EPICS At Phenix Information Page
General:

EPICS is database system that provides a means of preforming data acquistion and operational optimization, as well as supervisorary, closed-loop and sequential control. In the PHENIX Experiment, EPICS is used to provide control, operation, and maintainence of the High Voltage system. High Voltage is supplied to the various sub-systems by LeCroy High Voltage Modules; these modules are contained and powered by LeCroy High Voltage Mainframes. Groups of mainframes are controlled by a single Input-Output Controller (IOC). Databases created with EPICS are loaded onto these controllers. Changes made to the database are reflected in real-time in the HV modules, and vice versa. External programs can communicate with the IOC to modify and monitor the EPICS database, providing control for every mainframe connected to the IOC.

EPICS operates under a VxWorks operating system on the IOC. The EPICS database is composed of data structures called records, which hold data and can run specific routines when accessed (processed). Records can be processed by the command of an external program or by other records. Records files (called database definition files)can be constructed in a simple text-editor and loaded directly onto an IOC running VxWorks. A great deal of code used in the PHENIX EPICS system was modified from code developed for the CEBAF Hall B experiment, which had similiar voltage requirements and also used LeCroy mainframes and modules. Included in the borrowed code were several standardized database definition files.

EPICS Information Sources:

The detailed documentation about EPICS can be found in the EPICS Documentation Guide.
Information regarding EPICS records can be found in the EPICS Record Reference Manual.

MEDM (Motif Editor and Display Manager):

Medm is a GUI application builder that was developed at the same time as EPICS. It was designed to be directly copatable with the EPICS record system. Using Medm, a GUI application can be constructed that will allow the EPICS database to be modified and monitored in real-time. Medm allows the user to set global variables such as the refresh rate of the output data fields, and individual variables such as the size and color of GUI objects. Medm can read plain-text files to find instructions on how to design a GUI; it is possible to write a program to generate these files, automating the GUI design process. While Medm is directly compatable with EPICS, it does not make use of some of the more sophisticated aspects of modern window systems.

For more information, see the MEDM Reference Manual.

For information on the MEDM interface used during HV testing, as well as information on the MEDM Alarm Handler, look here.

Developing High Voltage Setups for Sub-Systems:

Eventually, each sub-system will have to establish software controlling the HV they use; each HV software set will be unique to the sub-system. In order to facilitate this process, and to provide the sub-system groups with additional knowledge, the ONCS group will invite one member from each sub-system to work with us. While here, the guest will learn enough of the data hierarchy, EPICS, and other software we use to establish the HV setup for his or her sub-system. The guest, upon returning to his or her sub-system group, will also be able to act as an informed source of HV expertise within that group.

EPICS Implementation:

A more detailed explaination of the EPICS definition files and the software used to control the mainframes can be found here.

EPICS Troubleshooting:

As we adapted High Voltage control code from its CEBAF origins to suit our needs, we discovered a variety of problems. For example, the CEBAF code never had to deal with 1469 or 1471 modules, so we had to make modifications. For a description of the difficulites we had and our method of dealing with them, click here.