Plastic Nuclear Track Detectors Research Articles

Simulation and experimental analysis of aerogel's attenuation for high-energy alpha particles in fission-fusion fragment rocket applications

Emerging studies are geared toward exploring new methods of nuclear rocket propulsion to provide more efficient space transit beyond Earth's orbit. One method is to employ a Fission Fragment Rocket Engine utilizing fissionable layers embedded in a low-density aerogel. A quantitative understanding of particle attenuation is essential for developing a functional prototype that permits fission fragments to escape the layers and contribute to specific impulse rather than being attenuated and generating waste heat. In this investigation, the MCNP code was used to theoretically analyze the attenuation of alpha particles from 241Am sources within aerogel materials. Simulations were conducted on aerogels with various densities and compositions. These simulations aimed to predict the expected intensity of alpha particles reaching a detector. CR-39 was employed as a Plastic Nuclear Track Detector to assess particle attenuation by the aerogels. The experimental and simulation results show that the threshold areal density of atoms was found to be high 1020 atoms/cm2 for the three materials studied in this project.

DNA damage response in a 2D-culture model by diffusing alpha-emitters radiation therapy (Alpha-DaRT)

Diffusing alpha-emitters radiation therapy (Alpha-DaRT) is a unique method, in which interstitial sources carrying 224Ra release a chain of short-lived daughter atoms from their surface. Although DNA damage response (DDR) is crucial to inducing cell death after irradiation, how the DDR occurs during Alpha-DaRT treatment has not yet been explored. In this study, we temporo-spatially characterized DDR such as kinetics of DNA double-strand breaks (DSBs) and cell cycle, in two-dimensional (2D) culture conditions qualitatively mimicking Alpha-DaRT treatments, by employing HeLa cells expressing the Fucci cell cycle-visualizing system. The distribution of the alpha-particle pits detected by a plastic nuclear track detector, CR-39, strongly correlated with γH2AX staining, a marker of DSBs, around the 224Ra source, but the area of G2 arrested cells was more widely spread 24 h from the start of the exposure. Thereafter, close time-lapse observation revealed varying cell cycle kinetics, depending on the distance from the source. A medium containing daughter nuclides prepared from 224Ra sources allowed us to estimate the radiation dose after 24 h of exposure, and determine surviving fractions. The present experimental model revealed for the first time temporo-spatial information of DDR occurring around the source in its early stages.

Optimization of laser-driven quantum beam generation and the applications with artificial intelligence

We have investigated space and astrophysical phenomena in nonrelativistic laboratory plasmas with long high-power lasers, such as collisionless shocks and magnetic reconnections, and have been exploring relativistic regimes with intense short pulse lasers, such as energetic ion acceleration using large-area suspended graphene. Increasing the intensity and repetition rate of the intense lasers, we have to handle large amounts of data from the experiments as well as the control parameters of laser beamlines. Artificial intelligence (AI) such as machine learning and neural networks may play essential roles in optimizing the laser and target conditions for efficient laser ion acceleration. Implementing AI into the laser system in mind, as the first step, we are introducing machine learning in ion etch pit analyses detected on plastic nuclear track detectors. Convolutional neural networks allow us to analyze big ion etch pit data with high precision and recall. We introduce one of the applications of laser-driven ion beams using AI to reconstruct vector electric and magnetic fields in laser-produced turbulent plasmas in three dimensions.

The contribution of high-LET track to DNA damage formation and cell death for Monoenergy and SOBP carbon ion irradiation

Carbon ion radiotherapy (CIRT) is a heavy ion charge particle therapy with 29 years of prominent use. Despite advantages like high relative biological effectiveness (RBE), improved quality of life, and reduced treatment time, challenges persist, especially regarding heavy nuclear fragments. Our research addresses these challenges in horizontal irradiation, aiming to comprehend Monoenergetic and Spread-Out Bragg peak (SOBP) carbon ion beam trajectories using cell survival analysis and visualizing biological effects through DNA damage (γ-H2AX). This reveals repair-related protein foci near the Bragg peak. CR-39, a plastic nuclear track detector, was explored to understand high-linear energy transfer (LET) tracks and radiation quality near the Bragg peak. Findings unveil high-LET DNA damage signatures through aligned γ-H2AX foci, correlating with LET values in SOBP. CR-39 visualized high-LET particle exposure, indicating comet-type etch-pits at the Bragg peak and suggesting carbon ion fragmentation. Unexpectedly, dot-type etch-pits in irradiated and post-Bragg peak regions indicated high-LET neutron production. This investigation highlights the intricate interplay of carbon ion beams, stressing the importance of understanding LET variations, DNA damage patterns, and undesired secondary exposure.

