MeV Proton Irradiation Research Articles

THE PHITS SIMULATION STUDY FOR AN ALTERNATIVE PRODUCTION OF ³²P RADIOISOTOPE BY SECONDARY NEUTRON BOMBARDMENT OF ³²S TARGET

Different methods of phosphorous-32 (32P) radioisotope production have been of great interest over the past few years due to the wide range of 32P applications in agriculture, health, and the environment. In this present study, using the PHITS simulation, 32P radioisotope was theoretically produced by bombarding a natural sulfur target with secondary neutrons generated from 13, 18, and 30 MeV proton irradiation of Ti targets with thicknesses of 0.7, 1.2, and 3.0 mm, respectively. The calculated results showed that secondary neutron flux ranging from 1.78x1012 to 9.46x1012 n/cm2s was generated from titanium-bombarded protons, which resulted in the 32P radioactivity yields of 0.200, 0.840, and 3.167 MBq/μAh for proton energies of 13, 18, and 30 MeV, respectively. For 13 MeV protons, no radioactive impurity was generated during the bombardment, while radioactive impurities such as 31Si, 30P, 28Al, and 31S were produced from 30 MeV proton bombardment. The 32P radioactivity yield s and the radioactive impurity yields increase further when the 32S target is increased to 10 grams.

Features of the Effects of Exposure to 90–170 MeV Proton Radiation on the Blood-Forming Organs in Mice under Total Irradiation with Proton Pencil Scanning Beam Depending on the Linear Energy Transfer of Particles

Features of the Effects of Exposure to 90–170 MeV Proton Radiation on the Blood-Forming Organs in Mice under Total Irradiation with Proton Pencil Scanning Beam Depending on the Linear Energy Transfer of Particles

Effect of 5 MeV proton irradiation on electrical and trap characteristics of β-Ga2O3 power diode

In this study, impact of 5 MeV proton irradiation with radiation fluence of 1013 cm−2 on β-Ga2O3 power diode is investigated by a β-Ga2O3 Schottky barrier diode (SBD). Via temperature-dependent measurements, carrier removal rate RC is determined to be 7.26 × 102 cm−1 at 300 K. Meanwhile, the threshold voltage (Von) and ideality factor (n) almost remain stable after proton irradiation. A close-to-unity n was observed for a wide temperature range indicating near-ideal Schottky characteristics. Dynamic degradation was observed at 300K, but was greatly suppressed at a low temperature of 100K. Meanwhile, two more bulk traps are discovered in proton irradiated β-Ga2O3 SBD by deep-level transient spectroscopy (DLTS). The larger corrected trap concentration (NTa) in proton irradiated β-Ga2O3 SBD was regarded as the reason behind slightly worsened dynamic on-resistance instability at 300 K. Furthermore, lower low frequency noise is revealed for proton irradiated device at room temperature and cryogenic temperature. The study demonstrates the competitive irradiation hardness of β-Ga2O3 power diodes and paves a solid path for the deployment of β-Ga2O3 in space.

Behavior of Fe-based alloys in a liquid lead-bismuth environment under simultaneous proton irradiation and corrosion

The performance and longevity of nuclear reactors are significantly influenced by the behavior of their structural materials, particularly under conditions of corrosion and irradiation. This study investigates the combined effects of corrosion and irradiation on three alloys: Fe-Ni-Cr-Al-Nb, Fe-Cr-Al-Y, and Fe-12Cr-2Si, exposed to a liquid Pb-4wt% Bi mixture at 675 °C for 4 h. 3 MeV proton irradiation was employed to understand the simultaneous effects of irradiation on the corrosion behavior of these alloys. When exposed to liquid lead-bismuth at 675 °C for 4 h, the Fe-Cr-Al-Y and Fe-12Cr-2Si alloys exhibited superior corrosion resistance compared to the Fe-Ni-Cr-Al-Nb alloy. Conversely, the Fe-Ni-Cr-Al-Nb alloy demonstrated significant Pb-Bi penetration, which was further accelerated by proton irradiation, resulting in increased penetration depth. This revealed that irradiation-induced damage can accelerate the corrosion rate of Fe-Ni-Cr-Al-Nb steel in lead-bismuth environments. Microstructural analysis using SEM/EDX, STEM, and diffraction patterns uncovered complex alloy interactions and potential chemical transformations in the irradiated Fe-Ni-Cr-Al-Nb alloy. This included the presence of lamellar or rod-like structures near Pb-Bi penetration sites and the selective retention of nickel by aluminum. In contrast, the Fe-12Cr-2Si alloy exhibited effective corrosion resistance attributed to a uniform distribution of elements and the formation of a protective Si-rich oxide layer. The Fe-Cr-Al-Y alloy developed distinct oxide layers, with chromium oxide predominating and a slight aluminum oxide layer, indicating the critical role of chromium oxide as a protective barrier.

