Dong, B

Tan, Y

Xiong, S

Yan, Y

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UPGRADING BEAM LINE INTERLOCK AND CONTROLSYSTEMS AT THE BSRFShenshou Xiong, Baozhong Dong, Yinglei Tan and Yonglian YanBeijing Synchrotron Radiation LaboratoryInstitute of High Energy PhysicsP.O. Box 918, Branch 2-7, Beijing 100039, ChinaAbstractAt the BSRF (Beijing Synchrotron Radiation Facility),the beam line interlock and control systems have been inuse for over ten years [1]. Since 1995, this system hasbeen gradually upgraded to improve hardware reliabilityand performance, to reduce faults and to provideadditional system functionality. The centralizedmonitoring system for BSRF beam lines has also beenredesigned at a reasonable cost. The old controllers havebeen replaced with new (Programmable Logic Controller)PLC-based ones.1 INTRODUCTIONAt present, there are four beam ports and nine beamlines installed around the BEPC(Beijing Electron-Positron Collider) storage ring at the BSRF. The ninephoton beam lines include five wiggler X-ray beam lines,an X-ray UHV compatible beam line, a VUV beam lineand two soft X-ray beam lines. All beam lines share acommon vacuum with the BEPC storage ring. Berylliumwindows are not used for VUV beam lines. For the X-raybeam lines 0.25-0.5 mm thick beryllium windows areused to separate the storage ring vacuum from the roughvacuum in the downstream beam line components, thusallowing the operation of monochromators, mirror boxesand sample chambers in rough vacuum or in heliumatmosphere.Because of beryllium window breakage or otheraccidents in beam lines, the possibility of vacuum failuresis substantial. Such a shock wave caused by berylliumwindow failure, bellow breakage or gas leakage at thebeam lines will result in serious damage to somecomponents and the vacuum of the storage ring. Acatastrophic damage would result in machine shutdownand interrupt the operation of all experimental stations.To protect the vacuum of the BEPC storage ring andother beam lines from such catastrophic vacuum failure ofa single beam line, each beam port has been equippedwith an independent vacuum protection system. At thesame time, the protection system can also protect beamline components from being damaged by thermal loadsproduced by high brilliance hard X-rays.In addition, synchrotron radiation produced by wiggleror bending magnet is introduced through the beam linesto the experimental stations. Thus radiation safetyinterlock systems are used to provide personnel (users)access control to prevent inadvertent entry intoexperimental stations when hazardous radiationconditions exist. This will also warn personnel of changesin safe operating conditions inside the experimentalstations.Consequently, each beam line interlock and controlsystem consists mainly of vacuum protection system forthe beam lines and radiation safety interlock systems forthe experimental stations.2 CENTRALIZED MONITORINGSYSTEMThe basic hardware configuration of the centralizedmonitoring system is shown in Fig .1.Fig.1. Block diagram of the hardware configuration forthe centralized monitoring system.This monitoring system will be used to collect, log, anddisplay the operation status from the beam line interlockMonitoring ComputerPC Pentium IIFX-485PC-IFRadiationSafetyInterlockSystemX2N--PLC 0FX2N--PLC 1FX2N--PLC 2FX2N--PLC 15FX2N-485-BD(Station No. 2)VacuumProtectionSystemInternational Conference on Accelerator and Large Experimental Physics Control Systems36International Conference  Accel rator and L rge Experim ntal Physics Control Systems, 1999, Trieste, Italyand control systems. The monitoring computer will beserially connected with 16 sets of FX2NPLCs via the FX-485PC-IF (RS232/RS485 converter) and the FX2N-485-BD (RS485 interface from station No. 0 to station No. 15)communication links [2].At BSRF, each old beam line interlock and controlsystem consists mainly of one vacuum protection systemfor beam lines and two (or three) radiation safetyinterlock systems for experimental stations. In order notto change the configuration of the old system,Programmable Logic Controllers (PLCs) are used to re-design the controllers in the system. In this system, thereare two types of new PLC-based controllers for eachbeam port. One controller is responsible for vacuumprotection system for beam lines, which includes thevacuum equipment interlock and controls, and the othercontrollers are used for the radiation safety interlocksystems for experimental stations. The interlock andcontrol program for each type of PLC-based controller isalmost the same.Each new controller includes a Mitsubishi FX2N PLC asa main hardware device. Each set of PLC consists of aCPU module, an ADC module, a digital I/O module, andan RS485 communication link. Each new PLC-basedcontroller is installed in a separate equipment chassis andthe operating panel is installed in front of each controllerfor local operation. All PLC-based controllers can beserially connected to the centralized monitoring computer(PC Pentium