RESPONSE OF PLASTIC TRACK DETECTOR OF THE TASTRAK TYPE TO NEUTRONS OF PU–BE SOURCE

The solid-state nuclear track detectors are widely used in a variety of nuclear physics experiments and radiation protection. The paper presents the first results of the newly acquired TASLImage™ neutron dosimetry system at the Slovak University of Technology in Bratislava. A comparison of experimental and calculated responses of a TASTRAK plastic nuclear track detector to neutron spectrum of Pu-Be source is presented. The ambient dose equivalents determined by the TASLImage™ system are compared with the ones measured by the NuDET-ENE neutron detector based on the use of ZnS(Ag) scintillator covered with a thin film of 6LiF thermal neutron converter accommodated inside the HDPE moderator. The first results are concluded, and further research needs are identified.

The total and the partial charge-changing cross sections of 40Ar fragmentation on elemental targets at 500 A MeV

The total and the partial charge-changing cross sections of 40Ar fragmentation on CH2, C, Al, Cu and Pb targets at the highest energy of 495 A MeV were investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target was calculated based on the results of polyethylene and carbon targets. It was found that the total charge-changing cross sections for fragmentation of 40Ar on H, C, Al, Cu and Pb targets were independent on the beam energy in our studied energies, and were consistent with the predictions of Bradt-Peters semi-empirical formula. Nilsen semi-empirical formula, NUCFRG2 and PHITS simulation codes given an underestimation of experimental data. The partial cross sections for projectile fragment production were independent on the beam energy in our studied energies for each target and do not show a significant odd-even effect. The partial cross sections for projectile fragment production were also compared with different empirical parametrization formulas, such as different version of Cummings, Nilsen, FRACS and EPAX3. Generally, EPAX3 and FRACS empirical parametrization can give a reasonable estimation of data within 25% relative errors.

Measurement of therapeutic 12C beam in a water phantom using CR-39

The motivation for this study was to explore a new method to test the particle spatial distribution for a therapeutic carbon beam. CR-39 plastic nuclear track detectors were irradiated to a 276.5 MeV u−1 mono-energy carbon beam at the heavy ion facility in the Shanghai Proton and Heavy Ion Center. The spatial distribution of the primary carbon beam and secondary fragments in a water phantom were systematically analyzed both in the transverse direction (perpendicular to the projection direction of the primary beam) and at different depths in the longitudinal direction (along the projection direction of the primary beam) with measured tracks on the CR-39 detectors. Meanwhile, the theoretically spatial distribution and linear energy transfer (LET) spectra of the primary beam and secondary fragments were calculated using the Monte Carlo (MC) toolkit Geant4. The results showed that the CR-39 detectors are capable of providing high lateral resolution of carbon ion at different depths. In the range of the primary carbon beam, the beam width simulated with MC is in good agreement with that of experimental measurement. The track size registered in the CR-39 has a good correlation with the particle LET. These findings indicate that the CR-39 can be used for measuring both the particle flux and its spatial distribution of carbon ions.

