Bremsstrahlung Energy Research Articles

Measurement of yield ratios for the isomeric pair 137m,gCe in the 141Pr(γ,x)137m,gCe reactions with bremsstrahlung end-point energies of 50-, 60-, and 70-MeV

We have measured the yield ratio of the high spin state to the low spin state of the isomeric pair 137m,gCe produced in the 141Pr(γ,x)137m,gCe reaction. The experiments were performed by irradiating three praseodymium foils with bremsstrahlung end-point energies of 50-, 60-, and 70-MeV. The induced activities of the 137mCe and 137gCe were measured by means of γ-ray spectroscopy. The γ-ray interference and the contributions of other radioisotopes to the measured activity of both the 137mCe and 137gCe were investigated and corrected. The obtained results are compared with the theoretical predictions using the computer code TALYS 1.8. The present results for the 141Pr(γ,x)137m,gCe reaction were determined for the first time.

CROSS-SECTIONS FOR PHOTONUCLEAR REACTIONS 93Nb(γ,n)92mNb AND 93Nb(γ,n)92tNb IN THE END-POINT BREMSSTRAHLUNG ENERGIES 36...91 MeV

The flux-weighted averaged over the energy range of bremsstrahlung spectrum from reaction threshold up to the maximum energy of γ-ray cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb photonuclear reactions were determined by the gamma-activation method within the end-point bremsstrahlung energies Еmax = 36…91 MeV. Activation of 93Nb targets has been done by a bremsstrahlung flux using an electron beam at the linear accelerator LUE-40 at RDC "Accelerator" NSC KIPT. The γ-ray spectra of irradiated targets were registered using the HPGe detector with an energy resolution of 1.8 keV for the 1332 keV line 60Co. To control the bremsstrahlung flux we used natMo witness-targets and a reaction cross-section of 100Mo(γ,n)99Mo. Obtained experimental cross-sections <σ(E)> of the studied reactions are in good agreement with the theoretical values calculated within TALYS 1.9 code and the results of other authors. The averaged cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb reactions in the energy range 35...45 MeV and > 70 MeV were obtained for the first time.

Excitation of 177,178Lu in reactions with bremsstrahlung with escaping of charged particles

Isomeric yields ratio and flux-weighted average cross-sections of 177Lum,g in (γ,α)- and 178Lum,g in (γ,pn)-reactions were determined for the first time for the bremsstrahlung end-point energies of 37 and 55 MeV, properly by activation and off-line γ-ray spectrometric technique. The results of modeling in the framework of the EMPIRE-3.2 code demonstrate the dominance of non-statistical processes.

Energy window optimization for Y-90 Bremsstrahlung SPECT imaging: A Monte Carlo simulation study

Introduction: In Y-90 imaging, image quality is highly dependent on choosing the energy window and collimator design because, the Y-90 bremsstrahlung photons have a continuous and broad energy distribution. The aim of this work was to optimize the bremsstrahlung energy window setting and collimator to improve both resolution and sensitivity. Materials and methods: We simulate the Siemens Medical System Symbia using the SIMulation of Imaging Nuclear Detectors (SIMIND) Monte Carlo program. The SIMIND was used to generate the Y-90 bremsstrahlung Single Photon Emission Computed Tomography (SPECT) projection of the point source. In order to assess the effect of the energy window on the resolution, six energy windows settings and two collimators denoted Medium Energy (ME) and High Energy (HE) were used. Results: The experimental measurement and simulation results exhibited a similar pattern in point spread functions (PSFs) with energy window. The simulation data show that, the geometric component reaches 73% for 51-120 keV energy window with HE collimator. In addition, the results showed that, the Full Width at Half Maximum (FWHM) and Full Width at Tenth Maximum (FWTM) (FWHM =7 mm + FWTM =35mm) was better in this window relative to other window. Conclusion: The optimal energy window for Y-90 bremsstrahlung SPECT imaging was 51- 120 keV. The obtained optimal energy window and optimal HE collimator has the potential to improve the image resolution and sensitivity of Y-90 SPECT images.

