Measurement of flux-weighted average natCd(,xn) and natCd(,pxn) reaction
cross-sections with the bremsstrahlung end-point energies of 50 and 60 MeV
Muhammad Nadeema , Md. Shakilur Rahmana, Guinyun Kima1 ,Kwangsoo Kima, Nguyen Thi Hiena,
a
Department of Physics, Kyungpook National University, Daegu 41566, Republic of Korea
Abstract
nat
The flux weighted average cross-sections of Cd(,xn)115m,115g,111m,109,107,105,104Cd and natCd(,pxn)113m+g,112,111g110m
Ag reactions have been studies with the photon end-point energies of 50,and 60 MeV via activation and
off-line γ-ray spectrometric technique at Pohang Accelerator Laboratory (PAL), republic of Korea. The fluxweighted average cross-sections of the above reactions were also theoretically calculated with the help of
computer codes Talys 1.8 and Empire 3.2.2 Malta 2014 while bremsstrahlung spectrum was simulated by
Geant4 code. Along with the measurements of reaction cross-sections, energy dependent radioactivity yield of
isotopes were also measured. The measured cross-sections are found to be in general agreement with the
theoretical values. It was observed that the average cross-sections increase with bremsstrahlung energy up to
the Gaint Dipole Resonance (GDR) and then decrease due to opening of other reaction channels.
1 Introduction
Many authors have studied GDR region with mono-energetic photon. But photo-induced reaction data with
energy higher than GDR region is scarcely available. Higher energy photon induced nuclear reaction
measurements with neutron and proton emission channels are important for nuclear and astrophysics subjects.
Photon induced nuclear reaction with the emission of neutrons is a best mechanism to investigate
electromagnetic effect on nucleus. [1]. The isotopic production yield due to nuclear reaction is depends upon
projectile energy. It is higher at higher projectile energy due to a continuous energy spectrum. It is also possible
to study multi-particle emission nuclear reactions at higher intense bremsstrahlung energy by separating single
or multi particle emission channels. [2]. Theoretical model calculations could also be refined by available
experimental data. It is therefore necessary to have sufficient experimental measurements in order to develop
confidence in model calculations. Cadmium and silver isotopes have medical and industrial applications. It is
better to make available of production cross section data for the isotopes at different possible projectile energy.
For the studied nuclides there is no experimental data above 30 MeV bremsstrahlung. Therefore experiment
was planned to study photonuclear reaction at higher bremsstrahlung energy. In the present work, the average
nat
Cd(,xn)115m,115g,111m,109,107,105,104Cd and natCd(,pxn)113m+g,112,111g-110mAg reaction cross-sections with the
bremsstrahlung end-point energies of 50 and 60-MeV were i experimentally determined. The isotopic
production integral yields in units of [Bq/g.u A·h] for all the nuclides were also measured. The average
weighted cross sections were calculated by TALYS 1.8 [3] and Empire 3.2.2 Malta codes [4] while quasi mono
energetic bremsstrahlung spectra was simulated by monte carlo Geant4 tool [5]
2 Experimental procedure
The experiment was carried out with 100 MeV electron linac of Pohang Accelerator Laboratory
(PAL), South Korea. The bremsstrahlung beams with end point energies of 50-,and 60-MeV are
produced by hitting pulsed electron beam on a thin tungsten (W) target of 0.1 mm thickness and of
10 cm × 10 cm size.. Two different sets of samples of high purity (99.99%) metallic 0.1 mm thick
nat
Cd target together with 0.1mm thick flux monitors foil 197Au were made for irradiations for duration
of 14170 sec and 7500 sec respectively. In the experiments pre-calibrated HPGe detector coupled to
a PC-based 4K channel analyzer was used for off line gamma spectroscopy.
3 Data analysis
3.1
Measurement of photon flux and average weighted cross section
Experimentally flux and average weighted cross sections were measured by using following equations;
1
Corresponding author. Tel.: +82 53 950 5320; fax: +82 53 939 3972.
E-mail address: [email protected] (G. N. Kim).
𝜑(𝐸𝑖 ) =
𝑆𝐴𝐸𝑖 (𝐶𝐿/𝐿𝑇). 
𝐼𝛾 𝜀𝑁0 < 𝜎𝑅 (𝐸𝑖 ) > 𝐹(1 − 𝑒 −𝑡𝑖 )𝑒 −𝑡𝑑 (1 − 𝑒 −𝑡𝑐 )
Eq. 1
Eq. 1 is used to determine photon flux using 197Au(,n)196Au monitor with known average weighted cross
section taken from[6] 𝑆𝐴𝐸𝑖 gamma counts area. 𝑁0 is target atoms, 𝜀, photo-peak efficiency of detector, ti,
the irradiation time, td, radioactive decay time, tc, counting time, < 𝜎𝑅 (𝐸𝑖 ) >, the average cross-sections F is
the cumulative correction factor due to target self-shielding and coincidence summing, and self-shielding.
Threshold energy of monitor reaction is different from the nuclides reaction threshold, it was therefore
necessary to calculate and multiply flux weighting factor with the flux value measured by using Eq. 1. The
same Eq.1 is manipulated to measure average nuclear reaction cross sections of the nuclides.
3.2
Calculation of average weighted cross section
By using TALYS-1.8/Empire-3.2.2 code and determination of quasi-mono energy neutron spectrum
using Geant4, the average weighted cross section is calculated by using Eq. 2.
3.3 Results
 x E  
E max

x
R
( Ei )  ( Ei )dE
Eth
E max
  ( E )dE
i
Eq. 2
Eth
Figure 1.a, Gamma line spectrum for all the interested nuclides,
Figure 1.b Average weighted cross sections for
109,115g,m
Cd
4 Conclusions
The flux weighted average photo-neutron cross-section for natCd(,xn)115m,115g,111m,109,107,105,104Cd and
nat
Cd(,pxn)113m+g,112,111g-110mAg reactions is measured with the bremsstrahlung end-point energies of 50-, and
60-MeV. The nuclear reaction model codes Talys 1.8, Empire 3.2.2 and simulation code GEANT4 were used
for photon flux and average cross section calculations. It is found that the cross sections remain almost same
in most of the studied nuclides in the discussed photon energy region.
5 Acknowledgment
The authors thank team of electron LINAC department at the Pohang Accelerating Laboratory (PAL),Korea,
for the excellent operation of the electron LINAC and facilitated for performing the experiment.
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