Proton Particle Research Articles

Nuclear radiation shielding competences of barium-reinforced borosilicate glasses

The gamma photon and neutron shielding effectiveness of borosilicate glasses with alumina in the chemical structure 40SiO2.10B2O3.xBaO.(45 − x)CaO.5Al2O3.yZnO.zMgO glasses (20 ≤ x ≤ 40 mol% and y = z = 6 wt%) was evaluated. The investigated glasses were coded as BCBSA-20B (barium oxide (BaO) = 20 mol%) to BCBSA-40B (barium oxide = 40 mol%). The results showed that the mass attenuation coefficient (MAC) increased when barium oxide increased in the samples, and the samples were arranged in order as BCBSA-20B < BCBSA-25B < BCBSA-30B < BCBSA-35B < BCBSA-40B. In terms of MAC values, the BCBSA-40B sample has the lowest values of half-value layer and mean free path but has the highest values of effective atomic number (Z eff). Moreover, the neutron shielding competences of glasses have been determined by way of calculating the removal cross-section for the fast neutrons, Σ R (cm−1), which was the highest for the BCBSA-40B glass (Σ R = 0.0994 cm−1) among the studied samples. In addition, mass stopping power (Ψ) and the projected range (Φ) for proton and alpha particles were also calculated. It was found that the BCBSA-40B sample has the lowest Ψ and Φ among the studied glasses. It can be concluded that the replacement of the calcium oxide (CaO) content with the barium oxide contents enhances the shielding capacity against the charged particles, electromagnetic radiation and the fast neutrons. The finding of recent investigations can be useful for advanced nuclear engineering and protection studies.

Study on the Dose Enhancement of Gold Nanoparticles When Exposed to Clinical Electron, Proton, and Alpha Particle Beams by Means of Geant4.

Background:Various factors effecting deposited energy and dose enhancement ratio (DER) in the simplified model of cell caused by the interaction of a cluster of gold nanoparticles (GNPs) with electron beams were assessed, and the results were compared with other sources through Geant4 Monte Carlo simulation toolkit.Method:The effect of added GNPs on the DNA strand breaks level, irradiated to electron, proton, and alpha beams, is assessed.Results:Presence of GNPs in the cell makes DER value more pronounced for low-energy photons rather than electron beam. Moreover, the results of DER values did not show any significant increase in absorbed dose in the presence of GNP for proton and alpha beam. Moreover, the results of DNA break with GNPs for proton and alpha beam were negligible. It is demonstrated that as the sizes of the GNPs increase, the DER is enlarged until a certain size for 40 keV photons, while there is no striking change for 50 keV electron beam when the size of the GNPs changes. The results indicate that although energy deposited in the cell for electron beam is more than low-energy photon, DER values are low compared to photon.Conclusion:Larger GNPs do not show any preference over smaller ones when irradiated through electron beams. It is proved that GNPs do not significantly increase single-strand breaks (SSBs) and double-strand breaks during electron irradiation, while there exists a direct relationship between SSB and energy.

Immunomodulatory Effects of Radiotherapy.

Radiation therapy (RT), an integral component of curative treatment for many malignancies, can be administered via an increasing array of techniques. In this review, we summarize the properties and application of different types of RT, specifically, conventional therapy with x-rays, stereotactic body RT, and proton and carbon particle therapies. We highlight how low-linear energy transfer (LET) radiation induces simple DNA lesions that are efficiently repaired by cells, whereas high-LET radiation causes complex DNA lesions that are difficult to repair and that ultimately enhance cancer cell killing. Additionally, we discuss the immunogenicity of radiation-induced tumor death, elucidate the molecular mechanisms by which radiation mounts innate and adaptive immune responses and explore strategies by which we can increase the efficacy of these mechanisms. Understanding the mechanisms by which RT modulates immune signaling and the key players involved in modulating the RT-mediated immune response will help to improve therapeutic efficacy and to identify novel immunomodulatory drugs that will benefit cancer patients undergoing targeted RT.

