目的:针对激光等离子体加速的质子束流特性,设计用于剂量递送的新型紧凑治疗头系统,并通过模拟计算验证该方法的有效性与适用性。方法:基于实验上已实现的激光质子束流参数,利用散射体设计软件NEU(Nozzles withEverything Upstream)进...目的:针对激光等离子体加速的质子束流特性,设计用于剂量递送的新型紧凑治疗头系统,并通过模拟计算验证该方法的有效性与适用性。方法:基于实验上已实现的激光质子束流参数,利用散射体设计软件NEU(Nozzles withEverything Upstream)进行流线型散射体设计。通过散角选择和能散调制进一步优化剂量递送效率,并利用蒙特卡罗模拟计算软件TOPAS(TOol for PArticle Simulation)及底层的Geant4(GEometry ANd Tracking)计算引擎分析并验证激光质子通过此剂量递送方法后水模体中的剂量分布。结果:在直径6cm、高5cm的圆柱形靶区内,深度剂量分布平坦度在±1%以内,横向剂量分布在±3%以内。结论:此剂量递送方法及系统适用于现阶段激光质子束流特性,水模体靶区内剂量递送均匀、高效且稳定。展开更多
A short overview of the theory of acceleration of thin foils driven by the radiation pressure of superintense lasers is presented. A simple criterion for radiation pressure dominance at intensities around 5×1020W...A short overview of the theory of acceleration of thin foils driven by the radiation pressure of superintense lasers is presented. A simple criterion for radiation pressure dominance at intensities around 5×1020W cm-2is given, and the possibility for fast energy gain in the relativistic regime is discussed.展开更多
Ionization-induced electron injection in laser wakefield accelerators, which was recently proposed to lower the laser intensity threshold for electron trapping into the wake wave, has the drawback of generating electr...Ionization-induced electron injection in laser wakefield accelerators, which was recently proposed to lower the laser intensity threshold for electron trapping into the wake wave, has the drawback of generating electron beams with large and continuous energy spreads, severely limiting their future applications. Complex target designs based on separating the electron trapping and acceleration stages were proposed as the only way for getting small energy-spread electron beams. Here, based on the self-truncated ionization-injection concept which requires the use of unmatched laser–plasma parameters and by using tens of TW laser pulses focused onto a gas jet of helium mixed with low concentrations of nitrogen, we demonstrate single-stage laser wakefield acceleration of multi-hundred MeV electron bunches with energy spreads of a few percent. The experimental results are verified by PIC simulations.展开更多
A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellips...A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately,especially at the relativistic region.The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model.The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons △E/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions.As a result,the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.展开更多
Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition ra...Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.展开更多
通过理论分析,建立了激光等离子体加速电子与固体靶相互作用产生相对论正电子的物理模型,以及Geant4模拟程序.以100 Me V量级的激光等离子体加速电子束参数为输入,模拟研究了不同靶材和靶厚条件下正电子束的产额、能量、角分布等主要物...通过理论分析,建立了激光等离子体加速电子与固体靶相互作用产生相对论正电子的物理模型,以及Geant4模拟程序.以100 Me V量级的激光等离子体加速电子束参数为输入,模拟研究了不同靶材和靶厚条件下正电子束的产额、能量、角分布等主要物理参数.结果表明:金靶和钽靶是较优秀的电子—正电子转换靶材;对于相同的金属靶材面密度,正电子产额与原子序数Z的四次方成正比,与原子质量数A的平方成反比,即Ne+∝(Z2/A)2;对于不同的靶材,正电子产额有Ne+∝d2,其中d为靶材厚度,但仍存在一个最佳靶厚度.与利用拍瓦、皮秒激光束与固体靶相互作用产生正电子束的方案相比,利用本方案有望获得更高能量以及更小角发散的相对论正电子束,其流强可达107/shot.展开更多
文摘目的:针对激光等离子体加速的质子束流特性,设计用于剂量递送的新型紧凑治疗头系统,并通过模拟计算验证该方法的有效性与适用性。方法:基于实验上已实现的激光质子束流参数,利用散射体设计软件NEU(Nozzles withEverything Upstream)进行流线型散射体设计。通过散角选择和能散调制进一步优化剂量递送效率,并利用蒙特卡罗模拟计算软件TOPAS(TOol for PArticle Simulation)及底层的Geant4(GEometry ANd Tracking)计算引擎分析并验证激光质子通过此剂量递送方法后水模体中的剂量分布。结果:在直径6cm、高5cm的圆柱形靶区内,深度剂量分布平坦度在±1%以内,横向剂量分布在±3%以内。结论:此剂量递送方法及系统适用于现阶段激光质子束流特性,水模体靶区内剂量递送均匀、高效且稳定。
基金Support from the Italian Ministry of University and Research via the FIR project ‘SULDIS’
文摘A short overview of the theory of acceleration of thin foils driven by the radiation pressure of superintense lasers is presented. A simple criterion for radiation pressure dominance at intensities around 5×1020W cm-2is given, and the possibility for fast energy gain in the relativistic regime is discussed.
基金supported by the National ‘973’ Program of China under Grant No.2013CBA01504supported by Shanghai Supercomputer Center and the center for high performance computing at Shanghai Jiao Tong University
文摘Ionization-induced electron injection in laser wakefield accelerators, which was recently proposed to lower the laser intensity threshold for electron trapping into the wake wave, has the drawback of generating electron beams with large and continuous energy spreads, severely limiting their future applications. Complex target designs based on separating the electron trapping and acceleration stages were proposed as the only way for getting small energy-spread electron beams. Here, based on the self-truncated ionization-injection concept which requires the use of unmatched laser–plasma parameters and by using tens of TW laser pulses focused onto a gas jet of helium mixed with low concentrations of nitrogen, we demonstrate single-stage laser wakefield acceleration of multi-hundred MeV electron bunches with energy spreads of a few percent. The experimental results are verified by PIC simulations.
基金Project supported by the Research Deputy Office in the Islamic Azad University of Maragheh Branch
文摘A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately,especially at the relativistic region.The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model.The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons △E/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions.As a result,the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.
文摘Laser plasma accelerators （LPAs） have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation （OTR） from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils （located at 2.3 m and 3.8 m away from the exit of the LPA） were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.
文摘通过理论分析,建立了激光等离子体加速电子与固体靶相互作用产生相对论正电子的物理模型,以及Geant4模拟程序.以100 Me V量级的激光等离子体加速电子束参数为输入,模拟研究了不同靶材和靶厚条件下正电子束的产额、能量、角分布等主要物理参数.结果表明:金靶和钽靶是较优秀的电子—正电子转换靶材;对于相同的金属靶材面密度,正电子产额与原子序数Z的四次方成正比,与原子质量数A的平方成反比,即Ne+∝(Z2/A)2;对于不同的靶材,正电子产额有Ne+∝d2,其中d为靶材厚度,但仍存在一个最佳靶厚度.与利用拍瓦、皮秒激光束与固体靶相互作用产生正电子束的方案相比,利用本方案有望获得更高能量以及更小角发散的相对论正电子束,其流强可达107/shot.