Unraveling the Degradation and Air-Induced Healing Mechanisms of Halide Perovskites under Proton Irradiation.

As exceptional potential candidates for future-generation space photovoltaics, perovskite solar cells (PSCs) have been proven to be radiation-tolerant and recoverable under proton irradiation. Nevertheless, a key point, the influence of the atmosphere, has often been overlooked in ground-based irradiation experiments. Here, the atmosphere-dependent radiation tolerance and healing of perovskite materials under MeV proton irradiation are demonstrated by utilizing in situ electrical characterizations. Significant degradation is observed in the electrical properties after irradiation, which can hardly be recovered in vacuum but can quickly be recovered to approach the initial state in the presence of oxygen. The atmosphere-dependent behaviors are related to the proton-induced iodine vacancies in perovskites through in situ and ex situ characterizations. Ultimately, the underlying degradation and healing mechanisms are unraveled by using simulation. This work aims to provide a more comprehensive assessment of radiation tolerance of perovskites. These results are of great significance for designing and optimizing PSCs for future space applications including rapid screening, encapsulation, and radiation hardening.

Proton irradiation Of Ga2O3 Schottky diodes and NiO/Ga2O3 heterojunctions

p-NiO/n-Ga2O3 heterojunction (HJ) diodes exhibit much larger changes in their properties upon 1.1 MeV proton irradiation than Schottky diodes (SDs) prepared on the same material. In p-NiO/Ga2O3 HJ diodes, the narrow region adjacent to the HJ boundary is found to contain a high density of relatively deep centers with levels near EC-0.17 eV and a depleted region in the immediate vicinity of the HJ boundary. The series resistance of the HJ diodes is slightly higher than for the Schottky diodes and shows a temperature dependence with activation energy ~ 0.12 eV, like the temperature dependence of the NiO film resistivity. Irradiation with 1.1 MeV protons leads to a decrease of the hole concentration in the NiO, with a high carrier removal rate of ~ 1.3 × 105 cm−1 and a strong compensation of the interfacial region where the concentration of the EC-0.17 eV centers decreases with a high rate of ~ 7 × 103 cm−1. The combined action of these two effects gives rise to the much stronger increase of the series resistance of the HJ diodes compared to Schottky diodes. The observed differences between the radiation response of the HJs and SDs cannot be credibly attributed to the changes of the density of any of the deep electron and hole traps detected in our experiments.

Effects of 100 MeV proton irradiation on the performance of P3HT-based perovskite solar cells

Perovskite solar cells (PSCs) are promising for space applications. In this work, P3HT-based PSCs were irradiated at room temperature with 100 MeV protons to various fluences. The efficiencies of the PSCs were significantly increased by 30–35 % after irradiation with low fluences up to 1 × 1011p/cm2. Meanwhile, the illumination yields and charge carrier lifetime of the perovskite films were found to be improved after irradiation, which is attributed to the irradiation-induced healing of lattice defects in perovskites. When irradiated to a higher fluence of 1 × 1012p/cm2, the transmittance of the glass substrates was distinctly reduced due to the formation of color-center defects, which resulted in the performance degradation of the cells. Considering that P3HT-based PSCs have better thermal stability in outer space than the widely used spiro-OMeTAD-based PSCs, the reported results may have important implications for space applications of PSCs.

Degeneration mechanism of 30 MeV and 100 MeV proton irradiation effects on 1.2 kV SiC MOSFETs

