Research for optimizing the performance of an LEF-TOF ion energy mass analyzer
- University of Tokyo, Yoshinodai, Sagamihara, Kanagawa, 3-1-1 (Japan)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai, Sagamihara Kanagawa, 3-1-1 (Japan)
There are few in-situ heavy ion observations from lunar soil or tenuous alkali atmosphere. It is commonly thought that the heavy ions around the Moon are produced by ion-induced desorption (sputtering) or photon-stimulated desorption from the lunar surface and by photoionization from the atmosphere. These ions are picked up and transported by the solar wind. IMA (Ion Mass Analyzer) on board the SELENE satellite will measure these picked-up ions around the Moon. IMA adopts foil-based LEF (Linear Electric Field) TOF (Time Of Flight) technique for mass analysis in order to discriminate heavy ions up to mass number 60. MgO-coated metal plate is installed at the upper part of the mass analyzer to generate TOF stop electrons efficiently. Though we empirically knew that stop electron generations were enhanced by MgO-coated metal plate, quantitative analyses for the efficiency were insufficient. We compared the efficiency of electron emitter plates with different substrate materials: CuBe and Al and with different MgO thickness: 20 nm, 500 nm and 1000 nm. We also changed the surface roughness of these base plates. Our experimental results showed there are notable differences in the electron emission efficiency between MgO-coated plates and non-coated plates. We also found that the thicker MgO emits secondary electrons more efficiently. The efficient electron emission was mainly caused by the enhancement of the secondary electron yields of a single ion impact because the pulse height distribution of the stop signals generated by MgO coated plates was higher than that of non-coated plates.
- OSTI ID:
- 21316802
- Journal Information:
- AIP Conference Proceedings, Vol. 1144, Issue 1; Conference: International conference on future perspectives of space plasma and particle instrumentation and international collaborations, Tokyo (Japan), 1-3 Nov 2006; Other Information: DOI: 10.1063/1.3169275; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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