Plans, prototypes, and initial test results for the charged-particle beam (e[sup [minus]],e[sup +]) diagnostic systems on the injector rings, their transport lines, and the storage ring for the Advanced Photon Source (APS) are presented. The APS will be a synchrotron radiation user facility with one of the world's brightest x-ray sources in the 10-keV to 100-keV regime. Its 200-MeV electron linac, 450-MeV positron linac, positron accumulator ring, 7-GeV booster synchrotron, 7-GeV storage ring, and undulator test lines will also demand the development and demonstration of key particle-beam characterization techniques over a wide range of parameter space. Some of these parameter values overlap or approach those projected for fourth generation light sources (linac-driven FELs and high brightness storage rings) as described at a recent workshop. Initial results from the diagnostics prototypes on the linac test stand operating at 45-MeV include current monitor data, beam loss monitor data, and video digitization using VME architecture

Chung, Y.

Decker, G.

Kahana, E.

Lumpkin, A. H.

Patterson, D.

Sellyey, W.

Votaw, A.

Wang, X.

UNT (University of North Texas) Digital Library

OVERVIEW OF CHARGED-PARTICLE BEAM DIAGNOSTICS FORTHE ADVANCED PHOTON SOURCE (APS)*A.H. Lumpkin, G. Decker, E. Kahana, D. Patterson, ANL/ASD/CP--77466W. Sellyey, A. Votaw, X. Wang, and Y. Chung D_.93 007898Argonne National Laboratory, Argonne, IL 60439ABSTRACTPlans, prototypes, and initial test results for the charged-particle beam (e,e .)diagnostic systems on the injector tings, their transport lines, and the storage ring forthe Advanced Photon Source (APS) are presented. The APS will be a synchrotronradiation user facility with one of the world's brightest x-ray sources in the 10-keV to100-keV regime. Its 200-MEV electron linac, 450-MEV positron linac, positronaccumulator ring, 7-GEV booster synchrotron, 7-GEV storage ring, and undulator testlines will also demand the development and demonstration of key particle-beamcharacterization techniques over a wide range of parameter space. Some of theseparameter values overlap or approach those projected for feurth generation lightsources (linac-driven FELs and high brightness storage tings) as described at a recentworkshop. Initial results from the diagnostics prototypes on the linac test standoperating at 45-MEV include current monitor data, beam loss monitor data, and videodigitization using VME architecture.INTRODUCTIONThe Advanced Photon Source (APS) will be a synchrotron radiation userfacility with one of the world's brightest x-ray sources in the 10-keV to 100-keVregime 1. Its 200-MEV electron linac, 450-MEV positron linac, positron accumulatorring (PAR), 7-GEV booster synchrotron, 7-GEV storage ring, and undulator test lineswill also provide the opportunity for development and demonstration of key particlebeam characterization techniques over a wide range of parameter space. Some ofthese values overlap or approach those projected for fourth generation light sources asdescribed at a recent workshop 2. The Accelerator Systems Division (ASD)Diagnostics Group is responsible for the design, procurement, testing, and operationof ali the diagnostic systems on the injector rings, their transport lines, the storagering, and the undulator test lines. A description of these plans using electricalconversion and optical conversion techniques and initial results from some prototypestested on the linac test stand operating at 45-MEV are presented briefly. These aresupplemented by more detailed reports given elsewhere at this workshop 37. A briefoutline of the undulator test line parameters and diagnostics are also presented.*Work supported by the U.S. Department of Energy, Office of Basic EnergyScience under Contract No. W-31-109-ENG-38.aI$TRIDUTIONOFTHISDOCUMENTIS UNLIMITi_-,bBACKGROUNDSpace precludes providing a complete description of the accelerator facilitiesfor the APS but some background information is needed. The baseline electronsource is a thermionic gun followed by a 200-MEV linac operating at a RF frequencyof 2.8 GHz and a maximum macropulse repetition rate of 60 Hz. The base injector(gun, bunchers, and 45-MEV accelerating structure) was operated April through June1992 as the injector linac test stand 8. The design goals include 14-ps longmicropulses, separated by 350 ps in a 30-ns macropulse _,ith a total macropulsecharge of 50 nC. The 200-MEV linac beam will be focused to a 3-mm spot at thepositron-production target. The target