view. Acknowledgements The by using the previously measured values for carbon. n this way the mass attenuation coefficients for various elements are estimated by measuring the coefficients of the respective compounds one by one and a series of 34 elements H Li B C N 0 Na Seltzerl4 Tables is done 3) from Hubbell & by calculating the = 2 Gagandeep Singh Kulwant Lark B S & Sahota H S App/ Radiat sot (200 ) (in press). 3 Gagandeep K Kaur Kumar V Dhami A K & Lark B S. 4 Singh K Gagandeep Nucl Sci Engg 1 32 ( 1 999). 5 Teli M T Chaudhari L M & Mahle S S App/ Radiat sot authors found the deviations mostly below 1% indicating the excellent measurements with agreement theory. of The linear the mass attenuation coefficient of the respective substance by its density. coefficients for 9 Teli M T & Chaudhari L M ndian J Pure & Appl Phys 33 ( 1 995) Teli M T & Chaudhari L M Appl Radiat sot 47 ( 1 996) elements Teli M T & Chaudhari L M Appl Radiat sot 46 ( 1 995) Teli M T & Chaudhari L M Radiat Phys & Chern. 47 ( 1 996) Conclusions values Teli M T Chaudhari L M & Malode S S Nucl nstrurn 369. attenuation coefficient is obtainable by multiplying theoretical Teli M T Chaudhari L M & Mahle S S ndian J Appl Meths A346 ( 1 994) 220. These are also presented in the Tables and the The Radiat Phys & Chern 53 ( 1 998) Phys 32 ( 1 994) x 1 00 P authors' to 45 ( 1 994) 987. heo -(%tp (%)(%) theo thereby thankful E-Katab Abdul-Hamid H App/ Radiat sot 42 ( )303. percentage deviation as:.. Ol -10 devlatlon much References The comparison of their measurements with the theoretical values (Figs 2 and very Department of Atomic Energy for financial support Dy has been spanned. The results are shown in the Table 2. are under BRNS Major Research grant. Mg A S C K Ca Ti V Cr Fe Co Ni Cu Zn Sr Zr Ag Cd Sn Sb Cs Ba Hg Bi Nd Sm and authors of mass are attenuation available from 13 Teli M T Appl Radiat sot 4 8 ( 1 997) 87. Hubbell J H Radiat Res 70 ( 1 977) 58; nt J Appl Radiat sot 33 ( 1 982) Hubbelll4 Tables and the authors carried out the 14 Hubbell J H & Seltzer S M NSTR ( 1 995) work of their experimental measurement for the first 15 time by devising a simple experimental method with Teli M T Radiat Phys & Chern 53 ( 1 998) Gerward L Radiat Phys & Chern 48 ( 1996) Gerward L Appl Radiat sot 47 ( 1 996) Teli M T Nathuram R & Mahajan C S Radial Meas 32 excellent accuracy and by efficiently employing the mixture rule. The agreement of the authors' so measured values with theory confirms the theoretical considerations of the contribution of (2000) 329.