Measurement of high-power proton beam-halo formation is the ongoing
scientific experiment for the Low Energy Demonstration Accelerator (LEDA)
facility. To attain this measurement goal, a 52-magnet beam line containing
several types of beam diagnostic instrumentation is being installed. The
Experimental Physics and Industrial Control System (EPICS) and commercial
software applications are presently being integrated to provide a real-time,
synchronous data acquisition and control system. This system is comprised of
magnet control, vacuum control, motor control, data acquisition, and data
analysis. Unique requirements led to the development and integration of
customized software and hardware. EPICS real-time databases, Interactive Data
Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation
Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which
interact using the EPICS Channel Access (CA) communication protocol.
Acquisition and control hardware technology ranges from DSP-based diagnostic
instrumentation to the PLC-controlled vacuum system. This paper describes the
control system hardware and software design, and implementation.Comment: LINAC2000 Conference, 4 pg

Barr, D.

Day, L. A.

Kasemir, K. U.

Pieck, M.

Quintana, B. A.

Salazar, G. A.

Stettler, M. W.

English

arXiv

UNT Digital Library

43IA-UR-00-3842Apprvvad forpublic release:distribution is unlimited.ITitle: CONTROL SYSTEM FOR THE LEDA 6.7 Me~ PROTONBEAM HALO EXPERIMENTIAuthor(s): L. A. Day, M. Pieck, D. Barr, K.U. Kasemir, B. A. Quintana,G. A. Salazar, M. W. StettlerSubmitted to: )()( International Linac ConferenceMonterey, CAAugust 21-25,2000IILos AlamosNATIONAL LABORATORYLos Alarms National Laboratow, an affirmative actionlequal opportunity employer, is operated by the University of California for the U.S.Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Governmentretains a nonexclusive, royalty-free license to publish or reproduce the published form of tis contribution, or to allow others to do so, for U.S.Government purposes. Los Alamos National Laboratory requests that tie publisher iden~this artkde as work performed under theauspices of the U .S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher’s tight topublish; as an institution, however, the Laborato~ does not endorse the viewpoint ofa publication or guarantee its technical correctness.Form 636 (8/00)DISCLAIMERThis report was prepared as an account of work sponsoredby an agency of the United States Government. Neitherthe United States Government nor any agency thereof, norany of their employees, make any warranty, express orimplied, or assumes any legal liability or responsibility forthe accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, orrepresents that its use would not infringe privately ownedrights. Reference herein to any specific commercialproduct, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constituteor impiy its endorsement, recommendation, or favoring bythe United States Government or any agency thereof. Theviews and opinions of authors expressed herein do notnecessarily state or refiect those of the United StatesGovernment or any agency thereof.DISCLAIMERPortions of this document may be illegiblein electronic image products. Images areproduced from the best available originaldocument.. <Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment’L. A. Day, M. Pieck, D. Barr, K. U. Kasemir, B. A. Quirttan~ G. A. Salaza.r, M. W. StettlerLos Alamos, Los Alamos National Laboratory, NM 87545, USAAbstractMeasurement of high-power proton beam-haloformation is the ongoing scientific experiment for theLow Energy Demonstration Accelerator (LEDA) facility.To attain this measurement goal, a 52-magnet beam linecontaining several types of beam diagnosticinstrumentation is being installed. The ExperimentalPhysics and Industrial Control System (EPICS) andcommercial software applications are presently beingintegrated to provide a real-time, synchronous dataacquishion and control system. This system iscomprised of magnet control, vacuum control, motorcontrol, data acquisition, and data analysis. Uniquerequirements led to the development and integration ofcustomized software and hardware. EPICS