Mass Attenuation Coefficient and Effective Atomic Number of Ag/Cu/Zn Alloy at Different Photon Energy by Compton Scattering Technique

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1 Avalable onlne at Proceda Engneerng 32 (2012) I-SEEC2011 Mass Attenuaton Coeffcent and Effectve Atomc Number of Ag/Cu/Zn Alloy at Dfferent Photon Energy by Compton Scatterng Technque P. Lmktjaroenporn a,b*, J. Kaewkhao a,b,c, W. Chewpradtkul d, P. Lmsuwan c,d a Center of Excellence n Glass Technology and Materals Scence (CEGM), Nakhon Pathom Rajabhat Unversty, Nakhon Pathom, 73000, Thaland b Scence Program, Faculty of Scence and Technology, Nakhon Pathom Rajabhat Unversty, Nakhon Pathom, 73000, Thaland c Thaland Center of Excellence n Physcs, CHE, Mnstry of Educaton, Bangkok 10400, Thaland d Department of Physcs, Faculty of Scence, Kng Mongkut s Unversty of Technology Thonbur, Bangkok, 10140, Thaland Elsever use only: Receved xx xx xxxx; Revsed: xx xx xxxx; Accepted:xx xx xxxx Abstract Mass attenuaton coeffcents and effectve atomc numbers of Ag/Cu/Zn alloy (14.80%/57.61%/27.59% weght fracton) were determned at energy range 220 to 662 kev usng gamma rays transmsson method. The photon energy has been changed by Compton scatterng technque. The results show that, the expermental values of mass attenuaton coeffcents and effectve atomc numbers are n good agreement wth the theoretcal values wth less than 1% of error. The mass attenuaton coeffcents and effectve atomc numbers were decreased wth ncreasng of gamma rays energes due to the hgher photon nteracton probablty of Ag/Cu/Zn alloy at lower energy Publshed by Elsever Ltd. Selecton and/or peer-revew under responsblty of I-SEEC2011 Open access under CC BY-NC-ND lcense. Keywords: alloy; mass attenuaton coeffcent; effectve atomc number 1. Introducton The total attenuaton cross-secton and effectve atomc number are basc quanttes requred n determnng the penetraton of X-ray and gamma rays n matter [1]. The knowledge of mass attenuaton coeffcents, atomc and electronc cross sectons and effectve atomc number s useful for understandng * Correspondng author. Tel.: E-mal address: golfpo@hotmal.com Publshed by Elsever Ltd. Open access under CC BY-NC-ND lcense. do: /j.proeng

2 848 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) ther physcal propertes [2] such as n bologcal and other mportant materals s of sgnfcant nterest for ndustral, bologcal, agrcultural and medcal applcatons [3]. In 1982 Hubbell publshed tables of mass attenuaton coeffcents and the mass energy absorpton coeffcents for 40 elements and 45 mxtures and compounds over energy range from 1 kev to 20MeV. These tables, although wdely used, should now be replaced by the Hubbell and Seltzer tabulaton for all elements (Z=1-92) and 48 addtonal substances for dosmetrc nterest [4]. Berger and Hubbell developed the theoretcal tables and computer program (XCOM) for calculatng mass attenuaton coeffcents for elements, compounds and mxtures for photon energes from 1 kev to 100 GeV[5,6]. Recently, ths well known and much used program was transformed to the Wndows platform by gerward et al. [7]; and the Wndows verson s beng called WnXCom. From the mass attenuaton coeffcent, a number of related parameters can be derved, such as the mass energy absorpton coeffcent, the total nteracton cross-secton, the molar extncton coeffcent, the effectve atomc number and the effectve electron densty [4]. Reports of attenuaton coeffcent and effectve atomc number for any materals are publshed by several authors [1-18]. In ths work, we have measured the mass attenuaton coeffcents and the effectve atomc numbers of Ag/Cu/Zn alloy at dfferent photon energy and then compare these parameters wth theory usng WnXCom program [7]. The photon energy has been changed by Compton scatterng technque. 2. Theory 2.1 Compton Scatterng The nelastc scatterng of X-rays and gamma rays from electrons had been known for a decade when the Amercan researcher A.H. Compton showed the relatonshp between ncdent and scattered gamma ray energes to be [19] E ' E (1) 1 mc 2 1 cos E / where E s the scattered gamma rays energy, ' E s the ncdent gamma rays energy, s the scatterng angle, and m s the electron rest mass. Ths formula s easly derved by assumng a relatvstc collson between the gamma ray and an electron ntally at rest. Of course, under normal crcumstances, all the electrons n a medum are not free but bound. If the energy of the photon, however, s of the order of kev or more, whle the bndng energy of the electron s of the order of ev, the electron may be consdered at rest. The collson s nelastc n the sense that one photon s absorbed and another of dfferent frequency and momentum s emtted. 2.2 Gamma-rays transmsson The mass attenuaton coeffcent s wrtten as [10] I ln( 0 ) I m (2) t Where s the densty of materal (g/cm 3 ), 0 I and I are the ncdent and transmtted ntenstes and t s the thckness of absorber (cm).

