Carcagno, R H

Orris, D

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A MODULAR AND EXTENSIBLE DATA ACQUISITION AND CONTROLSYSTEM FOR TESTING SUPERCONDUCTING MAGNETS∗D.F. Orris+, R. Carcagno, FNAL, Batavia, IL _______________________∗ Work supported by the United States Department of Energy+ orris@fnal.govAbstractThe Magnet Test Facility at Fermilab tests a variety offull-scale and model superconducting magnets for bothR&D and production. As the design characteristics andtest requirements of these magnets vary widely, themagnet test stand must accommodate a wide range ofData Acquisition (DAQ) and Control requirements.  Sucha system must provide several functions, which includes:quench detection, quench protection, power supplycontrol, quench characterization, and slow DAQ oftemperature, mechanical strain gauge, liquid helium level,etc.  The system must also provide cryogenic valvecontrol, process instrumentation monitoring, and processinterlock logic associated with the test stand.  A DAQ andControl system architecture that provides the functionalitydescribed above has been designed, fabricated, and putinto operation.  This system utilizes a modular approachthat provides both extensibility and flexibility.  As aresult, the complexity of the hardware is minimized whileremaining optimized for future expansion. Thearchitecture of this new system is presented along with adescription of the different technologies applied to eachmodule. Commissioning and operating experience as wellas plans for future expansion are discussed.1  INTRODUCTIONPower testing of superconducting magnets is dependant ontwo primary systems: one, the power supply system forsupplying current and providing a means for extractingenergy from the magnet; and two, the test standcryogenic/quench DAQ and Control system. The later,which is the focus of this paper, includes DAQ,Programmable Logic Controller (PLC) monitoring andcontrol, and quench management subsystems. The DAQ isused for reading out magnet temperature and strainsensors while the PLC system is used to monitorcryogenic sensors, control parameters such as liquidhelium level, and process test stand interlock logic. Thequench management system manages all magnet quenchcontrol hardware. Multiple power supply systems canexist, each having similar hardware architecture and thecapability of multiplexing its power bus to multiple TestStand Areas. Multiple Test Stand Areas exists and followthis extensible design: Each Test Stand Area canaccommodate multiple test stands. These systems have allbeen standardized and can therefore be easily expanded.Hence the modular approach. 2  TEST STAND AREA MODULARARCHITECTUREFor a given test stand area, more than one test stand can becooled down simultaneously.  Therefore, test standdependent PLC and DAQ hardware must be implementedfor each test stand added to the test stand area. However,since only one power system can be bussed to a given teststand area at a time, it follows that only one of its teststands can be powered. The quench management systemco-ordinates the quench detection and quench protectionhardware and provides hardware permits that allow thepower supplies and dump circuits to turn on.  Since onlyone test stand can be powered at a time, only one quenchmanagement hardware system is required for a given teststand area.  Local test stand area PLC controls insure theconcurrence of the test stand selection of the power bus,the quench management signals, and the magnetprotection Heater Firing Units (HFUs).  Figure 1 showsthe Test Stand Area Modular design.   Figure 1: Test Stand Area Module DAQ & Controls  2.1  Test Stand Process Control ModuleEach test stand has a fixed set of sensors and actuators toestablish and maintain test-operating conditions. Sensorstypically include Temperature, Pressure, Vacuum, Helium0-7803-7191-7/01/$10.00 ©2001 IEEE. 3463Proceedings of the 2001 Particle Accelerator Conference, ChicagoLiquid Level, and Switches. Actuators typically includeon/off valves, control valves, and control relays. There areapproximately 70 physical input/output (I/O) points in atest stand. Monitoring and control functions for thissystem are provided as a modular extension of the new1500W Refrigerator Control System [1]. Table TBDshows Hardware and Software components of thisindustrial control system.  