real-timedatabases, Interactive Data Language (IDL) programs,LabVIEW Virtual Instruments (VI), and State NotationLanguage (SNL) sequences are hosted on VXI, PC, andUNIX-based platforms which interact using the EPICSChannel Access (CA) communication protocol.Acquisition and control hardware technology ranges fromDSP-based diagnostic instrumentation to the PLC-controlled vacuum system. This paper describes thecontrol system hardware and software design, andimplementation.1 INTRODUCTIONAs part of the linac design for the acceleratorproduction of tritium (APT) project the fist 10-MeVportion of this 100-mA proton accelerator was assembledat the Los Alamos Neutron Science Center (LANSCE) in1999 and was in operation for over one year. Now, thisLow-Energy Demonstration Accelerator (LEDA)provides the platform for a new experiment: attainingmeasurements of high-power proton beam-haloformation. For this purpose a 52-magnet beam line hasbeen installed into the LEDA beam line between theRadio Frequency Quadruples (RFQ) and the HighEnergy Beam Transport (HEBT).LEDA is using the distributed control system based onEPICS [1, 2]. Extensions to the existing control systemwere developed for controlling the devices listed inTable 1 in section 3.2. This table also shows devicelocations as defined by the space upstream of thenumbered quadruple magnet.EPICS is a toolkit for building distributed controlsystems that originated at Los Alamos and is nowdeveloped jointly by a collaboration of over 100institutions [3]. It is the basis for operator controlsinterfacing. Specific extensions to EPICS CAcommunication protocol have been developed to integrateadditional controls configuration and visualizationoptions into EPICS. IDL, a commercial visualizationtool, has been integrated to provide more complex dataprocessing and visualization options. LabVIEW has beenintegrated to enable simple, cost effective PC solutions toselective instrumentation control.Provided below is a summary of the important controlsystem components. Brief descriptions of computersystem architecture, hardware, software, and externalinterfaces are presented. These designs have been, or arebeing integrated into the control system for LEDA.2 CONTROL SYSTEM STRUCTUREAND NETWORK TOPOLOGYThe Halo Experiment extends the LEDA controlshardware architecture by 3 PC-Input/Output Controllers(IOC)S and 2 VXI-IOCS. The extension is comprised of ,four principal systems covering Quadruple MagnetControl, Steering Magnet Control, Diagnostic, andVacuum System Control.The control system’s communication service is built ona TCP/IP-based network and uses EPICS CA as theprimary protocol. Access to the controls network islimited by an Internet fwewall for safety and trafticcongestion reasons. A second independent local areanetwork has been created to isolate the distributed I/Omodules flom the control system’s network.3 QUADRUPLE MAGNET CONTROLThe 52-quadrupole-magnet focus/defocus (FODO)lattice provides a platform to create phase space haloformation. The first four quadruple magnets are eachindependently powered by a 500AI 15V EMI/Alpha-Scientific power supply (Singlet). Depending on howthose magnets are adjusted, a match or mismatch of theRFQ output beam to the lattice is created.The next 48 magnets are powered in groups of 8. Eachset of magnets is powered by an Alpha-Scientific500A/100V Bulk Power Supply with an 8 Channel ShuntRegulator that allows an jndi&h@ &m~$nt E@.-,,Wi*,, .,$~:.4:,--,~. ),i.“uL %&M i & L.=.,+1 This work supported by the Department of Energy under contract W-7405-ENG-36.Now I ~ 20000 $.xI.certain magnet settings, the development of specific haloformations can be observed along the lattice.3.1 Quadruple Magnet Control HardwareThe quadruple magnet control subsystem uses as PC-IOC computer an Intel Pentium 11500Mhz equipped withtwo network cards. The fmt card establishes the physicalconnection to the LEDA controls network. The secondcard creates a local area network’ for National Instruments(NI) modular distributed I/O system called FieldPoint(FP). It includes analog and digital modules, andintelligent Ethernet network module that connects the I/Omodules to the PC-IOC computer.Using the