Measurement of natNi(γ, xn)57,56Ni and natNi(γ, pxn)58−55Co reaction cross sections in bremsstrahlung with end-point energies of 65 and 75 MeV

The cross sections of natNi(γ, xn)57,56Ni and natNi(γ, pxn)58−55Co reactions induced by bremsstrahlung end-point energies of 65 and 75 MeV were measured by using the method of activation along with off-line γ-ray spectrometric technique. The natNi(γ, xn)57,56Ni and natNi(γ, pxn)58−55Co reaction cross sections as a function of photon energy were also calculated by using TALYS 1.9 code. The flux-weighted average values at different end-point energies were obtained from the literature data, as well as from the theoretical values of TALYS and TENDL-2017 data library based on mono-energetic photons. Those were compared with the experimental data of present work and found to be in general agreement. It was also found that the experimental and theoretical cross-sections data increase with bremsstrahlung energy up to a certain value. After that the individual reaction cross sections slightly decrease with the increase of bremsstrahlung energy due to the opening of other reactions. As an example, the natNi(γ, xn)57Ni reaction cross section decreases when the natNi(γ, xn)56Ni reaction opens up. Similarly, the natNi(γ, pxn)58Co reaction cross section decreases when natNi(γ, pxn)57Co reaction opens up and so on. These observations indicate the role of excitation energy and its portion in different reaction channels.

Integrated Cross Sections of the Photo-Neutron Reactions Induced on \(^{197}\)Au with 60 \(\text{MeV}\) Bremsstrahlung

Abstract. Seven photo-neutron reactions 197Au(γ,xn)197-xAu (with x=1-7) produced by the bremsstrahlung end-point energy of 60 MeV were identified. In this work, we focus on the measurement of integrated sections. Experiments were carried out based on the activation method in combination with off-line gamma-ray spectrometric technique. The integrated cross sections of the investigated reactions were determined relative to that of the monitoring reaction 197Au(γ,n)196Au. To validate the experimental results, theoretical predictions were also made using the computer code TALYS 1.9. The current integrated cross-sections of the 197Au(γ,xn)197-xAu reactions with 60 MeV bremsstrahlung end point energy are measured for the first time.

A conceptual design study of a Compact Photon Source (CPS) for Jefferson Lab

This document describes the technical design concept of a compact high intensity, multi-GeV photon source. Capable of producing 1012 equivalent photons per second this novel device will provide unprecedented access to physics processes with very small scattering probabilities such as hard exclusive reactions on the nucleon. When combined with dynamic nuclear polarized targets, its deployment will result in a large gain in polarized experiment figure-of-merit compared to all previous measurements. Compared to a traditional bremsstrahlung photon source the proposed concept presents several advantages, most significantly in providing a full intensity in a small spot at the target and in taking advantage of the narrow angular spread associated with high energy bremsstrahlung compared to the wide angular distribution of the secondary radiation to minimize the operational prompt and activation radiation dose rates.

Double-layer targets for forming the beams of the high-energy photons on the electron accelerator of M-30 microtron

