MeV Bremsstrahlung Research Articles

Quantifying motion blur by imaging shock front propagation with broadband and narrowband X-ray sources

Time-integrated radiography using MeV Bremsstrahlung X-ray sources is the norm for imaging during system-level testing of components and structures under dynamic condition. One source of error in the analysis of the time-integrated radiography data sets stems from motion blur which smears out sharp interfaces to a greater degree with longer exposure times, which become necessary to provide sufficient signal-to-noise with low X-ray penetration of objects of interest. To quantify motion blur, a 1D shock wave through PMMA was investigated experimentally at The Dynamic Compression Sector at The Advanced Photon Source (DCS@APS) with tapered broadband and 25.46 ± 1.06 keV narrowband X-rays. Four cameras with different exposure times were used for each experiment to compare the effect that exposure time has on motion blur. In addition, our methodology to accurately simulate motion blur in terms of transmission and shape is presented and compared to our experimental results and quantified. There is a high level of agreement between the experimental and simulation results across the range of data sets investigated in this study with a percent difference range of 0.29–1.31% for the four shots. The methodology of this work serves as a steppingstone towards a physically validated model that could be used in conjunction with experimental results to deconvolve physical parameters, densities, and interfaces of interest in a way that would not be possible with experimental results alone.

Photonuclear reactions on 59Co at bremsstrahlung end-point energies of 40–130 MeV* *Supported in part by the Ministry of Science and Higher Education of the Russian Federation (075-15-2021-1360), and by the project of the National Center for Physics and Mathematics (NCPM) No. 6 ''Nuclear and Radiation Physics,'' direction 6.5.1

Relative yields were measured in the 40−130 MeV bremsstrahlung induced reactions of 59Co. The experiments were performed with the beam from the electron linear accelerator LINAC-200 using the activation and off-line γ-ray spectrometric techniques. The bremsstrahlung photon flux was calculated with the Geant4 program. The cross sections were calculated by using the computer code TALYS-1.96 with different models and were found to be in good agreement with the experimental data.

Measurement of isomeric yield ratios of 119m,gTe in the 60 and 70 MeV bremsstrahlung induced reaction of natTe

The isomeric yield ratio i.e. the yield ratio of high to low spin state (IR=Yh/Yl) of 119m,gTe in the natTe(γ,xn) reaction at the bremsstrahlung end-point energies (Ee) of 60-, and 70-MeV were measured for the first time by using an off-line gamma-ray spectrometric technique. The bremsstrahlung energies were generated by impinging pulsed electron energies of 60-, and 70-MeV on a thin W-target at the Pohang Accelerator Laboratory. The present data at 60 and 70-MeV and similar literature data at other energies shows that the IR values of 119m,gTe increases sharply from 10 MeV to 18 MeV, which indicates the role of excitation energy. Thereafter it increases marginally due the opening of other reaction channels, which indicates the partition of excitation energy in different reaction channels.

Fundamental limitations of dual energy X-ray scanners for cargo content atomic number discrimination

To combat the risk of nuclear smuggling, radiography systems are deployed at ports to scan cargo containers for concealed illicit materials. Dual energy radiography systems enable a rough elemental analysis of cargo containers due to the Z-dependence of photon attenuation, allowing for improved material detection. This work studies the capabilities for atomic number discrimination using dual energy MeV systems by considering dual energy {6,4}MeV, {10,6}MeV, and {10,4}MeV bremsstrahlung beams. Results of this analysis show that two different pure materials can sometimes produce identical transparency measurements, leading to a fundamental ambiguity when differentiating between materials of different atomic numbers. Previous literature has observed this property, but the extent of the limitation is poorly understood and the cause of the degeneracy is generally inadequately explained. This non-uniqueness property stems from competition between photoelectric absorption and pair production and is present even in systems with perfect resolution and zero statistical noise. These findings are validated through Monte Carlo transparency simulations. Results of this study show that currently deployed commercial radiographic systems are fundamentally incapable of distinguishing between high-Z nuclear materials and miscellaneous mid-Z cargo contents.

