Energy Gamma Research Articles

Development of an ion exchange resin for gadolinium-loaded water

Large water Cherenkov detectors have been successfully used for decades in high- and low-energy particle physics. Nevertheless, detecting neutrons remains a challenge for such detectors since a neutron capture on a hydrogen atom doesn't release a sufficient amount of gamma energy to be observed efficiently. The use of gadolinium in the form of soluble salts has been explored extensively to remedy this issue, as gadolinium exhibits both a very large neutron capture cross section and a subsequent high-energy gamma cascade. However, in order for large gadolinium-loaded detectors to operate stably over long time periods, water optical transparency must be maintained by in situ purification. New methods have been developed involving band-pass molecular filtering. While these methods are very successful, they are expensive and consume considerable power and space as they seek to minimize loss of gadolinium while removing other impurities. For smaller detectors where some gadolinium loss can be tolerated, a less expensive way to do this is very desirable. In this paper, we describe the design, development and testing of a system used to purify the gadolinium-loaded water in the 26-ton ANNIE neutrino detector.

Monte Carlo simulation of a NaI(Tl) detector efficiency

In radiation physics and dosimetry it is important to obtain an accurate analytical result for the measurements. This could be possible by controlling of some parameters of the experimental system. The detection efficiency is one of the most important parameter and it should be known in radiation measurements.In this study, the detection efficiency of a 3″ × 3″ NaI(Tl) scintillation detector has been simulated by FLUKA code for 6 different gamma ray energies at 1, 1.5, 2, 3, 5, 9, 15 cm source to detector distance. The simulated results were compared with the measurements done at 511, 662, 835, 1173, 1275, and 1332 keV gamma energies.

X-Ray-Based Irradiation of Larvae and Pupae of the Navel Orangeworm (Lepidoptera: Pyralidae).

The suitability of adult male the navel orangeworm, Amyelois transitella (Walker) for Sterile Insect Technique (SIT) has been reported for both high energy gamma (>1 MeV) and low energy x-ray (90 keV) sterilization. However, research regarding sterilization of NOW larvae and pupae by gamma irradiation indicated nonsuitability due to high mortality. Here, NOW larvae and pupae were irradiated to doses up to 50 Gy with 90 keV x-rays, then paired with nonirradiated colony mates. Sterility of surviving insects was determined by the presence or absence of hatched neonates. While presence of offspring does not guarantee viability, the absence does guarantee sterility (as is appropriate for SIT) and was thus the measure used here. Early stage larvae experienced 77% mortality at a dose of 30 Gy, versus 20% for nonirradiated control. At 40 Gy, mortality reached 98%. Of surviving early stage larvae at 30 Gy, 29% of moth pairs produced offspring. For late stage larvae, no offspring were produced at 40 Gy, but mortality was 73%. For pupae, mortality reached 53% at 30 Gy with 13% still producing neonates, while mortality reached 98% at 40 Gy. These results are consistent with reported results for gamma irradiation of NOW larvae where sterility was observed somewhere between the 30 Gy and 60 Gy data points, but mortality was high. This further confirms the lack of suitability of NOW irradiated in the larval stage, whether by gamma or x-ray, and supports the hypothesis that x-ray and gamma treatments are biologically equivalent at equal doses.

An investigation of gamma ray mass attenuation from 80.1 to 834.86 keV for fabric coating pastes used in textile sector

In the present study, we investigate several textile coating pastes used in the market based on their radiation protection capability for gamma rays. The gamma ray mass absorption coefficients of some coating pastes doped with antimony, boron and silver elements have been investigated. It has been determined that the gamma ray mass attenuation coefficient decreases rapidly as the energy of the gamma rays increases. It was determined that the doping of the main printing paste with silver and antimony considerably increased the gamma ray absorption capability of main paste. However, the doping of the paste with boron reduces the mass absorption of gamma rays. In particular, the gamma ray mass absorption power of the main paste doped with silver and antimony was determined to be useful in the gamma energy range from 80 to 140 keV. This indicates that the newly doped textile material may be considered for radiation protection in the case of low-energy gamma rays .

