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GSI-ACCELERATORS-12 GSI SCIENTIFIC REPORT 2009 140 ThenewProfileViewSoftwareforBeamInducedFluorescenceMonitors SystemSetup GSIacceleratorsarecurrentlyequippedwithfourBeam InducedFluorescence(BIF)monitors.Theydeterminethe transversebeamprofileswithoutbeamdisturbancebydetectingthefluorescencelightgeneratedbyexcitationofa workinggas(N2)withthepassingionbeam. Therefore, theyarewellsuitedtoobservethebeamatmultiplepositionssimultaneously[1]. The fluorescence photons are detected by two microchannelplate(MCP)basedimageintensifiersystemsusingFireWireCCDcamerastodeterminethehorizontaland verticalbeamprofile. Eachcameralenshasaremotecontrollable iris to adjust the number of photons hitting the photocathodeoftheintensifiersystem. IrisesandMCP amplificationarecontrolledbyanEthernetconnectedDAC electronics. Additionally, eachBIFmonitorcomprisesa pressurecontrolunittoinjectdefinedgaspressuresintothe beampipeandatimingdecodertotriggerthecamerasand theMCPs. SoftwareDesign ThesoftwareforthesystemconsistsofaserverpartwritteninLabView[2]andaclientpartwritteninC++. The server part is running on a powerful Windows PC (2.66 GHz,QuadCoreCPU).Theimagedataisreadoutfrom thecamerasandpre-processedaccordingtotheusersettings(e.g. imagerotation, mirroring, projectioncalculation). The resulting data is then forwarded via the network to a client PC running the C++ application called ProfileView. Indailyoperation, onlytheprojectionsare sentviathenetworkanddisplayedinthegraphical user interface. Additionally, unompressedrawimagescanbe transmittedforstorageandofflineanalysis. Thenetwork loadofa20HzdatastreamofoneBIFmonitorrisesconsiderablyfrom0.8MBit/s(projectionsonly)to110MBit/s whenboth,projectionsandrawimages,arerequested.For networkcommunication, standardTCP/IPsocketsovera gigabitEthernetconnectionareused. SupplementalhardwaredevicesarecontrolledbyProfileViewviaEthernet.Criticalsystems,likeMCPorpressure control, are implemented using separate threads for eachdevice. Therefore,extensivecalculationsinthemain eventloopoftheapplicationwillnotblockthecommunicationwiththesedevices.IftheconnectiontotheMCPamplificationdeviceislost,thehardwaresetsallvoltagestoa“savevalue”topreventdamageofthesystem.Toavoidaccidentalfloodingofthebeampipewithgas,pressurevaluesaredouble-checkedbyProfileViewandthepressurehardwarepriortovalveregulation. Thenetworkconnectionto R.Haseitl,F.Becker,P.Forck,andT.Hoffmann GSIAcceleratorBeamDiagnostics,Darmstadt,Germany Figure1:ScreenshotoftheProfileViewsoftware,showing twoactiveBIFmonitors(TK6,US1)andatestsignal. thetiminggeneratorisestablishedondemandandclosed afterthesuccessfuldispatchofthecommand.ProfileView usestheQtC++libraries[3]toachieveplatformindependenceandisexecutableonboth,WindowsandLinuxcomputers. UsingtheLinuxX-technology,thegraphicaluser interfaceshowninFig.1canbebeamedtoanyoftheterminalsintheGSImaincontrolroom.Additionalinformation onthesoftwarearchitecturecanbefoundin[4]. UserExperienceandOutlook ProfileView is used for the commissioning of the recentlyinstalledBIFmonitorsin2009.During2010afinal numberofsevenBIFmonitorswillbesetupatGSI.First experiencesshowagoodperformanceofthesystem. The abilitytoviewmultipleBIFimagessimultaneouslyandto storetheirrawdataisagreatbenefite.g. forbeamalignmentproceduresandqualityassurance. Userrequestsfor additionalfunctionalityhavebeencollectedandwillbeimplementedinthenextversionofProfileView. References [1] F. Becker, et al., “Beam Induced Fluorescence Monitor for Transverse Profile Determination”, DIPAC’07, Venice, (2007). [2] CompanyNationalInstruments,www.ni.com [3] CompanyNokia,http://qt.nokia.com/ [4] R. Haseitl, et al., “ProfileView - A Data Acquisition SystemforBeamInducedFluorescenceMonitors”,DIPAC’09, Basel,(2009).