Estimations of Cross-Sections for Photonuclear Reaction on Calcium Isotopes by Artificial Neural Networks

The nuclear reaction induced by photon is one of the important tools in the investigation of atomic nuclei. In the reaction, a target material is bombarded by photons with high-energies in the range of gamma-ray energy range. In the bombarding process, the photons can statistically be absorbed by a nucleus in the target material. Then the excited nucleus can decay by emitting proton, neutron, alpha and light particles or photons. By performing photonuclear reaction on the target, it can be easily investigated low-lying excited states of the nuclei. In the present work, (γ, n) photonuclear reaction cross-sections on different calcium isotopes have been estimated by using artificial neural network method. The method is a mathematical model that mimics the brain functionality of the creatures. The correlation coefficient values of the method for both training and test phases being 0.99 indicate that the method is very suitable for this purpose.

The Solar Orbiter Solar Wind Analyser (SWA) suite

The Solar Orbiter mission seeks to make connections between the physical processes occurring at the Sun or in the solar corona and the nature of the solar wind created by those processes which is subsequently observed at the spacecraft. The mission also targets physical processes occurring in the solar wind itself during its journey from its source to the spacecraft. To meet the specific mission science goals, Solar Orbiter will be equipped with both remote-sensing and in-situ instruments which will make unprecedented measurements of the solar atmosphere and the inner heliosphere. A crucial set of measurements will be provided by the Solar Wind Analyser (SWA) suite of instruments. This suite consists of an Electron Analyser System (SWA-EAS), a Proton and Alpha particle Sensor (SWA-PAS), and a Heavy Ion Sensor (SWA-HIS) which are jointly served by a central control and data processing unit (SWA-DPU). Together these sensors will measure and categorise the vast majority of thermal and suprathermal ions and electrons in the solar wind and determine the abundances and charge states of the heavy ion populations. The three sensors in the SWA suite are each based on the top hat electrostatic analyser concept, which has been deployed on numerous space plasma missions. The SWA-EAS uses two such heads, each of which have 360° azimuth acceptance angles and ±45° aperture deflection plates. Together these two sensors, which are mounted on the end of the boom, will cover a full sky field-of-view (FoV) (except for blockages by the spacecraft and its appendages) and measure the full 3D velocity distribution function (VDF) of solar wind electrons in the energy range of a few eV to ∼5 keV. The SWA-PAS instrument also uses an electrostatic analyser with a more confined FoV (−24° to +42° × ±22.5° around the expected solar wind arrival direction), which nevertheless is capable of measuring the full 3D VDF of the protons and alpha particles arriving at the instrument in the energy range from 200 eV/q to 20 keV/e. Finally, SWA-HIS measures the composition and 3D VDFs of heavy ions in the bulk solar wind as well as those of the major constituents in the suprathermal energy range and those of pick-up ions. The sensor resolves the full 3D VDFs of the prominent heavy ions at a resolution of 5 min in normal mode and 30 s in burst mode. Additionally, SWA-HIS measures 3D VDFs of alpha particles at a 4 s resolution in burst mode. Measurements are over a FoV of −33° to +66° × ±20° around the expected solar wind arrival direction and at energies up to 80 keV/e. The mass resolution (m/Δm) is > 5. This paper describes how the three SWA scientific sensors, as delivered to the spacecraft, meet or exceed the performance requirements originally set out to achieve the mission’s science goals. We describe the motivation and specific requirements for each of the three sensors within the SWA suite, their expected science results, their main characteristics, and their operation through the central SWA-DPU. We describe the combined data products that we expect to return from the suite and provide to the Solar Orbiter Archive for use in scientific analyses by members of the wider solar and heliospheric communities. These unique data products will help reveal the nature of the solar wind as a function of both heliocentric distance and solar latitude. Indeed, SWA-HIS measurements of solar wind composition will be the first such measurements made in the inner heliosphere. The SWA data are crucial to efforts to link the in situ measurements of the solar wind made at the spacecraft with remote observations of candidate source regions. This is a novel aspect of the mission which will lead to significant advances in our understanding of the mechanisms accelerating and heating the solar wind, driving eruptions and other transient phenomena on the Sun, and controlling the injection, acceleration, and transport of the energetic particles in the heliosphere.

