Thermal and mechanical characterizations of asubstrate-free focal plane array

We propose a substrate-free focal plane array (FPA) in this paper. The solid substrate is completely removed, and the microcantilevers extend from a supporting frame. Using finite element analysis, the thermal and mechanical characterizations of the substrate-free FPA are presented. Because of the large decrease in thermal conductance, the supporting frame is temperature dependent, which brings out a unique feature: the lower the thermal conductance of the supporting frame is, the higher the energy conversion efficiency in the substrate-free FPA will be. The results from the finite element analyses are consistent with our measurements: two types of substrate-free FPAs with pixel sizes of 200× 200 and 60× 60~μ m² are implemented in the proposed infrared detector. The noise equivalent temperature difference (NETD) values are experimentally measured to be 520 and 300~mK respectively. Further refinements are considered in various aspects, and the substrate-free FPA with a pixel size of 30× 30~μ m² has a potential of achieving an NETD value of 10~mK.     

Study on cooling process of cryogenic system for superconducting magnets of BEPCⅡ

In the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), three superconducting magnets are employed to realize the goal of two orders of magnitude higher luminosity. A cryogenic system with a total capacity of 0.5~kW at 4.5~K was built at the Institute of High Energy Physics (IHEP) to support the operations of these superconducting devices. For preparing the commissioning of the system, the refrigeration process was simulated and analyzed numerically. The numerical model was based on the latest engineering progress and focused on the normal operation mode. The pressure and temperature profiles of the cryogenic system are achieved with the simulation. The influence of the helium mass flow rates to cool superconducting magnets on the thermodynamic parameters of their normal operation is also studied and discussed in this paper.     

Study on ILC bunch compressor

In this paper, we have found a new set of parameters for the short two-stage     

渐变耦合脊波导晶体管探测器光响应分析

为提高InP基光探测器的吸收效率和工作速度,设计了一种渐变耦合脊波导单载流子传输异质结光敏晶体管探测器。采用有效折射率法和光束传播法,分析渐变耦合脊波导的光传输模式,优化后波导宽度和波导长度分别为2.6μm和250μm,可实现单模传输和高的光吸收效率。由于渐变耦合脊波导单载流子传输异质结光敏晶体管光传输方向与载流子运动方向垂直,分别优化光敏晶体管的吸收效率和速度,器件输出光电流和特征频率均得到改善。渐变耦合脊波导单载流子传输异质结光敏晶体管的响应度为33.83A/W,饱和输出光电流为90mA,最高特征频率达到87GHz,其饱和输出电流和特征频率相比于台面单载流子传输异质结光敏晶体管分别提高了20%和24%。但渐变耦合脊波导单载流子传输异质结光敏晶体管吸收体积大,获得饱和电流时的光功率也比较大,因此渐变耦合脊波导单载流子传输异质结光敏晶体管的响应度略小于台面的单载流子传输异质结光敏晶体管的响应度。     

ADS 650 MHz medium beta cavity study and design

The Accelerator Driven Sub-critical System (ADS) is under development aiming at safe disposal of nuclear waste and providing electric power in China. The main accelerator of ADS is composed of two injector sections and one main linear acceleration section. The 650 MHz β=0.82 superconducting cavities will be adopted to accelerate the proton bunches from 360 MeV to 1.5 GeV in the medium energy section. This paper presents the study and design results of this kind of superconducting cavity.     

红外显微观测被俘获吸光性颗粒

光镊技术被广泛应用在俘获和操纵微纳米尺寸颗粒, 目前被研究学者普遍接受的俘获吸光性颗粒的机理为光泳力. 本文实现了对空气中被俘获的吸光性颗粒的红外显微观测. 当激光器功率为1.0 W时, 成功观测到被俘获墨粉颗粒(直径约7 μm)和甲苯胺蓝颗粒(直径约为1–20 μm)的温升约为14 K, 为光泳力理论提供了强有力的证据. 另外, 首次用可见光显微镜和红外显微镜同时观测到被俘获颗粒的周期振荡现象, 并分析了振荡现象的产生机理. 关键词： 光镊 光俘获 红外显微     

Thermal simulation and analysis of the STF cryomodule

STF is a superconducting RF test facility constructed at the high energy accelerator research organization of Japan (KEK), as a main part of a R&;D project for the proposed International Linear Collider (ILC) in Asia. Thermal study of the STF 1.3 GHz 9-cell cavity cryomodule was carried out within a collaboration between China and Japan. Static and dynamic thermal behaviors of the STF cryomodule were simulated and analyzed with the FEM method, and some simulation results were compared with the available experimental data. This paper presents the details.     

Simulation study of electron injection into plasma wake fields by colliding laser pulses using OOPIC

An electron injector concept for a laser-plasma accelerator has been developed which relies on the use of counter propagating ultrashort laser pulses. In this paper, we use OOPIC the fully self-consistent, two-dimensional, particle-in-cell code to make a parameter study to determine the bunches that can be obtained through collisions of two collinear laser pulses in uniform plasma. A series of simulations show that one can obtain a short (<10fs) bunch with its charge of about 15pC, and energy spread of about 15%. We also discussed the variation of the transverse spot size of the electron bunch and found the bunch would undergo the betatron oscillations.     

Bunch transverse emittance increase in electron storage rings

In this paper a theoretical framework to estimate the bunch transverse emittance growing in electron storage rings due to short range transverse wakefield of the machine is established. New equilibrium emittance equations are derived and applied to explain the experimentally obtained results in ATF damping ring. This equation will be useful for linear collider damping ring design.     

光学读出微梁阵列红外成像性能分析与优化

系统响应率是光学读出微梁焦平面阵列(Focal Plane Array,FPA)红外成像的关键性能参数。在刀口滤波光学读出技术中,系统响应率的主要组成部分——光学读出灵敏度与微梁反光板的长度密切相关,并受到反光板弯曲变形的严重影响。由于残余应力在制作过程中不可避免地存在,微梁反光板都有弯曲变形,膜厚相同的反光板具有相同的变形曲率半径。本文利用傅里叶光学分析了反光板长度和弯曲变形对光学读出灵敏度的影响,构建并实验验证光学读出灵敏度理论模型。根据该模型,分析了系统响应率与反光板长度之间关系,理论分析与实验结果相符。结果表明,通过减薄SiNx厚度并使反光板处于该厚度下的最优长度,不仅能提高红外成像的系统响应率,而且能同时提高红外成像的空间分辨率。