Andre, C.

Bräuning, H.

Dorn, C.

Gorda, O.

Herfurth, F.

Hoffmann, T.

Kaufmann, W.

Reeg, H.

Reiter, A.

Sieber, T.

Vorobyev, G.

Walasek-Höhne, B.

Witthaus, M.

GSI Repository

Beam instrumentation for the RFQ injector at CRYRINGA. Reiter, C. Andre, H. Bra¨uning, C. Dorn, F. Herfurth, O. Gorda, T. Hoffmann, W. Kaufmann,H. Reeg, T. Sieber, G. Vorobjev, B. Walasek-Ho¨hne, M. WitthausGSI, Darmstadt, GermanyIn 2015 the CRYRING storage ring will resume oper-ation after its installation in Cave B [1]. Commissioningbegins with the compact injector, consisting of ion sourcebranch and radio-frequency quadupole (RFQ) linac. It willprovide beams of light charged particles for commission-ing of the experimental storage ring.The beam instrumentation of the injector consists of Fara-day cups, scintillating screens, and capacitive pickups. Alldetector systems are compliant to the new FAIR standardsand provide a front-end software architecture (FESA) inter-face to the accelerator control system. CRYRING will bethe first machine to be equipped with the new White-Rabbittiming system.Ion Source and Dipole SpectrometerBeams of light, singly-charged ions of 10 keV/u, mainlyD+, will be extracted from a MINIS source. Directly be-hind the ion source and behind the 90◦ spectrometer dipole,intensity and distribution of the DC beam can be measuredwith a Faraday cup (FC) or a scintillating screen (SCR).The compact diagnostics chamber with a single motor drivefor both detectors was originally designed by KVI Gronin-gen for the HITRAP facility . The driver unit and the con-troller are a joint FAIR development of GSI and Slovenianin-kind contributor Cosylab.Expected beam currents along the injector range from100µA after the source to 1 µA after the RFQ linac. Forthe multi-turn injection into CRYRING, the chopper be-hind the ion source cuts out a 25−100µs macropulse fromthe DC beam. Each FC is equipped with a low-noise ampli-fier, suited for DC and AC operation, with switchable gainsof 102 − 108 V/A. The output is sampled by a 100 MSa/sADC with 16 bit resolution in a VME system. Its embed-ded controller runs the ”CryCup” acquisition software.The SCRs are composed of 25 mm diameter multi-channelplates and P43 scintillators. Beam images are recordedwith triggered 10 bit digital CMOS cameras. They are con-trolled by an industrial PC which hosts the ”CUPID ” ac-quisition software. The application takes care of all datahandling (image rotation, region cuts, profile calculation)and acts as server to the control system clients [3].A special camera system with 75 mm fixed-focus lens andoptical x4 extender is mounted on the external 0◦ port ofthe dipole chamber and looks approx. 3 m upstream intothe ion source. During operation it monitors the plasmaaround the filament, after ion source service or exchangethe fixed camera is used to check the re-alignment. Thesystem resolution was measured to be about 20 pixel/mm.Figure 1: Schematic of RFQ injection for CRYRING; de-tector positions are indicated with symbols described in thelegend. The distance between RFQ and injection is∼10 m.RFQ linac and debuncherThe 108.4 MHz RFQ linac accelerates ions of q/A>0.36from 10 to 300 keV/u. The following debuncher reducesthe momentum spread ∆p/p to ∼ 1% and increases theinjection efficiency. The new bunch monitoring systemanalyses pairs of signals selected from 3 pickups (PHP) orRFQ and debuncher tank. The derived information may bethe beam energy via time-of-flight, phase relations betweenbeam and rf tank power or the verification of the debuncheroperation. Signals are amplified, in the case of PHPs, androuted via a remote-controlled switching matrix to a digital5 GSa/s oscilloscope. A FESA application integrates am-plifiers, switching matrix and data readout. The analysisprocedure is identical to the one employed at the HITRAPdecelerator and achieves a resolution of ∼10 ps [2].As in the source branch two FC/SCR pairs, one at theRFQ exit and one after the two quadrupole doublets, mea-sure intensity and distribution of the 300 keV/u beam. Inthe bakeable area after the switching dipole, a robust, heat-resistant Cromox screen is mounted close to the injectionseptum on a pneumatic drive. The detectors are part of thereadout systems described in the previous section.References[1] M. Lestinsky et al., ”CRYRING@ESR: A study group re-port”, June 2012[2] A. Reiter et al., MOPD35, DIPAC 2011, Hamburg, Germany[3] B. Walasek-Ho¨hne et al., TUPD062, IBIC 2014, Stanford,USAFG-GENERAL-16 GSI SCIENTIFIC REPORT 2014434 DOI:10.15120/GR-2015-1-FG-GENERAL-16

Beam instrumentation for the RFQ injector at CRYRING

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Beam instrumentation for the RFQ injector at CRYRING

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