Electron Cooling with and Ultracold Electron Beam and Related Applications

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Electron cooling is now becoming a very important method in atomic physics research as well as accelerator technology. The cooling time and the final accuracy in experiments are determined by the electron temperature which is limited by the cathode temperature at around 1000 ﾟC.If one can further reduce the electron temperature, more efficient cooling will be attained and the electron and ion beam quality will be improved. So far, the whole electron system had been immersed in a uniform solenoid field and the electron beam size was unchaged throughout the beam line. However, electron temperature can be reduced to a level less than the cathode temperature by expanding the electron beam adiabatically in a gradually decreasing solenoid field. Based on this principle, we modified the existing electron system to such adiabatic expansion type. We have chosen an expansion factor of 12.7 in the cross sectional area of the electron beam which was aimed at the maximum resolution. This expansion … More factor is the biggest in the existing electron coolers in the world. In the fiscal 1994, we completed the entire system after the deliberate disign, construction and installation in the storage ring.As the research competition in this area is furious, we started atomic physics experiments immediately after the completion of the device in the late 1994. Consequently, at the first experiment, we have discovered a fine structure in the dissociate recombination spectrum of the molecular ion HD^+. These data nicely compared with the theoretical predictions based on a multi-channel quantum defect theory. This is the first time for the good agreements between theory and experiment in dissociative recombination process. The results were published in the Physical Review Letters which is the most famous journal in physics and is well known for its highly rapid communication. Furthermore, strong isotope effects have been found in the dissociative recombinations of ^4HeH^+, ^3HeH^+, ^4HeD^+ and ^3HeD^+ with the ultracold electron beam. These results have been appreciated by domestic and foreign atomic physicists and were presented at the conferences in Israel, Canada and Japan. Now we are also designing a superconducting electron cooler aiming at ultrahigh accuracy. Less