Ground simulation tests of proton irradiation for Kapton films were conducted using the space synthesis irradiating facility,in which the energy of protons was chosen as 90 keV,and the flux was 5.0×1011 cm-2·...Ground simulation tests of proton irradiation for Kapton films were conducted using the space synthesis irradiating facility,in which the energy of protons was chosen as 90 keV,and the flux was 5.0×1011 cm-2·s-1.After proton irradiation some bulges like fingers appears on the surface of Kapton and the surface roughness increases apparently.UV/Vis analysis demonstrates that the irradiation leads to the red shifting in the edge of optical absorption and a strong increase in absorbance in the visible region.X-ray photoelectron spectroscopy(XPS) analysis indicates that the enrichment of carbon atom due to the bond breaking and reconstruction during the irradiation results in the degradation of the optical properties.展开更多
The effects of ionizing and displacement irradiation of high-energy x-ray and 2-MeV proton on GaN thin films were investigated and compared in this study.The electrical properties of both P-GaN and N-GaN,separated fro...The effects of ionizing and displacement irradiation of high-energy x-ray and 2-MeV proton on GaN thin films were investigated and compared in this study.The electrical properties of both P-GaN and N-GaN,separated from power devices,were gauged for fundamental analysis.It was found that the electrical properties of P-GaN were improved as a consequence of the disruption of the Mg-H bond induced by high-dose x-ray irradiation,as indicated by the Hall and circular transmission line model.Specifically,under a 100-Mrad(Si)x-ray dose,the specific contact resistance pc of P-GaN decreased by 30%,and the hole carrier concentration increased significantly.Additionally,the atom displacement damage effect of a 2-MeV proton of 1×10^(13)p/cm^(2)led to a significant degradation of the electrical properties of P-GaN,while those of N-GaN remained unchanged.P-GaN was found to be more sensitive to irradiation than N-GaN thin film.The effectiveness of x-ray irradiation in enhancing the electrical properties of P-GaN thin films was demonstrated in this study.展开更多
We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory....We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory. The diffusion coefficients are proportional to the electric field amplitude E, much greater than those for the regular first-order resonance, which are proportional to the electric field amplitudes square E^2. Numerical calculations for the pitch angle scattering are performed for typical energies of protons Ek = 50 keV and 100 keV at locations L = 2 and L = 3.5. The timescale for the loss process of protons by the Whistler waves is found to approach one hour, comparable to that by the EMIC waves, suggesting that Whistler waves may also contribute significantly to the ring current decay under appropriate conditions.展开更多
An analytical model for hole boring proton acceleration by a circularly-polarized CO_(2) laser pulse in a gas jet is developed.The plasma density profile near the density peak is taken to be rectangular,with inner reg...An analytical model for hole boring proton acceleration by a circularly-polarized CO_(2) laser pulse in a gas jet is developed.The plasma density profile near the density peak is taken to be rectangular,with inner region thickness l around a laser wavelength and density 10%above the critical,while the outside density is 10%below the critical.On the rear side,plasma density falls off rapidly to a small value.The laser suffers strong reflection from the central region and,at normalized amplitude a _(0)≥1,creates a double layer.The space charge field of the double layer,moving with velocity v_(f)z,reflects up-stream protons to 2v_(f) velocity,incurring momentum loss at a rate comparable to radiation pressure.Reflection occurs for v_(f)≤ω_(p)√z_(f)lm/m_(p),where m and m_(p) are the electron and proton masses,z_(f) is the distance traveled by the compressed electron layer and u p is the plasma frequency.For Gaussian temporal profile of the laser and parabolic density profile of the upstream plasma,the proton energy distribution is narrowly peaked.展开更多
