The space environment monitor aboard FY-2 satellite

The space environment monitor (SEM) aboard FY-2 satellite consists of the high energy particle detector (HEPD) and the solar X-ray flux detector (SXFD). The SEM can provide real-time monitoring of flare and solar proton event for its operation at geostationary orbit and is also the first Chinese space system for monitoring and alerting solar proton event. During the 23rd solar maximum cycle, almost all the solar proton events that took place in this period are monitored and some of them are predicted successfully by analyzing the characteristics of X-ray flare monitored by the SEM. Some basic variation characteristics of particle at geostationary orbit are found such as day-night periodic variation of particle flux, the electron flux with energy >1.4 MeV in the scope from 10 to 200/cm2 s sr and the proton flux with energy >1.1 MeV in the scope from 600 to 8000/cm·s·sr during the time with no magnetic storm and solar eruption.     

Design and simulations for the detector based on DSSSD

The present paper describes the design and simulation results of a position-sensitive charged particle detector based on the Double Sided Silicon Strip Detector （DSSSD）. Also, the characteristics of the DSSSD and its testing result were are discussed. With the application of the DSSSD, the position-sensitive charged particle detector can not only give particle flux and energy spectra information and identify different types of charged particles, but also measure the location and angle of incident particles. As the detector can make multi-parameter measurements of charged particles, it is widely used in space detection and exploration missions, such as charged particle detection related to earthquakes, space environment monitoring and solar activity inspection.     

How Will a Particle Detector Respond in Massless Complex Scalar Field？

I study the response of a particle detector coupled to quantized massless complex scalar field in four dimensional Minkowski spacetime through nonlinear Lagrangian. I find that as in the real scalar field： the particle detector will not respond when it is in inertial motion; If accelerated in its own frame reference, it does respond and feel the same temperature. But different from the real scalar field case, the detector＇s transition amplitude is concerned with particle-antiparticle creation, and the response of the detector is （1/α^2 ＋ ε^2）/24π^2 times of that in real scalar field, with 1/α the accelerator of the detector and e the energy gap between the detector＇s two energy level. It is due to the nonlinear property of the coupling Lagrangian. Whether the total charge of the system constructed by the particle detector and vacuum is conserved is also considered and analyzed.     

用于辐射复合与双电子复合实验的低能离子闪烁探测器

为了在CSRm的电子冷却器上进行辐射复合以及双电子复合实验, 需要探测能量小于4 MeV/u的离子, 因此设计了新的置于超高真空环境的CsI(Tl)闪烁探测器, 探测器采用的光电倍增管为R7525(Hamamatsu）。 介绍了新闪烁探测器的结构, 并对其进行了性能测试。 测试结果表明, 该探测器对高、 低能离子均有良好的响应, 探测器的信号十分明显。 探测器的最高计数率可以达到106 ions/s, 并且探测器附近的真空度可达10-10 Pa量级, 能够满足辐射复合与双电子复合实验以及储存环对真空的要求, 为今后在CSRm上进行复合实验打下了良好的基础。 A new CsI(Tl) scintillation detector readout with R7525 PMT(Hamamatsu）is designed to detect low energy (<4 MeV/u) ions in radiative recombination and dielectronic recombination experiments at the main cooler storage ring in Lanzhou. The structure of the scintillator detector is described in this paper. The detector is tested with α source and ion beams, respectively. The signals from background, 200 MeV/u C6+ and alpha radioactive source are recorded and analyzed. The results show that the detector has good response to high and low energy ions. The maximum counting rate of the detector can reach 106 ions/s and the vacuum level near the detector can reach 10-10 Pa, both are good for recombination experiments. The installation of the new detector to CSRm is of great help for future radiative recombination and dielectronic recombination experiments.     

Accuracy Measurements of the CAS-LIBB Single-Particle Microbeam for Single Cell Irradiation

A single-particle microbeam facility has been constructed at the Laboratory of Ion Beam Bioengineering (LIBB),Chinese Academy of Sciences. The system is designed to deliver the defined number of hydrogen ions, covering a range of energy from 1.0 to 3.5 MeV, into an area smaller than the nuclei of individual living cells. Accuracy of the particle detection system and the cell targeting system in the facility has been assessed using CR39 (nuclear track detector) for 2.3 MeV protons. The results demonstrate that the particle detection efficiency is above 98%,and the overall targeting accuracy of the microbeam is limited within 3μm for more than 90% hits.     

Simulation of the Galactic Cosmic Ray Shadow of the Sun

The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth–Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.     

Two-dimensional photon counting imaging detector based on a Vernier position sensitive anode readout

A two-dimensional photon counting imaging detector based on a Vernier position sensitive anode is reported. The decode principle and design of a two-dimensional Vernier anode are introduced in detail. A photon counting imaging system was built based on a Vernier anode. The image of very weak optical radiation can be reconstructed by image processing in a period of integration time. The resolution is superior to 100 μm according to the resolution test. The detector may realize the imaging of very weak particle flow of high-energy photons, electrons and ions, so it can be used for high-energy physics, deep space exploration, spectral measurement and bio-luminescence detection.     

