A new pulsed helium nano droplets machine has been constructed. The droplets were gener- ated by expansion of the pure helium through the cryogenic valve attached to a closed-cycle cryostat. The mean size of helium dr...A new pulsed helium nano droplets machine has been constructed. The droplets were gener- ated by expansion of the pure helium through the cryogenic valve attached to a closed-cycle cryostat. The mean size of helium droplets can be controlled between 103 and 105 helium atoms by tuning the backing pressure （10-40 bar） and temperature （10-30 K）. Compared with the continuous-flow beam source, the density of droplet is at least one order of magni- tude higher, which offers the opportunity to combine the system with the commercial pulsed laser to study chemical reactions inside of the superfluid helium at ultra-low temperature. The performance for the system has been checked by studying the photodissociation of CH3I doped droplets at 252 nm with the velocity map imaging technique. The photofragments, CH3, were detected by （2＋1） resonance enhanced multiphoton ionization. The speed and angular distributions derived from resulting images show clear evidence of the relaxation effect by the surrounding helium atoms. The pulsed helium droplets depletion spectroscopy was also demonstrated. The depletion spectrum of benzene doped helium droplets indicates that less than 3% depletion can be observed with the newly constructed apparatus.展开更多
In many experiments, plastic scintillators are used as a counter instead of Geiger Muller counter, because they are so fast and they are used for pulsed neutron sources. So a silver activation counter has been constru...In many experiments, plastic scintillators are used as a counter instead of Geiger Muller counter, because they are so fast and they are used for pulsed neutron sources. So a silver activation counter has been constructed by plastic scintillator plates along with silver foils for determination the neutron yield of a 2.48 kJ plasma focus device, SBUPF1. This counter was calibrated by source removal method with an Am-Be 5 Ci neutron source which was placed above the anode of plasma focus device. Deuterium gas up to 8 mbar pressure was injected to this device, and the neutron yield produced by pulsed D-D fusion of plasma focus device was measured by the counter. The neutron yield of SBUPF1 in 8 mbar pressure was obtained （3.71± 0.32）×10^7 neutrons per shot. This result has relatively agreed with the neutron yield measured by silver activation Geiger counters.展开更多
Y98-61429-192 9907417用高功率离子束改进基于 Al、Fe 和 Ti 的金属的特性的表面处理和合金=Surface treatment and alloyingwith high-power ion beams to improve properties in Al-,Fe-,and Ti-based metals[会,英]/Renk,T.J.&B...Y98-61429-192 9907417用高功率离子束改进基于 Al、Fe 和 Ti 的金属的特性的表面处理和合金=Surface treatment and alloyingwith high-power ion beams to improve properties in Al-,Fe-,and Ti-based metals[会,英]/Renk,T.J.&Buchheit,R.G.//1997 IEEE 11th International PulsedPower Conferenee,Vol.1.—192～197(AG)Y98-61442-377 9907418微电子器件生产用的激光化学汽相淀积=Laser chem-ical vapor deposition for microelectronics production[会,展开更多
基金The authors would like to thank Dr. Ze-feng Ren for the assistance with the design at the early stage, and Prof. Andrey Vilesov for helpful discussions. This work was supported by the Startup Grant of Dalian In- stitute of Chemical Physics, one Hundred Talents Pro- gram of Chinese Academy of Sciences, the Knowledge Innovation Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China （No.21073187）.
文摘A new pulsed helium nano droplets machine has been constructed. The droplets were gener- ated by expansion of the pure helium through the cryogenic valve attached to a closed-cycle cryostat. The mean size of helium droplets can be controlled between 103 and 105 helium atoms by tuning the backing pressure （10-40 bar） and temperature （10-30 K）. Compared with the continuous-flow beam source, the density of droplet is at least one order of magni- tude higher, which offers the opportunity to combine the system with the commercial pulsed laser to study chemical reactions inside of the superfluid helium at ultra-low temperature. The performance for the system has been checked by studying the photodissociation of CH3I doped droplets at 252 nm with the velocity map imaging technique. The photofragments, CH3, were detected by （2＋1） resonance enhanced multiphoton ionization. The speed and angular distributions derived from resulting images show clear evidence of the relaxation effect by the surrounding helium atoms. The pulsed helium droplets depletion spectroscopy was also demonstrated. The depletion spectrum of benzene doped helium droplets indicates that less than 3% depletion can be observed with the newly constructed apparatus.
文摘In many experiments, plastic scintillators are used as a counter instead of Geiger Muller counter, because they are so fast and they are used for pulsed neutron sources. So a silver activation counter has been constructed by plastic scintillator plates along with silver foils for determination the neutron yield of a 2.48 kJ plasma focus device, SBUPF1. This counter was calibrated by source removal method with an Am-Be 5 Ci neutron source which was placed above the anode of plasma focus device. Deuterium gas up to 8 mbar pressure was injected to this device, and the neutron yield produced by pulsed D-D fusion of plasma focus device was measured by the counter. The neutron yield of SBUPF1 in 8 mbar pressure was obtained （3.71± 0.32）×10^7 neutrons per shot. This result has relatively agreed with the neutron yield measured by silver activation Geiger counters.
文摘Y98-61429-192 9907417用高功率离子束改进基于 Al、Fe 和 Ti 的金属的特性的表面处理和合金=Surface treatment and alloyingwith high-power ion beams to improve properties in Al-,Fe-,and Ti-based metals[会,英]/Renk,T.J.&Buchheit,R.G.//1997 IEEE 11th International PulsedPower Conferenee,Vol.1.—192～197(AG)Y98-61442-377 9907418微电子器件生产用的激光化学汽相淀积=Laser chem-ical vapor deposition for microelectronics production[会,