Determination of the bremsstrahlung spectra by unfolding technique based on [formula omitted]Bi([formula omitted], xn) reactions

This work explores and describes the possibility of assessment of high energy bremsstrahlung spectrum, through the use of photonuclear reactions. Experimentally obtained values of saturation activities of various Bi isotopes, created by 209Bi(γ, xn) reactions in the 100 MeV bremsstrahlung beam were used in calculations. The photon spectrum is obtained by utilizing the unfolding techniques and cross sections data calculated by the TALYS 1.96 code. The experimental results were compared with the results obtained by Geant4 Monte Carlo simulation.

Predictors of radiation-induced skin reactions in patients with T-cell skin lymphomas after total skin irradiation: retrospective cohort study

INTRODUCTION: Skin reactions negatively affect a patient’s quality of life and may require radiation therapy premature interruption, what impairs illness control. Numerous agents determine tissue radiosensitivity, but demographic and lifestyle factors remain poorly understood. Those kind of patients herapeutic algorithm demands studies.OBJECTIVE: Radiation-induced skin reactions (RISR) formation and severity prognostic factors determination for primary malignant skin lymphomas patients.MATERIALS AND METHODS: 45 patients malignant T-cell skin lymphoma study, aged 38 to 82 years (29 mycosis fungoides patients, 2 lymphomatoid papulosis, 14 patients with primary anaplastic large cell skin lymphoma) received fast electrons total skin irradiation on the basis of the Federal State Institution «Russian Radiology and Surgical Technologies Scientific Center named after Academician A.M.Granov» of the Ministry of Health of the Russian Federation from 2012 to June 2022. Radiation therapy performed in the usual fractionation mode on linear electron accelerators Elekta Precise with 4–6 MeV bremsstrahlung total doses from 14 to 30 Gy (22±2.4 Gy). In order to identify the role of possible prognostic factors of skin toxicity — gender, age, body mass index (BMI), smoking status, lymphoma body surface area (BSA), the presence of concomitant diseases (diabetes mellitus and arterial hypertension) and previous chemotherapy.Statistics: Statistical analysis was performed using the IBM SPSS Statistics v. 26 program (developed by IBM Corporation). The value of p<0.05 was considered statistically significant. Verification of the sample belonging to the normal general population was carried out using the Shapiro–Wilk criterion. Spearman's rank correlation coefficient was used for correlation analysis. The regression parameters were estimated using the least squares method.RESULTS: The analysis revealed positive associations between the severity of RISR and predictor factors: BMI (r=0.799, p<0.01), smoking status (r=0.655, p<0.01), age (r=0.534, p<0.05), presence of diabetes mellitus (r=0.456, p<0.05), arterial hypertension (r=0.227, p<0.05), previous chemotherapy (r=0.422, p<0.01) and lymphoma body surface area (r=0.378, p<0.01). Severity of RISR scale value increase by those parameters. Negative links found between the severity of RISR and the total focal dose (SOD) of the beginning of their formation (r=–0.109, p<0.05).CONCLUSION: Formation and severity prognostic factors for the RCC upon fast electrons total skin exposure for patients with primary malignant T-cell skin lymphomas (mycosis fungoides, lymphomatoid papulosis, primary anaplastic large cell lymphoma of the skin) were identified.

Rhodotron and rotating target: A solution towards micro-spot for high energy and high dose rate bremsstrahlung sources

High energy over MeV bremsstrahlung sources that employ normal conducting radio frequency linear accelerators have expanding applications in industrial computerized tomography (CT) for non-destructive inspection and evaluation. The X-ray spot size that mainly affects the imaging quality is yet limited by the electron beam width in the high resolution CT systems. In a short exposure time, high beam power is required to generate sufficient photons to improve the signal to noise ratio of imaging. However, with ∼kW level of average beam power these linear accelerators usually have a beam spot size over 1 mm since the temperature rising due to the beam energy deposition in the target should be far below its melting point. We propose a concept of using a Rhodotron-based accelerator to provide high power electron beams in a long duration pulse and a rotating target to mitigate the overheating issue, such that the gap between micro-spot and high dose rate can be bridged in the high energy bremsstrahlung sources. This article presents an in-depth simulation work to discuss and evaluate this scheme of X-ray source. The simulations of beam dynamics in the accelerator and bremsstrahlung process in the target predict the generated X-rays with a spot size as small as 68 μm at full-width half-maximum and a dose rate as high as 4700 cGy/min from a 9 MeV electron beam interacting with a 1 mm thickness tantalum target. Further thermal analysis in the rotating target indicates a significant improvement of beam power handling in comparison with the conventional stationary one.