NPN-input bipolar operational amplifiers LM741 were irradiated with ^60Coγ-ray, 3 MeV protons and10 MeV protons respectively at different biases to investigating the proton radiation response of the NPN-input operati...NPN-input bipolar operational amplifiers LM741 were irradiated with ^60Coγ-ray, 3 MeV protons and10 MeV protons respectively at different biases to investigating the proton radiation response of the NPN-input operational amplifier. The comparison of protons with^60Coγ-rays showed that the proton radiation mainly induced ionization damage in LM741. Under different bias conditions, the radiation sensitivity is different; zero biased devices show more radiation sensitivity in the input biased current than forward biased devices. Supply current（±Icc）is another parameter that is sensitive to proton radiation,^60Coγ-ray, 3 MeV and 10 MeV proton irradiation would induce a different irradiation response in ±Icc, which is caused by different ionization energy deposition and displacement energy deposition of^60Coγ-ray, 3 MeV and 10 MeV proton irradiation.展开更多
Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly...Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly understood, while the alternations could be sensitively detected by proton （~H） nuclear magnetic resonance spectroscopy （MRS）. In this study, we investigated the metabolic characteristics of radiation-induced brain injury through a long-term tbllow-up after radiation treatment using MRS m vivo. Methods： A total of 12 adult Sprague-Dawley rats received a single dose of 30 Gy radiation treatment to semi-brain （field size： 1.0 cm x 2.0 cm; anterior limit： binocular posterior inner canthus connection; posterior limit： external acoustic meatus connection; internal limit： sagittal suture）. Conventional magnetic resonance imaging and single-voxel H-MRS were performed at different time points （in month 0 before irradiation as well as in the 1st, 3rd, 5th, 7th, and 9th months after irradiation） to investigate the alternations in irradiation field. N-acetylaspartate/choline （NAA/ChoL NAA/creatinine （Cr）, and Cho/Cr ratios were measured in the bilateral hippocampus and quantitatively analyzed with a repeated-measures mixed-effects model and multiple comparison test. Results： Significant changes in the ratios of NAA/Cho （F = 57.37, P 〈 0.001）, NAA/Cr （F = 54.49, P 〈 0.001） and Cho/Cr （F = 9.78, P = 0.005） between the hippocampus region of the irradiated semi-brain and the contralateral semi-brain were observed. There were 〈, significant differences in NAA/Cho （F = 9.17, P 〈 0.001 ） and NAA/Cr （F = 13.04, P 〈 0.001 ） ratios over time. The tendency of NAA/Cr to change with time showed no significant difference between the irradiated and contralateral sides. Nevertheless, there were significant differences in the Cho/Cr ratio between these two sides. Conclusions： MRS can sensitively detect metabolic alternations. Significant changes of metabolites ratio in the first few months after radiation treatment reflect the metabolic disturbance in the acute and early-delayed stages of radiation-induced brain injuries.展开更多
基金This work is financially supported by Key Program of National Natural Science Foundation of China(No 50431020)
文摘Ground simulation tests of proton irradiation for Kapton films were conducted using the space synthesis irradiating facility,in which the energy of protons was chosen as 90 keV,and the flux was 5.0×1011 cm-2·s-1.After proton irradiation some bulges like fingers appears on the surface of Kapton and the surface roughness increases apparently.UV/Vis analysis demonstrates that the irradiation leads to the red shifting in the edge of optical absorption and a strong increase in absorbance in the visible region.X-ray photoelectron spectroscopy(XPS) analysis indicates that the enrichment of carbon atom due to the bond breaking and reconstruction during the irradiation results in the degradation of the optical properties.
文摘The effects of ionizing and displacement irradiation of high-energy x-ray and 2-MeV proton on GaN thin films were investigated and compared in this study.The electrical properties of both P-GaN and N-GaN,separated from power devices,were gauged for fundamental analysis.It was found that the electrical properties of P-GaN were improved as a consequence of the disruption of the Mg-H bond induced by high-dose x-ray irradiation,as indicated by the Hall and circular transmission line model.Specifically,under a 100-Mrad(Si)x-ray dose,the specific contact resistance pc of P-GaN decreased by 30%,and the hole carrier concentration increased significantly.Additionally,the atom displacement damage effect of a 2-MeV proton of 1×10^(13)p/cm^(2)led to a significant degradation of the electrical properties of P-GaN,while those of N-GaN remained unchanged.P-GaN was found to be more sensitive to irradiation than N-GaN thin film.The effectiveness of x-ray irradiation in enhancing the electrical properties of P-GaN thin films was demonstrated in this study.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40774078, 40404012, 40474064 and 40674076, and the Visiting Scholar Foundation of State Key Laboratory for Space Weather, Chinese Academy Sciences.
