Development of Neutral Mass Spectrometer using Time-of-flight Technique for Space Flight

四极杆式和磁偏转式中性质谱计是航天飞行中常用的两种中性质谱计。然而，这两种类型都存在测量空间中性质量分布的基本问题。这些是1。对靶气体与几百公里高空大气中主要成分原子氧的复合效应进行了评价，原子氧是仪器表面吸收的主要成分。目标气体的速度识别函数信息丢失。最近我们提出了一种新型的中性质谱计，利用飞行时间技术消除了仪器内部的复合效应，实现了对目标气体分布函数的测量。在该基金的支持下，我们开发了该探测器的关键部件（脉冲离子源，飞行时间（TOF）加速部分，以及测量飞行时间和二维位置的探测器），然后将它们集成到火箭飞行系统中。的dev ...更多信息 私奔的要素是：1.灯丝电源为发射电子束的灯丝提供恒定的低电压电源，用于电离目标中性气体。输出功率由输入控制电压控制。输入和输出之间的漏电流被最小化，以便能够正确地测量发射电流。飞行时间加速部分在电离部分和加速部分之间放置网格。在使用脉冲电子束的电离期间，网格电位被设置为0 V。这种网格可以有效地抑制由于不存在网格时存在的势梯度而产生的额外光束发散。电离周期结束时，网栅电位变为-10V，加速离子探测器前进。网格电位的高速切换（0->-10V，20 nS内）使得能够最小化由电离点的差异引起的TOF的分散。探测器3级MCP用于探测器。在MCP和位置敏感阳极之间放置网格。TOF脉冲由来自该网格的信号测量。进一步改进：本文提出的方法对靶气体分布函数的采样频率有一定的限制。这一限制来自于TOF和位置检测的复杂测量要求每个脉冲束的离子数小于1。为了克服这一限制，我们开始了使用CCD相机作为位置检测和开关MCP HV用于质量选择的系统的可行性研究。少

Quadropole type and magnetic deflection type neutral mass spectrometer are commonly used for space flight. However both type have basic problems for measuring neutral mass distribution in space. Those are 1. evaluation of the effect with the recombination of target gas and atomic oxygen, which is major component of the several hundred km height atomosphere and absorb on the surface of the instrument, 2. loss of velocity idstribution function information of target gas. Recently we proposed a new tuype neutral mass spectrometer using time-of-flight technique to eliminate the effect of the recombination inside the instrument and to achieve the measurement of distribution function of target gas. With the support of this grant, we have developed the key components of this detector (pulse ion source, acceleration part for time-of flight (TOF), and detector which measures time-of-flight and 2 dimensional position, simultanously) and then integrate them into a system for rocket flight. The dev … More eloped elements are :1. Filament power supplySupply constant power with low voltage to filament which emits electron beam for ionization of target neutral gas. Output power is controled by the input control voltage. Leak current between input and output is minimized to be able to measure the emission current correctly.2. Acceleration part for time-of-flightA mesh is placed between ionization part and acceleration part. Mesh potential is set to OV during ionization period using pulse electon beam. This mesh is effective to suppress extra beam divergence due to the potential gradient which exists when the mesh is not exist. Mesh potential is changed to -10V when ionization period is finished to accelerates the ion torward detector. High speed switching (0->-10V within 20nS) of the mesh potential enabled to minimize the dispersion of TOF caused by the difference of the ionizing point.3. Detector3 stage MCP is used for detector. A mesh is placed between MCP and position sensitive anode. TOF pulse is measured by the signal from this mesh. Using this mesh with position sensitive anode enables simultanous measurement of TOF and position of the ionized particle.Further improvement :The method which we are developed has a limitation of the sampling frequency of the distribution function of target gas. This limitation comes from the fact that the simultanous measurement of TOF and position detection requires that number of ions per 1 pulse beam should be less than 1.To overcome this limitation, we have starting the feasibility study of the system which uses CCD camera as position detection and switch MCP HV for mass selection. Less