3 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) Theoretcal values of the mass attenuaton coeffcents of mxture or compound have been calculated by WnXCom, base on mxture rule [4]. m w ( m ) (3) Where w s weght fracton of element n alloy, element n alloy. (m ) s mass attenuaton coeffcent for ndvdual The value of mass attenuaton coeffcents can be used to determne the total atomc cross-secton ) by the followng relaton [4] ( t, a ( m ) alloy t, a (4) n N ( w A ) Where N A s Avogradro s number, A s atomc weght of consttuent element of alloy. Also the total electronc cross-secton ( ) for the element s expressed by the followng formula [4] t, el A n 1 f A t, el ( m ) (5) N Z Where f s the number of atoms of element relatve to the total number of atoms of all elements n alloy, Z s the atomc number of the th element n alloy. Total atomc cross-secton and total electronc cross-secton are related to effectve atomc number ( Z eff ) of the compound through the formula [16] A Z eff t, a (6) t, el 3. Expermental Setup The compostons of 14.80%/57.61%/27.59% fractonal weght for Ag/Cu/Zn alloy was analyzed by energy dspersve x-rays fluorescence spectrometer (Panalytcal Mnpal-4).The thckness (0.05 mm) of the Ag/Cu/Zn alloy was measured usng a mcrometer Densty of glass samples were measured by Archmedes prncple usng dstlls water as the lqud. The densty s calculated accordng to the formula; w A dstllwater (7) wa wb Where w A s the weght of the sample n ar, w B s the weght of the sample n water and densty of dstll water s 1 g/cm 3.

4 850 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) The expermental arrangement s shown n Fg. 1. The source system was mounted on a composte of adjustable stands. Ths setup can move n the transverse drecton for proper beam algnment. The 137 Cs radoactve source of 15 mc (555 MBq) strength was obtaned from the Offce of Atom for Peace (OAP), Thaland. The alumnum rod was used the scatterng rod. The Compton scattered -rays were measured on a rotatable scntllator detector n the scatterng plane by usng the 22 NaI(Tl) detector havng an energy resoluton of 8% at 662 kev (BICRON model 2M2/2), wth CANBERRA photomultpler tube base model The optmum dstance between the source and the scatterer was chosen to be 20 cm and that between the scatterer and detector, 20 cm. The spectra were recorded usng a CANBERRA PC-based mult-channel analyzer (MCA). The spectrum on the MCA of detector gave nstance counts n each of 1024 bns dvded by voltage. To measure the angular dependence of Compton scatterng, we frst perform a calbraton relatng the channel number of the MCA spectrum to the energy of known gamma-ray sources. We vary the angle of the scatter detector and acqure measurements on the MCA. The dfferent angles () were used to produce the dfferent gamma rays energes. The gamma rays energy spectrum for the NaI(Tl) detector was a Gaussan shaped peak. For each full energy peak, the centrod and full wdth at half maxmum (FWHM) of the full energy peak were obtaned from Gaussan fttng software of Canberra MCA. The statstcal error of scattered gamma rays n ths experment were calculated from full wdth at half maxmum (FWHM) of the full energy peak. The wdth of a Gaussan dstrbuton s related to the standard devaton by [19] FWHM 2 2 ln 2 (8) An optmum sample thckness (0.5 x 5.0) was selected n ths experment on the bass of the Nordfors crtera [20, 21]. To measure mass attenuaton coeffcent, we placed the sample between the scatterng rod and detector, and detecton the acqured MCA spectra of the scattered gamma rays photopeak through sample thckness at dfferent angles. Integrated count rates were determned from Gaussan fts and used to determne an attenuaton coeffcent. The statstcal error n ths experment calculated from the standard error of 3 tems () ray-sum measurement, whch calculated from experment, the ray-sum s product of lnear attenuaton coeffcent () wth thckness (x), () densty measurement and () thckness measurement [17]. Fnally, the total standard error has been determned by combnng errors for the ray-sum measurement, densty measurement and thckness measurement n quadrature. Fg. 1. Schematc of the Compton scatterng experment

