Nuclear Science and Technology No2-2013

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ISSN 1810-5408 Nuclear Science and Technology Volume 3, Number 2, June 2013 Published by VIETNAM ATOMIC ENERGY SOCIETY NUCLEAR SCIENCE AND TECHNOLOGY Volume 3, Number 2, June 2013 Editorial Board Editor-in-chief Tran Huu Phat (VINATOM) Executive Editors Vuong Huu Tan (VARANS) Le Van Hong (VINATOM) Cao Đình Thanh (VINATOM) Editors Phan Sy An (HMU) Cao Chi (VINATOM) Nguyen Nhi Dien (VINATOM) Bui Dieu (NCI) Le Ngoc Ha (Tran Hung Dao Hospital) Duong Ngoc Hai (IOM) Le Huy Ham (VAAS) Nguyen Quoc Hien (VINATOM) Bui Hoc (HUMG) Nguyen Phuc (VINATOM) Nguyen Tuan Khai (VINATOM) Hoang Anh Tuan (VAEA) Ngo Quang Huy (HUI) Le Hong Khiem (IOP) Dao Tien Khoa (VINATOM) Do Ngoc Lien (VINATOM) Dang Duc Nhan (VINATOM) Nguyen Mong Sinh (VINATOM) Le Xuan Tham (DOST of Lamdong) Tran Duc Thiep (IOP) Le Ba Thuan (VINATOM) Huynh Van Trung (VINATOM) Dang Thanh Luong (VARANS) Nguyen Thi Kim Dung (VINATOM) Pham Dinh Khang (VINATOM) Foreign Editors Pierre Darriulat (INST) Myung Chul Lee (WFNM) Hideki Namba (JAEA, Japan) Philippe Quentin (CENBG, CNRS, France) Yang (KAERI, Korea) Kato Yasuyoshi (TIT, Japan) Managing Secretary Nguyen Trong Trang (VINATOM) Science Secretary Hoang Sy Than (VINATOM) .................................................................................................................................................................................................................... Copyright: ©2008 by the Vietnam Atomic Energy Society (VAES), Vietnam Atomic Energy Institute (VINATOM). Pusblished by Vietnam Atomic Energy Society, 59 Ly Thuong Kiet, Hanoi, Vietnam Tel: 84-4-39420463 Fax: 84-4-39424133 Email: nuscitech@vinatom.gov.vn Vietnam Atomic Energy Institute, 59 Ly Thuong Kiet, Hanoi, Vietnam Tel: 84-4-39420463 Fax: 84-4-39422625 Email: infor.vinatom@hn.vnn.vn .................................................................................................................................................................................................................... INSTRUCTIONS FOR AUTHORS GENERAL INFORMATION MANUSCRIPT PREPARATION Nuclear Science and Technology (NST), an international journal of the Vietnam Atomic Energy Society (VAES), quarterly publishes articles related to theory and application of nuclear science and technology. All papers and technical notes will be refereed. It is understood that the paper has been neither published nor currently submitted for publication elsewhere. The copyright of all published papers and notes will be transferred in VAES. Manuscripts must be written in English with adequate margins and indented paragraph. All manuscript must use SI (metric) units in text, figures, and tables. Manuscripts should in general be organized in the following order: title, names of authors and their complete affiliation including zip code, abstract (not exceeding 200 words), keywords (up to 7), introduction, main body of a paper, acknowledgments, references, appendices, table & figure captions, tables and figures. Unnecessary sections may be omitted. DETAILED FIELDS NST coves all fields of nuclear science and technology for peaceful utilization of nuclear energy and radiation. Authors should choose one of the following fields at the time they submit their manuscript: 1) Nuclear Physics, 2) Nuclear Data, 3) Reactor Physics, 4) Thermal Hydraulics, 5) Nuclear Safety, 6) Nuclear I&C, 7) Nuclear Fuel and Materials, 8) Radioactive Waste Management, 9) Radiation Protection, 10) Radiation Technology, 11) Nuclear Techniques in Food and Agriculture, 12) Nuclear Medicine and Radiotherapy, 13) Nuclear Techniques in Industries, 14) Environment Radioactivity, 15) Isotope Hydrology, 16) Nuclear Analytical Methods, 17) Health Physics, 18) Fusion and Laser Technology. MANUSCRIPT SUBMISSION Manuscript for publication should be submitted to the Editorial Office in triplicate by postal mail. For electronical submission