The impact of PbF2 on the ionizing radiation shielding competence and mechanical properties of TeO2–PbF2 glasses and glass-ceramics

The influence of adding PbF2 on the elastic properties and radiation shielding competences of nine different samples labelled as TPb10-TPb90 with the form of (100-X)TeO2-XPbF2: (where X = 10–90 in steps of 10 mol%) glasses and glass-ceramics was investigated via the bond compression model and WinXcom software. The average cross-link density (n‾c) increased from 2.2 to 3.8 and the average atomic ring size (l) decreases from 0.390 to 0.356 nm with the increase of Pb ions content in the TPb10-TPb90 samples. The KBC increased from 84.47 GPa to 111.09 GPa and Young's modulus (EBC) increased from 136.89 GPa to 199.60 GPa for TPb10 to TPb90 samples. Poisson's ratio (σBC) decreased from 0.229 to 0.200, while the hardness (H) increased from 10.02 GPa to 16.59 GPa. The MAC of the glasses follows the order throughout the energy spectrum: TPb10 < TPb20 < TPb30 < TPb40 < TPb50 < TPb60 < TPb70 < TPb80 <TPb90. The maximum value of LAC obtained at 15 keV were: 290, 348, 405, 462, 519, 575, 632, 688, and 744 cm−1 for TPb10, TPb20, TPb30, TPb40, TPb50, TPb60, TPb70, TPb80, and TPb90, respectively. HVT and MFP are inversely proportional to LAC, hence, the highest and the lowest values of HVT and MFP were obtained for TPb10 and TPb90 samples at all energies. The TPb90 had the highest Zeff while TPb10 had the least. The buildup factors of TPb10 was highest at all depths while TPb90 had the least buildup factors. The obtained results showed that the addition of Pb to the proposed samples improves their mechanical and radiation shielding properties. Therefore, TPb90 sample has a better photon, fast neutron, proton, and alpha particle absorber compared to the other eight glass species in this study.

Training and education of pediatric radiation oncologists: A survey from the 2019 Pediatric Radiation Oncology Society meeting.

To examine the educational background, clinical practice, and preferences regarding continuing medical education (CME) among radiation oncologists who attended the 2019 meeting of the Pediatric Radiation Oncology Society (PROS), a survey consisting of 20 questions was distributed asking for demographic and educational background, clinical practice, and preferences regarding pediatric radiation oncology CME. Of 188 participants, 130 (69.2%) returned the questionnaire. More than 80% reported access to CT simulation, three-dimensional radiotherapy, and general anesthesia while <30% had access to intraoperative radiotherapy, proton, and heavy particle therapy. After residency, 12.1% did further training in pediatric radiation oncology. When asked about further training in pediatrics after residency, 88.8% answered that there should be a formal training program beyond residency in order to treat children. More than 75% acquired knowledge in pediatric radiation oncology through journals, books, live meetings, and tumor boards. The results of this survey may help Pediatric Radiation Oncology Society (PROS) in creating guidelines and recommendations for improvement in pediatric radiation oncology training and practice support as well as the development of CME activities most likely to benefit practitioners.

Quantum Impedance of Proton and Beta Particle by Employing the DE-Broglie Hypothesis alongside Heisenberg’s Uncertainty Principle

IN this paper, alongside Heisenberg's principle of uncertainty, the De-Broglie wavelength hypothesis was used to conclude at a new understanding of the quantum impedance shown by the proton when interacting with the material. It also extracted the quantum impedance, speed, and frequency of electron (a beta particle with energy below 1MeV). This assumed that the electrons and protons have the same wavelength when interacting with the material at a high- voltage vacuum power supply. These formulas can be considered as one of the important applications in nanotechnology that can be used in the field of radiotherapy. The findings obtained concerning beta particle velocity showed that they are compatible with their established formulations, but with a new method. Furthermore, the Beta particle frequency formula may be viewed as a new version. The use of uncertainty in determining the location and momentum of the proton and the beta particle has also been found to have a significant impact in achieving their quantum impedances. Besides that, the quantum impedance of beta particle was obtained according to the principle of conductivity. The results showed the relevance of equation 8 when evaluating the impedance of the proton. It is attributed to the inclusion of the Mp / Me ratio, in addition to the similarity of the remaining variables with the content of the beta particle's quantum impedance formula. The Die-Broglie wavelength was determined, as opposed to the usual. Results showed that a linear relationship between the velocity of the beta ray and its frequency with the power supply.