Sub-System  Choice Programmable LogicController (PLC) Siemens 505-454 PLC Input/Output (I/O)Cards Siemens 505 seriesControl Network Ethernet with TCP/IP in a routednetworkPLC ProgrammingLanguageSiemens 505 SoftShop Operator InterfaceSoftwareFIX32 from Intellution Electrical Loops 24 VDC for discrete I/O, 4-20 mAor 0-5 VDC for analog I/O. Temperature sensors Lakeshore CERNOX RTDs withModel 234 temperaturetransmitter cards and Pt RTDswith Model 231P cards. Liquid Helium LevelProbesAmerican Magneticssuperconducting level sensors andModel 135 liquid helium levelmonitorExternal Interface ODBC interface to FIX32 real-time database Table TBD: Test Stand Process Control System  The test stand Control System is a completely independentmodule, with a separate PLC and SCADA node.Therefore, any failure of this system does not affect therefrigerator operability. The test stand control system isalso completely independent from the test stand DAQsystem. As a result, test stand operations are not affectedby DAQ system downtime due to system reconfiguration,troubleshooting, or failures. Operators can bring up teststand operator displays from any operator station, so theycan easily navigate between refrigerator control displaysand test stand control displays. A software link allowstwo-way communication between the test stand controlsystem database and the DAQ system, and an integratedpager system provides remote notification of alarmconditions to operators. 2.2  Test Stand Data Acquisition ModuleThe Test Stand DAQ System provides accurate 4-wiremeasurements of devices such as Temperature Sensorsand Strain Gauges. Fast sampling of these devices is nottypically required, so this system is designed for relativelylow sampling frequencies (~8 Channels/sec). Sensors areconnected to the DAQ system using in-house designedand built 16-Channel “switchboxes”. These switchboxeshave several features to allow easy insertion or removal ofa sensor to a current chain, chain current measurement viaa precision shunt resistor, and test points fortroubleshooting. Several sensors are typically connected toa current source chain for excitation, and the resultingsensor voltage is multiplexed via HP 1351 16-ChannelFET Multiplexors to an HP 3458A Digital Multimeter(DMM) along with the chain current for accurate 4-wireresistance measurements. Software running in a VMEprocessor configures the multiplexor (MUX) scanning listvia the VME backplane. It also configures the DMM, andthe programmable current sources via GPIB. The DMMtriggers control the MUX advance to close the nextchannel in the scanning list, and after the voltage of allMUX channels in the scanning list have been measured bythe DMM the results are transferred to the VMEprocessor.  The measured resistance is then converted toits corresponding value in engineering units usingcalibration curves previously loaded into the software.  Tominimize sensor self-heating effects the DAQ systemoptimizes the chain current so that the maximum sensorvoltage is around 5 mV. In addition, the DAQ systemperforms polarity reversal for RTD measurements. As anexample of the DAQ system accuracy, assuming that allRTD temperature sensors in a current chain are at around4K the absolute measurement error introduced by theDAQ system is approximately ±4 mK. The DAQ system is highly modular. Expandability iseasily accomplished by adding more switchboxes and FETMUX VME modules, possibly more current sources, andmodifying the software configuration to reflect the newconfiguration. 2.3  Test Stand Area Quench ManagementSystem Module The Quench Management System performs the followingtasks: it monitors/controls the magnet protectionhardware, which includes the magnet heater power and theDump extraction resistor; provides permits to the powersystem to turn on; and it monitors the magnet for theonslaught of resistive voltages (quench detection).  In theevent of a quench, it carries out the necessary actions inorder to shut down the power supplies and extract theenergy from the magnet while logging magnet voltagedata at a fast rate in order to characterize the quench.  Thequench management signals have been standardized sothis system can be easily multiplexed to several teststands.  The primary hardware component of the quenchmanagement system is the quench logic module (QLM).The QLM is an in-house built VME module and is thedevice that monitors the hardware status of the Dumpresistor, the HFU load and charged statuses, and themagnet quench status.  It also provides the power supply,3464Proceedings of the 2001 Particle Accelerator Conference, Chicagothe Dump, and the HFUs with the permits required toturn-on via contact closure. It also carries out thenecessary logic for protecting the magnet, such as phasingback the power supply, firing the magnet protectionheaters, and firing the Dump. User programmed delaysmay also be initiated.  A heartbeat is also implemented toestablish system integrity: Loss of a heartbeat causes asystem trip similar to a quench. User interfaces are used toconfigure the QLM for magnet tests [2]. Since the magnet current often exceeds 10,000Amps,the response of the quench detection system must be veryfast in order to prevent damage to the magnet -- typicallyless than 5msec.  