use nuscitech@vinatom.gov.vn. Submission Address Department of Planning, R&D Management Vietnam Atomic Energy Institute, 59 Ly Thuong Kiet Street, Hanoi, Vietnam E-mail: nuscitech@vinatom.gov.vn. Headings: Use I, II,… for major headings and A, B, … for secondary headings. Mathematical formulas: All mathematical formulas should be clearly written, with special consideration to distinctive legibility of sub-and superscripts. Equation (at least the principal ones) should be numbered consecutively using Arabic numerals in parentheses in the right hand margin. Tables and Figures: Tables should be numbered with Roman numerals. Figures should be numbered consecutively with Arabic numerals in order of their first appearance and have a complete descriptive title. They should be typed on separate sheets. Tables should no repeat data which are available elsewhere in the paper. Figures should be original ink drawing or computer drawn figures in the original and of high quality, ready for direct reproduction. Figures should be referred to in the text as, for example, Fig. 1., or Fig. 2. . Reference: References should be listed at the end of the text and presented as follows: [1] C. Y. Fu et al., Nuclear Data for Science and Technology, S. M. Qaim (Ed.), p. 587 (1991). [2] C. Kalbach, Z. Phys, A283, 401 (1977). [3] S. Shibata, M. Imamura, T. Miyachi and M. Mutou, “Photonuclear spallation reactions in Cu”, Phys. Rev. C 35, 254 (1987). KHOA HỌC VÀ CÔNG NGHỆ HẠT NHÂN Chịu trách nhiệm xuất bản TRẦN HỮU PHÁT Chịu trách nhiệm nội dung TRẦN HỮU PHÁT TRẦN CHÍ THÀNH LÊ VĂN HỒNG CAO ĐÌNH THANH Trình bày LÊ THÚY MAI DOÃN THỊ LOAN In 200 cuốn, khổ 19x26,5cm tại Công ty Mỹ thuật Trung ương Giấy đăng ký kế hoạch xuất bản số: 770/GP-BTTTT cấp ngày 20 tháng 5 năm 2011 In xong và nộp lưu chiểu Quý II năm 2013 25 000đ Nuclear Science and Technology, Vol. 3, No. 2 (2013), pp. 1-6 Studies of multiparticle photonuclear reactions in natural iron induced by 2.5 GeV bremsstrahlung Pham Duc Khue*, Kim Tien Thanh, Nguyen Thi Hien Institute of Physics, VAST, 10 Dao Tan, Ba Dinh, Hanoi, Vietnam * Email: pdkhue@iop.vast.ac.vn (Received 27 June 2013, accepted 26 September 2013) Abstract: Multiparticle photonuclear reactions produced on natural iron target with maximum endpoint energy of 2.5 GeV bremsstrahlung have been investigated by using the activation method in combination with -ray spectrometric techniques. The -spectra were measured with a high energy resolution -spectrometer based on HPGe detector. The radioactive residual nuclei formed via nuclear reactions were identified based on their half-lives and -ray energies. The yields of reaction products were determined based on their -activities. In order to improve the accuracy of the experimental results a series of -spectra were measured at different cooling times and the necessary corrections were made. More than twenties radioactive nuclei formed via the following photonuclear reactions: nat Fe(,xn), natFe(,xnyp) and natFe(,-xn) have been identified and their yields have been determined. The present experimental results are compared with reference data and analyzed with an empirical formula given by Rudstam. Keywords: Bremsstrahlung; Activation method; Gamma spectrometer, Reaction yield. I. INTRODUCTION The photonuclear reactions with high energy bremsstrahlung photons generated from the electron linear accelerators (linac) have been the subject of many investigations. The photon interacts with nuclei in different ways depending on the photon energy. When high energy photons interact with the target nuclei a number of radioactive products are induced as a result of different reaction mechanisms such as (1) giant dipole resonance (GDR) in the energy region from about 10 MeV to 30 MeV, (2) quasi-deuteron resonance (QDR) from about 30 MeV to 140 MeV and intranuclear cascade and evaporation at energy greater than 140 MeV. Generally, the possible photonuclear reactions can be classified into four