Purpose. The bremsstrahlung received at electron accelerators is widely used to study the characteristics of photonuclear reactions and to solve a wide spectrum (series) of applied problems. Basically the output of bremsstrahlung depends on the electron energy, the material of the target converter (Ta) and its effective thickness. The optimum thickness of the converter (when the output of the bremsstrahlung is at its maximum) is significantly less than the electron path in it. This is the reason for the presence of high-energy electrons in bremsstrahlung. Therefore, there is a need to clean the bremsstrahlung beams from residual electrons. The aim of the work is to experimentally determine the optimal parameters (thicknesses) of double-layer targets for obtaining separated bremsstrahlung beams for an energy range of 6.5 – 17.75 MeV in electron accelerator M-30 microtron. Methods. Experimental studies of the relative absorption coefficient of electrons in the investigated materials (C (reactor graphite), Al, Ta) were carried out on the M-30 microtron using the transmission method. The measurements of the outputs of the electrons from the accelerator and the residuals that have passed through the layer of absorbing material were carried out using a pass-through chamber and a Faraday cup, respectively. Studies of the absorption of high-energy photons by single-layer targets (C (20 mm), Al (20 mm)) using activation detectors have been carried out. Results. The electron absorption coefficients in single- (C (7 – 46 mm), Al (8 – 48 mm), Ta (0.1 – 1 mm)) and in double-layer targets (Ta (1 mm) + C (7 – 39 mm) and Ta (1 mm) + Al (8 – 40 mm)) were measured for the electron energy 6.5 – 17.75 MeV. The values of the total electron absorption thickness for C, Al, and Ta are in good agreement with the calculated values of the practical electron path (database «ESTAR») for the indicated energy range. The experimentally established values of the thicknesses of materials (C and Al at a thickness of Ta – 1 mm) of doublelayer targets, which ensure the complete absorption of electrons for the indicated energy range. The absorption of high-energy photons by single-layer targets (C (20 mm), Al (20 mm)) for bremsstrahlung energy of 17.5 MeV was evaluated. Conclusions. The optimal parameters (thicknesses) of double-layer targets (Ta (1mm) + C (20 mm) and Ta (1 mm) + Al (20 mm)) or (Ta (1mm) + C (39 mm) and Ta (1 mm) + Al (32 mm)) were established experimentally to form the separated bremsstrahlung beams in the electron accelerator – M-30 microtron for energy region 6.5 ч 17.75 MeV. The use of two-layer targets allows us to carry out procedures to form of high-energy photon beams with the parameters necessary for performing specific experimental studies on electronic accelerators, which will increase the accuracy and reliability of the results.

Photo-neutron reaction cross-sections of 59Co in the bremsstrahlung end-point energies of 65 and 75 MeV

The flux-weighted average cross-sections for the 59Co($ \gamma$, xn)58-55Co reactions have been measured with the bremsstrahlung end-point energies of 65 and 75 MeV by using the activation method in combination with the off-line $ \gamma$-ray spectrometry. The measured cross-sections for the $ (\gamma,\mathrm{n})$, $ (\gamma,2\mathrm{n})$, $ (\gamma,3\mathrm{n})$ and $ (\gamma,4\mathrm{n})$ reactions of 59Co at 65 MeV are $ 15.828\pm 0.491$, $ 5.003\pm 0.206$ , $ 0.408\pm 0.047$ and $ 0.039\pm 0.008$ mb, whereas at 75 MeV are $ 15.653\pm 0.361$, 4.965±0.289, $ 0.389\pm 0.062$ and $ 0.036\pm 0.007$ mb, respectively. The 59Co($ \gamma$, xn) reaction cross-sections as a function of photon energy were also theoretically simulated by using TALYS 1.9 code. Then the flux-weighted average cross-sections at different bremsstrahlung energies were obtained from the theoretical values and the literature data at lower energy based on mono-energetic photons. The present data are measured for the first time and are found to be in good agreement with the theoretical flux-weighted average values. It was found that the 59Co($ \gamma$, xn)58-55Co reaction cross-sections increase from their threshold values to a certain bremsstrahlung energy. After a certain energy, the individual 59Co($ \gamma$, xn) reaction cross-sections decrease with the increase of bremsstrahlung energy due to opening of other reaction channels. These two observations indicate the role of excitation energy and its partition in different reaction channels. All the four cobalt isotopes produced from the 59Co($ \gamma$, xn) reactions have medical and other applications.

Converter optimization for photonuclear production of Mo-99

We used Monte Carlo simulations to study optimal configuration of bremsstrahlung converter for photonuclear production of 99Mo. To account for details of bremsstrahlung photons production and energy dependency of photonuclear reaction cross section we introduced a new metric – the effective bremsstrahlung efficiency criterion. Monte Carlo simulations using PHITS transport code showed that converter optimization using this criterion allows to achieve 2–2.8% increase in 99Mo production in a thick radioisotope producing target.