Shielding effectiveness: A weighted figure of merit for space radiation shielding

The risk to space crew health and safety posed by exposure to space radiation is regarded as a significant obstacle to future human exploration missions to the Moon, Mars, and beyond. Engineers developing future spacecraft or planetary surface habitats can benefit from detailed knowledge of a broad range of possible materials that could provide improved protection to space crews from the deleterious effects of prolonged exposure to the space radiation environment. As one step towards providing this knowledge base, we have developed an empirical weighted figure of merit, referred to as shielding effectiveness, that quantifies the ability of a candidate material to shield space crews from the space radiation environment. The shielding effectiveness, as formulated in this study, accounts for the competing physical aspects of target and projectile fragmentation to provide a comprehensive assessment of radiation protection with regard to passive shielding for space applications. The empirical data used in determining shielding effectiveness was obtained from proton and heavy ion accelerator-based experiments wherein Al2O3:C optically stimulated luminescence dosimeter and CR-39 plastic nuclear track detector were irradiated behind candidate space radiation shielding materials of varying composition and depth. As a test case, the experimental setup was exposed to nominal beams of 1 GeV protons, and 1 GeV/n 28Si and 56Fe heavy ions, the latter serving as a sample of the high linear energy transfer portion of the galactic cosmic ray spectrum. Established radiation dosimetry techniques were used to obtain linear energy transfer spectra, absorbed dose, and dose equivalent as a function of depth. Based on the measurement results, a shielding effectiveness value was computed, quantifying the efficacy of the candidate material as a function of depth, with cumulative weighting factors accounting for the measured percent composition of baryonic matter in the galactic cosmic ray spectrum, and the measured percent contribution to absorbed dose and dose equivalent. The methodology for shielding effectiveness was tested using the common materials of aluminum, copper, graphite, and water, with polyethylene serving as the standard reference. The preliminary shielding effectiveness values for these materials confirm the low Z principle for effective space radiation shielding, and, furthermore, these values tend to be lower when the effectiveness calculation is based on dose equivalent. Of the common materials studied here, at a bulkhead depth of 5 g/cm2, all materials provide a similar level of radiation protection to within standard error. In addition, this method can be used to supplement and/or verify similar findings obtained from transport models.

Detection of alpha and 7Li particles from 10B(n, α)7Li reactions using a combination of CR-39 nuclear track detector and potassium hydroxide-ethanol-water solution in accelerator-based neutron fields

We investigated the optimum etching condition for potassium hydroxide-ethanol–water solution (PEW) to detect only alpha and 7Li particles from 10B(n, α)7Li reactions registered in a CR-39 plastic nuclear track detector. The background recoil protons, which are induced by fast neutrons with energies of <2 MeV produced by 9Be(p, n)9B reactions in accelerator-based neutron sources, were discriminated by the desensitization effect with PEW. We found that an ethanol concentration of ≥15 wt% in a PEW solution discriminated recoil proton tracks with energies of <2 MeV. The optimized conditions will be applicable for evaluating dose distribution in tissue in accelerator-based boron neutron capture therapy.

Investigation of Radium Contents and Radon Exhalation Rates in Soil Samples in Menge District, Ethiopia

Radon has been recognized as one of the major contributor to the natural radiation and health hazards in the human dwellings, working places and mining areas. Even lung cancer is expected if it is present in enhanced levels beyond maximum permissible limit. We have studied radium contents and radon exhalation (both mass and surface) rates in Menge mining and non-mining areas of the Benishangul Gumuz region in Western Ethiopia using the sealed Can technique and LR-115 type II plastic nuclear track detectors. Fifteen soil samples were collected over the study area according to the fraction of the populations and mining and non-mining areas. It is found that the values of radium contents vary from 1.20 to 3.94 Bq.kg^-1 with an average value 2.44 Bq.kg^-1. It is also found that gold mining areas have had relatively higher radium contents as compared to the other samples which are collected from non-mining areas. And radon exhalation study is important for understanding the relative contribution of the material to the total radon concentration found inside the study area. The radon mass and surface exhalation rates for the studied samples had the mean values of 2.16×10^-6 Bq.kg^-1.d^-1 and 1.14×10^-4 Bq.m^-2.d^-1 respectively.