In this study, we evaluated and characterized the effects of various proton irradiation energies and fluences on the electrical characteristics of SiC MOSFETs using a proton accelerator. The devices under test (DUTs) were fabricated utilizing 1.2 kV SiC MOSFET processes. To assess the impact of total ionizing dose (TID) and displacement damage (DD) on SiC MOSFETs, the DUTs were exposed to protons irradiation at energies of 30 MeV and 100 MeV, under ambient temperature conditions. Additionally, we examined the radiation hardness of DUTs under varying proton fluences, including 1 × 1012 cm−2, 1 × 1013 cm−2, 5 × 1013 cm−2, and 1 × 1014 cm−2.The results demonstrate that the threshold voltage (Vth) of the irradiated devices exhibited a negative shift, attributable to radiation-induced positive oxide trapped charges. This negative shift in Vth, coupled with the accumulation of positive trapped charges in the field limiting ring (FLR) oxide, resulted in augmented output currents and diminished breakdown voltage (BV) values. A significant reduction in current, ranging from 70% to 99%, was observed in the DUT subjected to irradiation at of 30 MeV and 1 × 1014 cm−2, highlighting the influence of DD. Conversely, irradiation at 100 MeV primarily revealed TID effects, characterized by a negatively shifted Vth. The on-state current at a gate voltage of 10 V and a drain voltage of 5 V of the DUT with irradiation of 100 MeV and 1 × 1014 cm−2 was a higher than that of DUT without irradiation because of a reduction of Vth.

Role of severe plastic deformation on mechanical behavior of irradiated materials: A case study with Nb-1Zr alloy

In this investigation, the effect of 5.6 MeV proton irradiation on the microstructure and mechanical properties of coarse grained (CG) and nanocrystalline (NC) Nb-1wt.%Zr (NZ) has been analysed. Bulk nanocrystalline microstructure was obtained by subjecting the alloy to room temperature high pressure torsion under 6 GPa hydrostatic pressure and 5 rotations. The CG and NC samples were irradiated at doses of 1.9 × 1017 p/cm2 and 1.8 × 1017 p/cm2, respectively. Microstructural parameters like crystallite size, dislocation density, and dislocation arrangements were studied in detail using X-ray line profile analysis (XLPA) by Convolutional Multiple Whole Profile (CMWP) fitting. Microscopic observations were made with electron microscopy techniques in the scanning and transmission modes. Differential Scanning Calorimetry (DSC) was performed to estimate the concentration of vacancies after HPT processing and irradiation. Tensile tests of irradiated CG and NC irradiated samples were performed and compared to those in unirradiated conditions. In the NC condition, not only did the irradiated sample show higher ultimate tensile strength but also twice the amount of uniform elongation as compared to the irradiated CG sample. The fracture surface clearly exhibited this higher plasticity post-irradiation in the NC samples. The change in deformation mechanisms due to nano-structuring of the microstructure has been anticipated to be a reason for the increase in ductility in a single-phase alloy has been explained thereafter.

Effect of Proton Irradiation on Thin-Film YBa2Cu3O7-δ Superconductor.

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa2Cu3O7-δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6×1016 p/cm2. Upon irradiation, Tc was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above Tc. This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between Tc and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov-Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress Tc.

Radiation effects modeling of InP-based HEMT based on neural networks

This paper has proposed a novel radiation effects modeling methodology based on neural networks for InP-based high-electron-mobility transistors (HEMTs). 2 MeV proton radiation has been performed with dose of 1 × 1012 H+/cm2, 5 × 1012 H+/cm2, 1 × 1013 H+/cm2, 5 × 1013 H+/cm2, 1 × 1014 H+/cm2. The radiation neural network models were comparatively constructed based on Feedforward Neural Network (FNN), Recurrent Neural Network (RNN), and Long Short-Term Memory (LSTM). Results indicate that the LSTM network outperforms the FNN and RNN networks in the modeling for both drain-source current (IDS) and S-parameters, which demonstrates superior prediction accuracy with smaller fitting error. The proposed modeling approach offers an accurate characterization for the radiation effects of InP-based HEMT devices, without the need to consider the complex degradation process associated with radiation, thus providing practical guidelines for the space applications of such devices.

Impact of proton radiation and annealing of CMOS image sensors on star sensor performance

Star sensors play a crucial role as high-precision optical attitude navigation devices in satellite attitude control systems. The CMOS image sensor is an important component of the imaging system of the star sensor and experiences performance degradation due to the total ionizing dose effect and displacement damage effect in the radiation environment of its long-term operational workspace. As a result, the detection capability and attitude positioning accuracy of the star sensor gradually deteriorate. The performance of CMOS image sensors can be partially restored after annealing but the impact on the performance of star sensors is unclear. This study conducted 100 MeV proton irradiation experiments with different fluences on CMOS image sensors and performed room temperature and high temperature annealing treatments. By testing and analyzing the performance of star sensors equipped with irradiated and different annealing treatments on CMOS image sensors, the impact mechanism of CMOS image sensor radiation damage and annealing recovery on the performance variation of star sensors was obtained. This study provides theoretical support for reliability of long-term in-orbit star sensors.