Preliminary Empirical study of the Rayleigh to Compton scattering ratio for elements at gamma energy 59.5 keV using Si(Li) detector

The characteristic parameters of a material relation to photon interactions such as: mass attenuation coefficient, effective atomic number, effective electron density are required to provide essential data in diverse works such as nuclear diagnostic and cancer radiotherapy, industrial irradiation, radiation dosimetry, radiation protection and shielding, analyzing of the concentration of elements and radioactive isotopes. In this paper, the theoretical models such as non-relativistic form factor (NRFF), relativistic form factor (RFF), and modified form factor (MFF) were used to calculate the ratio Rayleigh-Compton for elements with at gamma energy 59.5 keV. The results showed that there was a discrepancy between the theoretical modes at a high atomic number. The mean value of the Rayleigh-Compton ratio depends on the atomic number, which shows the quadratic function of the correlation coefficient R2 = 0.996 as well. Besides, the experimental system was set-up and measured for some targets such as aluminum, copper, and lead at a scattering angle 150o using 241Am source by Si(Li) detector to confirm the theoretical values. The preliminary result showed that there was a good agreement with experimental and theoretical results is lower than 20%. Further investigation will be measured by the samples for more detailed evaluation.

Prompt gamma spectroscopy for absolute range verification of 12C ions at synchrotron-based facilities

The physical range uncertainty limits the exploitation of the full potential of charged particle therapy. In this work, we face this issue aiming to measure the absolute Bragg peak position in the target. We investigate p, 4He, 12C and 16O beams accelerated at the Heidelberg Ion-Beam Therapy Center. The residual range of the primary 12C ions is correlated to the energy spectrum of the prompt gamma radiation. The prompt gamma spectroscopy method was demonstrated for proton beams accelerated by cyclotrons and is developed here for the first time for heavier ions accelerated by a synchrotron. We develop a detector system that includes (i) a spectroscopic unit based on cerium(III) bromide and bismuth germanium oxide scintillating crystals, (ii) a beam trigger based on an array of scintillating fibers and (iii) a data acquisition system based on a FlashADC. We test the system in two different scenarios. In the first series of experiments, we detect and identify 19 independent spectral lines over a wide gamma energy spectrum in the presence of the four ion species for different targets, including a water target with a titanium insert. In the second series of experiments, we introduce a collimator aiming to relate the spectral information to the range of the primary particles. We perform extensive measurements for a 12C beam and demonstrate submillimetric precision for the measurement of its Bragg peak position in the experimental setup. The features of the energy and time spectra for gamma radiation induced by p, 4He and 16O are investigated upstream and downstream from the Bragg peak position. We conclude the analysis by extrapolating the required future developments, which would be needed to achieve range verification with a 2 mm accuracy during a single fraction delivery of physical dose.

Hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling theory of gravity

In this work we analyze hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. We begin with the derivation of the hydrostatic equilibrium equations for the f(R, L) gravity theory, where R and L are the Ricci scalar and Lagrangian of matter, respectively. We assume f(R,L)=R/2+[1+sigma R]L, with sigma constant. To describe matter inside neutron stars we assume a relativistic polytropic equation of state p=K rho ^{gamma }, with rho being the energy density, K and gamma = 5/3 being constants. We also consider the more realistic equation of state (EoS) known as SLy4, which is a Skyrme type one based on effective nuclear interaction. We show that in this theory it is possible to reach the mass of massive pulsars, such as PSR J2215 + 5135, for both equations of state. Also, results for mass-radius relation in GMC gravity are strongly dependent on the stiffness of the EoS.

The degradation of gamma-ray mass attenuation of UOX and MOX fuel with nuclear burnup

Nondestructive gamma-ray spectrometry of nuclear fuel is routinely performed in axial gamma scanning devices and more recently with gamma emission tomography. Following the irradiation of a fresh nuclear fuel with high intensity neutron flux in a nuclear reactor core, a great number of gamma-emitting radionuclides are created. These can be utilized for gamma spectrometric techniques. However, due to the high density and atomic number of the nuclear fuel, self-attenuation of gamma-rays is a challenge, which requires attenuation correction in order to perform accurate analysis of the source activity in the fuel.In this study, the degradation of the gamma-ray mass attenuation with burnup was investigated and, in addition, a predictive model was created by investigating the attenuation change at various gamma energies caused by the burnup of the nuclear fuel. This model is intended for use by spectrometry practitioners inspecting nuclear fuel. To this aim, the energy-dependent gamma-ray mass-attenuation coefficients were investigated as a function of burnup for UOX, and three MOX fuels having different initial Pu contents. The Serpent 2 reactor physics code was used to simulate the burnup history of the fuel pins. The nuclide inventory of the Serpent 2 output is combined with the NIST XCOM database to calculate the mass attenuation coefficients.The mass attenuation coefficient of the fuel was found to decrease with the fuel burnup, in the range of a few percent, depending on the burnup and gamma energy. Also, a theoretical burnup dependent swelling model was imposed on fuel density to see how linear attenuation coefficient of fuel material is changed. Furthermore, greater effect may be expected on the transmitted intensity, where a simulation study of a PWR assembly revealed that the contribution from the inner rods in a scanned fuel assembly increased by tens of percent compared to the one with non-irradiated fresh fuels, when shielded by the outer rods of the assembly. A sensitivity analysis was performed in order to test the effect of a number of geometrical and operational reactor parameters that were considered to potentially effect the mass attenuation coefficient. Finally, a simple-to-use predictive model was constructed providing the mass-attenuation coefficient [cm2/g] of fuel as a function of burnup [MWd/kgHM] and initial Pu content [wt%]. The resulting predictive model was optimized by using the nonlinear regression method.