groups, namely simple reactions; spallation reactions; fission; and fragmentation. The knowledge of the reaction channels and yields of the reaction products from the de-excitation of the nuclei can help in understanding the interaction process [1-4]. Recently, with the fast development of high energy electron accelerators the studies of photospallation reactions for light, medium and heavy weight targets have been made at energies up to 5 GeV [4-11]. The aim of the present work is to investigate the multiparticle photonuclear reactions on medium iron target nuclei bombarded by 2.5 GeV bremsstrahlung. The main attentions were to identify the reaction products and to determine the reaction yields. The obtained yields are analyzed by means of Rudstam' five parameters formula. The experiment work was carried out at the 2.5 GeV electron linac of the Pohang Accelerator Laboratory (PAL), POSTECH, Pohang, Korea. II. EXPERIMENTAL The experiment was carried out at the 10o beam line of the 2.5 GeV electron linac of the PAL. The details of the 2.5 GeV electron linac and its applications were described elsewhere [12]. The bremsstrahlung photons were ©2013 Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute STUDIES OF MULTIPARTICLE PHOTONUCLEAR REACTIONS IN … where  is the detection efficiency, an represents the fitting parameters, and E is the energy of the photopeak, E0 = 1 keV. The detection efficiencies as a function of the photon energy measured at different distances between the source and the surface of the detector were illustrated in ref. [13]. produced when a pulsed electron beam hit a thin W target with a size of 50 mm  50 mm and a thickness of 0.2 mm. The W target is located at 38.5 cm from the beam exit window. In this work, the high purity (99.559%) natural iron foil made by Reactor Experiments Inc. (USA), in disc shape with diameter of 1/2 inch and thickness of 0.05 inch was used. The activation foil was placed in air at 24 cm from the W bremsstrahlung target and they were positioned at zero degree with the direction of the electron beam. The irradiation time was 4 hours. During the irradiation, the electron linac was operated with a repetition rate of 10 Hz, a pulse width of 1 ns, and the electron energy of 2.5 GeV with total electron beam current of 2.19 × 1014 electrons. For the measurements, the cooling and the measuring times were chosen based on the activity and the half-life of each radioactive isotope considered. In order to optimize the dead time losses and the coincidence summing effect we have also chosen the appropriate distance between the foil sample and the detector for each measurement. Generally, the dead times were kept below 1.0 % during the measurement. Typical -ray spectra from the irradiated iron foil taken at different waiting time were shown in Fig. 1 and Fig. 2. The energy values of the -rays were taken from ref. [14]. After an irradiation and an appropriate waiting time, the irradiated iron foil was taken off, and then the induced gamma activities of III. DATA ANALYSIS AND RESULTS the irradiated foil were measured by using a gamma spectrometer. The gamma The nuclear reaction products were identified based on their half-lives and gamma ray energies. In this work, total of 27 radioactive nuclei were measured, such as 53 Fe, 52Fe, 56Mn, 54Mn, 52mMn, 52gMn, 51Cr, 49 Cr, 48Cr, 48V, 48Sc, 47Sc, 46Sc, 44mSc, 44gSc 43 Sc, 45K, 43K, 42K, 41Ar, 39Cl, 3S8Cl, 34mCl, 24 Na, 22Na, 55Co and 56Co. These isotopes were formed from the different channels such as multineutron emission reactions natFe(,xn); photospallation reactions natFe(, xnyp) and photopion reactions natFe(,xn-), where x and y being the number of neutrons and protons emitted. Obviously, the photospallation reaction was the most dominant competitive channel among others. The maximum number of neutrons and protons emitted from the spallation reaction 58Fe(,21n15p) 22Na were 21 and 15. Two products 55Co and 55Co were produced in