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title: PHENIX.ONCS.tn.17.0
file: anc-sys-req-rich.html
Ancillary Systems Technical Note
RICH SUBDETECTOR
ANCILLARY SYSTEM REQUIREMENTS
E. Desmond
RICH Computer Liason: Y. Akiba
April 4, 1995
The RICH detector subsystem consists of two arms. Each arm contains a self-supporting radiator gas vessel in which two mirrors and two focal plane detectors are mounted. The detectors consist of arrays of photomultiplier tubes of which there are currently 5120 in number. The components of the RICH subdetector which are of interest to ancillary systems are the high voltage supplies for the photomultipliers, the gas purity of the radiator gas, temperatures of the photomultipliers and the gas vessel, and leak detectors around the gas vessel.
The RICH detectors are arranged into 4 focal plane detectors of which 2 are located on each detector arm.
The photomultipliers which make up the detector elements of the four focal plane detectors consist of a total of 5120 photomultiplier tubes. These tubes are arranged into modules each of which is a 2 by 16 array. Forty of these arrays of modules together comprise a sector. Each sector makes up a single focal plane.
The high voltage supply for the photomultiplier tubes is arranged so that each high voltage generator/controller will supply 8 photomultiplier tubes. Thus, there will be 640 high voltage supplies which need to be controlled and monitored.
At present a prototype high voltage supply system has been developed at INS in Japan. This supply system consists of a DC controllable power supply which is capable of providing output voltage of up to 1.8 Kv at a maximum of 3 ma. This unit is controlled by individual DC voltage setpoints which range from 4 to 6 Vdc. Voltage readback is supplied by a DC voltage with a range from 0 to 1.8 volts providing a scale of 1 volt per Kv. The control requirements are for < .1 % peak to peak voltage ripple and an accuracy of +- 5 %. Voltage monitoring requires at least 10 bits resolution
It is anticipated that there will be a proposal for a universal high voltage source for PHENIX subsystem detectors. If such a system should become available which meets the requirements of the RICH detector then the RICH high voltage system will likely be supplied by this system. The present schedule calls for a request for proposal for the PHENIX high voltage supply to be issued to potential suppliers by July 1995. A request for quote is expected during 1997.
Each high voltage control unit will be individually controllable. For the RICH system then the photomultipliers will be controllable in units of 8 tubes. The individual control units must be able to be enabled or disabled both before and during run time. In addition, each module and sector must be able to be initialized and run without the presence of the other arrays. It is expected that each sector will be constructed and tested as separate units.
The setpoints for the high voltage will be in units of Kv.
The output voltage and current will be continuously monitored. It is estimated that the monitor rate will be approximately 1/2 hertz. Display clients will be notified of significant changes in the output voltage. A significant change is individually setable for each voltage monitored. The current requirement is to notify clients on the change of greater than 10 volts. Each high voltage supply will have separate warning and severe alarm limits. All alarm conditions will be logged. Each log entry will contain the name of the high voltage channel, the value at which the alarm occurred and the time of the alarm. The occurrence of a severe alarm will cause the automatic shutdown of the alarming high voltage channel. The limit values for the warning alarm and severe alarm condition remain to be specified The alarm response time requirements have not been determined at this time.
All high voltage channels will be logged every 30 minutes. Each log entry will contain the channel name, data value and a time stamp. The format and location of the logging has not been determined at this time. There is a logging facility which is part of the EPICS control system which is being used for ancillary controls for PHENIX. It has not been determined at this time if this archiver meets the requirements for data logging for PHENIX.
In the RICH subsystem the temperature of the photomultiplier tubes and the temperature inside the gas vessel must be monitored. The specifications for the temperature monitoring should include the following:
The radiator gas vessel will be monitored for gas purity, and gas flow rate. The instrumentation and the interface to the gas purity measurement system has not been determined at this time. It is anticipated that the gas monitoring system will provide for continuous monitoring as well as logging and operator notification facilities. Similarly the gas flow rate will be monitored and provisions will be supplied to log and notify operators of the present flow rates and alarm conditions.
The gas leak detector system is a potential personnel as well as instrument safety issue. It remains to be established what the PHENIX policy will be regarding systems for monitoring and controlling systems with potential personnel safety, and mission critical safety issues. At this point it has not been determined whether the PHENIX ancillary control system will provide more than monitoring and logging services regarding the gas leak detector system.
Operator display screens will be developed to display the status of all monitored devices in the RICH detector subsystem. Operator screens will also be provided for individual control of the separately controllable elements of the detector system. The display screens will be viewable from any X Window capable display terminal. The display screens will consist of indicator icons to graphically present the fault status of a monitored detector element. Where values are appropriate, the display screen will consist of text fields or bar or chart graphs.
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