The use of rocks in lieu of bricks and concrete as radiation shielding barriers at low gamma and nuclear medicine energies

Occupational and public radiation exposure could be minimized with the use of rocks. Rocks are relatively high-density materials, which could be used as a protective shielding barrier at facilities where ionizing radiation is used. These can include medical diagnostic radiology (Dental, Mammography, General and CT) and nuclear medicine (NM) centers. There is need to know potential shielding capabilities of rocks at low gamma and nuclear medicine energies; and compare with brick and concrete. In the present study, mass attenuation coefficients (MACs), effective atomic number (EAN) and effective electron density (EED) of the different rock samples were determined using WinXCom computer program and other relevant equations at 20, 30, 40, 60, 140 (Tc-99 m) and 364 keV (I-131). The results were compared with that of concrete and brick at the energies of interest. The result of this work shows that rocks are better used instead of concrete and brick at 20, 30, 40 and 60 keV. At 140 and 364 keV, all the considered materials performed nearly same which implies all could be used while the optimum considering all other necessary factors should be preferred.

Preliminary study of prompt gamma neutron activation analysis for Melamine

Prompt gamma neutron activation (PGNA) technique can be applied for detecting explosives in hidden places by using spontaneous fission source 252Cf source or neutron generator that emits thermal and cold neutrons. Some of emitted neutrons will be captured by nuclei and results in production of prompt gamma rays. Explosive materials can be identified by observing prompt gamma energy spectrum using high purity germanium (HPGe) detector. Gamma energy peaks indicate the presence of corresponding explosive nuclei in scanned materials. This paper describes the experiments conducted to investigate the possibility of explosive detection by using PGNA with 241Am/Be neutron source and limitations that come with it.

Measurement of prompt fission neutron and gamma spectra in the fast neutron induced fission of $$^{232}$$Th

Measurements of prompt fission neutrons and gamma rays spectra have been carried out in the fast neutron induced fission of $$^{232}$$Th at an average neutron energy of 2.6 MeV. The energy spectrum of neutrons is obtained from the time-of-flight spectrum measured using EJ301 detectors with respect to a twin section trigger fission chamber, while the energy spectrum of prompt gamma rays is obtained after unfolding the measured pulse height spectrum using the response matrix of the CeBr$$_{3}$$ detectors. The Maxwellian temperature obtained from the prompt fission neutron spectrum is found to be 1.22 ± 0.03 MeV. The low efficiency and limited resolution of the gamma set up, in addition to the low cross section of the reaction which result into poor statistics, made the reliable extraction of the detailed fine structure in the prompt fission gamma spectrum difficult. However, a reasonable estimate of the average gamma energy could be obtained as 0.91 ± 0.04 MeV. The extracted observables are then compared with the values predicted by the GEF model. It is found that, while the measured prompt fission neutron spectrum and the extracted Maxwellian temperature agree reasonably well when compared with the predictions of the GEF model, the average gamma ray energy from the measured prompt fission gamma spectrum is found to be lower by $$\sim $$ 17$$\%$$ from the predictions of the model. A rough estimate of average neutron and gamma multiplicities are also obtained from the measurements.

Estimation of varUpsilon hbox {(1S)} production in ep process near threshold

The near-threshold photo-productions of heavy quarkonia are important ways to test the QCD-inspired models and to constrain the gluon distribution of nucleon in the large x region. Investigating the various models, we choose a photon–gluon fusion model and a pomeron exchange model for hbox {J}/varPsi photo-production near threshold, emphasising on the explanation of the recent experimental measurement by GlueX at JLab. We find that these two models are not only valid in a wide range of the center-of-mass energy of gamma and proton, but also can be generalized to describe the varUpsilon hbox {(1S)} photo-production. Using these two models, we predict the electro-production cross-sections of varUpsilon hbox {(1S)} at EicC to be 48 fb to 85 fb at the center-of-mass energy of 16.75 GeV.