robust Ethernet networking technology toposition intelligent, distributed I/O devices closer to thesensors, or units under test, leads to a significant costsavings and performwce improvement. The most obviousbenefit to this solution is the savings in signal wiring.Replacing long signal wires with a single, low costnetwork cable saves significant time and money duringinstallation and testing. Furthermore, distributed I/Osystems, such as NI FP, also include special capabilitiesto improve the reliability and maintainability by using thebuilt-in, onboard diagnostic capabilities.Table 1. Halo lattice beam line comDonent locationsDevice Locations(Quadruple Magnet #)Singlet PS 1.2.3.4Bulk PS /Shunts 5-12, 13-20,21:28,37-44,45-52Steerers 4.6.15.17.26.28.36.38. 47.49Fast Valve 2Beam Line Valves 17,36,52Ion pumps 6, 10, 15,21,28,34,40,44Ion Gauges 13,31,42Wsms 5,21,23,25,27,46,48, 50,523.2 Quadruple Magnet Control Sc@wareThe NI LabVIEW-based quadruple magnet controlsystem that runs on the Windows NT operating systemconsists of 60 subroutines combined into 10 processes (4Singlets + 6 Bulk/Shunt Regulator). These independentsoftware processes share CPU cycles based on priority.To ensure proper operation, the control processes for theset-points have highest priority, while the dispIay relatedprocesses have lower priorities.The LabView uses an in-house built ActiveXAutomation Server allowing the integration of theLabVIEW system in the EPICS environment by servingvalues of general interest to Graphical User Interfaces(GUI) that are clients to CA.Using the EPICS GUI called Display Manager (DIM),the controi processes drive the power supply values andset-points by interpreting mouse clicks and text entriesinto commands.To meet the magnetic field stability specifications,magnet hysteresis must be compensated by ramping thefield past the set-point and then reducing the field to theset-point. This led to a control process solution for theBulk and Singlet power supplies that operates in form ofa State Machine where the states are idle, ramp up, soakand ramp down. According to the magnet specificationthe process control ramps up to a desired set-point,overshoots, stays for a specific time at that overshootvalue and ramps back down to the operator desired set-point. Ramp up rate (Amps/step), overshoot value (Ampsabove desired set-point), soak time (see), and ramp downrate (Amps/step) are individual settable by the operator.Basic binary operation like AC Voltage On/Off, DCVoltage On/Off, and interlock reset are provided as well.The display processes are limited to voltage andcurrent read backs, status indication for PS interlocks, andLocal/Remote status.4 STEERING MAGNET CONTROLThetask of the beam’s 10 steering magnets (horizontaland vertical) is to correct the position of the beam at theend of every set of BPM/steering magnet associated pairthat is separated by approximately 10 quadruplemagnets (see Table 1). Since the FODO-lattice periodhas a phase advance of approximately 80 degrees, eachpair of BPMs can detect and each pair of steeringmagnets can correct the beam’s position and angle thatmight be caused by misaligned, quadrupoles.4. I Steering Magnet Control HardwareThe steering magnet control system uses an IntelPentium II 450Mhz PC-IOC equipped with one networkcard and two NI Plug & Play PCI General-PurposeInterface Bus (GPIB/IEEE 488.2) controller cards. Thisso called two-bus GPIB controller system interfaces 20KEPCO 20V/5A power supplies, 10 for horizontal and 10for vertical. All 10 power supplies on each bus are linkedtogether in a linear configuration (daisy-chain). Thishardware architecture combines the cost-effectiveness ofgeneral-purpose PCs with the standardized and widelyused GPIB solution. Due to the limitation of GPIB (maxcable length 20m) the PC-IOC is located next to the 2racks of steering power supplies.4.2 Steering Magnet Control So@areThe NI LabVIEW-based steering magnet controlsystem that runs on a Windows NT operating systemconsists of 80 subroutines incorporated into 1 process.This all-in-one design follows a iterative control sequencebetween the individual power supplies on both buses: 1)writing to the first power supply on the fust