Dependence of the Silicon Carbide Radiation Resistance on the Irradiation Temperature

The effect of high-temperature electron and proton irradiation on SiC-based device characteristics is being investigated. Industrial integrated 4H-SiC Schottky diodes, each with an n-type base and a blocking voltage of either 600 V, 1200 V, or 1700 V, manufactured by Wolfspeed, are being studied. 0.9 MeV electron and 15 MeV proton irradiation were applied. It has been found that the irradiation resistance of silicon carbide Schottky diodes at high temperatures significantly exceeds their resistance at room temperature. This effect is attributed to the annealing of compensating defects induced by high-temperature irradiation. The parameters of radiation-induced defects are determined using the method of deep level transient spectroscopy (DLTS). Under high-temperature ("hot") irradiation, the spectrum of radiation-induced defects introduced into SiC appears to differ significantly from the spectrum of defects introduced at room temperature. It is suggested that approximately half of the compensation is due to radiation-induced defects formed in the bottom part of the bandgap.

Single-event burnout in β-Ga2O3 Schottky barrier diode induced by high-energy proton

Single-Event Burnout (SEB) can cause hard damage to devices, leading to permanent failure. However, previous studies have rarely explored the effects of high-energy proton irradiation-induced SEB in β-Ga2O3 Schottky Barrier Diode (SBD), and the underlying mechanisms remain largely unexplored. Experimental results indicate that the reverse bias voltage during irradiation is a critical factor influencing the failure of β-Ga2O3 SBD. Compared to 300 MeV proton irradiation without bias, the introduction of a 300 V reverse bias voltage results in a significant reduction in forward current density (JF). When the reverse bias voltage reaches 400 V or higher, the 300 MeV proton induces SEB in the device. The SEM image of the damaged region reveals that the irradiated device has “voids” formed due to the melting of the Ga2O3 material. Geant 4 and TCAD simulation results indicate that the burnout phenomenon is caused by the elevated lattice temperature inside the device, which results from the implantation of secondary particles under a high reverse bias voltage. As the reverse bias voltage increases, the maximum lattice temperature of β-Ga2O3 SBD also rises. When the reverse bias voltage is sufficiently high, the local lattice temperature inside the device reaches the melting point of Ga2O3 material, ultimately leading to SEB.

Suppression of irradiation effect on electrical properties of silicon diodes by iron in p-silicon

Radiation-hardness of silicon (Si) has been the subject of interest due to the damage of the material-based detectors during and after operation. In this work, the effects of 4 MeV proton-irradiation on the electrical properties of devices fabricated on undoped and Fe-doped p-Si were investigated using current-voltage (I-V) and capacitance-voltage (C-V) techniques. A decrease in current and capacitance is less pronounced and the conduction mechanism remains unchanged on Fe-doped p-Si diode after proton-irradiation. This insignificant change of electrical parameters of the Fe-doped diode after proton-irradiation indicates the suppression of the radiation effect by Fe in Si. The electrical properties of the diode are less dependent on incident radiation, because of the possible prevention of further dislodgement of atoms by incident radiation. As a result, the material becomes resistant to radiation damage, making the electrical properties of the diode independent of incident radiation due to Fe atoms in Si. As a result of the ohmic behaviour displayed by the Fe-doped Si diode, it is possible that in Si, Fe is responsible for generation-recombination (g-r) centres, which are defect levels positioned at the middle of the energy gap of Si. The possibility of these defects being responsible for the suppression of the radiation effect is explained in this work, making Fe a promising dopant to improve the radiation-hardness of Si.

An MeV Proton Irradiation Facility: DICE.

Materials applied in nuclear environments such as fission or fusion power-plants face severe conditions. The irradiation by neutrons induces thermal loads and irradiation damage. Furthermore, coolants in contact with the materials induce corrosion, which is particularly challenging for liquid salts intended for the next generation of fission reactors. A new device (DICE) is installed at the 3.5 MV accelerator at DIFFER for the accelerated testing of such materials under combined irradiation and corrosion conditions. The DICE enables irradiation of samples at temperatures of up to 1050 K and in contact with liquid salts. An integrated shielding and a low power temperature control concept based on radiation cooling enables high-duty cycle application in a standard accelerator laboratory. Ion currents of up to 30 µA are possible with continuous irradiation. This work outlines the technical concept of the device and presents the first data.

