The HESR Stochastic Cooling System, Design, Construction and Test Experiments in COSY

The construction phase of the stochastic cooling tanks for the HESR has started. Meanwhile two pickups (PU) and one kicker (KI) are fabricated. One PU and one KI are installed into the COSY ring for testing the new stochastic cooling system with real beam at various momenta. Small test-structures were already successfully operated at the Nuclotron in Dubna for longitudinal filter cooling but not for transverse cooling and as small PU in COSY. During the last COSY beam-time in 2017 additional transverse and ToF cooling were achieved. The first two series high power amplifiers were used for cooling and to test the temperature behavior of the combiner-boards at the KI. The system layout includes all components as planned for the HESR like low noise amplifier, switchable delay-lines and optical notch-filter. The HESR needs fast transmission-lines between PU and KI. Beside air-filled coax-lines, optical hollow fiber-lines are very attractive. First results with such a fiber used for the transverse signal path will be presented

First Experiences with HESR Stochastic Cooling System

The stochastic cooling system of the HESR (High Energy Storage Ring) is based on completely new structures especially designed for the HESR. Each beam surrounding slot of these so called slot-ring couplers covers the whole image current without a reduction of the HESR aperture and without any plunging system. One pickup and one kicker have been already fabricated and installed into the COSY ring to demonstrate stochastic cooling in all three dimensions with only one structure. First results of commissioning with proton beams will be presented. The longitudinal cooling system at HESR is based on filter cooling with an optical notch-filter and ToF cooling. The demanding accuracy concerning phase stability requires dedicated control of the notch-frequency. The optical COSY filter has been modified and can be proven in long term runs together with the new stochastic cooling system

The Concept of Antiproton Accumulation in the RESR Storage Ring of the FAIR Project

The RESR storage ring of the FAIR projectwas designed for use as an accumulator ring for antiprotons. Therefore its optical design offers a large momentum acceptance and large flexibility in the choice of the working point. This is crucial, if longitudinal stacking with a stochastic cooling system is planned. The accumulation system has been studied in simulations which include both the properties of the optical design and details of the stochastic cooling system. The simulations confirm that the stochastic cooling system can support the accumulation with a repetition rate of 10 s for the injection of pre-cooled batches of 108 antiprotons from the collector ring CR. A maximum of intensity of 1011 accumulated antiprotons can be achieved as required for high luminosity experiment

Recommissioning of the CERN AD Stochastic Cooling System in 2021 after Long Shutdown 2

The power system of the Stochastic Cooling System of the anti-proton decelerator AD at CERN, installed on top of the shielding blocks of the AD ring, was completely dismantled during the long shutdown 2 (LS2) at the end of the 2018 run in order to gain access to the accelerator for magnet consolidation. At start-up, this required finding and verifying the correct delays for all 48 power amplifiers feeding to the two kickers by means of beam transfer functions for the two cooling plateaus at 3.57 GeV/c and 2 GeV/c. We describe the methods used for the setting up and the results of the optimization for the cooling in all three planes, longitudinal, horizontal and vertical. An experimental set-up has been put into operation for the automatic monitoring and correction of the notch position of the longitudinal cooling at 3.57 GeV/c with optical delay lines. We also comment on the lessons learnt during the recommissioning including the repair work for a vacuum leak in the water cooling circuits of the kicker following bake-out and the verification of the internal loads by RF reflectometry

The CLIC RF power source: a novel scheme of two-beam acceleration for electron-positron linear colliders

We discuss a new approach to two-beam acceleration. The energy for RF production is initially stored in a long-pulse electron beam which is efficiently accelerated to about 1.2 GeV by a fully loaded conventional, low-frequency (approx. 1 GHz) linac. The beam pulse length is twice the length of the high-gradient linac. Segments of this long pulse beam are compressed using combiner rings to create a sequence of higher peak power drive-beams with gaps between. This train of drive beams is distributed from the end of the linac in the opposite direction to the main beam down a common transport line so that each drive beam can power a section of the main linac. After a 180-degree turn, each high-current, low-energy drive beam is decelerated in low-impedance decelerator structures, and the resulting power is used to accelerate the low-current, high-energy beam in the main linac. The method discussed here seems relatively inexpensive, is very flexible, and can be used to accelerate beams for linear colliders over the entire frequency and energy range