yield is about 0.0083 positrons per incidentelectron with a solid angle of 0.15 sr and an energy range of 8+ 1.5 MeV. Thepositrons will then be focused by a pulsed solenoid and about 60% of them will beaccelerated to 450 MeV. Commissioning of these two linacs is to be completed byDecember 1993. The 450-MEV positrons are injected into the horizontal phase spaceof the PAR at a 60-Hz rate. As many as 24 macropulses can be accumulated as asingle bunch during each 0.5-s cycle of the injector synchrotron. The injector (orboos:or) synchrotron accelerates the positrons to 7 GeV at which energy they can beextracted and injected into the designated RF bucket of the storage ring. Figure 1shows a schematic of the APS accelerators and lists the number of diagnostic stations.,,,ocl,o. \o ,,Mloc.,oo. / \: ;:::;::°;2222°° .... /LINACPAR o t6 8PHso I FCR4._0 H=VI FAST CURRENT MONITOR[1 DC CURRENT MONITORFig. 1 A schematic layout of the APS accelerator and diagnostics.Several features of the subsystems are provided in Table I. The peak current, bunchlength, and charge per pulse are given for the low energy transport (LET) linesbetween the linac and the PAR and the PAR and synchrotron, respectively. The highenergy transport (HET) parameters are also provided. The revolution time, bunchlength, and average currents are provided for the rings.TABLE IAPS PARAMETERS FOR BEAM DIAGNOSTICS,_ ,. i i"_-_.__. LET 1 LET 2 HETPEAK CURRENT 8 mA .. 11.9 A 28.9 A_ .-BUNCH LENGTH 30 ns 0.29 ns 122 ps..INTENSITY PER PULSE 1.sxlO*positi'ons 2.2 x 101° 2.2 x 10la....CHARGE PER PULSE 240 pC 3.5 nC 3.5 nC,,. ,,. ,.-PULSE RATE 60 Hz 2 Hz '. ,-Iz.,. i i i i ii • i iiii ., ...... n iPAR IS SRRF FREQUENCY 9.77 or 117 MHz 351.93 MHz 351.93 MHz,. ,,,,.REVOLUTION TIME 102.3 ns 1.228 us 3.68 us,,-NUMBER OF BUNCHES 1 1 1 to 60MIN BUNCH SPACING / / 20 ns......BUNCH LENGTH 30 -. 0.29ns 122 ps 35 tO100 psns<_. 0,92 ns,,1.4 mA _ 0.22 rnaMIN AVE BEAM CURRENT iI l'macpulso injected for single bunch _5 mAMAX AVE BEAM CURR_;qT 33.4 rna 4.7 mAZL ,"mac;=d=_s_jeCIKI for single _un¢._,,MAX INTENSITY 3.6 x 101° 3.6 x 10_° 2.2 × 10!°2,1_a¢ pulse=_jected per _unch per ,'nAii i iPROCEDURES AND RITSLL. l'SThe basic charged-particle parameters such :ts I',catn position, profile, current,bunch length, energy, and beam loss are to be addressed, Both intercepting andnonintercepting techniques are combined. Some of these have initial prototype resultsfrom the linac test stand this year. Some will be tested at other operating storage ringfacilities around the country in the next year.A strong cotnponent of the beam position monitoring (BPM) involves RF BPMpickup elements and their electronics. The prototype button feedtbrough for thestorage ring is shown in Fig. 2; over 18130have been received and electrically tested.In addition to these, there will be intercepting beam profile screens and the use ofsynchrotron radiation from at least one bending magnet in each of the rings, Gated,inmnsified cameras will supplement standard television viewing cameras to provideindividual bunch and/or single pass capability.Fig. 2 Photo_,raph= of the RF button fcedthr,_q'-h_ f,:,r the storage ring beamposition monitor.Because the pulse structures of the electron linac will be representative of beamin the linac-to-par transport line or LET 1, the prototype current monitor system basedon a fast current transformer manufactured by Bergoz and in-house electronics wastested on the linac test stand, lt was installed with a shield at the end of the beamlinejust before a Faraday cup. Test results for a 30-ns macropulse and the 100 mAcurrent level are reported in Ref. 5.The loss monitor system which will cover the entire extent of beamlines andaccelerators was tested as a prototype. A gas-filled coaxial cable acting as anionization chamber was installed along the length of the linac test stand. Preliminarytests showed the effects of applied high voltage to the cable, gas mix, gas pressure,cable diameter, and cable impedance. The rise time of the system is less than 15 nswhen the high voltage is set to 500 volts so axial location determination by signalarrival time analysis is under investigation. Position resolution of 7 feet or less maybe practical. Sample data are shown in Ref. 6 where applied voltage polarity flips theobserved signal polarity. The system also picked up a noticeable amount of noisefrom the RF modulator tank located a few meters away beyond the radiation shieldingwall.The imaging techniques can be applied to several aspects of the diagnosticsproblems. Initial tests included a VME-architecture-based video digitizing systemlinked to a Sun workstation. The beam image digitized was one of the first in thestartup tests on the linac test stand. Background subtraction, pseudo-color intensity,pseudo-3D display, and beam profiles are demonstrated in the composite image ofFig. 