the photopion reactions. Some reaction products are in isomeric state (52mMn, 44m Sc and 34mCl). spectrometer used for the measurements was a coaxial CANBERRA high-purity germanium (HPGe) detector with a diameter of 59.2 mm and length of 30 mm. The HPGe detector was coupled to a computer-based multichannel analyzer card system, which could determine the photopeak-area of the gamma ray spectra by using the GENIE2000 (Canberra) computer program. The energy resolution of the detector was 1.80 keV full width at half maximum (FWHM) at the 1332.5 keV peak of 60Co. The photopeak efficiency curve of the gamma spectrometer was calibrated with a set of standard gamma sources such as 241Am, 137Cs, 54 Mn, 22Na, 60Co, 133Ba and 152Eu. The measured detection efficiencies were fitted by using the following function: 5 ln    a n ln E / E0  n (1) n 0 2 PHAM DUC KHUE, KIM TIEN THANH, NGUYEN THI HIEN Fig. 1. Typical gamma-ray spectrum from natural Fe irradiated with 2.5 GeV bremsstrahlung with ti= 240 min, td = 40 min and tc = 10 min. Fig. 2. Typical gamma-ray spectrum from natural Fe irradiated with 2.5 GeV bremsstrahlung with ti= 240 min, td = 8395 min and tc = 120 min. where N0 is the number of the target atoms,  is the absolute photopeak efficiency, I is the gamma ray intensity, f is the correction factor,  is the decay constant of the product nucleus,  is pulse width, ti is the irradiation time, tw is the waiting time, tc is the counting time, T is cycle period,  is the flux of the photon beam,  is the reaction cross section, Eth the By considering the pulse nature of the bremsstrahlung beam, the photopeak area or the number of detected gamma rays, C, can be expressed as follows: C N0I f (1  e )(1  eti )et w (1  et c )  (1  e T )  E m ax E th  ( E ) ( E )dE (2) 3 STUDIES OF MULTIPARTICLE PHOTONUCLEAR REACTIONS IN … threshold reaction energy, and Emax the maximum bremsstrahlung energy. characteristic only for spallation. Meanwhile yield of the products from the natFe(,xn) and nat Fe(,-xn) nuclear reactions can not be described by the Rudstam’s formula. For any nuclear reaction, the yield is given by [10]: Y  No  E m ax E th (E)(E)dE We plot the yield data of natFe irradiated with 2.5 GeV bremsstrahlung obtained in this work together with those data obtained by G. Kumbartzki et al., [6] at 1.5 GeV bremsstrahlung in Fig. 4, and it is shown that the present yields are in good agrement with most of the reference data. (3) On basis of the equations (2) and (3), the experimental yield can be derived from the measured activity, C, as follows: Y C(1  e  T ) I  f (1  e  )(1  e t i )e t d (1  e t m ) (4) The main sources of the errors are due to statistical error, detection efficiency, photopeak area determination, coincidence summing effect and nuclear data used. In order to improve the accuracy of the experimental results, corrections for -ray interferences, self-absorption of -rays and coincidence summing effect were taken into account. The total uncertainties were estimated to be 5 - 10%. The measured yield was obtained by averaging over several measurements. In the present work, the reaction yields were determined relative to that of 54Mn where the yield of 54Mn is normalized to unity. The obtained data were analyzed by using the Rudstam’s formula as follows [3-6]: (A, Z)  3/ 2 ˆ PR 2 / 3 exp[ PA  R Z  SA  TA2 ] (5) PAt 1.79(e  1) where: (Z,A) is the cross section for the production of the residual nucleus with charge Z and mass number A; At is mass number of target; P, R, S, T and ˆ are free parameters with P  6.08  At0.89 =0.1695, R  11.8 At0.45 =1.93, S=0.485; T=0.00032, At = 55.845, max ˆ  (0.81  0.192 ln E max )A1t.13 = 65.213, E  IV. CONCLUSION Multiparticle photonuclear reactions on Fe induced by 2.5 GeV bremsstrahlung have been investigated by using the activation method. Total of 27 radioactive nuclides with half-lives ranging from 8.51 min (53Fe) to 2.6109 yr (22Na) have been found. Most of the reaction products