Projectile fragment emission in the fragmentation of $$^{\bf 56}\mathbf{Fe}$$ on Al, C, and $$\mathbf{CH}_{\mathbf{2}}$$ targets

The emission angle distribution of projectile fragments (PFs) and the temperature of PF emission sources for fragmentation of $$^{56}\hbox {Fe}$$ on polyethylene, carbon, and aluminum targets at the highest energy of 497 A MeV are investigated on the basis of corrected data, using a CR-39 plastic nuclear track detector. It is found that the average emission angle of PFs increases with the decrease in PF charge for the same target, and no obvious dependence of angular distribution on the mass of the target nucleus is found for the same PF. The cumulative squared transverse momentum distribution of PFs can be well represented by a single Rayleigh distribution. The temperature of PF emission sources is extracted from the distribution, and it is about 1.0–8.0 MeV and does not depend on the mass of the target for PFs with charges of $$9\le {Z}\le 25$$.

Analysis of SPICE microbeam size using fluorescent nuclear track detector (FNTD)

Single Particle Irradiation system to Cell (SPICE) facility at the National Institute of Radiological Sciences (NIRS) provides a magnetically focused 3.4 MeV proton microbeam. Throughout the radiobiological studies using SPICE over the years, we have realized that biological effect can be affected by the highly localized dose distribution of the microbeam and results may differ from that of broad beam irradiation. Previously, we have reported that the beam size of the SPICE microbeam was approximately 2 µm in diameter; the proton traversal was identified as etch pits produced on plastic nuclear track detectors, CR-39. However, this widely used method cannot distinguish individual proton tracks of highly focused microbeam due to the overlapping of etch pits, which was major limitation for beam size analysis as well as estimation of localized dose distribution in the cells. To overcome this limitation, we used fluorescent nuclear track detectors (FNTD; Al2O3: C, Mg) to investigate the beam size and its proton-number dependence (7–1000 protons per position). Detail analysis of Z(optical axis)-stacks of fluorescent images of the FNTD with a confocal laser scanning microscope clearly demonstrated that FNTDs has better spatial resolution and detection sensitivity compared to the conventional CR-39 detectors. The overall beam size was evaluated as elliptical shape or rectangular shape and determined to be in the range of 2.0 × 1.5–3.1 × 2.4 μm, depending on the number of protons per position. This result suggests that out-focused fraction of the incident protons contributes the broadening of the beam size. Throughout the present study, the FNTD irradiation and related image processing technology have demonstrated the feasibility of high-resolution measurement of the microbeam size over a wide range of the microbeam intensity.

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on Al, C and CH2 targets

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on polyethylene, carbon and aluminum targets at the highest energy of 496 A MeV are investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target is calculated based on the results of polyethylene and carbon targets. It is found that the total charge-changing cross sections for fragmentation of 56Fe on hydrogen, carbon and aluminum targets are independent on the beam energy in our studied energies, and are consistent with the predictions of Bradt–Peter semi-empirical formula, Nilsen parameterized formula, NUCFRG2 and QMSFRG theoretical simulation codes. The partial cross sections for projectile fragment production are independent on beam energy in our studied energies for each targets and do not show a significant even-odd effect.

Contribution to dose in healthy tissue from secondary target fragments in therapeutic proton, He and C beams measured with CR-39 plastic nuclear track detectors

The linear energy transfer (LET) spectrum, absorbed dose and dose equivalent from secondary particles of LET∞H2O ≥15 keV/μm deposited within the plateau of the Bragg curve in primary particle-induced nuclear target fragmentation reactions in tissue during proton and heavy ion radiotherapy were measured using CR-39 plastic nuclear track detectors and analyzed by means of atomic force microscopy. It was found that secondary target fragments contributed 20% to dose equivalent for primary protons (157 MeV), 13% for primary helium ions (145 MeV/n) and 4% for primary carbon ions (383 MeV/n), respectively. Little research has been done on the contribution from these particles to primary given dose. The smaller contribution measured for energetic carbon ion beams compared to proton beams can be considered an advantage of carbon ion radiotherapy over proton radiotherapy.

DISCRIMINATION METHOD FOR GAMMA RAY DOSES IN NEUTRON FIELDS USING AN IONIZATION CHAMBER WITH ATTENUATION FILTERS.

