Studies on Secondary Electron Emission in Antiproton-Foil Collisions
Grant-in-Aid for international Scientific Research
|Allocation Type||Single-year Grants|
|Research Institution||College of Arts and Sciences, University of Tokyo|
YAMAZAKI Y. Institute of Physics, Univ. Tokyo, 教養学部, 助教授 (30114903)
東 俊行 東京大学, 教養学部, 助手 (70212529)
小牧 研一郎 東京大学, 教養学部, 助教授 (40012447)
HVELPLUND P. Institute of Physics, Univ. Aarhus
UGGERHOJ E. Institute of Physics, Univ. Aarhus
KOMAKI K. Institute of Physics, Univ. Tokyo
AZUMA T. Institute of Physics, Univ. Tokyo
ELSENER K. CERN
|Project Period (FY)
1989 – 1990
Completed(Fiscal Year 1990)
|Budget Amount *help
¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 1990 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1989 : ¥1,800,000 (Direct Cost : ¥1,800,000)
|Keywords||slow antiproton / wake-riding electron / convoy electron / secondary electron / chargedparticlesolid interaction|
At LEAR (Low Energy Antiproton Ring) of CERN, high quality beams of slow antiprotons are provided not only for elementary physics, but also for solid state and atomic physics. In atomic and solid state physics, "heavy" particles with negative charge like antiprotons, negative muons are fantastic probes to investigate charge asymmetry effects. Among others, antiproton beams from LEAR are the best in the sense of their narrow energy and angular spread and their intensity.
This project was planned to persue the possibility to employ this high quality slow antiprotons as "heavy" negative particles. Our first step had been devoted to a research on "wake-riding" electrons through measurements of energy spectra of secondary electrons emitted in the forward direction in antiproton-foil collisions. The wake-riding electron is an electron trapped in the attractive part of the oscillatory potential (wake potential) which trails behind the projectile with wavelength ^-2piupsilon_P/omega_<pl>, where upsilon_P is the projectile velocity, and omega_<pl> the plasmon frequency of the target. It is noted that positive particles like protons can never extract any reliable information on the wake-riding electrons separating it from huge convoy electrons.
We have performed a couple of experiments to compare the electron spectra produced in antiproton-carbon foil collisions and proton-carbon foil collisions. Our principal observations are (1) for antiproton impacts, the spectra around upsilon_e ^-upsilon_P, where upsilon_e is the electron velocity, are rather smooth with very weak indications of an "anticusp" as opposed to simpleminded predictions, and (2) a small bump is observed about 50eV below upsilon_e ^-upsilon_P, the energy position and its relative intensity of which are found to be consistent with theoretical evaluations employing a Monte Carlo simulation.
Research Output (13results)