A comprehensive study on resonant scattering of electrons form atmospheric molecules using a new method

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 09440152
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 物理学一般
• Research Institution: The University of Electro-Communications
• Principal Investigator: CURRELL Frederck J. Faculty of Electro-Communications, The University of Electro-Communications, Lecturer, 電気通信学部, 講師 (40262365)
• Co-Investigator(Kenkyū-buntansha): カレル フレデリックジョン 電気通信大学, 電気通信学部, 講師 (40262365)
• Project Period (FY): 1997 – 1999
• Keywords: Electron Collision / Atmospheric Molecules / Trochidal Analyzer

Research Abstract

Trochoidal dispersive devices have been used in electron spectroscopy to both prepare and energy analyze electron beams. Fantastic sensitivity has been achieved although the resolution of these devices has not been as good as other types of electron spectrometer. The primary difficulty in obtaining high resolution can be traced to an aberration related to the input position of the electrons perpendicular to the trochoidal dispersing plates. Electrons nearer to the positive plate travel through the cross field region quicker and so suffer less dispersion than similar electrons travelling near the negative plate. Indeed, it could be argued that these devices are low-pass filters, not energy analysers. A second problem is that the dispersion tends to be small in these devices- This means that the resolution obtained is limited by mechanical constraints such as the minimum practical slit size. We have overcome both of these limitations by creating a new multi-pass trochoidal dispersive dev ice. Electrostatic mirrors are positioned at either end of the trochoidal dispersing plates so that the electrons can bounce a number of times through the device before leaving the exit aperture. A small pre-selector is used to limit the energy range of electrons entering the multi-pass device. This ensures the electrons only exit the device after a certain number of passes. The voltages applied determine this number of passes. We have carefully designed the electrostatic mirrors so that they act to cancel the aberration described above. Ray-tracing calculations show that this results is a device which should be comparable to hemispherical analysers in terms of resolution whilst retaining the sensitivity associated with the in-line magnetic configuration of usual trochoidal spectrometers. Using this new electron-optical device, we have designed and are in the process of constructing a new electron spectrometer nicknamed SHACHI. This an acronym for Spectrometer with High Aberration Compensation and High Intensity. Other innovative features incorporated into the design of SHACHI, include double differential pumping with gives a pressure differential of about 100. The power supplies are all computer-controlled using a novel system that is much cheaper than traditional systems. This is achieved by emulating the way power supplies float in software. All supplies are referenced to ground so standard analog to digital converter cards can be used without the need for isolation. The output from these cards is then amplified using high voltage operational amplifiers to give the required voltage range.