II) via the FX-485PC-IF (RS232/RS485converter) and FX2N-485-BD (RS485 interface)communication links.The beam line interlock and control systems alsoincludes 2 programs: One runs in the PLC (the actualinterlock and control programs), which has beencompleted, and the other is a user interface andmonitoring program running on the centralizedmonitoring computer (PC Pentium II). However, themonitoring program on the PC is currently underdevelopment.3 VACUUM PROTECTION SYSTEMSThe main functions of the vacuum protection system forBSRF beam lines was to protect the BEPC storage ringand other photon beam lines from sudden catastrophicvacuum failure at a single beam line. The second goalwas to protect the uncooled beam line components fromexposure to synchrotron radiation and the water-cooledbeam line components from the interruption of thecooling water flow.The new hardware for the vacuum protection systems isbased on the PLCs. The basic design requirements andconfigurations of the new systems are much the samewith the old systems described previously [1]. The newPLC-based vacuum interlock system is used to replace theold relay-based vacuum interlock systems. This includesFX2N PLC with about 90 I/O points, an ADC module(FX2N-4AD) with 4 input channels, and a RS485 serialcommunication link (FX2N- 485-BD). The I/O points areused to acquire status from the field devices (e.g.,positions of water-cooled movable mask, all-metal UHVvalve and fast-closing valve, as well as ionization gaugesoutput relays, pressure switches for cooling-water flow tocooled components and compressed air, etc) in addition tosending commands to them. The ADC channels are usedto read the analogue outputs of ionization gauges. ThePLC-based controller for each vacuum protection systemcan be serially connected to a centralized monitoringcomputer (Pentium II) via the RS485 link.The software for the vacuum interlock and controlsinvolves two tasks: drawing the ladder diagram andentering it into the PLC via a special packet (MEDOC).The new PLC-based vacuum controller is a highreliability fail-safe interlock and control device. Theoperating panel is installed in the front of each new PLC-based controller for local operation.For the 3W1 high-power (2.54 KW) wiggler beamlines, the challenge of the PLC-based controller for thevacuum protection system is to protect the fast-closingvalve from synchrotron radiation when it is triggered toclose. The closure time for the fast-closing valve is lessthan 7 milliseconds. In order to prevent the blade of thefast-closing valve from overheating before the water-cooled movable mask closes (about 2 seconds of closuretime), a titanium-alloy blade with melting point of 1680°C is used.4 RADIATION SAFETY INTERLOCKSYSTEMSThe new PLC-based controllers for the RadiationSafety Interlock System (RSIS) replaces the old radiationsafety interlock systems based on relays. Each set of thePLC-based for the RSIS hardware contains a FX2N PLCwith an RS 485 interface. Components include usercontrol panel and status displays, door position sensors(limit switches), electrically-driven door lockingmechanism, search-and-secure boxes, emergency beam-stop, voice alarm and visible warning indicators, safetyshutter and photon shutter, etc. The equipment cabinet foreach set of the RSIS is placed close to each experimentalstation.Personnel/users access into these stations can becontrolled via the RSIS during beam line operation. Thesystem hardware provides for emergency beam shut-offand emergency egress. A station search and secure mustbe completed before synchrotron radiation is transportedinto a station. During this procedure the users are forcedto depress the search buttons inside the station in apredetermined sequence and close the station doorswithin a given time period (~20 sec) to mark the stationas secure for radiation. Voice alarm and visual indicatorare given during the search process. At the completion ofa successful search, the safety shutter and photon shuttercan be opened if the other interlock conditions are alsosatisfied. The opening of the doors and the shutters are37fully controlled by the interlock system. In the oppositionway, if one of the interlock conditions is not satisfied,only one of the two shutters can be opened.The RSIS control chassis is the station control panel.This panel is used to open and close safety shutters andphoton shutters, gain safe access to the experimentalstation and display the status of the safety shutters andphoton shutters. as well as other devices related to theRSIS. For example, the LED indicators in the panel aregreen if the safety shutters are opened and are red if thesafety shutters are closed.5. REFERENCES[1] Xiong Shen-shou et al, " The vacuum control andprotection system for BEPC synchrotron radiationbeam lines", Nucl.Instr. and Meth. A282 (1989) 418-421.[2] User's manual for the FX2N PLC, M I TSUBISHI.38

Upgrading Beam Line Interlock and Control Systems at the BSRF

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