bus thenwriting to the first power supply on the second bus. 2)4,.. *reading from the first power supply on the fwst bus andthen reading from the first power supply on the secondbus. ‘IMs continues until the 10* power supply has beeniterated and then starts over again. This strategy waschosen for possible closed-loop beam correction wherethe amount of beam spill is critical. Having the desm”bedprocedure in place reduces possible beam spill byreducing the reaction time of two corresponding steeringpower supplies to a minimum of 4ms.The developed GUI shows the change of current andvoltage read backs as the operator changes the currentset-points via text entry fields and slider controls.Furthermore, the most important information about thestatus of the power supplies is read out from the 16-bitstatus register.5 VACUUM SYSTEMThe devices for the vacuum system for the HaloExperiment beam-line comprise of one Fast Beam-lineIsolation Valve, three Beam Line Valves, three IonGauges, three Convection Gauges, and 8 Ion Pumps.5.1 Vacuum System Control HardwareThe vacuum control subsystem operates as astandalone system. That is, all hardware components arelocal to the Halo Beam-line, hardwired together, networkisolated and filly functional, i.e., the subsystem, containsall interlocks and requires no input fkom remote computercontrol equipment during normal operation.Remote accessibility is established through the NIdistributed I/O modules called FP (see section 3,2).~.2 Vacuum System Control So~areThe DirectSotl PLC is the heart of the vacuum controlsystem and has incorporated all functionality. There is nodirect access to the PLC’S CPU/memory componentsduring normal operation. TINS, all signals are propagatedthrough the associated PLC input.loutput modules. Acustom ladder logic program containing equipmentinterlocks, resides and runs (continuous loop) in thevoIatile memory of the CPU module. Though, theprogram is lost during a power shut down, the ladderlogic program is loaded tiom the flash memory andstarted shortly after power is resumed. Its initial stateafter reboot is a safe mode state in which all devices areturned off.6 WIRE SCANNER/HALO SCRAPERThere are nine Wire Scanner / Halo Scraper (WS/HS)assemblies installed into the LEDA Halo Beam-line [5].These assemblies contain three measurement devices foreach horizontal and vertical axis. Data acquired fromthese devices is used to provide projected beamdistribution information. One wire scanner devicemeasures beam core distribution within +/- 3 rms widthswhile two halo scraper devices measure the edges ofbeam distribution outside 2.5 rms widths. These devicesare attached to an actuator driven by a stepper motor [6],which drives either the WS or one of the HS into thebeam in incremental steps. At each WS step, the amountof secondary electrons (SE) generated is measured andnormalized against synchronous beam current data [7]. Ateach HS step, the proton beam charge is measured andnormalized against the overlapping WS data. Together,this provides a complete beam distribution profile.6.1 Control SolutionsMeasurement control uses CA Server to communicatebetween EPICS modules running on Kinetic Systems’HKBaja60’ in VXI IOCS, LabVIEW ruining on a PCIOC, rmd IDL running on Sun Workstations. The abilityof CA Server to provide a communication means betweensoftware applications running on different platformsallows the flexibility to choose tools that best suit thespecific requirements.EPICS real-time processing meets the requirement toacquire synchronous beam pulse data at the rates of 1-6Hz. Data is continuously acquired ftom beam currentmonitors, wires, and scrapers by DSPS mounted on theVXI boards into local circular buffers. Data is extractedfrom these buffers by the EPICS database when triggered.LabVIEW offers timely and cost effective methods forcontrolling actuator motion. VIS were implemented tointerface with off-the-shelf motor drivers. CA Client runson the PC to enable communications between LabVIEWand the other control system modules.IDL provides flexible data processing and visualizationoptions. Operators have the flexibility to process dataindependently and fine-tune the processing