Nuclear shielding properties of B2O3–Pb3O4–ZnO glasses: Multiple impacts of Er2O3 additive

This study aimed to examine nuclear radiation shielding properties of a novel glass system, which has nominal compositions (40-x) B2O3 +40Pb3O4 +20ZnO + xEr2O3 with several substitution proportions of Er2O3 (x = 0, 1, 2, 3, 4 and 5). The conventional solid-state method was utilized to fabricate the Er2O3 doped glasses. To obtain the amorphous nature of manufactured glass samples, X-ray diffraction (XRD) patterns were investigated. Moreover, mass attenuation coefficients (μ/ρ) of the prepared glasses were adjusted by employing MCNPX simulation code. Other important gamma-ray attenuation parameters namely Half Value Layer (HVL), Mean Free Path (MFP), Effective and Equivalent Atomic Numbers (Zeff and Zeq) and Exposure Buildup Factor (EBF) of the glasses were also extensively addressed by obtaining mass attenuation coefficients (μ/ρ). The outcomes indicated that the Er2O3 additive enhances the photon attenuation qualification of the glasses. Moreover, the success of glasses in reducing fast neutrons was judged by calculating effective removal cross sections (ΣR). The results showed that increasing Er2O3 additive upgraded the prepared glasses in the attenuation of neutrons as in gamma rays. In addition, the protection ability of the fabricated glasses against alpha and proton charged particles was also evaluated. Charged alpha and proton particles in BPZE5 glass have the shortest projected ranges which are 50.38 μm and 436.36 μm respectively. It was seen that the increase of Er2O3 additive upgraded the prepared glasses in terms of attenuation of all of the selected radiation types. It can be deduced that these results might help for estimating the effect of Er2O3 on different glass systems in the future.

Synthetic polymer hydrogels as potential tissue phantoms in radiation therapy and dosimetry

The efficacy of synthetic polymers as hydrogel phantoms for radiation therapy and dosimetry has been investigated for photon and charged particle (electron, proton and alpha particle) interactions. Tissue equivalence has been studied in terms of photon mass energy-absorption coefficients, KERMA (kinetic energy released per unit mass), equivalent atomic number and energy absorption build-up factors, relative to human tissues (skin, soft tissue, cortical bone and skeletal muscle), in the energy range 0.015–15 MeV. For charged particle interactions, ratio of effective atomic number is examined for tissue-equivalence in the energy region of 10 keV–1 GeV. Well established theoretical formulations are used for computation of photon mass-energy absorption effective atomic number, electron density and KERMA. Five-parameter geometric progression (G-P) fitting approximation is used to compute the values of energy absorption build-up factors. Effective atomic number for charged particle interaction is determined using logarithmic interpolation method. Using the analytical methodology, it has been revealed that all the selected synthetic polymers have good tissue-equivalence relative to all tissue except cortical bone. In particular, polyglycolic acid (PGA) and poly-lactic-co-glycolic acid (PLGA) prove to be best substitute material for photon interactions. On the other hand, % difference between effective atomic number for charged particle relative to human tissues is found least for polyethylene glycol (PEG) demonstrating adequate tissue-equivalence. Therefore, the present study is expected to be useful to choose most appropriate phantom material for radiation therapy.

Elastic moduli, photon, neutron, and proton shielding parameters of tellurite bismo-vanadate (TeO2–V2O5–Bi2O3) semiconductor glasses

In this research, elastic moduli, photon, neutron, proton, and alpha particle shielding parameters for tellurite bismo-vanadate (TeO2–V2O5–Bi2O3) were estimated and theoretically presented. Makishima–Mackenzie's (M-M) model and Phy-X/PSD software were used to achieve the required calculations. Young's modulus varied from 72.68 to 59.41 GPa while shear modulus varied from 28.75 to 23.66 GPa. Bulk modulus changed from 51.34 to 40.51 GPa, while Poisson's ratio changed from 0.264 to 0.255. The trend of the projected range for alpha and proton particles follows the order: (TVB00)Range > (TVB05)Range > (TVB10)Range > (TVB15)Range > (TVB20)Range > (TVB25)Range. The mass attenuation coefficient of the TVB glasses follows the order: (TVB00)μm < (TVB05)μm < (TVB10) μm < (TVB15) μm < (TVB20) μm < (TVB25) μm at all energies. The MFP follows a similar trend as HVT, where TVB00 glass has the highest MFP and HVT among the considered glasses. The lowest range of Zeff was achieved TVB00 glass and the highest for TVB25 glass. The f-factor of the TVB-glasses were almost equal due to similar number of electrons per unit mass. The variations in buildup factors with photon energy were identical for all glass materials and penetration depth (mfp). Results revealed that the inclusion and increase of Bi in the TVB-glass systems improves its radiation shielding capacity.

