Katsumata, M

Kobayashi, C

Kondo, T

Takada, E

Torikoshi, M

Yamada, S

CERN Document Server

PRESENT STATUS OF CONTROL SYSTEMS OFHIMAC ACCELERATOR COMPLEXE. Takada, M. Torikoshi, S. Yamada, NIRS, Chiba, JapanC. Kobayashi, T. Kondo, M. Katsumata, AEC, Chiba, JapanE-mail: takada@nirs.go.jpAbstractHIMAC has been in operation as an ion-therapyfacility since June ’94. More than 660 targets in 639patients have been treated with carbon beams of 290 to400 MeV/u in this period. A reliable control system isan indispensable element to supply beams for medicalpractice. The system must be easy to operate becausedaily operation of the accelerator is carried out byoperators who are not necessarily accelerator experts.The present status of the control systems is presented foreach sub-system: injector linac, synchrotron rings, andbeam transports. Changes and improvements in recentyears are reported, together with problems we haveexperienced.1 INTRODUCTIONThe HIMAC accelerator complex has successfullysupplied carbon beams for clinical study of cancertreatment since June 1994. 639 patients have completedtheir treatments by this August. For a generaldescription of the accelerator complex, see [1] andreferences therein.In 5 years of operation since the first patient, ourefforts have been to provide stable beams for ongoingclinical trial, on the one hand, and to extend the capacityof the machine for more advanced clinical use on theother.In the following, we would like to describemodifications and improvements that we have made oneach sub-system of HIMAC, i.e., injector linac,synchrotron rings, and beam transport. A precedingreport can be found in [2].2 INJECTOR LINAC CONTROL2. 1 Time Sharing AccelerationAs mentioned in a previous ICALEPCS report [2], weput “Time Sharing Acceleration” of the injector systemin work. Since we added an 18 GHz ECR ion source tothe original PIG and 10 GHz ECR sources, threedifferent ion species can be supplied to the RFQ and DTLlinacs, by changing the excitation of switching magnetbetween the sources and linacs, pulse by pulse. Wemodified the trigger system to each device to havetriplicate input, and device controllers to have three-foldbuffers to store different parameter values appropriate toeach of the three ions. The modification has beencompleted in March, ’98, and experiments during nightand weekend shifts are carried out with “Time SharingAcceleration” in about a half of the scheduled machinetime.It should be noted that part of the beam tuning isdifficult because mechanical pieces don’t quite fit to thepulse-to-pulse operation in few seconds cycle. RFmatching of the linac tank is performed at the highestlevel among three ions in operation, and beam intensityis monitored with a pick-up type non-destructivemonitor, instead of a Faraday cup.2. 2 Operation Terminal ReplacementWe have been using several sets of touch-panel-equipped 14-inch CRT display terminal as a main man-machine-interface devices since the installation in ’90.However, terminal production had been discontinued andmaintenance service termination was announced to beeffective on April 1999. Since all of the three sub-systems were equipped with the same type of terminal,we decided to replace them by March, ’99.Due to a different phase of the control system lifespanin each sub-system, we decided to replace terminals insuch a manner that the new ones emulate the oldterminals and the host system is left unchanged as muchas possible. Nevertheless, the hardware of the newterminals should be unified across the sub-systems, sothat a single backup can serve all of the 12 terminals inoperation.An equivalent-sized LCD was selected as a replacmentdisplay for the 14” CRT, and new touch-panel devicethat utilises damping of the glass surface elastic wave bysoft substance like finger or eraser was chosen. Since anLCD has a straight end as opposed to the curved one of aCRT, the touch panel glass can be an ordinary flat-plate,which allows easy maintenance and substitution of theterminals.The replacement was successfully carried out during amonth-long maintenance period during March, ’99. Weadopted an IBM-PC + Windows95 as a platform, and thetouch panel was incorporated as a pointing devicecompatible with a mouse. In a half-year of operationInternational Conference on Accelerator and Large Experimental Physics Control SystemsInternational Conference on Accelerator and Large Experimental Physics Control Systems683International Conference  Accel rator and L rge Experim ntal Physics Control Systems, 1999, Trieste, Italysince the replacement, much improved display qualityand generally improved response to a touch are awelcomed feature by operators, and no trouble that needsan exchange of a terminal has been experienced.Although there have been a few instances that forced areboot of the PC, which need to be investigated, the newsystem is working satisfactorily.2. 3 Display Terminal ReplacementWe use a couple of 20” CRT’s mainly for display of themachine status etc. These CRT’s are also to be replacedbecause of a similar situation as for the 14” CRTterminals. We are planning to replace them in a samemanner as for operation terminals.3 SYNCHROTRON CONTROL3. 1 Control for Respiration-Gated TreatmentIn the synchrotron control system, a modification tothe supply of a clinical beam through a gate system thatlimits beam extraction only at exhale period of a patientwas implemented and used since May, ’96.[3] Themodification was to add several events to the timingcontrol, and to enhance the RF waveform control for thetransverse field that kicks out the beam, from thestandpoint of control. The addition of event timingsignals such as, defining the extractable period during amachine cycle, start of the decelerating B-dot chainperiod and end of it, were carried out within the existingtiming control system. RF waveform control, however,needed a new interface because the function generator weadopted for the RF-KO extraction was equipped onlywith a GP-IB interface.3. 