5 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) Results and dscussons Gamma ray spectrometer s calbrated by usng standard calbraton sources at dfferent energes ( 241 Am 59.5 kev, 133 Ba 356 kev, 22 Na 511 kev and 137 Cs 662 kev). Each of the calbraton sources s placed at the scatterer poston and ts spectrum s recorded. The FWHM of the Compton photopeaks hgher than FWHM of pont sources attrbuted to Compton scatterng experment several broadenng effects contrbutng to our statstcal error, and some neglgble effects relevant to hgher resoluton measurements. Inherent to our expermental setup s the spread of the beam profle (3 o ) of the 137 Cs source over the surface of the scatter detector that contrbutes to a Gaussan spread of measured scatterng events. The Ferm moton of electrons n the detector has a fnte momentum dstrbuton contrbutng to Lorentzan lne broadenng beyond the resoluton of the NaI scntllator. Addtonally, the moton of electrons about the bndng potental of the nucleus. Doppler broadens the apparent energy of ncdent photons from our source, thereby broadenng the Compton peak for a gven scatterng angle[22]. The scattered gamma ray energes and statstcal error at dfferent angles shown n Table 1. The theoretcal values ( E' (th) ) were calculated by usng Eq. (1) and the expermental values ( E' (ex) ) were measured. The relatve dfference between theoretcal values and expermental values showed the results less than 1%, ths results reflect the good geometry n detecton system setup for Compton scatterng experment. Table 1. The scattered gamma rays energes at dfferent angles (deg) E' (th) (kev) E' (ex) (kev) %RD ± ± ± ± ± ± ± % RD = [(Theoretcal value Expermental value)/ Theoretcal value] x 100 The mass attenuaton coeffcents of Ag/Cu/Zn alloy as shown n Table 2 were evaluated from ncdent (I 0 ) and transmtted (I) ntenstes and compare wth theoretcal values were calculated by WnXCom program [7]. By usng the expermental data of total mass attenuaton coeffcents, the effectve atomc numbers (Z eff ) have been determned usng Eq. (6) and shown n Table 2. Fg. 2 and Fg. 3 showed the good agreement between expermental values and theoretcal values of mass attenuaton coeffcents and effectve atomc numbers respectvely. It has been found that the mass attenuaton coeffcents and effectve atomc numbers were decreased wth ncreasng of gamma rays energes. From the decreasng of these parameters, we obtaned the photon nteracton probablty s decrease wth hgher gamma rays energy, these results showed the mass attenuaton coeffcents and effectve atomc numbers of ths work (Ag/Cu/Zn alloy) s hgher than Cu/Zn alloy n publshed lterature [16]. It s due to Ag component n alloy.

6 852 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) Table 2. Total mass attenuaton coeffcents and effectve atomc numbers of Ag/Cu/Zn alloy E (kev) m(th) (10-2 cm 2 /g) m(ex) (10-2 cm 2 /g) %RD Z eff(th) (e - /atom) Z eff(ex) (e - /atom) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.39 Fg. 2. Varaton of mass attenuaton coeffcent values for the Ag/Cu/Zn alloy as a functon energy. The lne s theoretcal value and pont n ths fgure s expermental value Fg. 3. Varaton of Effectve atomc number values for the Ag/Cu/Zn alloy as a functon energy. The lne s theoretcal value and pont n ths fgure s expermental value