New measurements of cumulative photofission yields of 239Pu, 235U and 238U with a 17.5 MeV Bremsstrahlung photon beam and progress toward actinide differentiation

In the frame of a long-term research program on the characterization of large radioactive waste packages by photofission, the Nuclear Measurement Laboratory of CEA IRESNE has measured cumulative yields of 239Pu, 235U and 238U photofission products by using a Bremsstrahlung photon beam produced by a 17.5 MeV linear electron accelerator. A characterization of the energy of the Bremsstrahlung photon beam has been carried out by photon activation analysis with different samples of gold, nickel, uranium, zinc and zirconium. The contribution of neutron fission in the different samples has also been estimated by MCNP simulations in order to assess as precisely as possible the photofission yields. Finally, 26 cumulative photofission product yields are reported for 239Pu, 28 for 238U and 26 for 235U, with half-lives ranging from 14 min to more than 3 days, some of them being not recorded so far in the literature. Among these reported photofission product yields, 18 have been measured for all 3 actinides, which can thus be used for their discrimination. A differentiation criterion based on delayed gamma-ray ratios has been established to determine the most efficient photofission product couples to estimate the enrichment of a 235U/238U mixture or the fissile fraction (235U+239Pu)/actinide mass in a mixture of uranium and plutonium.

Activation cross section measurements and estimation of photon and neutron induced nuclear reactions for ytterbium isotopes with covariance analysis

The cross sections of the 168Yb(n,2n)167Yb, 174Yb(n,p)174Tm, 173Yb(n,p)173Tm, 174Yb(n,α)171Er, 170Yb(n,2n)169Yb and 176Yb(n,2n)175Yb nuclear reactions at 14.77 MeV neutron energy and the flux weighted average cross sections of the 168Yb(γ,n)167Yb, 170Yb(γ,n)169Yb and 176Yb(γ,n)175Yb nuclear reactions at 10 and 15 MeV bremsstrahlung endpoint energies are measured using offline gamma spectroscopy. The bremsstrahlung photon-induced reactions are reported for the first time at these energies. The results are compared with the evaluated nuclear data from the ENDF/B.-VIII.0, JEFF-3.3 and TENDL-2019 libraries. The theoretical model calculations are performed with the TALYS-1.95 nuclear code with parameters tuned to reproduce the measured data. The measured cross sections are in good agreement with the literature and evaluated data. The results are significant for the experimental nuclear database and reactor technology development.

Cholesteric liquid-crystalline DNA – a new type of chemical detector of ionizing radiation

ABSTRACT Liquid crystals (LCs) can be promising for detection of ionising radiation (IR). However, there is little information about their interaction with IR and there are no systemic studies of the dosimetric application of LCs. In this communication, we show for the first time the capabilities of a new type of radiation detector – cholesteric liquid-crystalline dispersion (CLCD) of DNA obtained using polyethylene glycol (PEG) and salt indued condensation. Irradiation of the DNA CLCD samples with 0–100 kGy of 7.6 MeV bremsstrahlung led to significant change in their circular dichroism (CD): ≈5% and ≈12% increase in the signal was observed at 10 and 20 kGy, while in the range of 20–90 kGy the CD signal decreased linearly. Thus, detectors based on DNA CLCD could be of interest for such application of IR as material modification or radiation sterilisation. At the same time irradiation can help to stabilise dispersion particles and can be used to prevent their sedimentation. Unirradiated samples degraded within 24 h after preparation, while the irradiated ones were able to maintain the intensity of CD signal for more than 168 h.Schematic representation of the dual effect of radiation exposure the DNA CLCD.