A New Method of Measuring Electron Emission Induced by Low Energy Ions from Solids

A new mathematical method of measuring electron emission induced by low energy ions from solids is described and used to calculate secondary electron emission according to the recorded pulse-height spectra of ions and ultraviolet （UV） photons. Using the UV single secondary electron spectra, we predict the shape of many secondary electron distributions under consideration of detection efficiency of MCP detector. These calculated distributions allow us to characterize the secondary electrons yield, and to give a secondary electron distribution for measured data. It seems rather feasible to determine secondary electron yield emitted by low energy ions at very low ion uxes.     

Design and performance study of the LEPD silicon tracker onboard the CSES satellite

The low energy particle detector (LEPD) is one of the main payloads onboard the China seismic electromagnetic satellite (CSES). The detector is designed to ascertain space electrons (0.1-10 MeV) and protons (2-50 MeV). It has the capability of identifying the electrons and protons, to measure the energy spectrum and the incident angle of the particles. The LEPD is made up of a silicon tracker system, a CsI (Tl) mini-calorimeter, an anti-coincidence system made by plastic scintillator, as well as electronics and a data acquisition system (DAQ). The tracker is also a kind of E-E telescope; it consists of two layers of double-sided silicon strip detectors (DSSD). The signals emerging from the silicon tracker can be read out by two pieces of application specific integrated circuit (ASIC), which also can generate an event trigger for the LEPD. The functions of the DSSD system in the LEPD for charged particles were tested by 241Am @5.486 MeV α particles. The results show that the DSSD system works well, and has high performance to detect charged particles and measure the position of incident particles.     

High resolution solar soft X-ray spectrometer

A high resolution solar soft X-ray spectrometer (SOX) payload onboard a satellite is developed. A silicon drift detector (SDD) is adopted as the detector of the SOX spectrometer. The spectrometer consists of the detectors and their readout electronics, a data acquisition unit and a payload data handling unit. A ground test system is also developed to test SOX. The test results show that the design goals of the spectrometer system have been achieved.     

Design and simulations for the detector based on DSSSD

The present paper describes the design and simulation results of a position-sensitive charged particle detector based on the Double Sided Silicon Strip Detector (DSSSD). Also, the characteristics of the DSSSD and its testing result were are discussed. With the application of the DSSSD, the position-sensitive charged particle detector can not only give particle flux and energy spectra information and identify different types of charged particles, but also measure the location and angle of incident particles. As the detector can make multi-parameter measurements of charged particles, it is widely used in space detection and exploration missions, such as charged particle detection related to earthquakes, space environment monitoring and solar activity inspection.     

Comment on the use of GOES solar proton data and spectra in solar proton dose calculations.

There is a need to understand the calibration and response of the GOES solar particle detectors since the GOES data are being used to evaluate high energy solar particle events. We share some of our experience in utilizing these data in the analysis of solar particle ground-level events (GLEs). For the 29 September 1989 event, we have evaluated the solar proton and alpha particle spectral characteristics throughout the event. The results show that the solar cosmic ray spectrum is extremely hard at low energies with the magnitude of the slope increasing with increasing energy and with time.     

一维游标位敏阳极光子计数探测器

报道了一维游标位敏阳极光子计数探测器,详细介绍了一维游标位敏阳极的解码原理和设计结果.搭建了基于一维游标位敏阳极探测器的紫外光子计数探测系统.该系统工作于光子计数模式,可同时测量单光子事件的一维坐标.获得了对应入射光空间强度一维分布的脉冲计数分布图.通过测试,系统的分辨率优于100μm.该探测器可以实现极微弱的高能光子、电子和离子等粒子流强度分布的一维探测,因此可以用于深空探测、光谱测量、高能物理以及生物发光探测.     

星上定标漫射板远紫外BRDF测量方法

针对星载漫射板远紫外波段(140~240nm)的双向反射分布函数测量过程中,探测器响应线性问题和紫外光源稳定性差的问题,提出一种采用光源监测比例补偿的相对测量方法.根据测量方法设计了一种基于六自由度转台结构形式的测量系统,该系统采用漫射板两维平移+两维转动、探测器两维转动的组合运动形式,可实现漫射板半球空间内任意点、任意方位的双向反射分布函数测量.用所提方法进行测量实验,并对影响系统测量结果的主要因素进了不确定度分析,结果表明总测量不确定度约为5.5%.     

非视线紫外光信号传输时间特性的数值模拟

在研究紫外光学非视线通信技术中,需要深入了解由于紫外大气散射效应所带来的各种信号畸变.传统的单次散射近似方法在进行较远距离、复杂天气条件下非视线光传输模拟时误差很大,采用基于Monte Carlo(MC)方法改进算法进行非视线紫外光信号传输的数值模拟,通过随机抽样的方法模拟光子在大气系统中的随机游动,在光子被大气中的粒子散射时计算其进入探测器的概率,模拟大气系统的脉冲响应函数.模拟结果表明:采用光子散射探测概率方法改进后的MC模型在模拟非视线光信号传输时计算效率显著提高;大气系统对非视线传输时的紫外光脉冲具有很强的展宽效应;随着光信号传输距离的增大,信号强度呈近似指数衰减的趋势.     