文摘We present a study on the second-order resonant interaction between the ring current protons with Whistler-mode waves propagating near the quasi electrostatic limit following the previous second-order resonant theory. The diffusion coefficients are proportional to the electric field amplitude E, much greater than those for the regular first-order resonance, which are proportional to the electric field amplitudes square E^2. Numerical calculations for the pitch angle scattering are performed for typical energies of protons Ek = 50 keV and 100 keV at locations L = 2 and L = 3.5. The timescale for the loss process of protons by the Whistler waves is found to approach one hour, comparable to that by the EMIC waves, suggesting that Whistler waves may also contribute significantly to the ring current decay under appropriate conditions.
文摘An analytical model for hole boring proton acceleration by a circularly-polarized CO_(2) laser pulse in a gas jet is developed.The plasma density profile near the density peak is taken to be rectangular,with inner region thickness l around a laser wavelength and density 10%above the critical,while the outside density is 10%below the critical.On the rear side,plasma density falls off rapidly to a small value.The laser suffers strong reflection from the central region and,at normalized amplitude a _(0)≥1,creates a double layer.The space charge field of the double layer,moving with velocity v_(f)z,reflects up-stream protons to 2v_(f) velocity,incurring momentum loss at a rate comparable to radiation pressure.Reflection occurs for v_(f)≤ω_(p)√z_(f)lm/m_(p),where m and m_(p) are the electron and proton masses,z_(f) is the distance traveled by the compressed electron layer and u p is the plasma frequency.For Gaussian temporal profile of the laser and parabolic density profile of the upstream plasma,the proton energy distribution is narrowly peaked.
文摘NPN-input bipolar operational amplifiers LM741 were irradiated with ^60Coγ-ray, 3 MeV protons and10 MeV protons respectively at different biases to investigating the proton radiation response of the NPN-input operational amplifier. The comparison of protons with^60Coγ-rays showed that the proton radiation mainly induced ionization damage in LM741. Under different bias conditions, the radiation sensitivity is different; zero biased devices show more radiation sensitivity in the input biased current than forward biased devices. Supply current（±Icc）is another parameter that is sensitive to proton radiation,^60Coγ-ray, 3 MeV and 10 MeV proton irradiation would induce a different irradiation response in ±Icc, which is caused by different ionization energy deposition and displacement energy deposition of^60Coγ-ray, 3 MeV and 10 MeV proton irradiation.
文摘Background： In head and neck neoplasm survivors treated with brain irradiation, metabolic alterations would occur in the radiation-induced injury area. The mechanism of these metabolic alterations has not been tillly understood, while the alternations could be sensitively detected by proton （~H） nuclear magnetic resonance spectroscopy （MRS）. In this study, we investigated the metabolic characteristics of radiation-induced brain injury through a long-term tbllow-up after radiation treatment using MRS m vivo. Methods： A total of 12 adult Sprague-Dawley rats received a single dose of 30 Gy radiation treatment to semi-brain （field size： 1.0 cm x 2.0 cm; anterior limit： binocular posterior inner canthus connection; posterior limit： external acoustic meatus connection; internal limit： sagittal suture）. Conventional magnetic resonance imaging and single-voxel H-MRS were performed at different time points （in month 0 before irradiation as well as in the 1st, 3rd, 5th, 7th, and 9th months after irradiation） to investigate the alternations in irradiation field. N-acetylaspartate/choline （NAA/ChoL NAA/creatinine （Cr）, and Cho/Cr ratios were measured in the bilateral hippocampus and quantitatively analyzed with a repeated-measures mixed-effects model and multiple comparison test. Results： Significant changes in the ratios of NAA/Cho （F = 57.37, P 〈 0.001）, NAA/Cr （F = 54.49, P 〈 0.001） and Cho/Cr （F = 9.78, P = 0.005） between the hippocampus region of the irradiated semi-brain and the contralateral semi-brain were observed. There were 〈, significant differences in NAA/Cho （F = 9.17, P 〈 0.001 ） and NAA/Cr （F = 13.04, P 〈 0.001 ） ratios over time. The tendency of NAA/Cr to change with time showed no significant difference between the irradiated and contralateral sides. Nevertheless, there were significant differences in the Cho/Cr ratio between these two sides. Conclusions： MRS can sensitively detect metabolic alternations. Significant changes of metabolites ratio in the first few months after radiation treatment reflect the metabolic disturbance in the acute and early-delayed stages of radiation-induced brain injuries.