2 Timing Clock for InjectionThe TSA at the injector linac called for an adjustmentat the timing system. In the original design, response fora request for beam injection was thought to be within afew tens of msec, while the introduction of pulsed powersupply for linac-synchrotron transport necessitates about400 ms delay between the trigger and actual beam. Thislong interval spawns non-negligible jitters of the timingbecause the clock was made differently in both systems:synchrotron with PLL from the utility and linac from thesystem-clock. We installed a small delay counter systemfor injection bump trigger so that the fast-bump magnetsfor multi-turn injection are excited in closesynchronisation to the incoming beam, while an RFcapture and main magnets excitation still have a few tensof micro-second of timing fluctuation. In the presentpractice, the fluctuation does not cause a feasibleoscillation in beam intensity.3. 3 Installation of DPO/I and DTO modulesA new series of fast dual-port memory modules forVME systems has been developed and partly installedduring recent years. The details of modules weredescribed in a previous ICALEPCS [4]. Installation in astep-by-step fashion is under way to secure stableoperation for clinical trials. At present, modules areinstalled in the existing system and emulate the oldmemory modules in most cases. We are going tointroduce a new system that can exploit features ofDPI/O series, new memory modules.3. 4 New Device-Monitoring SystemIn an effort to upgrade the running system, a new setof server and display has been introduced in parallel tothe present system. An additional programmablecontroller, which monitors errors and interlocks ofmagnet power supplies in more detail than the presentsystem, was also implemented and connected to the newserver. The server analyses device-faults in frequencyand interlock-chain etc., and provides results to a newdisplay terminal upon request as well as the presentstatus of devices. The new connection between devicecontrollers and server forms a basis of dual MMI andthus smooth transition from one to the other.3. 5 Installation of Electron Cooling SystemAn electron cooling system [5] is going to be installedinto the lower ring in the next March. Since the systemis in an experimental stage for enhancement of qualityand quantity of the beam, the control system is beingdesigned to be as independent as possible from thepresent system. It will require further tuning of the mainmagnet power supply and relevant functions such as theclock, interlocks, etc.4 BEAM TRANSPORT CONTROL4. 1 Upgrade for Secondary Beam LinesA secondary beam line for therapeutic use has beenconstructed at HIMAC. Devices for the application, suchas scanning magnet etc., is under construction. Thecontrol system for the beam line is described in detail inRef. [6]. The addition of the secondary beam controlsystem required an upgrade of the HEBT (high energybeam transport) control system, because the two systemscouple closely in control and monitor of several beamline devices. HEBT-SCU, System Control Unit (In Ref.[6], it was denoted erroneously as Secondary Control684Unit.), was enhanced by transforming into “dual”-cpusystem from the original single cpu configuration, in ’97.However, the two cpu’s are assigned to different tasksafter an analysis of the load, rather than running in aparallel configuration.4. 2 Replacements of TerminalsIn the HEBT control system, the replacement of theoperation terminal involved a more extensive revision ofthe application software, but the replacement wascompleted successfully as mentioned earlier.4. 3 Development for Beam TransportA development for quick beam transport tuning hasbeen carried out and reported in PAC99[7]. The work isbased on a software of the HEBT control system.4. 4 Beam Integration for Radiation ControlA beam integration with a MWPC-type chambersignal has been tested to develop a tool for safetyregulation that integrates beam intensity.5 SUMMARYCarbon beams from the HIMAC accelerator complexhave been successfully provided to cancer radiotherapy ina stable and reliable manner for more than 5 years.Control systems of the HIMAC complex have served wellin this beam supply. Several updating efforts in thesystem, 14” terminals, for example, have been exercisedtogether with the incorporation of new features to thesystem, such as TSA, respiration-gate, and secondarybeams. It is also to be noted that proton beams, as wellas heavier ions, e.g., Fe and Xe, have been accelerated,which have widened the scope of clinical study,biological and physical experiments.6 ACKNOWLEGEMENTSThe authors would like to express their thanks to Dr.F. Soga and members of Accelerator Physics &Engineering Division of NIRS, and to the acceleratorcrew of AEC, lead by Messers H. Ogawa and Y. Sano.They are also grateful to many colleagues in companieswho contributed in building and improving HIMAC.REFERENCES[1] S. Yamada et al., “HIMAC and Medical AcceleratorProjects in Japan”, APAC’98, Tsukuba, March 1998,pp.885-889.[2] E. Takada et al., “Status Report of the HIMACControl System –Reliable Beam Supply for CancerRadiotherapy with Carbon”, ICALEPCS’95,Chicago, 1995, F-PO-66.[3] K. Noda et al., “Performance of a Respiration-GatedBeam Control System for Patient”, EPAC’96,Barcelona, 1996, pp.2656-2658.[4] N. Araki et al., “Design of a Synchrotron ControlSystem with DPO Series for Advanced TherapyOperations”, ICALEPCS’97, Beijing, 1997, T3B-6,ID157.[5] K. Noda et al., “Electron Cooler for Medical andOther Application at HIMAC”, ECOOL’99,Uppsala, May, 1999, in press.[6] S. Koda et al., “Control System of HIMACSecondary Beam Course for Medical Use”,ICALEPCS’97, Beijing, 1997, W-P-62, ID139.[7] M. Torikoshi et al., “A Development of AutomaticTuning for High Energy Beamlines at HIMAC”,PAC’99, New York, pp.1309-1311685

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