A novel method for velocity measurement is presented. In this scheme, a parallel-linear-polarization dual- frequency laser is incident on the target and senses the target velocity with both the frequencies, which can ...A novel method for velocity measurement is presented. In this scheme, a parallel-linear-polarization dual- frequency laser is incident on the target and senses the target velocity with both the frequencies, which can increase the maximum measurable velocity significantly. The theoretical analysis and verification experiment of the novel method are presented, which show that high-velocity measurement can be achieved with high precision using this method.展开更多
A cw terahertz （THz） transmission imaging system is demonstrated and a high-quality THz image can be obtained using a pyroelectric detector. The factors that affect the imaging quality, such as the THz wavelength, s...A cw terahertz （THz） transmission imaging system is demonstrated and a high-quality THz image can be obtained using a pyroelectric detector. The factors that affect the imaging quality, such as the THz wavelength, spot size on the sample surface, step length of the motor, and frequency of the chopper, are theoretically and experimentally investigated. The experimental results show that the maximum resolution of the THz image can reach 0.4mm with the THz wavelength of 118.8μm, the spot size of 1.8mm and the step length of 0.25mm.展开更多
Jet spreading width is one of the important characteristics of water jets discharging into the air.Many researchers have dealt with measuring this width,and contact measuring methods on the water jet surface were empl...Jet spreading width is one of the important characteristics of water jets discharging into the air.Many researchers have dealt with measuring this width,and contact measuring methods on the water jet surface were employed in a lot of the cases.In order to avoid undesirable effects caused by the contact on the jet surface,we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width.In measurements,a transmitter emits sheet-like laser beam to a receiver.The water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow.The minimum and maximum values of the shadow width are measured.In addition,pictures of the water jet are taken with a scale,and the shadow width is measured from the pictures.The experiments on various needle strokes were performed.Three kinds of width consistent with the jet structure were obtained.In the results,it can be concluded that our non-contact measuring methods are feasible.The data of jet spreading widths and jet taper were obtained and are useful for future applications.展开更多
Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the targ...Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11MeV and energy spread of ＆#8710; ε/ε about 0.18 is achieved by using a 3.45×1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.展开更多
文摘A novel method for velocity measurement is presented. In this scheme, a parallel-linear-polarization dual- frequency laser is incident on the target and senses the target velocity with both the frequencies, which can increase the maximum measurable velocity significantly. The theoretical analysis and verification experiment of the novel method are presented, which show that high-velocity measurement can be achieved with high precision using this method.
文摘A cw terahertz （THz） transmission imaging system is demonstrated and a high-quality THz image can be obtained using a pyroelectric detector. The factors that affect the imaging quality, such as the THz wavelength, spot size on the sample surface, step length of the motor, and frequency of the chopper, are theoretically and experimentally investigated. The experimental results show that the maximum resolution of the THz image can reach 0.4mm with the THz wavelength of 118.8μm, the spot size of 1.8mm and the step length of 0.25mm.
文摘Jet spreading width is one of the important characteristics of water jets discharging into the air.Many researchers have dealt with measuring this width,and contact measuring methods on the water jet surface were employed in a lot of the cases.In order to avoid undesirable effects caused by the contact on the jet surface,we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width.In measurements,a transmitter emits sheet-like laser beam to a receiver.The water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow.The minimum and maximum values of the shadow width are measured.In addition,pictures of the water jet are taken with a scale,and the shadow width is measured from the pictures.The experiments on various needle strokes were performed.Three kinds of width consistent with the jet structure were obtained.In the results,it can be concluded that our non-contact measuring methods are feasible.The data of jet spreading widths and jet taper were obtained and are useful for future applications.
基金Supported by the National Key Basic Research Program of China under Grant No 2006CB806004, the National Natural Science Foundation of China under Grant Nos 10675155 and 10834008, Scientific Research Foundation for Awarder of Excellent Doctor Thesis, and President Award of Chinese Academy of Sciences （No 0801051-X00）.
文摘Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11MeV and energy spread of ＆#8710; ε/ε about 0.18 is achieved by using a 3.45×1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.