Quench threshold detection is performedby the Digital Quench Detection (DQD) system [3]. Thecomponents used for DQD are a Motorola VMEPowerPC, an Analogic DVX2503 ADC, and an in-housebuilt anti-aliasing Bessel filter. The ADC samples at11,520Hz.  Since a 40tap FIR filter is implemented as adecimation filter via the PowerPC, a group delay of~1.7msec is incurred. Moreover, the anti-aliasing filter hasa group delay of 0.23msec, yielding a system total groupdelay of ~1.93msec. The decimation rate is typically set to2400Hz, which limits the resolution of the quenchdecision to ~0.4msecs. This is a very reliable and easilyconfigured system, however, Analog Quench Detectioncircuits (AQD) are also used as hardware backup forsafety. Other VME modules that are part of the QuenchManagement System include a VMIC 1160C Change ofState (COS) and a Matrix MD-DAADIO module. TheCOS module, which is used for first faultdetection/diagnostics, is optically coupled and has 1msecresolution. The DAADIO module is used for controllingand monitoring the HFUs and for reading out the Dumpresistance. It includes digital I/O, Digital to AnalogConverter (DAC), and an Analog to Digital Converter(ADC) all on the same board. Pentek 4275B Sigma Delta ADCs, sampling at 7142Hz,are used to log magnet voltage tap data in order todetermine quench location and propagation.  Initializationand quench events for data saving are provided by thequench management software and a hardware quenchtrigger is provided by the QLM. 2.4  Test Stand Selection Testing a magnet requires the implementation of astandard set of quench management signals.  The HFUcurrent bus and the power system current bus must also beconnected to the test stand as well.  It is imperative that allthree systems are in concurrence in order to safely powerthe magnet and protect it in the event of a quench.  This isdone via a PLC system and hardwire interlock.  When thequench management signals are selected for a particulartest stand, both the HFU current bus and the power systemcurrent bus must be connected to the same test stand or thePLC system will prevent the power supplies from turningon (Figure 1). 2.5 Test Stand Area Expandability Since the Test Stand Area design has been standardizedand is modular, the Quench Management signals, thepower system bus, and the HFU current bus multiplexingare all part of its infrastructure.  Therefore, expanding thenumber of test stands within the Test Stand Area isstraightforward.  Moreover, new test stands can have aunique set of instrumentation channels since the test standDAQ and PLC modules are also standardized andindependent of the test stand area.  The Test Stands aretherefore easily expandable as well. 2.6 Operating Experience A Horizontal Test Stand Area for testing cryostatedaccelerator magnets has been built and tested.  A full scaleLHC quadrupole magnet has been cooled below thelambda point and power tested at currents exceeding12Kamps.  A second facility, used since 1997 for thetesting of model magnets in a vertical cryostat (VMTF)[4], is now being upgraded to the new standardizeddesign.  Multiplexing of these two Test Stand Areas hasbeen successfully tested and the addition of three existingtest stands to the Horizontal Test Stand Area (futureexpansion) is planned for the near future.3  CONCLUSIONS The design and implementation of a DAQ and Controlssystem for testing superconducting magnets has beencompleted.  A modular approach was taken in order toaccompany future expansion of magnet test stands whileremaining flexible to unique test stand instrumentationrequirements.  Since the hardware system developed hasbeen standardized and designed for expansion, the reuseof key systems has reduced additional engineering,complexity, and subsequently the cost of new systems.4  REFERENCES[1] R. H. Carcagno and R. J. Rabehl, “Controls Upgradeof the Fermilab Magnet Test Facility 1500W HeliumRefrigerator,” Advances in Cryogenic Engineering, Vol.45, p. 1795-1802, Plenum Press, New York, (2000).[2] J.M.Nogiec, E.Desavouret, M.Lamm, D.Orris,S.Sharonov, J.Sim, "Architecture of a Software QuenchManagement System"PAC'01, Chicago, (2001).  [3] D.F. Orris, S. Feher, M.J. Lamm, J. Nogiec, S.Sharonov, M. Tartaglia, and J. Tompkins, "DigitalQuench Detection System for SuperconductingMagnets", PAC'99, New York, (1999)  [4] M.J. Lamm et al., "A New Facility to testSuperconducting Accelerator Magnets", PAC'97,Vancouver, Canada, 19973465Proceedings of the 2001 Particle Accelerator Conference, Chicago

A Modular and Extensible Data Acquisition and Control System for Testing Superconducting Magnets

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