Neutron fields produced by an accelerator-driven neutron source are generally mixed radiation fields that consist of fast neutrons and gamma rays. To estimate the biological effects of fast neutrons precisely, the gamma ray dose contamination must be evaluated in neutron fields. In this work, we developed a discrimination technique for absorbed doses (60Co gamma-ray equivalent) of fast neutrons and gamma rays using an ionization chamber. The filter thickness dependences of the absorbed doses of fast neutrons and gamma rays are different for a given filter material. Thus, the absorbed doses of each type of radiation were distinguished by fitting the dose attenuation curve, which was measured with an ionization chamber and attenuation filters, with a two-component exponential function. The absorbed dose of fast neutrons and gamma rays with no attenuation filter was evaluated from the y-intercept of the fitting function. This technique was demonstrated in two neutron fields produced by 4 MeV proton and deuteron bombardment of a 9Be target. The thicknesses of the polyethylene attenuation filters were 0-350 mm. The dose attenuation coefficients of fast neutrons obtained by the two-component exponential fitting function for the 9Be(p,n)9 and 9Be(d,n) reactions showed differences of 1.5 and 1.7%, respectively, from the reference measurements using a CR-39 plastic nuclear track detector. The absorbed dose contributions of gamma rays in neutrons fields of the 9Be(p,n)9B and 9Be(d,n) reactions were evaluated as 30.2 ± 3.24% and 20.4 ± 5.16%, respectively, without polyethylene filters.

Measurement Radon Gas Concentration in Selected Soil Samples of The of Al-Nada District in Najaf

In this study fifty (50) of soil samples of AL-Nada district-Najaf Governorate –Iraq have been collected randomly and studied using solid state nuclear track detectors (CR-39) to determined 226Ra through counting the number of radon tracks by using CR-39 plastic nuclear track detector ,a long- term measurement technique has been considered using special tube of mean (2.5cm) diameter .The detector was placed at (5cm) height and irradiated for 90 days. The chemical etching performed by using (NaOH) solution of 6.25 normality at etching temperature (70C°)for etching period of (7 hrs ).Concentration of radon 222Rn has ranged from (171.237±0.0062) Bq/m3 to (31.982±0.0027) Bq/m3with average value (99.222±0.2476) Bq/m3 while the specific activityof radon has been ranged from (0.471±1.794) Bq/kg to (0.090±7.682) Bq/kg with average value (0.277 1.320)Bq/kgThe results were found to be comparable or lower than similar global reporting data. Accordingly, this area of soil can be considered to have normal levels of natural background radiation.

IMAGING URANIUM DISTRIBUTION ON RAT KIDNEY SECTIONS THROUGH DETECTION OF ALPHA TRACKS USING CR-39 PLASTIC NUCLEAR TRACK DETECTOR.

Uranium is renowned as a global contaminant, and attracts major concern with regards to the health risks involved because its nephrotoxicity. This paper discusses the development of a simple method to identify accumulated regions or localized sites of uranium within kidneys using the CR-39 plastic nuclear track detector. To demonstrate the proposed method, renal cryo-sections (5 μm-t) from Wistar male rats, subcutaneously administered with uranyl acetate (2 mg/kg), were prepared on day one after administration. Concerned sections were subsequently placed on CR-39, stored for 1.25 years, and then etched in a 7 M NaOH solution at 70°C for 3 h. α-tracks were then detected in the form of etch pits, corresponding to uranium, and also the tissue shape and structure were transferred as a roughness on the surface of CR-39. As observed, the proposed method served to facilitate simultaneous detection and identification of localized regions of uranium accumulation within kidneys.

Evidence of Local Concentration of α-Particles from 211At-Labeled Antibodies in Liver Metastasis Tissue.

