Barker, D.

Böhm, R.

Dimopoulou, C.

Dolinska, M.

Hettrich, R.

Kelnhofer, M.

Krieg, J.

Maier, W.

Menges, R.

Peschke, C.

Rossbach, J.

Thorndahl, L.

GSI Repository

Developments for the CR Stochastic Cooling SystemC. Dimopoulou1, D. Barker1, R. Bo¨hm1, M. Dolinska2, R. Hettrich1, W. Maier1, M. Kelnhofer1, J.Krieg1, R. Menges1, C. Peschke1, J. Rossbach1, and L. Thorndahl31GSI, Darmstadt, Germany; 2Frankfurt University; 3CERN, Geneva, SwitzerlandThe large-acceptance Collector Ring (CR) is designedto provide fast stochastic cooling (SC) of antiproton andrare isotope beams. A detailed specification document [1]describing the complete CR SC system in the frequencybandwidth 1-2 GHz has been released. Intensive in-houseengineering activities, preparation of the technical infras-tructure taking into consideration electrical and mechani-cal safety issues as well as critical procurements of systemcomponents have taken place during 2013.Electrodes and pick-up tanks,Simulations of the system performanceThe layout and testing challenges of the prototype pick-up tank are explained in [1]. The new water-cooled lin-ear motor drive units have been tested at room temperaturewith different acceleration profiles set by a control soft-ware. The linear motor drives fulfill the following spec-ifications: (i) their maximum range of plunging is 70 mmfollowing the shrinking beam size during stochastic coolingand (ii) at the end of the cycle, they move back out to theirmaximum aperture within 200 ms, before a new beam isinjected. Their synchronous operation remains to be testedafter re-assembly in the tank.Figure 1: Up: Copper cryoshield before mounting in theprototype tank. Down: Cryoshield parts after gold plating.The intermediate cryoshield, which will be held at 80 Kinside the pick-up tank, was successfully inserted into theprototype tank at room temperature. It consists of 4 half-shells, each 1 m long, and bears holes for the motor drivesand for assembling, it is made of oxygen-free copper (Fig.1, up). Afterwards, its pieces were polished and galvani-cally gold plated (Fig. 1, down), so as to reach very lowthermal emissivity. The preparation of the cryoshield wasa complex interdisciplinary task completed at GSI.Simulations with the HFSS code have converged to pos-sible designs of the Faltin-type electrodes of the Palmerpick-up [2]. The Palmer cooling performance in the CRhas been calculated using a Fokker-Planck approach, mod-ified for this purpose, and implementing the properties ofthe suggested electrodes. With the confidence thus gained,engineering work on electrode prototypes could start.In parallel, a numerical model for simulating the Palmerstochastic cooling of ions in the time domain has been writ-ten, cross-checked against analytical formulae, and subse-quently applied to the CR case as well as to experimentaldata from ESR operation.RF signal processing and operation codesThe RF block diagram of the complete SC system andits integration into the building has been refined [3] so asto save electrical length, since the flight time of the quasi-relativistic particles from pickup to kicker is very short.After releasing the technical specification of the very de-manding 1-2 GHz power amplifiers, the procurement pro-cedure was launched. It has led to a first round of intensivetechnical negotiations with potential providers, aiming atawarding the contract beginning of 2014.The design of the notch filters was optimized and theirmeasured RF properties lie within the specifications. Themechanical assembly, including the thermally stabilizeddelay line, has been finalized.Conformal to the defined standards of the FAIR con-trol system, a new operation program covering all coolingbranches of the ESR SC system has been developed andimplemented to the existing RF hardware. This is a majorstep towards the preparation of such operation codes for theCR system.References[1] Doc F-DS-BC-01-SC-CR-v1.0.pdf, GSI EDMS Doc.1316650/1; CR Technical Design Report 2014.[2] D. Barker et al., JACoW Proc. COOL’13, WEPPO21.[3] C. Peschke et al., JACoW Proc. COOL’13, WEPPO20.FG-CR-02 GSI SCIENTIFIC REPORT 2013362 doi:10.15120/GR-2014-1-FG-CR-02

Developments for the CR Stochastic Cooling System

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Developments for the CR Stochastic Cooling System

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