Flux-weighted average cross sections of medical isotopes in the 127I(γ,xn) reactions with the bremsstrahlung end-point energies of 50 and 70MeV

The flux-weighted average cross sections of 127I(γ,xn)126,124,123I reactions were experimentally determined with the bremsstrahlung end-point energies of 50 and 70 MeV by activation and off-line γ-ray spectrometric technique, using the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The 127I(γ,xn)126−121I reaction cross sections as a function of photon energy were theoretically calculated using the TALYS 1.8 code. The flux-weighted average cross sections of 127I(γ, xn)126,124,123I reactions as a function of bremsstrahlung end-point energies were also obtained from the literature and TALYS data based on mono-energetic photons and are found to be in close agreement with the present data. The experimental and theoretical 127I(γ, xn)126−121I reaction cross-sections increase with bremsstrahlung energy, which indicates the role of excitation energy. After a certain energy, the individual 127I(γ, xn)126−121I reaction cross sections decrease with increase of bremsstrahlung energy due to opening of other reactions, which indicates sharing of energy in different reaction channels. The radioactive iodine isotopes production cross-sections are important for the useful medical purpose.

Isomeric yield ratios of 195m,gHg and 197m,gHg in the 196Hg(γ, n) and 198Hg(γ, n) reactions induced by bremsstrahlung energy within giant dipole resonance region

We have measured the isomeric ratios of isomeric pairs 195m,gHg and 197m,gHg produced in 196Hg(γ, n)195m,gHg and 198Hg(γ, n)197m,gHg reactions within the giant dipole resonance (GDR) region by the activation method. In order to improve the accuracy of the experimental results, the necessary corrections were made in the gamma activity measurements and data analysis. The results were analyzed, discussed and compared with the similar data from literature to examine the role of excitation energy, nucleon configuration and the reaction channel effects in the isomeric ratios. The isomeric ratios from 18 to 24 MeV for 197m,gHg and from 14 to 24 MeV for 195m,gHg are the first time measurements.

Excitation of 179Hfm2 with (γ,n)-reaction

Isomeric yields ratio, the integral and flux-weighted average cross-sections of 179m2Hf population were determined for the first time in (γ,n)-reaction for the bremsstrahlung end-point energies of 14.5 and 14.8 MeV by activation and off-line γ-ray spectrometric technique. The results of modeling in the framework of the TALYS-1.6 and EMPIRE-3.2 codes demonstrate the dominance of non-statistical processes.

Measurement of half-lives for 87m,gY and 196m,g,194Au produced from the photon and neutron induced reactions of 89Y and 197Au

We have measured the half-lives of 87mY and 87gY produced from the 89Y(γ, 2n) and 89Y(n, 3n) reactions with the bremsstrahlung end-point energy of 65 MeV and the average neutron energy of 37.2 MeV using an activation and an off-line γ-ray spectrometric technique, respectively. The bremsstrahlung photon was produced by using the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL), whereas the fast neutron was produced from the 9Be(p, n) reaction by using the 45 MeV proton of the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). We have also measured the half-lives of 194Au and 196m2,gAu produced from the 197Au(γ, xn; x = 1, 3) and 197Au(n, xn; x = 2, 4) reactions with the bremsstrahlung end-point energy of 60 MeV and the average neutron energy of 37.2 MeV using the same technique and the same facilities as mentioned above. The induced γ-ray activities of the irradiated samples were measured by using an energy- and efficiency calibrated high purity germanium (HPGe) detector. The spectrum analysis has been done by using the ROOT software to separate signals from background. The measured half-lives are compared with the literature values and are in general agreement with each other within the uncertainties.