We investigated the local concentration of α-particles from 211At-labeled trastuzumab antibodies against human epidermal growth factor receptor type 2 antigens in liver metastasis tissue of mice. Methods: Mice carrying metastatic cancer in their liver were injected with 211At-agent. After 12 h, the liver was removed and sliced, and 2 tissue samples of liver tissues without lesions and one containing metastatic lesions were mounted on the CR-39 plastic nuclear track detector. Microscope images of the tissues on the CR-39 were acquired. After irradiation for 31 h, the tissues were removed from the CR-39. A microscope image of α-particle tracks on the CR-39 was acquired after chemical etching. The positions of each tissue sample and the emitted α-particle tracks were adjusted to the same coordinates. Results: The positional distribution of α-particle tracks emitted from 211At was consistent within the tissue. The α-particle tracks were mainly allocated in the tumor region of the tissue. The absorbed dose in individual cells segmented by 10-μm intervals was obtained by the spectroscopic analysis of the linear-energy-transfer spectrum. The concentration efficiency—the track density ratio of α-particle tracks in the necrotized tissue, which was the tumor region, to the normal tissue—was found to be 6.0 ± 0.2. In the tumor region, the high–linear-energy-transfer α-particles deposited a large enough dose to cause lethal damage to the cancer cells. Conclusion: The total absorbed dose ranged from 1 to 7 Gy with a peak at around 2 Gy, which would correspond to a 2–3 times higher biologically equivalent dose because of the high relative biological effectiveness of the α-particles emitted from 211At.

A LiF and BeO TLD based microdosimeter for space radiation risk assessment of astronauts

The ratio of thermoluminescence glow curve area of BeO and LiF dosimeters was found to be proportional to average LET and quality factor (Q) of impinging mixed radiations. Using this phenomenon and widely available Thermoluminescence Dosimeter TLD-700 (7LiF: Mg,Ti) and BeO (Thermolux 995) chips a TLD-Microdosimeter (LiBe-14) emulating a much larger gas-filled Tissue Equivalent Proportional Counter (TEPC) was developed. The TEPC is an essential device of space radiation dosimetry widely used by international space agencies. The LiBe-14 is capable of assessing the LETTissue (5–300 keV/μm), quality factor Q (1–30) and associated dose equivalent H (0.1–1000 mSv) of any mixed radiation fields of interest, including space radiations predominant in Low Earth Orbit (LEO) environment. The TLD microdosimeter was calibrated using the secondary radiation fields produced by bombarding a 25 cm × 25 cm × 35 cm polystyrene phantom with 81, 119, 150, 177, 201 and 231 MeV protons from a Proton Therapy Medical Cyclotron. The TLD pair (BeO/LiF) was attached to the TEPC and placed lateral to the proton beam. The characteristics of space radiation inside the spacecraft are complex. Hence, personal dosimetry of astronauts in the space habitat is performed using “multi-element” dosimeters made of different types of TLD and CR-39 plastic nuclear track detector (PNTD). The TLD and PNTD are used to assess the sparsely (low LET) and densely (high LET) ionising radiation component respectively. This report elucidates the feasibility of LiBe-14 microdosimeter for the estimation of overall dose equivalent and “risk of exposure induced death” (REID) of astronauts working in LEO space stations.

Radiation Measured for Chinese Satellite SJ‐10 Space Mission

AbstractsSpace biological effects are mainly a result of space radiation particles with high linear energy transfer (LET); therefore, accurate measurement of high LET space radiation is vital. The radiation in low Earth orbits is composed mainly of high‐energy galactic cosmic rays (GCRs), solar energetic particles, particles of radiation belts, the South Atlantic Anomaly, and the albedo neutrons and protons scattered from the Earth's atmosphere. CR‐39 plastic nuclear track detectors sensitive to high LET are the best passive detectors to measure space radiation. The LET method that employs CR‐39 can measure all the radiation LET spectra and quantities. CR‐39 detectors can also record the incident directions and coordinates of GCR heavy ions that pass through both CR‐39 and biosamples, and the impact parameter, the distance between the particle's incident point and the seed's spore, can then be determined. The radiation characteristics and impact parameter of GCR heavy ions are especially beneficial for in‐depth research regarding space radiation biological effects. The payload returnable satellite SJ‐10 provided an excellent opportunity to investigate space radiation biological effects with CR‐39 detectors. The space bio‐effects experiment was successfully conducted on board the SJ‐10 satellite. This paper introduces space radiation in low Earth orbits and the LET method in radiation‐related research and presents the results of nuclear tracks and biosamples hitting distributions of GCR heavy ions, the radiation LET spectra, and the quantities measured for the SJ‐10 space mission. The SJ‐10 bio‐experiment indicated that radiation may produce significant bio‐effects.