Charged particles and gamma-ray shielding features of oxyfluoride semiconducting glasses: TeO2-Ta2O5-ZnO/ZnF2

In this study, the uncharged/charged and photon shielding features of TeO2.Ta2O5.ZnO/ZnF2 tellurite-rich glass system with different ZnO/ZnF2 ratio (encoded as TTZ, TTZF4, TTZF8, TTZF12 and TTZF16) were comprehensively discussed. The mass attenuation coefficients (MAC) were achieved employing MCNPX simulation codes and the outcomes were verified with theoretical data computed by WinXCOM software. The MACs varied between 47.667 to 0.034 for TTZ glass (for ZnO=16 mol%) and the largest MAC values were gained for TTZ glass among the others. Several MAC-based photon attenuation parameters, Half Value Layer (HVL), equivalent atomic number (Zeq) and Exposure Buildup Factor (EBF), of TTZF glasses were also determined for the energy range of 0.015–15 MeV. The results indicated that the enhancement in ZnO grows the gamma-ray attenuation competences of TTZF glasses. Furthermore, removal cross section of fast neutrons (∑R) for TTZF glasses was found and it has been noted that higher glass density has enhanced the ∑R values. The ΣR values of TTZF glasses change between 0.1103-0.1174 cm-1. At last, projected range (PR) and mass stopping power (MSP) for charged particles has been investigated within the kinetic energy range between 0.01–10 MeV. It is found that all TTZF glasses possess nearly close MSP and PR values for proton and alpha particles. We trust that the results of this study will guide the radiation protection capabilities of tellurite-rich glass systems.

Iron (III) oxide doped lithium borate glasses: structural and charged particles/photon shielding properties

The elemental composition and surface morphologies of the (Li2B4O7) (100-x) - (Hematite) x glass samples (here x = 10,20, 30 and 40% weight) were acquired by SEM/EDX measurements. Using the EDX results, the mass attenuation coefficient (µ/ρ in units of cm2/g) of the glasses were generated with MCNPX simulation codes and calculated by XCOM software. Both results were matched by utilizing relative deviations. Next, Half Value Layer (HVL), Effective Atomic Number (Zeff), Mean Free Path (MFP), Exposure Buildup Factors (EBF), Energy Absorption Buildup Factors (EABF), Fast Neutron Removal Cross Sections (ΣR) and Relative Dose Distribution (RDD - for gamma and neutron) were calculated. Mass Stopping Power (MSP) and Projected Range (PR) values were calculated to examine the proton and alpha shielding properties of the hematite doped glass samples. According to the results obtained, µ/ρ, Zeff, and ΣR values increase as the percentage of hematite mineral in the glass samples increases. In addition, it was observed that HVL, MFP, EBF, EABF and RDD values decreased with increasing hematite percentage. The increase in the rate of hematite in the glass provided alpha and proton particles to have shorter ranges. Among the studied glass samples, lithium borate glass with 40% hematite mineral ratio is the sample with the best gamma, neutron and charged particles shielding features.

Physical design and multi-particle simulations of a compact IH-DTL with KONUS beam dynamics for proton therapy

A compact room-temperature inter-digital H-mode (IH) drift tube linac (DTL) with Kombinierte Null Grad Struktur beam dynamics is proposed in this paper. The proposed IH-DTL, which operates at 325 MHz, accelerates 18 mA proton particles from 3.0 to 7.0 MeV as part of a proton synchrotron-based therapy system. It is composed of two main sections, namely a bunching section (− 30°) and accelerating section (0°). There is no transverse focusing element inside the cavity, which increases the acceleration gradient and reduces the cavity length and power consumption. In our physical designs, LORASR code is utilized for beam dynamics design and multi-particle simulations. The synchronous particle energy, injection phase, and acceleration voltage of each gap are optimized carefully to increase transmission efficiency while minimizing beam emittance growth and beam loss. The total length of the cavity is 0.82 m and the acceleration gradient reaches 4.88 MV/m, resulting in a transmission efficiency of 100% and beam emittance growth less than 10%. The details of the specific work undertaken in this study are presented in this paper.