Measurements and estimation of cross sections of neutron and bremsstrahlung induced nuclear reactions for neodymium isotopes with covariance analysis

The cross sections of the nuclear reactions 142Nd(n,2n)141Nd, 148Nd(n,2n)147Nd, 150Nd(n,2n)149Nd, 142Nd(n,2n)141mNd and 146Nd(n,p)146Pr at 14.77 MeV neutron energy and the cross section of the 142Nd(γ,n)141Nd, 148Nd(γ,n)147Nd and 150Nd(γ,n)149Nd nuclear reaction at 10 and 15 MeV bremsstrahlung endpoint energies were measured using offline gamma spectroscopy. The photon-induced cross sections are reported for the first time at 10 MeV and 15 MeV bremsstrahlung endpoint energies. The uncertainties in the measured data were calculated using covariance analysis. The experimental results were compared with the previously reported EXFOR data and with the evaluated nuclear data libraries ENDF/B.-VIII.0, JEFF-3.3, JENDL-4.0, CENDL-3.2 and TENDL-2019. The theoretical nuclear model calculations were performed using the TALYS-1.95 code with default and optimized input parameters tuned to reproduce the present and literature data. The present data are in good agreement with other literature and evaluated data. The results are useful for the development of particle accelerators, reactors and the EXFOR database.

Compact spectroscopy of keV to MeV X-rays from a laser wakefield accelerator

We reconstruct spectra of secondary X-rays from a tunable 250–350 MeV laser wakefield electron accelerator from single-shot X-ray depth-energy measurements in a compact (7.5 × 7.5 × 15 cm), modular X-ray calorimeter made of alternating layers of absorbing materials and imaging plates. X-rays range from few-keV betatron to few-MeV inverse Compton to > 100 MeV bremsstrahlung emission, and are characterized both individually and in mixtures. Geant4 simulations of energy deposition of single-energy X-rays in the stack generate an energy-vs-depth response matrix for a given stack configuration. An iterative reconstruction algorithm based on analytic models of betatron, inverse Compton and bremsstrahlung photon energy distributions then unfolds X-ray spectra, typically within a minute. We discuss uncertainties, limitations and extensions of both measurement and reconstruction methods.

Radiation Inactivation of Coronavirus Infection Pathogen by the Example of Transmissible Gastroenteritis Virus.

In recent years, members of the Coronaviridae family have caused outbreaks of respiratory diseases (MERS, SARS, and COVID-19). At the same time, the potential of radiation-induced inactivation of this group of viruses have been little studied, although radiation technologies can be widely used both in the processing of personal protective equipment and in the sterilization of vaccines. In the present work, the effect of 10 MeV electron beams and 7.6 MeV bremsstrahlung on the coronavirus infection pathogen (transmissible gastroenteritis virus) has been studied in vitro. In the given experimental conditions, irradiation with photons turned out to be more effective. The virus-containing suspension frozen at –86°C was the most resistant to radiation: the dose required for complete inactivation of the virus in this case was from 15 kGy, while for the liquid suspension and lyophilized form the sterilizing dose was from 10 kGy. At lower radiation doses for all samples during passaging in cell culture, residual infectious activity of the virus was observed. These differences in the efficiency of inactivation of liquid and frozen virus-containing samples indicate a significant contribution of the direct effect of radiation.

Measurement of cumulative photofission yields of 235U and 238U with a 16 MeV Bremsstrahlung photon beam

In the frame of a long-term research program on the characterization of large radioactive waste packages by photofission, the Nuclear Measurement Laboratory of CEA IRESNE, France, has measured cumulative photofission yields of 235U and 238U short-lived and long-lived fission products by using a Bremsstrahlung photon beam produced by a 16 MeV electron linear accelerator (LINAC). To this aim, a characterization of the Bremsstrahlung photon beam has been carried out by photon activation analysis with different samples of gold, nickel, uranium and zirconium. The residual neutron flux exiting the LINAC head (lead collimator, borated polyethylene and cadmium shield) has also been characterized by neutron activation analysis with indium samples to estimate the contribution of photoneutron fissions in the uranium samples used to assess the photofission yields. Finally, 49 fission product yields are reported for 238U and 26 for 235U, with half-lives ranging from 64 s to more than 3 days, some of them not recorded so far in the literature Some photofission products cumulative yields show significant differences between 235U and 238U, which confirms the possibility of an isotopic discrimination method based on delayed gamma-ray ratios analysis for radioactive waste characterization.