identified were formed via the spallation reactions, and their yields can be described by empirical Rudstam’s formula. The agreement between the measured and predicted yields for the photospallation reactions is quite satisfactory. The obtained data have yielded valuable information not only for the understanding of reaction mechanisms and testing the validity of the nuclear model, but also for the application to other field such as astrophysics, shielding physics, activation analysis, isotope production and transmutation of nuclear wastes. nat = 2500 MeV. The yields for the natFe(,xn) reactions can be approximated by the following formula [15]: (, xn )  0.058A0t.684 exp[ 37A t 0.864(x 1)5 / 4 ] (6) Rudstam’s five parameter formula is based on the evaporation model and experimental data. It allows one to represent the mass distributions of the residual nuclei in an analytical form. The experimental and calculated yields were plotted against the mass number of the product nuclei and shown in Fig. 3. As can be seen, our experimental yields are well consistent with the prediction values. The yield distribution curves seem to be 4 PHAM DUC KHUE, KIM TIEN THANH, NGUYEN THI HIEN Relative Yield 100 10 nat Sc K Ar Cl Na calculation Co Fe Mn Cr V 1 Fe(,xnyp) Cr Mn Fe V Sc 0.1 Ar Cl 0.01 K Na Co 1E-3 20 25 30 35 40 45 50 55 60 Mass number , A Fig. 3. Mass distribution of radioactive nuclei produced in natFe irradiated with 2.5 GeV bremsstrahlung. The curves were calculated by Rudstam's formula. 10 Relative Yield This wor k (2.5 GeV) Ref. [6] (1.5 GeV) 1 0.1 0.01 1E-3 20 25 30 35 40 45 50 55 60 Mass number , A Fig.4. Realative yields of radioactive nuclei produced in natFe induced by 2.5 GeV () and 1.5 GeV () bremsstralung photons. ACKNOWLEDGMENTS completion of this experiment. This work is also supported in part by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.04-2012.21. The authors are very grateful to Prof. Nguyen Van Do for his encourage and support. We would like to thanks to the Pohang Accelerator Laboratory, POSTECH, Korea for the invitation and support during the 5 STUDIES OF MULTIPARTICLE PHOTONUCLEAR REACTIONS IN … Young Seok Lee, Youngdo Oh, Hee-Seock Lee, Moo-Hyun Cho, In Soo Ko and Won Namkung, “Isomeric cross-section ratios for 45 nat the Sc(,n)44m,gSc, Ti(,xn1p)44m,gSc, nat 44m,g nat Fe(,xn5p) Sc and Cu(,xn8p)44m,gSc reactions induced by 2.5 GeV Bremsstrahlung”, Nucl. Instr. and Meth., B266, 5080 (2008). REFERENCES [1] G. Rudstam, “The evaporation step in spallation reactions”, Nucl. Phys. A 126, 401 (1969). [2] J. R.Wu and C.C. Chang, “Pre-equilibrium particle decay in the photonuclear reactions”, Phys. Rev. C 16, 1812 (1977). [3] K. Lindgren and G. G. Jonsson, “Photoninduced nuclear reaction above 1 GeV”, Nucl. Phys., A197, 71(1972). [11] Nguyen Van Do, Pham Duc Khue, Kim Tien Thanh and Nguyen Thi Thanh Van, “High energy photon induced nuclear reactions in natural copper”, Comm. in Phys., Special issue, 19,177 (2009). [4] A.S. Danagulyan, N.A.Demekhina and G.A. Vartapetyan, “Photonuclear reactions in medium weight nuclei 51V, 55Mn and Cu”, Nucl. Phys. A 285, 482 (1977). [12] H. S. Lee, S. Ban, T. Sato, K. Shin, J. S. Bak, C. W. Chung, H. D. Choi, “Photoneutron Spectra from Thin Targets Bombarded with 2.0 GeV Electrons”, J. Nucl. Sci. and Tech. Supplement 1, 207 (2000). [5] S. Shibata, M. Imamura, T. Miyachi and M. Mutou, “Photonuclear spallation reactions in Cu”, Phys. Rev. C 35, 254 (1987). [6] G. 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Terranova and O.A.P.Tavares, “Total Nuclear Photoabsorption Cross Section in the Range 0.2-1.0 GeV for Nuclei throughout the Periodic Table”, Phys. Scri. 49, 267 (1994). [9] Koh Sakamoto, “Radiochemical study on photonuclear reactions of complex nuclei at intermediate energies”, J. Nucl. Radiochem. Sci. 4, 9 (2003). [10] Nguyen Van Do, Pham Duc Khue and Kim Tien Thanh, Le Truong Son, Guinyum Kim, 6
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