Micro-pillar compression of proton-irradiated chromium examined using cross-sectional site selection, electron microscopy, and molecular dynamics simulation

Deformation of proton-irradiated chromium was investigated using micro-pillar compression and electron microscopy. After 2 MeV proton irradiation at 350 °C, four micro-pillars were prepared from a single grain on the polished specimen cross section. Depending on the distance away from the irradiated surface, hardness as a function of local damage level was studied. All pillars developed a narrow deformation band on one set of near-adjacent {110} planes, arising from closely-positioned parallel gliding. The critical resolved shear stress for gliding along 〈111〉/{110} was measured to be 59.6 MPa in unirradiated material beyond the proton range. The critical stress increased by 20 % after 0.5 dpa, and by 58 % after 1 dpa, with saturation of hardening occurring by 0.7 dpa. Post-compression characterization using transmission electron microscopy showed extensive formation of nanometer size voids in a matrix dominated by tangled dislocations. No twinning was observed. The experimental observations are in good agreement with molecular dynamics simulation of pillar compression of chromium, showing dislocation gliding along 〈111〉/{110} and 〈111〉/{112}. The continued stability of chromium for LWR application requires extension of the exposure level from 1 dpa to ∼15 dpa expected for typical fuel pin exposure.

Forward bias annealing of proton radiation damage in NiO/Ga2O3 rectifiers

17 MeV proton irradiation at fluences from 3–7 × 1013 cm−2 of vertical geometry NiO/β-Ga2O3 heterojunction rectifiers produced carrier removal rates in the range 120–150 cm−1 in the drift region. The forward current density decreased by up to 2 orders of magnitude for the highest fluence, while the reverse leakage current increased by a factor of ∼20. Low-temperature annealing methods are of interest for mitigating radiation damage in such devices where thermal annealing is not feasible at the temperatures needed to remove defects. While thermal annealing has previously been shown to produce a limited recovery of the damage under these conditions, athermal annealing by minority carrier injection from NiO into the Ga2O3 has not previously been attempted. Forward bias annealing produced an increase in forward current and a partial recovery of the proton-induced damage. Since the minority carrier diffusion length is 150–200 nm in proton irradiated Ga2O3, recombination-enhanced annealing of point defects cannot be the mechanism for this recovery, and we suggest that electron wind force annealing occurs.

Enhancing radiation-hardness of Si-based diodes: An investigation of Al-doping effects in Si using I–V measurements

The impact of radiation on Si-based detectors garnered interest due to the observed degradation in their stability in high-radiation environments. In this study, we examined the effects of 3 MeV proton irradiation on both undoped and Al-doped n-Si diodes using I–V technique. The results revealed a decline in current trends for both types of diodes post-irradiation. This decrease was attributed to defects created by proton irradiation, which acted as recombination or trapping centres. However, the Al-doped n-Si diodes experienced a lesser decline in measured current, hinting at the radiation suppression effect of Al doping in Si. Additionally, Al-doped n-Si diodes displayed minimal changes in their diode parameters after irradiation, and their conduction mechanism remained unchanged. These results suggested that Al-doped n-Si diodes had superior stability compared to their undoped counterparts, implying that the presence of Al enhanced the diodes' resistance to radiation. The radiation suppression effect of Al seemed to stem from its ability to produce defects that improve Si's radiation-hardness, thereby mitigating the introduction of additional instability-causing defects during proton irradiation. Thus, incorporating Al was recommended for research aiming to improve the radiation resistance of Si.

15.5 MeV proton irradiation treatment of liquid phase exfoliated graphene

Exceptional Physical properties, including lightweight nature of graphene make it a highly promising material for space applications. However, the impact of proton irradiation, a common phenomenon in space environments, on the structural integrity and functional properties of graphene remains a critical area of research. This study aims to fill this gap by investigating the effects of proton irradiation on liquid-phase exfoliated graphene. We focus specifically on the alterations in infrared spectra and structural characteristics of graphene induced by irradiation with 15.5 MeV protons. Our analysis reveals that organic molecules and functional groups adsorbed on graphene during exfoliation elevate the Fermi level, suppressing graphene's infrared absorption through the Pauli blocking effect. We demonstrate that proton irradiation, at fluences up to 1 × 1015 proton/cm2, effectively removes adsorbed molecules and functional groups, thereby eliminating Pauli blocking effect. These findings contribute to a better understanding of the behavior of graphene under proton irradiation, essential for its utilization in space-centric applications such as thermal coatings, electronics, and optical devices.