TSL, Uppsala
JINR, Dubna, Moscow Region
The HESR will work in a high-resolution mode with 1·1010 stored antiprotons and a high-luminosity mode with 1·1011 stored antiprotons. It will be equipped with both stochastic cooling and electron cooling systems. The main purpose of the electron-cooling system is to provide relative momentum spread in the antiproton beam of a few 1·10-5 (90 %) during experiments with an internal hydrogen pellet target and with luminosity 2·1031 – 2·1032 cm-2s-1. The hydrogen pellet target is expected to produce a stream of frozen hydrogen pellets with diameter 30 μm, which move with 60 m/s and at a rate of 20,000 s-1. The pellet stream is expected to have a diameter of 2–3 mm. Therefore, in order to avoid excessive fluctuations in the count rate, the antiproton beam size at the target must not be too small. This is solved by slightly tilting the electron beam with respect to the antiproton beam, thus making use of a so-called Hopf bifurcation. In order to get a high duty factor on another time scale, while not sacrificing momentum acceptance, a barrier-bucket rf. system will be employed. The electron-cooling system will initially be built for an antiproton energy range from 800 MeV to 9 GeV, but will be built so that its energy can be extended to the full energy of the HESR (14 GeV) at a later stage. The paper discusses the choice of parameters for the electron cooling system and presents simulations.
TSL, Uppsala
MSL, Stockholm
The HESR-ring of the future FAIR-facility at GSI will include both electron cooling and stochastic cooling in order to achieve the demanding beam parameters required by the PANDA experiment. The high-energy electron cooler will cool antiprotons in the energy range 0.8 GeV to 8 GeV. The design is based on an electrostatic accelerator and shall not exclude a further upgrade to the full energy of HESR, 14.1 GeV. The beam is transported in a longitudinal magnetic field of 0.2 T and the requirement on the straightness of the magnetic field is as demanding as 10-5 radians rms at the interaction section. Furthermore, care must be taken in order to achieve an electron beam with sufficiently small coherent cyclotron motion and envelope scalloping. This puts demanding requirements on the electron beam diagnostics as well as the magnetic field measuring equipment. Prototype tests of certain components for these tasks are being performed. The paper will discuss these tests and recent development in the design including the high-voltage tank, electron gun and collector, magnet system, electron beam diagnostics and the magnetic field measuring system.
