In the Chinese ADS front-end demo superconducting radiofrequency linac(CAFe)at the Institute of Modern Physics,a burst-noise signal-triggered cavity fault frequently appears during beam commissioning.These events are ...In the Chinese ADS front-end demo superconducting radiofrequency linac(CAFe)at the Institute of Modern Physics,a burst-noise signal-triggered cavity fault frequently appears during beam commissioning.These events are characterized by a rapid burst noise in the cavity pick-up,which may lead to an unexpected low-level radiofrequency(LLRF)response that eventually causes a cavity fault.To eliminate the undesirable reaction of the LLRF control loop,we propose a method that uses a burstnoise detection and processing algorithm integrated into the LLRF feedback controller.This algorithm can prevent undesired regulations in LLRF systems.Data analysis revealed that some burst-noise events did not exhibit measurable energy loss.In contrast,the other events were accompanied by a rapid loss of cavity stored energy and exhibited similarities to the‘‘E-quench’’phenomena reported in other laboratories.A particle-in-cell simulation indicated that the suspected E-quench phenomenon may be related to a plasma formation process inside the cavity.Fortunately,the LLRF algorithm is robust to the two different types of burst-noise events and can significantly mitigate the corresponding cavity faults in CAFe beam commissioning.展开更多
The possible decomposition of metastable austenite during the partitioning process in the high end quenching and partitioning （Q＆P） steels is somewhat neglected by most researchers. The effects of primary martensit...The possible decomposition of metastable austenite during the partitioning process in the high end quenching and partitioning （Q＆P） steels is somewhat neglected by most researchers. The effects of primary martensite and alloying elements including manganese, cobalt and aluminum on the isothermal decomposition of austenite during typical Q＆P process were studied by dilatometry. The transformation kinetics was studied systematically and resulting microstruc tures were discussed in details. The results suggested that the primary martensite decreased the incubation period of isothermal decomposition by accelerating the nucleation process owing to dislocations especially on phase and grain boundaries. This effect can be eliminated by a flash heating which recovered dislocations. Co addition significantly promoted the bainite transformation during partitioning while A1 and Mn suppressed the isothermal bainite transformation. The bainite transformation played an important role in carbon distribution during partitioning, and hence the amount and stability of austenite upon final quenching. The bainite transformation during partitioning is an important factor in optimizing the microstructure in Q＆P steels.展开更多
Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The ...Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v'=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB34010000)Large Research Infrastructures China initiative Accelerator Driven System(2017-000052-75-01-000590)+1 种基金National Natural Science Foundation of China(No.12175283)Studies of intelligent LLRF control algorithms for SC RF cavities(No.E129851YR0).
文摘In the Chinese ADS front-end demo superconducting radiofrequency linac(CAFe)at the Institute of Modern Physics,a burst-noise signal-triggered cavity fault frequently appears during beam commissioning.These events are characterized by a rapid burst noise in the cavity pick-up,which may lead to an unexpected low-level radiofrequency(LLRF)response that eventually causes a cavity fault.To eliminate the undesirable reaction of the LLRF control loop,we propose a method that uses a burstnoise detection and processing algorithm integrated into the LLRF feedback controller.This algorithm can prevent undesired regulations in LLRF systems.Data analysis revealed that some burst-noise events did not exhibit measurable energy loss.In contrast,the other events were accompanied by a rapid loss of cavity stored energy and exhibited similarities to the‘‘E-quench’’phenomena reported in other laboratories.A particle-in-cell simulation indicated that the suspected E-quench phenomenon may be related to a plasma formation process inside the cavity.Fortunately,the LLRF algorithm is robust to the two different types of burst-noise events and can significantly mitigate the corresponding cavity faults in CAFe beam commissioning.
基金financial support from National Natural Science Foundation of China(Grant No.51574080)the National Key R&D Program of China(No.2017YFB0304201)
文摘The possible decomposition of metastable austenite during the partitioning process in the high end quenching and partitioning （Q＆P） steels is somewhat neglected by most researchers. The effects of primary martensite and alloying elements including manganese, cobalt and aluminum on the isothermal decomposition of austenite during typical Q＆P process were studied by dilatometry. The transformation kinetics was studied systematically and resulting microstruc tures were discussed in details. The results suggested that the primary martensite decreased the incubation period of isothermal decomposition by accelerating the nucleation process owing to dislocations especially on phase and grain boundaries. This effect can be eliminated by a flash heating which recovered dislocations. Co addition significantly promoted the bainite transformation during partitioning while A1 and Mn suppressed the isothermal bainite transformation. The bainite transformation played an important role in carbon distribution during partitioning, and hence the amount and stability of austenite upon final quenching. The bainite transformation during partitioning is an important factor in optimizing the microstructure in Q＆P steels.
基金Project supported by the National Natural Science Foundation of China and by the Cross-Century Talent Foundation of Shandong University.
文摘Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v'=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed.