The flux weighted cross sections of 179Hf(γ,γ’)179mHf and natHf(γ,x)179mHf reactions at 8 MeV and 15 MeV bremsstrahlung end point energies

For the hafnium element, the cross sections of 179Hf(γ,γ′)179mHf and natHf(γ,x)179mHf reactions were measured at 8 MeV and 15 MeV bremsstrahlung end point energies respectively using activation method and off-line gamma-ray spectroscopy. The bremsstrahlung radiation spectra were generated by bombarding a 0.1 mm tungsten target with 8 MeV and 15 MeV electrons at 5 μA beam current and also theoretically simulated by GEANT4 computer code. The flux weighted average cross sections of 179Hf (γ,γ′)179mHf and natHf(γ,x)179mHf reactions were measured by using 115In(γ,γ’)115mIn and 197Au(γ,n)196Au as flux monitor reactions at 8 MeV and 15 MeV bremsstrahlung radiation respectively. The measured cross sections are found close to the corresponding theoretical cross sections estimated by TALYS 1.95 and TENDL 2019 computer codes. These hafnium cross sections at 8 MeV and 15 MeV bremsstrahlung radiation will be new additions to the EXFOR library, as so far not reported in literature.

High-current laser-driven beams of relativistic electrons for high energy density research

We report on enhanced laser driven electron beam generation in the multi MeV energy range that promises a tremendous increase of the diagnostic potential of high energy sub-PW and PW-class laser systems. In the experiment, an intense sub-picosecond laser pulse of ∼1019 Wcm−2 intensity propagates through a plasma of near critical electron density (NCD) and drives the direct laser acceleration (DLA) of plasma electrons. Low-density polymer foams were used for the production of hydrodynamically stable long-scale NCD-plasmas. Measurements show that relativistic electrons generated in the DLA-process propagate within a half angle of 2 ± 1° to the laser axis. Inside this divergence cone, an effective electron temperature of 10–13 MeV and a maximum of the electron energy of 100 MeV were reached. The high laser energy conversion efficiency into electrons with energies above 2 MeV achieved 23% with a total charge approaching 1 μC. For application purposes, we used the nuclear activation method to characterize the MeV bremsstrahlung spectrum produced in the interaction of the high-current relativistic electrons with high-Z samples and measured top yields of gamma-driven nuclear reactions. The optimization of the high-Z target geometry predicts an ultra-high MeV photon number of ∼1012 per shot at moderate relativistic laser intensity of 1019 Wcm−2. A good agreement between the experimental data and the results of the 3D-PIC and GEANT4-simulations was demonstrated.

Production of Zirconium-89 by photonuclear reactions

The study provides an alternative method of producing the medically interesting 89Zr isotope by using 55 MeV bremsstrahlung irradiation of natural niobium and natural molybdenum samples. The yields of the natNb((γ,4n)+(γ,p3n))89Nb−89Zr, 92Mo((γ,3n)+(γ,p2n))89Nb−89Zr and 94Mo(γ,αn) 89Zr reactions were obtained as a result of the research. It was estimated that after irradiation of 1 g of natural niobium target with a current of 1 μA for the duration of 1 h 300 kBq of 89Zr was formed.

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.

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.

Simulations of hard X-ray generation by hot electrons in a silver target

A semi-analytical model is developed for the generation of X-ray bremsstrahlung in metallic targets with the inclusion of hot electron recirculation (refluxing). The hard bremsstrahlung and characteristic X-ray yields are calculated in relation to the thickness of a silver target for an s-polarised subpicosecond laser pulse intensity of 2 × 1019 W cm–2. The effect of hot electron recirculation in thin foils is shown to significantly improve the Kα radiation and bremsstrahlung yields in a photon energy of 10 – 100 keV. By contrast, the 0.1 – 1 MeV bremsstrahlung photon yield from thin foils with hot electron recirculation corresponds approximately to the highest photon yield from those targets in which recirculation is insignificant. We make a comparative analysis of the highest laser-to-X-ray energy conversion efficiencies obtained to date.