低能强流质子束空间电荷补偿度研究(英文)

对于低能强流离子束来说,空间电荷效应的存在将导致束流发散、发射度增加等一系列问题,从而降低束流品质。幸运的是,当束流由离子源引出通过低能传输线时会与其中的剩余气体发生电离反应,产生二次电子与二次离子;二次电子在束流自身产生的电场作用下,在束流中积累并中和部分空间电荷,达到抑制空间电荷效应的效果。为了测量空间电荷中和程度,中国科学院近代物理研究所研制了一台三栅网式能量分析仪用以测量电离过程中产生的二次离子能量来间接计算空间电荷中和度。实验结果表明,对于40 keV, 18.5 mA的质子束,真空度为1.510*3 Pa 时得到最佳补偿度;真空度一定的情况下,空间电荷补偿度随束流流强增加而变大。For high-intensity low-energy ion beams, space charge effect is a main cause of beam divergence  and emittance growth. Fortunately, residual gas molecules in the drift space tend to be ionized and neutralize the beam space charge spontaneously. The level of Space Charge Neutralization (SCN)is measured through the detection of created secondary ion energy distribution in the beam region. A so-called non-interceptive Three-grid Energy Analyzer (TEA) has been designed and manufactured at Institute of Modern Physics, Chinese Academy of Sciences (IMP). This paper will present the detailsof the TEA detector and the application to diagnose proton beam SCN level in the Low Energy Beam Transport (LEBT) line. As a preliminary result, for an 18.5 mA proton beam a best compensating point appears at the vacuum pressure of 1.510*3 Pa. And the neutralization level is advanced with thegrowth of beam current in a constant vacuum pressure.     

Probabilistic model for fluences and peak fluxes of solar energetic particles.

The model is intended for calculating the probability for solar energetic particles (SEP), i.e., protons and Z=2-28 ions, to have an effect on hardware and on biological and other objects in the space. The model describes the probability for the > or = 10 MeV/nucleon SEP fluences and peak fluxes to occur in the near-Earth space beyond the Earth magnetosphere under varying solar activity. The physical prerequisites of the model are as follows. 1. The occurrence of SEP is a probabilistic process. 2. The mean SEP occurrence frequency is a power-law function of solar activity (sunspot number). 3. The SEP size (taken to be the > or = 30 MeV proton fluence size) distribution is a power-law function within a 10(5)-10(11) proton/cm2 range. 4. The SEP event particle energy spectra are described by a common function whose parameters are distributed log-normally. 5. The SEP mean composition is energy-dependent and suffers fluctuations described by log-normal functions in separate events.     

空间辐射环境及人体剂量蒙特卡罗模拟

针对空间辐射环境进行了理论分析,并使用蒙特卡罗方法,对银河宇宙射线及典型太阳质子事件进行了模拟。通过分析常规屏蔽对空间辐射场及人体剂量的影响、屏蔽下的次级粒子产额等,验证了蒙特卡罗工具包Geant4应用于空间辐射防护研究的准确性。模拟发现:在常规屏蔽厚度的情况下,对于太阳质子事件,由于其能量主要分布在低能量段(100 MeV以下),屏蔽效果随屏蔽厚度的增加明显增大,1 g/cm2 Al等效厚度屏蔽皮肤剂量可降低至其初始剂量值的8%左右,10 g/cm2 Al等效厚度的屏蔽可降低至初始剂量值的048%左右;而对于银河宇宙射线,由于其平均能量较高,屏蔽层的屏蔽作用并不明显,在浅层组织剂量甚至有所增加。     

Comparison of the SPE model with proton and heavy ion data.

Proton data from the GOES 6 and 7 satellites and heavy ion data from the IMP-8 satellite have been compared to the expected results of Nymmik's new model for solar particle event fluences. This model calculates the energy spectra of ions for protons through nickel for solar particle events, based upon the observed proton integral fluence above 30 MeV. Based upon 27 observed proton events of solar cycle 22, and three large historical events, with integral fluences above 30 MeV of greater than 10(6) particles/cm2, a reasonable agreement with model predictions is seen for more than half of the events. However, several events show a marked departure from the model predictions, leading to the conclusion that there may exist more than a single class of event, or that it may be necessary to include additional parameters within the model, such as solar disk position of the source flare, or height of disturbance in the solar corona. Data for heavy ions, (oxygen and iron), were limited to a total of six solar particle events, of which only two occurred in solar cycle 22. The agreement between data and the model predictions appeared to be quite good, however this agreement was sensitively dependent upon the value taken for the proton fluence above 30 MeV.