Antiproton Acceleration and Deceleration in the HESR

Abstract

The High Energy Storage Ring (HESR) is a part of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt [1,2]. The ring is used for hadron physics experiments with a pellet target and the PANDA detector, and will supply antiprotons of momenta from 1.5 GeV/c to 15 GeV/c. To cover the whole energy range a flexible adjustment of transition energy and the corresponding tr value is foreseen. For injection and accumulation of antiprotons delivered from the CR at a momentum of 3.8 GeV/c ( =4.2), the HESR optics will be tuned to tr =6.2. For deceleration down to a momentum of 1.5 GeV/c this optic is suitable as well. Stochastic cooling at an intermediate energy is required to avoid beam losses caused by adiabatic growth of the beam during deceleration. For acceleration to 8 GeV/c ( =8.6) the optics will be changed after accumulation of the antiproton beam to tr =14.6. For momenta higher than 8 GeV/c the beam will be debunched at 8 GeV/c, optics will be changed to tr =6.2, and after adiabatic rebunching the beam will be accelerated to 15 GeV/c (=16). Simulations show the feasibility of the described procedures with practically no beam losses. INTRODUCTION The High Energy Storage Ring HESR is dedicated to the field of high energy antiproton physics with high quality beams over the broad momentum range from 1.5 to 15 GeV/c to explore the research areas of hadron structure and quark gluon dynamics, e.g. non perturbative QCD, confinement, and chiral symmetry. An important feature of the new facility is the combination of phase space cooled beams with internal targets which opens new capabilities for high precision experiments. Wide international collaborations (e.g. PANDA [3]) with a rich scientific program are working on new experiments with antiprotons in the energy range between the CERN Antiproton Decelerator AD and the Tevatron energies. Special equipment enables the high performance of this antiproton machine, which will make high precision experiments feasible that are not possible up to now. Key tasks for the design work to fulfil these requirements are:  multi harmonic RF cavities [4],  high sensitivity stochastic cooling pickups for the frequency range 2-4 and 4-6 GHz,  powerful beam cooling systems to counteract beam heating (from beam target interaction and intra beam scattering) to achieve high luminosity and high beam quality. Stochastic cooling will be used for the injection and accumulation process and to counteract the beam heating caused by the target of the PANDA experiment. Figure 1: Schematic view of the HESR ring, the target position for PANDA is in the middle of the right straight section. Injection is placed on the bottom right, positions of stochastic cooling pickups and kickers are indicated. ___________________________________________ # b.lorentz@fz-juelich.de THPF030 Proceedings of IPAC2015, Richmond, VA, USA ISBN 978-3-95450-168-7 3758 Co py rig ht © 20 15 CC -B Y3. 0 an d by th er es pe ct iv ea ut ho rs 4: Hadron Accelerators A23 Accelerators and Storage Rings, Other Table 1: Lattice Properties lattice type FODO with dispersion suppression magnet type normal conducting number of dipoles 44 length of dipole 4.2 m dipole field 0.17 1.7 T deflection angle 8.2 deg, number of quadrupoles 50 (arcs) + 34 (straights) quadrupole length 0,5 m max, gradient 25 T/m working point 7.61 arc xy 24 80 m Dx 2 8.5 m straight xy 490 m 110 m