on-linewithout interrupting beam operations. The results aredisplayed ~g-aphicallyin plots as they are calculated.The EPICS’ display manager (DM) serves as theinterface for operator control. Operators controlmeasurement parameters and view measurement status ona DM GUI.6.2 ImplementationThe operator sets parameters and starts themeasurement from the WS/HS controls DM GUI. EPICSdatabase process variables are used to pass data andcommands between EPICS WS/HS data acquisition,LabVIEW motor control, and IDL dataprocessip~’visualization modules. A SNL sequencemanages the execution of the separate control modules bysetting process variables to known command values.These variables are monitored through CA by associatedmodules. When the expected command is received by amodule, execution is initiated. This flow is illustrated inFigure 1.For each step in a measurement, the SNL sequencesends motor parameters to LabVIEW via a process* . ..,-variable specifying Z location, horizontal or vertical axis,and stepper motor position. LabVIE W sets a ‘responsevariable to notify the sequence when the stepper motorhas reached the required destination.KineticSystems VXI Actuator PcHKBaja60VXi Mo&de . 4:- ‘--~ ;spAcquisitiOnNI Motion Control7Ii -_ I4 Wire&scraper msensors ~;i :+.. —.._. ._.. _ .. —..—-.—..—... ... ... . .. ..j~.. —..—..—..—.. —..—.. —..—.. —..- .. —.-—.;‘------kz!_J-L..__-“=dE_.lFigure 1: Wire Scan/Halo Sctaper ControlMeanwhile, each WS and HS pair has its SE chargewaveform signal acquired by its DSP during every beampulse. When LabVIEW notifies the SNL sequence thatthe stepper motor is in position, the sequence sets aprocess variable to trigger the database to upload theactive wire or scraper’s data along with the associatedbeam cument monitor’s data, for normalizing, intowaveforms.This synchronous data is locally processed within theEPICS database and also processed in IDL routines. Thelocal processing completes automatically within thedatabase. These fimctions produce results of globalcontrol system interest such as unit conversion andaveraging. Because the EPICS database is loaded at boottime, these functions are fwed, i.e, the majority ofparameters cannot be conveniently modified. However,the results are time-stamped, therefore, they can bearchived and made available for synchronous dataretrieval.IDL is utilised for specialized and flexible processingand visualization. Functions can be created and/ormodified on-line fi-omthe control room without affectingbeam operations. Furthermore, IDL provides morecomplex options for viewing data. After data acquisitionis complete, the SNL sequence notifies IDL at which timeIDL gets all necessary data for processing. The WS or HSdata is normalized and plotted against the motor’sposition producing the beam’s profile visually in realtime. Operators are able to view the measurement’sprogress and abort the scan if undesirable results arepresented. Processing parameters can be adjusted ifdesired, and a new measurement started.—..—[1][2)[3][4][5][6][7L.R.Ethernet (CA)SNL CommunicationDatabase CommunicationReferencesDalesio et all., Nucl. Instrum. Meth. In PhysResearch A352 ( 1994), 179-184D. Moore and L.R. Dalesio, “A Development andInte~tion Analysis of Commercial and In-HouseControl Subsystems” Conf. Proc. LINAC98, ChicagoAugust 1998M. Thuot, et al., “The Success and the Future ofEPICS” LJNAC96, Geneva, Aug. 1996.D. Moore and L.R. Dalesio, “A Development andIntegration Analysis of Commercial and In-HouseControl Subsystems”, LINIAC98, Chicago, Aug.1998.J. D. Gilpatrick, et all, “Beam DiagnosticsInstrumentation for a 6.7-MeV Proton Beam HaloExperiment: these proceedings.R. Valdiviez, et al., “Intense Proton Core and HaloBeam Profile Measurement: Beam Line ComponentMechanical Design,” these proceedings.Power, J., et al, “Beam Current Measurements forLEDA;’ Proceedings of the 1999 ParticleAccelerator Conference, New York, 1999

Control System for the LEDA 6.7 MeV Proton Beam Halo Experiment

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Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment

Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment

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