Исследование потока тормозных фотонов и нейтронов при работе медицинского ускорителя электронов

Purpose: To estimate the contribution of the secondary neutron flux to the total radiation flux during the operation of Trilogy linear medical accelerator and Varian’s Clinac 2100 accelerator for assessment of impact on the health of patients and medical personnel. 
 High-energy linear accelerators operating at energies higher than 8 MeV generate neutron fluxes when interacting with accelerator elements and with structural materials of the room for treating patients. Neutrons can form at the accelerator head (target, collimators, smoothing filter, etc.), the procedure room, and directly in the patient’s body.
 Because of the high radiobiological hazard of neutron radiation, its contribution to the total beam flux, even at a level of few percent, substantially increases the dose received by the patient.
 Material and methods: Secondary neutron fluxes were investigated during the process of the linear medical accelerators Trilogy and Clinac 2100 of Varian operation by the photoactivation method using (γ, n) and (n, γ) reactions on the detection target of natural 181Ta. In addition, measurements of neutron spectra were carried out directly in the room during the operation of a medical accelerator using a spectrometer-dosimeter SDMF-1608.
 Results: It was determined that the neutron flux on the tantalum target is 16 % of the gamma-ray flux on the same target when the accelerator is operated with a 18 MeV bremsstrahlung energy and 5 % when the accelerator is operated with a 20 MeV excluding thermal neutrons.
 Conclusion: Finally, it may be noted that, taking into account the coefficient of relative biological efficiency (RBE) of neutron radiation for neutrons with energies of 0.1–200 keV equal to 10 compared with the RBE coefficient for gamma quanta (equal to 1), even preliminary analysis demonstrates significant underestimation of the contribution of neutrons dose to the total dose received by the patient in radiation therapy using bremsstrahlung of 18 and 20 MeV.

Double-layer targets for forming the beams of the high-energy photons on the electron accelerator of M-30 microtron

Purpose. The bremsstrahlung received at electron accelerators is widely used to study the characteristics of photonuclear reactions and to solve a wide spectrum (series) of applied problems. Basically the output of bremsstrahlung depends on the electron energy, the material of the target converter (Ta) and its effective thickness. The optimum thickness of the converter (when the output of the bremsstrahlung is at its maximum) is significantly less than the electron path in it. This is the reason for the presence of high-energy electrons in bremsstrahlung. Therefore, there is a need to clean the bremsstrahlung beams from residual electrons. The aim of the work is to experimentally determine the optimal parameters (thicknesses) of double-layer targets for obtaining separated bremsstrahlung beams for an energy range of 6.5 ÷ 17.75 MeV in electron accelerator M-30 microtron. Methods. Experimental studies of the relative absorption coefficient of electrons in the investigated materials (C (reactor graphite), Al, Ta) were carried out on the M-30 microtron using the transmission method. The measurements of the outputs of the electrons from the accelerator and the residuals that have passed through the layer of absorbing material were carried out using a pass-through chamber and a Faraday cup, respectively. Studies of the absorption of high-energy photons by single-layer targets (C (20 mm), Al (20 mm)) using activation detectors have been carried out. Results. The electron absorption coefficients in single- (C (7 ÷ 46 mm), Al (8 ÷ 48 mm), Ta (0.1 ÷ 1 mm)) and in double-layer targets (Ta (1 mm) + C (7 ÷ 39 mm) and Ta (1 mm) + Al (8 ÷ 40 mm)) were measured for the electron energy 6.5 ÷ 17.75 MeV. The values of the total electron absorption thickness for C, Al, and Ta are in good agreement with the calculated values of the practical electron path (database «ESTAR») for the indicated energy range. The experimentally established values of the thicknesses of materials (C and Al at a thickness of Ta – 1 mm) of doublelayer targets, which ensure the complete absorption of electrons for the indicated energy range. The absorption of high-energy photons by single-layer targets (C (20 mm), Al (20 mm)) for bremsstrahlung energy of 17.5 MeV was evaluated. Conclusions. The optimal parameters (thicknesses) of double-layer targets (Ta (1mm) + C (20 mm) and Ta (1 mm) + Al (20 mm)) or (Ta (1mm) + C (39 mm) and Ta (1 mm) + Al (32 mm)) were established experimentally to form the separated bremsstrahlung beams in the electron accelerator – M-30 microtron for energy region 6.5 ÷ 17.75 MeV. The use of two-layer targets allows us to carry out procedures to form of high-energy photon beams with the parameters necessary for performing specific experimental studies on electronic accelerators, which will increase the accuracy and reliability of the results

