Study of Heavy-Ion Beam Cooling using the Electron Cooling Method

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Electron cooling is very attractive subject of physics as well as accelerator technology. This research project aims primarily at the study of the cooling process itself and is intended to extend the technology of proton cooling to heavier ions.A device to cool light to heavy ions up to the energy of 200 MeV/u was designed and constructed. The maximum electron energy is 120 keV, which is equivalent to 200 MeV/u ion beam energy. The length of interaction region between electrons and ions is 1.5 m. The electron beam diameter is 50 mm and maximum current density is 0.5 A/ <cm^2> . Electron optics consists of a Pierce electrode, an anode and accelerating electrodes. A flat cathode is immersed in a uniform solenoid. Computer simulation studies show that transverse electron temperature of around 0.1 eV can be realized at the solenoid field less than 1.2 kG. Electron gun and collector were carefully designed taking account of the vacuum, high voltage and high temperature. The main parts of th … More e electron guiding coil consists of three solenoids and two 45゜-toroids. A good homogeneity of the magnetic field than <+!-> 2x <10^(-4)> was realized at the central solenoid. The high voltage system to accelerate electrons consists of 120 kV high voltage power supply and some other power supplies. A good stability is required for this HVPS since the longitudinal temperature of electron beam is mainly determined by the variation of the acceleration voltage. A good stability of <+!-> 1x <10^(-5)> was achieved at 120 kV. A vacuum chamber made of SUS316L stainless steel can attain the vacuum pressure of <10^(-11)> Torr. Inside the chamber we have drift tubes, position monitors and antenna to pick up microwave. Electron orbit was studied using a small electron beam. The electron path starting from the gun and ending in the collector was visually observed by viewing the light emitted from fluorescent plates. The fraction of deveation of electron trajectory at the cooling solenoid was less than <+!-> 2x <10^(-4)> , which is consistent with the result of the magnetic field measurements. Electron cooling process was studied by simulation and it was found that the cooling time of the order of second can be realized. A microparticle internal target for the electron cooler was developed. A flow of charged microparticles was produced by a simple method of contact-charging and accelerating fine metal powder. The obtained thickness between <10^(14)> and <10^(16)> atoms/ <cm^2> is just the desirable value for an internal target for a cooler ring.The construction of the ion beam storage ring to execute the beam cooling is now under construction. Im-mediately after the first beam, we intend to start the electron cooling studies, firstly for proton and then for heavy ions. The balance between target heating and electron cooling is also our important theme in future. Less