7 P. Lmktjaroenporn et al. / Proceda Engneerng 32 (2012) Conclusons In the Compton scatterng expermental setup, there are correspondng of scattered gamma rays energes between theoretcal and expermental values, ths reflect the superb detecton system setup. The mass attenuaton coeffcents and effectve atomc numbers of Ag/Cu/Zn alloy were measured at the dfferent energy of -rays usng the Compton scatterng technque. The results are good agreement wth the theoretcal values. In ths range of gamma rays energy (220 to 662 kev), the mass attenuaton coeffcents and effectve atomc numbers decrease wth ncreasng of gamma rays energy. Ths attrbuted to the hgher photon nteracton probablty of Ag/Cu/Zn alloy at lower energy. Acknowledgements P. Lmktjaroenporn and J. Kaewkhao specal thanks to Natonal Research Councl of Thaland (NRCT) for fundng ths research. W. Chewpradtkul and P. Lmsuwan would lke to thanks Kng Mongkut s Unversty of Technology Thonbur for partally fundng under Natonal Research Unversty project. References [1] Cevk U, Baltas H. Measurement of The Mass Attenuaton Coeffcents and Electron Denstes for BPbSrCaCuO Superconductor at Dfferent Energes, Nuclear Instruments and Methods n Physcs Research Secton B 2007; 256: [2] Han I, Demr L, Sahn M. Determnaton of Mass Attenuaton Coeffcents, Effectve atomc and Electron Numbers for Some Natural Mnerals Radaton Physcs and Chemstry 2009; 78: [3] Manohara S.R., Hanagodmath S.M. Studes on effectve atomc numbers and electron denstes of essental amno acds n the energy range 1 kev 100 GeV Nuclear Instruments and Methods n Physcs Research Secton B 2007; 258(2): [4] Sngh K, Sngh H, Sharma V, Nathuram R, Khanna A, Kumar R, Bhatt S.S., Sahota H.S. Gamma-Ray Attenuaton Coeffcents n Bsmuth Borate Glasses, Nuclear Instruments and Methods n Physcs Research Secton B 2002; 194: 1-6. [5] Sngh N, Sngh K.J., Sngh K, Sngh H. Comparatve Study of Lead Borate and Bsmuth Lead Borate Glass Systems as Gamma-Radaton Sheldng Materals Nuclear Instruments and Methods n Physcs Research Secton B 2004; 225: [6] Sngh S, Kumar A, Sngh D, Sngh K., Mudahar G.S. Barum-Borate-Flyash Glasses:As Radaton Sheldng Materals Nuclear Instruments and Methods n Physcs Research Secton B 2008; 266: [7] Gerward L, Gulbert N, Jensen K.B., Levrng, H. WnXCom-A Program for Calculatng X-Ray Attenuaton Coeffcents Radaton Physcs and Chemstry 2004; 71: pp [8] Sngh N, Sngh K.J., Sngh K., Sngh H. Gamma-Ray Attenuaton Studes of PbO-BaO-B 2 O 3 Glass System Radaton Measurement 2006: 41: [9] Sngh M.P., Sandhu B.S., Sngh, B. Measurement of Effectve Atomc Number of Composte Materals Usng Scatterng of -Rays, Nuclear Instruments and Methods n Physcs Research Secton A 2007; 580, [10] Sngh K., Kaur R., Vadana, Kumar V. Study of Effectve Atomc Numbers and Mass Attenuaton Coeffcents n Some Compounds Radaton Physcs and Chemstry 1996; 47(4): [11] Kaewkhao J, Pokapst A, Lmsuwan P Study on Borate Glass System Contanng wth B 2 O 3 and BaO for Gamma-Rays Sheldng Materals: Comparson wth PbO Journal of Nuclear Materals 2010; 399: [12] Sngh K.J., Sngh N, Kaundal R.S., Sngh K. Gamma-Rays Sheldng and Structural Propertes of PbO-SO 2 Glasses Nuclear Instruments and Methods n Physcs Research Secton B 2008; 266: [13] Baltas H, Celk S, Cevk, U, Yanmaz E. Measurement of Mass Attenuaton Coeffcents and Effectve Atomc Numbers for MgB 2 Superconductor Usng X-Ray Energes, Radaton Measurement 2007; 42: [14] Akkurt I, Klncarslan S, Basygt C. The Photon Attenuaton Coeffcents of Barte, Marble, and Lmra Annals of Nuclear Energy 2004; 34: [15] Sngh K, Sngh H, Sharma G., Gerward L, Khanna A, Kumar R, Nathuram R, Sahota H.S. Gamma-Rays Sheldng Propertes of CaO-SrO-B 2 O 3 Glasses Radaton Physcs and Chemstry 2005; 72: [16] Kaewkhao J, Laopaboon J, Chewpradtkul W. Determnaton of Effectve Atomc Numbers and Effectve Electron Denstes of Cu/Zn Alloy, Journal of Quanttatve Spectroscopy and Radatve Transfer 2008; 109: [17] Lmktjaroenporn P, Kaewkhao J, Lmsuwan P, Chewpradtkul W. Physcal, Optcal, Structural and Gamma-Ray Sheldng Propertes of Lead Sodum Borate Glasses Journal of Physcs and Chemstry of Solds 2011; 72: [18] Korkut T, Korkut H, Karabulut A, Budak G. A New Radaton Sheldng Materal: Amethyst ore Annals of Nuclear Energy 2011; 38:

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