GSI SCIENTIFIC REPORT 2009 GSI-ACCELERATORS-13 Imaging-Spectroscopy for BIF-Monitors in Rare Gases and Nitrogen F. Becker ∗1 , P. Forck 1 , R. Haseitl 1 , B. Walasek-Hoehne 1 , P.A. Ni 2 , and D.H.H. Hoffmann 3 1 GSI, Darmstadt, Germany; 2 LBNL, Berkeley, CA 94720, USA; 3 IKP, TU-Darmstadt, Germany For transverse profile determination a non-intercepting Beam Induced Fluorescence (BIF)-monitor was developed. The BIF-monitor detects fluorescence light emitted by residual gas molecules after atomic collisions with beam ions [1]. Using an imaging spectrograph the spectral response was mapped and associated with the corresponding gas transitions in helium, argon, krypton, xenon and nitrogen. Spectrally resolved beam profiles were obtained from the spectrographic images simultaneously. The present study with 5 MeV/u proton, S 6+ and Ta 24+ -ions reproduced the results of earlier studies with a 95 keV proton beam [2]. Moreover, the camera system connected to the spectrograph was image intensified, to provide single photon detection in order to resolve even weak transitions [3]. Figure 1: Fluorescence images of 3,2·10 11 S 6+ ions with Ekin = 5.16 MeV/u in 10 −3 mbar N2 (left) and He (right) for 5 ms pulse duration at GSI-UNILAC. The fluorescence light emitted by the residual gases was imaged with a chromatically corrected quartz-lens (UV- VIS) to the adjustable entrance slit of an imaging spectrograph [3]. A holographic grating with 285 grooves/mm provides 1.5 nm spectral resolution. The spatial resolution was determined to be 40 µm/pixel. Exemplarily for other gases, fluorescence images for a S 6+ -beam in N2 and He are shown in Fig. 1. In order to purify the gas atmosphere, the chamber was evacuated to the base pressure of 10 −8 mbar and carefully flushed with each gas species before taking spectral data. Beam profiles obtained for N2, Ar, Kr and Xe show reasonable profile widths and correspond well with each other. He however is the only gas that generates significantly broadened profiles, see Fig. 2. All fluorescence spectra were calibrated and transitions could be identified with the help of spectroscopic databases [3]. Furthermore, results from spectroscopy show that rare gases have only 25% of the induced light yield (normalized with respect to the differential energy loss) achieved in nitrogen, [3]. Additionally, the fluorescent light of N2 is concentrated in a few transitions, see Fig. 3. Thus N2-gas seems to be the best choice and is therefore used at 7 BIF-stations along the UNILAC, which are currently installed and commissioned. ∗ frank.becker@gsi.de Figure 2: Beam profiles of S 6+ ions in different purified gas-species at 10 −3 mbar, for beam parameters see Fig. 1. Figure 3: Fluorescence spectra of different working gases, induced by the S 6+ -beam described in Figure 1. The indexed transitions can be found in [3]. References [1] P. Forck and A. Bank, Residual Gas Fluorescence for Profile Measurements at the GSI UNILAC, EPAC’02, 2002, Paris, p. 1885-1887 [2] P. Ausset, S. Bousson, D. Gards, A. C. Mueller, B. Pottin, R. Gobin, G. Belyaev and I. Roudskoy, Optical Transverse Beam Profile Measurements for High Power Proton Beams, EPAC’02, 2002, Paris, p. 1840-1842 [3] F. Becker, C. Andre, F. M. Bieniosek, P. Forck, R. Haseitl, A. Hug, P. A. Ni, D. H. H. Hoffmann, B. Walasek-Hoehne, BIF-Monitor & Imaging Spectrography of Different Working Gases, DIPAC’09, 2009, Basel, p. 161-163 141
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