Population cross-section of 179m2Hf from the reactions on hafnium and tantalum targets

The integral and flux-weighted average cross-sections of the 180Hf(γ,n)179m2Hf and 181Ta(γ,pn(d))179m2Hf reactions for the bremsstrahlung end-point energy of 37 MeV were determned by activation and off-line γ-ray spectrometric technique. Also by this techinque, the cross-section of the 178Hf(nr,γ)179m2Hf reaction was determined for reactor neutrons.

Photon activation analysis of sand samples from Antalya in Turkey with a clinical electron linear accelerator

Abstract The purpose of this study is to demonstrate the feasibility of elemental analysis of sand samples by photon activation induced by high energy bremsstrahlung photons at an end point energy of 18 MeV from a clinical electron linear accelerator. The γ-ray spectra of the activated samples were collected using a high resolution spectrometer. Qualitative analysis of major and trace components of the samples (12 in total) was carried out whilst the spectra of eight of the samples were evaluated quantitatively. The contents of elements obtained by photon activation analysis were compared with values obtained by X-ray fluorescence.

Ytterbium ( $\gamma$ γ , n) average cross-sections data near to photodisintegration reaction threshold

The thick foils activation technique has been applied to estimate the average cross-sections of 168,170,176Yb $(\gamma, \mathrm{n})$ reaction near to photodisintegration threshold. The $(\gamma, \mathrm{n})$ cross-sections are derived using the integrated photon flux at any energy range from the reaction threshold to the bremsstrahlung end-point energy. The photon flux is estimated using a calibration photodisintegration set of foils and taking in advance the spectrum linearity at high energies. The p-nuclei 168Yb average cross-section is $ 106 \pm 21$ mb corresponding to $E_{\mathrm{mean}} = 10$ MeV. The 170Yb average cross section is $ 117 \pm 31$ mb matching $ E_{\mathrm{mean}} = 9$ MeV while the 176Yb one is $ 123 \pm 36$ mb corresponding to $ E_{\mathrm{mean}} = 8$ MeV. The experimental results associate to statistical model simulations performed by the TALYS code. The simulated data of 168Yb ranges 83–139 mb, while 170Yb and 176Yb vary between 89–152 and 84–170mb; which agree with the measurements within uncertainties. The simulated average cross-section of natYb $(\gamma, \mathrm{n})$ reaction is $ 127 \pm 25$ mb corresponding to energy ranges 6.6-14 MeV. The simulation results based on Lorentzian $ \gamma$ -strength considerations with the density level of Fermi gas plus the constant temperature model are closest to the average cross-sections measured.

Flux weighted average cross-sections of natNi(γ, x) reactions with the bremsstrahlung end-point energies of 55, 59, 61 and 65 MeV

We measured the flux weighted average cross-sections of the natNi(γ,xn)56,57Ni and natNi(γ, pxn)55,56,57,58Co reactions with the bremsstrahlung end-point energies of 55, 59, 61 and 65 MeV by using an activation cum off-line γ-ray spectrometric technique at the Pohang Accelerator Laboratory (PAL), Korea. The natNi(γ, xn) and natNi(γ, pxn) reaction cross-sections as a function of monoenergetic photon were calculated theoretically by using the computer code TALYS-1.8. The flux-weighted average cross-sections of the natNi(γ, xn) and natNi(γ, pxn) reactions from the present work were compared with the similar data from the literature as well as the theoretical values from the TALYS-1.8 code and the TENDL-2015 data library. Both the experimental and theoretical values increase sharply from the reaction threshold to a maximum value where the next reaction channel opens. After the maximum value, individual reaction cross section decreases slowly with increase of bremsstrahlung end-point energy, which may be due to the opening of other possible reaction channels.