Process Variables for SSRL Beamline Users and Other SLAC Projects

Some users, external to SPEAR accelerator controls, need access to a small subset of EPICS process variables (PVs) to get general SPEAR and beamline status, coordinate their activities with SPEAR injection, and move beamline inserion devices (IDs). These users include SSRL experiment users and other SLAC projects such as LCLS. An EPICS PV gateway process, providing read-access to all SPEAR PVs and limited write-access to ID PVs, is available and runs on one of the SPEAR servers. These slaconly instructions describe how to connect to the PV gateway from an EPICS channel access (CA) client process.

All SPEAR PVs listed by device in the PV database are available (read-only for most cases) to all CA clients but it's difficult to find a specific item of interest from this list. The ID control PVs and how to use them are described in the Remote Control of SPEAR Insertion Devices engineering note. Other popular PVs are listed here. The current value of some of these PVs are shown graphically on the SPEAR Status web page.

Analog PVs

PV Name Description
SPEAR:BeamCurrAvg SPEAR beam current averaged over 1 sec
SPEAR:BeamCurrDes Target current for injection
SPEAR:BeamCurrAvgMin Minimum current above which frequent fill is possible

Digital PVs

PV Name Description State Value State Name State Description
SPEAR:State SPEAR machine mode 0 Beams Beam to users
1 Inject Injecting below 50mA, beamlines closed
2 AccPhy Accelerator physics testing in progress, beamlines closed
3 Down Machine is down
SPEAR:InjectState SPEAR injection status 0 No Injection No injection in progress
1 Beamline Wait About to inject - wait for SPEAR:InjectDelay seconds
2 Injection Injection in progress


Contact: Stephanie Allison
Last Modified: June 16, 2010