装有贝塞尔盒型能量分析仪的电离规和四极质谱计的研制

贝塞尔盒型能量分析仪由三部分组成 :一个圆筒形电极、一个中心圆盘和两个带中心孔的侧板 ,该分析仪结构简单、结实 ,十分适用于电离规和四极质谱计上。对电离规而言 ,分析仪被放置于电离器及离子收集器之间。在栅型电离器中所产生的离子被分离并注入到能量分析仪中。分析仪依据其激发的能量把电离器中产生的气相离子和栅网表面上脱附的电子激励解吸的离子分离开。如果应用一个法拉第杯型离子收集器和一个灵敏的直流放大器来进行离子流测量的话 ,那么该电离规测量范围在 10 - 1 0 ～ 10 - 3Pa之间。当二次电子倍增器采用脉冲计数方法时 ,所测量的压力范围在 10 - 1 1～ 10 - 6 Pa之间 (Ax TRAN,ISX2 ,U L VAC公司 ) .其典型灵敏度对氮气而言为 (6 .7± 0 .2 )× 10 - 3Pa- 1 和对氢而言为 (2 .3± 0 .0 4 )× 10 - 3Pa- 1 。对四极质谱计而言 ,能量分析仪被置于在电离器和四极滤质器之间。装有该分析仪的质谱计 ,给出了没有电子激励解吸离子的简单质谱。该分析仪能使四极质谱计的离子收集器免受从栅网表面发射的 X射线的辐射 ,和从电离器中的离子以及被激发的分子在退激励过程中释放的紫外线的辐射。这种屏蔽作用改善了在 10 - 3Pa范围内的气体中微量杂质的检测极限 ,使之降至亿分之几

Development of the ionization gauge and the quadrupole mass spectrometer with a Bessel-box type energy analyzer

A Bessel-box type energy analyzer consists of a cylinderical electrode, a center disc, and two endplates with center hole. The analyzer has simple and substantial structure suitable for the application to ionization gauge and a quadrupole mass spectrometer.For an ionization gauge, the analyzer is placed between the ionizer and the ion collector. The ionsgenerated in the grid type ionizer are extracted and injected into the energy analyzer. The analyze rseparates the gas phase ions generated in the ionizer and the electron stimulated desorption (ESD) ions desorbed on the grid surface according to their energy energies. If the direct current measurement of the ion current with a Faraday cup type ion collector and a sensitive DC amplifier is used, the gauge is possible to measure the pressure between 10-10 to 10-3 Pa. When the pulse counting method with a secondary electron multiplier is used, the range of pressure measurement becomes between 10-11 Pa and 10-6 Pa (AxTRAN, ISX2, ULVC Inc.). The typical sensitivity factors are (6.7±0.2)×10-3 Pa for N2 and (2.3±0.04)×10-3 Pa-1 for H2.For a quadrupole mass spectrometer (QMS), the energy analyzer is placed between the ionizer and the quadrupole mass filter. The spectrometer with the analyzer gives simple mass spectra without ESD ions. The energy analyzer screens the ion collector of the QMS from the irradiations of the x-rays emitted on the grid surface, and of the ultraviolet light released in the de-excitation processes of ions and excited molecules in the ionizer. The screening effect improves the detection limit of minute impurities in the gases of 10-3 Pa region down to a few tens ppb.