An experimental work on radiation protection features of some bioactive compounds of Mannich bases

In the present research, seven Mannich bases, bioactive compounds, as anticancer drug proposed which have different chemical composition has been studied comprehensively in terms of photons and charged particles protecting features. Aryl part of the compounds was changed as phenyl, 4-methylphenyl, 4-fluorophenyl, 4-bromophenyl, 4-methoxyphenyl, 4-nitrophenyl and 4-chlorophenyl. The experimental values of mass attenuation coefficients (μm) were obtained by the help of HPGe detector for 8.04–59.54 keV photon energies. Experimental results of μm were matched by the theoretical results which were found by using WinXCOM program. It has been obtained that the μm values of the samples, arly part is varied with 4-bromophenyl (S4) and 4-chlorophenyl (S7), are largest than that of other samples. In addition, other basic photon attenuation parameters, equivalent and effective atomic numbers (Zeq and Zeff) and energy absorption buildup factor (EABF) values for the proposed compounds have been achieved in the range of 0.015–15 MeV. While the highest Zeff and Zeq values belong to the S4 sample, the EABFs were obtained to be the smallest for the S4 sample according to the other sample. Lastly, the attenuating capacity of the compounds against charged particles such as alphas and protons was estimated by calculating the mass stopping power (MSP) and the range of the particles. The S4 sample with 4-bromophenyl aryl part was found to be outstanding in stopping alpha and proton particles. It was deduced that the S4 sample is a better drug candidate for photon and particle radiations protection applications among the other compounds. The present data will be useful to determine the radiation parameters of further drug candidates in medical oncology and nuclear medicine.

Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and nuclear radiation shielding properties of [α-Fe3+O(OH)]-doped lithium borate glasses

Goethite [α-Fe3+O(OH)]-doped lithium borate glasses in the chemical form of [(100 − x) Li2B4O7 mineral x = 10, 20, 30, 40 wt%] were synthesized and investigated in terms of their ability to protect the human being and environment from ionizing radiation. Elemental analysis of four different goethite [α-Fe3+O(OH)]-doped lithium borate glass samples called GOG10, GOG20, GOG30 and GOG40 prepared in different contribution rates was tested using energy-dispersive X-ray technique. In addition, the surface morphology of the manufactured glass samples was determined by scanning electron microscopy. The glass samples subject to the study were evaluated in terms of radiation shielding properties by calculating the shielding parameters such as mass attenuation coefficient (μm), half value layer, mean free path, effective atomic number (Zeff), exposure and energy absorption build-up factors, effective removal cross section (ΣR) for fast neutron and RDD (for gamma and neutron) with the help of the XCOM and MCNPX simulation code. Mass stopping power and projected ranges values of the studied glass samples were calculated in order to consider the shielding performance against proton and alpha particles. The results showed that increase in goethite additive increases the gamma protection capacity of glasses. As a result, the glass sample with the highest goethite contribution encoded with GOG40 has better shielding efficiency in terms of the gamma and neutron radiation shielding.

Tl₂ZrCl₆ and Tl₂HfCl₆ Intrinsic Scintillators for Gamma Rays and Fast Neutron Detection

Thallium zirconium chloride (Tl2ZrCl6) and its hafnium analog (Tl2HfCl6) are intrinsic scintillators that have been recently reported, primarily for gamma-ray detection and spectroscopy. These crystals are especially useful for dual-mode detection, gammas exploiting the highly effective $Z$ of the materials, and fast neutrons using the (n, p) and (n, $\alpha$ ) reactions with chlorine. $Z_{\mathrm {eff}}$ (70.7) and high photoelectric conversion efficiency of the zirconium variant without any activator makes it particularly attractive in this regard. We report here on the growth of undoped Tl2ZrCl6 and Tl2HfCl6 crystals using vertical Bridgman technique. The X-ray emission spectrum shows a broadband in the range of 400–600 nm with a peak around 470 nm for both crystals. The light yields (LYs) of these crystals were measured under irradiation by a 137Cs gamma source (662 keV) and compared with that from the commercial Tl-doped NaI crystal. Normalized for the quantum efficiency of the photomultiplier (PMT) at the relevant emission wavelengths, the respective LYs of Tl2ZrCl6 and Tl2HfCl6 are estimated to be 40 000 and 18 000 photons/MeV with corresponding energy resolution of 5% and 9%, respectively. We have demonstrated for the first time the neutron detection capability of these materials showing excellent pulse shape discrimination (PSD) with figure of merit on the order of 2.4. PSD measurement of Tl2ZrCl6 using a 241AmBe source demonstrates well-separated gamma, recoiled proton, and alpha particle bands.