A multi-stop time-of-flight spectrometer for the measurement of positron annihilation-induced electrons in coincidence with the Doppler-shifted annihilation gamma photon.

In this study, we describe an advanced multi-functional, variable-energy positron beam system capable of measuring the energies of multiple "positron-induced" electrons in coincidence with the Doppler-shifted gamma photon resulting from the annihilation of the correlated positron. The measurements were carried out using the unique characteristics of the digital time-of-flight spectrometer and the gamma spectrometer available with the advanced positron beam system. These measurements have resulted in (i) the first digital time-of-flight spectrum of positron annihilation-induced Auger electrons generated using coincident signals from a high-purity Ge detector and a micro-channel plate, (ii) a two-dimensional array of the energy of Doppler-broadened annihilation gamma and the time-of-flight of positron-annihilation induced Auger electrons/secondary electrons measured in coincidence with the annihilation gamma photon, and (iii) the time-of-flight spectra of multiple secondary electrons ejected from a bilayer graphene surface as a result of the impact and/or annihilation of positrons. The novelty of the gamma-electron coincidence spectroscopy has been demonstrated by extracting the Doppler-broadened spectrum of gamma photons emitted due to the annihilation of positrons exclusively with 1s electrons of carbon. The width of the extracted Doppler-broadened gamma spectrum has been found to be consistent with the expected broadening of the annihilation gamma spectrum due to the momentum of the 1s electrons in carbon.

Evaluation of digital pulse processing techniques for a β-γ coincidence counting system

Signal processing is a core part of any electronic chain for radioactivity measurement systems and can influence measurement results drastically. A thorough study of the different alternatives for this treatment is especially worthwhile when developing a new digital system.This article describes an evaluation performed to optimize the digital pulse processing stage of the β-γ coincidence counting system at the Institute of Radiation Physics (IRA) designated laboratory for the activity unit. This study is a part of IRA's digitalization project to modernize the aging analog electronic hardware of its primary measurement systems.The β-γ coincidence counting system consists of a plastic scintillation detector in the beta channel and a well-type NaI detector in the gamma channel. Six pulse shaping digital filters along with amplitude calculation algorithms were implemented to obtain beta and gamma pulse amplitude values. In addition, four timing digital filters and time pick-off methods were set up to calculate arrival times (timestamps) for the pulses generated by both detectors.Filter parameters and algorithm settings were adjusted to obtain the best performance. Combination of filters into traditional two channel (fast for timing and slow for shaping) or one channel configuration using dCFD (digital constant fraction discrimination) and LE (leading edge) time pick-off methods were also tested and compared to study the whole digital pulse processing system, using both real measurement signals (241Am, 137Cs, 60Co and 166mHo) and simulated reference pulses. The results of these tests were quantified by evaluating the following metrics: processing speed, signal-to-noise ratio (SNR) at different energies, gamma energy resolution, time measurement accuracy, time resolution and detection efficiency. The results of this evaluation provide a rational ground to assess the system and help decide which digital pulse processing (DPP) method should be the most appropriate.

Comparison of shielding properties of various marble concretes using GEANT4 simulation and experimental data

The linear attenuation coefficients (μ) of various marble concretes have been studied in gamma energies 662, 1173, and 1332 keV by using the GEANT4 Monte Carlo simulation. The simulated results were then compared with experimental data, and a good agreement was observed for the concretes involved. The obtained results reveal that the concrete namely NM20 has higher μ and lower transmission factor among the selected concretes.

Improvement of a spectrum-to-dose conversion function for electronic personal dosimeters

For electronic personal dosimeters (EPDs) based on a spectroscopy system, it is necessary to accurately measure the dose in real-time from the gamma energy spectra. The method of spectrum-to-dose conversion is being used instead of the method of count-to-dose conversion. The G(E) function, a typical method of spectrum-to-dose conversion has been applied to various instruments due to its good dose measurement performance and the advantage of real-time measurements. In this manuscript, we present a method to increase the accuracy of G(E) function for the EPD consisting of a 3 × 3 mm2 PIN diode coupled with a 3 × 3 × 3 mm3 CsI(Tl) scintillator. The new G(E) function was calculated using the adaptive moment estimation (ADAM) method based on Monte Carlo simulation. The proposed G(E) function is verified by comparison with the least-square method (LSM), which is the conventional method for calculating the G(E) function and with the gradient-descent method (GDM), which is the basis for the ADAM. The relative difference was acquired to compare the converted dose value using each G(E) function by using 241Am, 57Co, 22Na, 137Cs, 54Mn and 60Co radioisotopes. In addition, the energy response to 137Cs of each G(E) function was obtained. The relative difference of G(E) function according to LSM, GDM, and ADAM was in the range of ±28.54, ±12.59, and ±9.9%, respectively, and the energy response to 137Cs was 0.71 to 1, 0.87 to 1.02, and 0.9 to 1.03, respectively.

