KUROKI Kenro National Institute for Police Science, 主任研究官
AZUMA Toshiyuki Institute of Physics, University of Tokyo, 教養学部, 助手 (70212529)
KOMAKI Ken-ichiro Institute of Physics, University of Tokyo, 教養学部, 教授 (40012447)
HVELUND Preben Institute of Physics, University of Arhus
ELSENER Kourad CERN
KNUDSEN Helge Instituti of Physics, University of Arhus
In atomic and solid state physics, "heavy" particles with negative charge like antiprotons, negative muons etc., can be fantastic probes to investigate Charge asymmetry effects. Among others, antiproton beams from LEAR at CERN are the best because of its high quality and high intensity.
The present research is an extension of the previous project, "Studies on Secondary electron emission in antiproton-foil collisions (#0104403 : 1989-1990). Our first step had been devoted to the investigation on "wake-riding" electrons through measurements of energy spectra of secondary electrons emitted in the forward direction in antiproton-foil collisions. We have performed a couple of experiments degrading 5.9MeV antiproton beams (the lowes possible energy upto now)to several hundred KeV degrader foils, where one can only get a beam of wide energy and angular distribution. Our principal observations have been, (1)the spectra around v_p-v_e, where upsilone is the electron velocity, are rather smooth with very weak indication of an anticusp as opposed to simple-minded predictions, and (2) a small bump is observed at the right energy position with reasonable intensity, which is consistent with theoretical evaluations.
As a reference experiment, we have also measured the intensity of ionized electrons emitted in the forward direction in coincidence with primary electrons scattered in the same direction for He gas target, where an anticusp is clearly observed which is in good contrast with antiproton experiment.
Recent development of RFQ accelelator technique enables us to get "deccelelated"monoenergetic antiproton beam as low as -200KeV. We are on the way to extend our experiment with this high quality ultra slow beams, which will provide, e.g., the definite answer on the existence of the wake riding electrons, and further the possibility of channeling of slow heavy particles through crystals, etc.