Analysis of superconducting cavity quench events at SSRF

Quench is important and dangerous to superconducting RF cavities. This paper illustrates the mechanism of quench and how a quench detector works, and analyzes the quench events happening during beam operations and cavity conditioning. We find that the quench protection is mostly triggered by some reasons such as fluctuation of cavity voltage, multipacting or arc, rather than a real cavity thermal breakdown. The results will be beneficial to optimize the operation parameters of superconducting cavities, to discover the real reasons for beam trip by quench interlock, and to improve the operation stability of superconducting RF systems.     

Theoretical investigation of the Gamow-Teller transition across N=40 shell

The Gamow-Teller transitions for pf shell nuclei with proton number less than 40 and neutron number larger than 40 were believed to be blocked, due to the full filling of the neutron orbit. However, recent experimental research shows that the Gamow-Teller transitions for these kinds of nuclei are not blocked. In this paper, we systematically calculate the GT transition of pf shell nuclei ⁷⁶Se in different truncations, and the results are compared with experimental results. It is shown that, due to correlations, the believed blocked GT transition occurs, and the shell model calculations reproduce the experimental GT strength. In addition, the electron capture rates in a stellar environment are calculated and discussed.     

Multi-modal calculations of prompt fission neutrons from 238U（n,f） at low induced energy

Properties of prompt fission neutrons from ²³⁸U(n, f) are calculated for incident neutron energies below 6 MeV using the multi-modal model, including the prompt fission neutron spectrum, the average prompt fission neutron multiplicity, and the prompt fission neutron multiplicity as a function of the fission fragment mass υ(A) (usually named “sawtooth” data) The three most dominant fission modes are taken into account. The model parameters are determined on the basis of experimental fission fragment data. The predicted results are in good agreement with the experimental data.     

Cosmic ray test for a T0 detector

The endcap of time-of-flight (ETOF) detector in BES (Beijing Spectrometer) III is planned to be upgraded by using multi-gap resistive plate chambers (MRPCs) and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero (T0) detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a T0 detector is built using plastic scintillator tiles (BC420) to couple with four fast phototubes (PMTs, Hamamatsu H6533). The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. T0 detector timing resolutions of ～41-62 ps are achieved, which means that the T0 detector can be used in the MRPC beam test.     

基于高斯混合模型移动因子补偿的说话人识别方法

提出一种模型补偿方法,以克服基于高斯混合模型的文本无关说话人识别系统性能随目标话者训练语料长度减小而下降的问题.该方法首先构造了一个低维的移动空间,每个训练语料较充分说话人模型的自适应过程均可用该空间中的移动因子表示,然后在目标话者训练语料较不充分的条件下,从受训练语料长度影响较小的话者模型分量中学习移动因子,并依据它对受语料长度影响较大的分量进行参数补偿.和基线系统相比,该方法在相同的训练和评测集上,等错误率指标下,获得相对约7％的性能提升.     

高分辨差分比热测量方法及在高温超导体研究中的应用

差分比热实验方法是测量两个样品的比热差,具有高达万分之一的比热测量分辨率,适合测量相变时微小的比热变化及宽温区的电子比热.文章介绍了高分辨连续升温差分比热实验的测量原理和测量方法,并以铜氧化物高温超导体Y0.8Ca0.2Ba2Cu3O6+x为例,介绍了差分比热实验手段在宽温区电子比热的获得、正常态赝能隙及超导凝聚能研究等方面的应用.     

线-板式脉冲电晕放电反应器的发射光谱研究

以发射光谱法为基础,检测了常压状态线-板式脉冲电晕放电过程OH自由基在反应器内的空间分布;研究了线电极直径,线线间距以及线板间距对生成OH自由基的影响;从而明确脉冲电晕放电反应器的性能。结果显示:OH自由基浓度沿线电极X轴方向逐渐降低,活化区域半径20mm左右,沿Y轴方向先升高后降低,活化区域半径大于30mm;线电极的直径小于2mm时,OH自由基的光谱强度基本不变,线电极直径继续增大,发射光谱强度随之迅速下降。线线间距逐渐增大,OH自由基的发射光谱强度随之增强。OH自由基的发射光谱强度随着线板间距的增大而降低。