Gamma spectrum denoising method based on improved wavelet threshold

Adverse effects in the measured gamma spectrum caused by radioactive statistical fluctuations, gamma ray scattering, and electronic noise can be reduced by energy spectrum denoising. Wavelet threshold denoising can be used to perform multi-scale and multi-resolution analysis on noisy signals with small root mean square errors and high signal-to-noise ratios. However, in traditional wavelet threshold denoising methods, there are signal oscillations in hard threshold denoising and constant deviations in soft threshold denoising. An improved wavelet threshold calculation method and threshold processing function are proposed in this paper. The improved threshold calculation method takes into account the influence of the number of wavelet decomposition layers and reduces the deviation caused by the inaccuracy of the threshold. The improved threshold processing function can be continuously guided, which solves the discontinuity of the traditional hard threshold function, avoids the constant deviation caused by the traditional soft threshold method. The examples show that the proposed method can accurately denoise and preserves the characteristic signals well in the gamma energy spectrum.

Radiation shielding properties of silicon polymers

We have studied the X-ray and gamma radiation shielding parameters such as mass attenuation coefficient, linear attenuation coefficient, Half Value Layer (HVL), Tenth Value Layer (TVL), effective atomic number, electron density and specific gamma ray constant in some silicon polymers of different composition such as Polymer A- Poly dimethyl siloxane (C2H6OSi), Polymer B- Polymethyl Hydro silaxane (CH4SiO), Polymer C- Per hydro poly silaxane (H3SiN), Polymer D-poly dimethyl silaxane (C2H6Si), Polymer E− Methylsilses quioxane (C12H32O8Si8), and Polymer F- Silalkalyene polymer (SiC3H8). We have also measured the mass attenuation coefficient at gamma energies 84 keV to 1.3 MeV. We have also studied the neutron shielding properties such as coherent neutron scattering length, incoherent neutron scattering lengths, coherent neutron scattering cross section, incoherent neutron scattering cross sections, total neutron scattering cross section and neutron absorption cross sections in the silicon polymers. We have compared the shielding properties among the studied different silicon polymers. From the detail study, it is clear that the silicon polymer per hydro poly silaxane is good absorber for X-ray, gamma radiation and neutron. Hence, we suggest that the perhydropoly silaxane is good shielding material for X-ray, gamma and neutrons.

Mutational signatures in tumours induced by high and low energy radiation in Trp53 deficient mice

Ionising radiation (IR) is a recognised carcinogen responsible for cancer development in patients previously treated using radiotherapy, and in individuals exposed as a result of accidents at nuclear energy plants. However, the mutational signatures induced by distinct types and doses of radiation are unknown. Here, we analyse the genetic architecture of mammary tumours, lymphomas and sarcomas induced by high (56Fe-ions) or low (gamma) energy radiation in mice carrying Trp53 loss of function alleles. In mammary tumours, high-energy radiation is associated with induction of focal structural variants, leading to genomic instability and Met amplification. Gamma-radiation is linked to large-scale structural variants and a point mutation signature associated with oxidative stress. The genomic architecture of carcinomas, sarcomas and lymphomas arising in the same animals are significantly different. Our study illustrates the complex interactions between radiation quality, germline Trp53 deficiency and tissue/cell of origin in shaping the genomic landscape of IR-induced tumours.

Investigation and Analysis of Soil Radioactivity Level in Parks in a City

Using a portable microcomputer multi-channel gamma spectrometer to directly measure the radioactive content in the soil, the on-site gamma energy spectrum measurement was carried out on the soil of 7 parks in a certain city. The survey results show that the specific activity of 40k in the urban park soil ranges from 470.88 bq/kg to 640.2 bq/kg. The specific activity of 238u ranges from 26.77 bq/kg to 33.31 bq/kg. The specific activity of 232th ranges from 42.14 bq/kg to 54.72 bq/kg. The content of the three radionuclides in the soil in the park is lower than the national average, and far lower than the radioactivity of ordinary building materials.