3. The digitizing scheme can be applied to particle energy spectra (images froman energy-dispersive region) and particle bunch length (video readout of a streakcamera). The imaging initiative also includes further evaluation of optical transitionradiation (OTR) and synchrotron radiation angular distribution and polarizationeffects.UND(JLATOR TEST LINESThe undulator test lines are being considered at 650 MeV and 7 GeV. In thefirst case, the tungsten positron conversion target will be retracted and the 450-MEVlinac rephased to accelerate the electrons to 650 MeV. A key point here would be theswitch to the RF thermionic gun which is projected to provide normalized, edgeemittance of about I0 _r mm rad, a few orders of magnitude colder than the standardthermionic gun 9. This gun also may allow micropulse bunch lengths of less than 1 psto be attained via filtering and magnetic compression techniques. The emittance at200 to 650 MeV will be measured in a straight 10-m long section that bypasses thePAR. Cross-comparison of several techniques, including three-screen, two-screen,optical transition radiation interferometry, and quadrupole field scan, is planned.Bunch length will be determined by a streak camera using either OTR 7or some otherFig. 3 Composite image of an initial beamspot recorded at a position just afterthe accelerator. VME-based hardware, a Sun workstation, and PV-wavedisplay software platform were used.prompt mechanism. As shown in Table II, many of the critical beam parametersidentified in the 4th Generation Light Source Workshop 2 will be approached by theproposed undulator test line e beam.SUMMARYIn summary, key charged particle beam parameter characterizations are beingaddressed at the APS. Due to the diverse parameter space involved, a number ofcomplementary intercepting and nonintercepting beam techniques are beingemployed. In the rings, of course, nonintercepting techniques are dominant. Theundulator test line initiative will address transport of high brightness beams toundulators at energies that happen to be of interest to the next generation of lightsources.TABLEIi Beamparametersfor the undulatortest lineatAPSas comparedto4thGenerationWorkshopvalues(ref.2)Parameter _ 4thGenerationWorkshop(Lin_Emittance(n mmmrad) 2 1.5(rms, normalized)PeakCurrent(kA) . 1/2 to I 1BunchLength(ps) <1 to 15 -1Energy(MEV) 200-650 100-1000EnergySpread 0.1% 0.05%MacropulseBunchLength 30 nsACKNOWLEDGMENTSThe authors are indebted to George Mavrogenes and John Galayda for theirsupport, to the linac test stand operations crew including Ray Fuja, Bill Berg, and BillWesolowski for beam time, and to Ned Arnold and Eric Ko of the C,Jntrols Group fordata acquisition and analysis support.REFERENCES1. D.E. Moncton, E. Crosbie and G.K. Shenoy, "Overview of the AdvancedPhoton Source," Rev. Sci. Instrum., 60, (7), July 1989.2. Proceedings of the Fourth Generation Light Source Workshop, Feb. 24-27,1992, Stanford, California, SSRL 92-02.3. E. Kahana and Y. Chung," Test Results of a Monopulse Beam Position Monitorfor the Advanced Photon Source," these proceedings.4. A.J. Votaw, "Preliminary Design of the Memory Scanner for the AdvancedPhoton Source," these proceedings.5. X. Wang, "Design and Initial Tests of Beam Current Monitoring Systems forthe APS Transport Lines," these proceedings.6. D.R. Patterson, "Preliminary Design of the Beam Loss Monitor System for theAdvanced Photon Source," these proceedings.7. A.H. Lumpkin and M. D. Wilke, "Further Time-Resolved Electron-BeamCharacterizations with Optical Transition Radiation," these proceedings.8. G. Mavrogenes et al., Proceedings of the Linac Conference, Ottawa, Canada,August 24-28, 1992.9. M. Borland, Private Communication (July 1992), APS, Argonne NationalLaboratory.DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the a_uracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Government or any agency thereof.i

Overview of charged-particle beam diagnostics for the Advanced Photon Source (APS)

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Overview of charged-particle beam diagnostics for the Advanced Photon Source (APS)

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