Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ...Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an Na I scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 Me V/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.展开更多
Heavy-ion-driven fusion （HIF） is a scheme to achieve inertial confinement fusion （ICF）. Investigation of the non-uniformity of heavy-ion beam （HIB） irradiation is one of the key issues for ICF driven by powerful...Heavy-ion-driven fusion （HIF） is a scheme to achieve inertial confinement fusion （ICF）. Investigation of the non-uniformity of heavy-ion beam （HIB） irradiation is one of the key issues for ICF driven by powerful heavy-ion beams. Ions in HIB impinge on the pellet surface and deposit their energy in a relatively deep and wide area. Therefore, the non-uniformity of HIB irradiation should be evaluated in the volume of the deposition area in the absorber layer. By using the OK1 code with some corrections, the non-uniformity of heavy-ion beam irradiation for the different ion beams on two kinds of targets were evaluated in 12-beam, 20-beam, 60-beam and 120-beam irradiation schemes. The root-mean-square （RMS） non-uniformity value becomes aRMS = 8.39% in an aluminum mono-layer pellet structure and aRMS = 6.53% in a lead-aluminum layer target for the 12-uranium-beam system. The RMS non-uniformity for the lead-aluminum layer target was lower than that for the mono-layer target. The RMS and peak-to-valley （PTV） non-uniformities are reduced with the increase in beam number, and low at the Bragg peak layer.展开更多
为实现光纤光栅的高速精确解调,设计了3 d B带宽在1~3 nm之间的宽带布拉格光栅,进行波长寻峰分析,并进行了实验验证。实验结果表明,使用CCD检测光栅反射光谱信号时,像素点间波长间距固定,带宽较高的布拉格光栅可得到更多有效像素点,从...为实现光纤光栅的高速精确解调,设计了3 d B带宽在1~3 nm之间的宽带布拉格光栅,进行波长寻峰分析,并进行了实验验证。实验结果表明,使用CCD检测光栅反射光谱信号时,像素点间波长间距固定,带宽较高的布拉格光栅可得到更多有效像素点,从而提高了光栅中心波长解调精度。温度测量对比实验表明,宽带FBG的解调精度相比普通光纤光栅提高了37.7%。展开更多
基金supported by the National Natural Science Foundation of China(Nos.11375073 and U1232206)
文摘Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an Na I scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 Me V/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.
文摘Heavy-ion-driven fusion （HIF） is a scheme to achieve inertial confinement fusion （ICF）. Investigation of the non-uniformity of heavy-ion beam （HIB） irradiation is one of the key issues for ICF driven by powerful heavy-ion beams. Ions in HIB impinge on the pellet surface and deposit their energy in a relatively deep and wide area. Therefore, the non-uniformity of HIB irradiation should be evaluated in the volume of the deposition area in the absorber layer. By using the OK1 code with some corrections, the non-uniformity of heavy-ion beam irradiation for the different ion beams on two kinds of targets were evaluated in 12-beam, 20-beam, 60-beam and 120-beam irradiation schemes. The root-mean-square （RMS） non-uniformity value becomes aRMS = 8.39% in an aluminum mono-layer pellet structure and aRMS = 6.53% in a lead-aluminum layer target for the 12-uranium-beam system. The RMS non-uniformity for the lead-aluminum layer target was lower than that for the mono-layer target. The RMS and peak-to-valley （PTV） non-uniformities are reduced with the increase in beam number, and low at the Bragg peak layer.
文摘为实现光纤光栅的高速精确解调,设计了3 d B带宽在1~3 nm之间的宽带布拉格光栅,进行波长寻峰分析,并进行了实验验证。实验结果表明,使用CCD检测光栅反射光谱信号时,像素点间波长间距固定,带宽较高的布拉格光栅可得到更多有效像素点,从而提高了光栅中心波长解调精度。温度测量对比实验表明,宽带FBG的解调精度相比普通光纤光栅提高了37.7%。