A new approach to modeling the microdosimetry of proton therapy beams.

To revisit the formulation of the mean chord length in microdosimetry and replace it by the particle mean free path appropriate for modelings in radiobiology. We perform a collision-by-collision followed by event-by-event Geant4 Monte Carlo simulation and calculate double-averaged stepping length, 〈〈l〉〉, for a range of target sizes from mm down to μm and depth in water. We consider 〈〈l〉〉 to represent the particle mean free path. We show that 〈〈l〉〉 continuously drops as a function of depth and asymptotically saturates to a minimum value in low energies, where it exhibits a universal scaling behavior, independent of particle nominal beam energy. We correlate 〈〈l〉〉 to linear density of DNA damage, complexities of initial lethal lesions and illustrate a relative difference between predictive RBEs in model calculations using mean chord length vs the proposed mean free path. We demonstrate consistency between rapid increase in RBE within and beyond the Bragg peak and 〈〈l〉〉, a decreasing function of depth. An interplay between localities in imparted energy at nanometer scale and subsequent physio-chemical processes, causalities and pathways in DNA damage requires substitution of geometrical chord length of cell nuclei by mean-free path of proton and charged particles to account for a mean distance among sequential collisions in DNA materials. To this end, the event averaging over cell volume in the current microdosimetry formalism must be superseded by the collision averaging scored within the volume. The former, is fundamentally a global attribute of the cell nuclei surfaces and boundaries and is characterized by their membrane diameters, hence such global indices are not appropriate to quantitatively represent the radiobiological strength of the particles and their RBE variabilities that is associated with the sensitivities to local structure of the collisions and their spatio-temporal collective patterns in DNA materials.

Influence of Ag2O insertion on alpha, proton and γ-rays safety features of TeO2.ZnO.Na2O glasses: Potential use for nuclear medicine applications

Influence of Ag2O insertion on the nuclear radiation safety features of sodium zinc-tellurite glasses has been reported. To this end, six glasses of 80TeO2.10ZnO.[(10-x)Na2O.xAg2O)]: x = 0–10 mol% abbreviated as (TZNA0-TZNA10) have been chosen. The mass attenuation coefficients (μ/ρ) were simulated using MCNP-5 simulation codes and the results were matched with which calculated via XCOM software. In term of μ/ρ, half value layer, mean free path (HVL, MFP), effective atomic number, equivalent atomic number (Zeff, Zeq), exposure and energy absorption buildup factors (EBF, EABF), Mass Stopping Power (MSP) and the Projected range (PR) of the proton and alpha particles have been evaluated. Results reveal that the increase in Ag2O from 0–10 mol % enhances the attenuation properties of TZNA glasses and the μ/ρ takes the order that TZNA10>TZNA8>TZNA6>TZNA4>TZNA2>TZNA0. The insertion of Ag2O in the TZNA glasses reduced the HVL, MFP, and exposure buildup factors (EBF and EABF). In addition, the smallest values of MSP and PR for proton and alpha particles observed for TZNA10 glass. Moreover, the insertion of Ag2O leads to enhance the radiation safety capability of the TZNA glasses to apply in various medical applications.

Simulation of direct DNA damages caused by alpha particles versus protons

Geant4-DNA was used to calculate the direct DNA breaks due to the alpha and proton particles. For alpha particles with the energy of smaller than 1 MeV, the number of Single-Strand Breaks (SSBs), Double-Strand Breaks (DSBs) and the dose were found to increase. Beyond 1 MeV energy, SSB, DSB and Dose had a falling trend. In the case of DSBs, however, the alpha yields increased from 3.67 (GyGbp)−1 with the energy of 0.1 MeV to 6.43 (GyGbp)−1 at 1 MeV. Beyond 1 MeV energy, the yields decreased to 1.37 (GyGbp)−1 at 30 MeV. The ratio of alpha DSB yields to proton DSB yields increased from 0.1 MeV to 0.5 MeV, but, after 0.5 MeV, the trend changed to a decrease. The calculated results, demonstrated that the difference between alpha and proton SSB yields is not significant, while it is considerable for DSB yields especially with the energy of 2 MeV.