Barker, D.

Böhm, R.

Dimopoulou, C.

Thorndahl, L.

GSI Repository

Developments of the Palmer pickup tank for stochastic cooling in the CRD. J. Barker1, R. Bo¨hm1, L. Thorndahl2, and C. Dimopoulou11GSI, Darmstadt, Germany; 2CERN, Geneva, SwitzerlandIntroductionThis report details the design and construction progressmade on the Palmer pickup tank for the stochastic coolingsystem of the collector ring (CR) during 2014 at GSI. TheCR is designed for the stochastic cooling of antiprotons andRIBs. For details of the complete stochastic cooling sys-tem including particle beam parameters see [1]. For thestochastic pre-cooling of RIBs, we use the Palmer methodin combination with pickups of large acceptance to cool in-jected hot ion beams with large momentum spread. For thispurpose Faltin type pickups have been designed and pub-lished previously [2]. The Faltin rail is a travelling wavepickup in the form of a rectangular coaxial structure withslots in the top which couple to the beam.Drawing and ConstructionDrawing work on the full tank began and finished 2014as shown in figure 1, although work on the Faltin rails it-self continues. To test the pickup designs prototypes weremade. During 2014 drawing work on three different proto-types was completed. Construction and procurement of theprototypes was finished in December. The prototypes areshown in figure 2. The robustness of the assembly methodwas tested. Microwave measurements made on the proto-types which showed good agreement with simulations andare shown in figure 3.Figure 1: Cross sectional preliminary drawing of the fullPalmer pickup tank(2 m installation length).SimulationsSeveral unwanted modes which interfere with beamcooling were discovered and simulations with lossy fer-rite material were conducted in order to damp these modes.Ferrite or some other lossy material will definitely be nec-essary within the pickup tank to maintain beam coolingperformance. In 2014 a program was written which takesFigure 2: Three Faltin prototypes of one quarter of thepickup.impedance and phase data of these waveguide pickups andadds signals from several of these pickups using delay linesof specific length to produce a flat impedance and linearphase over a desired band. This process was optimised us-ing a genetic algorithm. This will be used for further opti-misation of the pickup.0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5−45−40−35−30−25−20−15−10−50f(GHz)S21(db)Measurment DataHFSSFigure 3: Comparison of measurements of S21 using a net-work analyser and S21 data from HFSS simulations.References[1] CR Technical Design Report 2014 and C.Dimopoulou et al.,this report.[2] D. Barker et al., JACoW Proc. COOL’13, WEPPO21.FG-GENERAL-35 GSI SCIENTIFIC REPORT 2014452 DOI:10.15120/GR-2015-1-FG-GENERAL-35

Developments of the Palmer pickup tank for stochastic cooling in the CR

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Developments of the Palmer pickup tank for stochastic cooling in the CR

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