Beamline interlock

The X1 beamline has three interlocks:

Front end interlock

Designed and maintained by the NSLS, the front end interlock takes care of personnel safety and ring vacuum protection. It provides a relay output to the X-1A beamline interlock on the status of the front end vacuum, on when the mask/shutter is open, and when the mask/shutter are set to automatically open when shutters are enabled. The X-1A beamline provides relay outputs to the front end interlock indicating when it is OK to have the mask/shutter enabled, when X-1A is capable of taking beam, when X-1B is capable of taking beam, and relay inputs to request opening and closing the mask/shutter.

X-1A interlock

This interlock controls the X-1A valves according to vacuum conditions. It interacts with the front end interlock as described above, and with the X-1B interlock as described below.

X-1B interlock

This interlock controls the X-1B valves. It provides to the X-1A beamline interlock a mask enable relay output which says that X-1B is in a condition where it is safe to open the mask/shutter, and a relay output which tells when X-1B is capable of taking beam. It receives from the X-1A beamline interlock a relay output indicating the status of G2, a gauge in the X-1B mirror chamber through which both the X-1A and X-1B photons travel.

Besides protecting people and equipment, the interlock system allows one to open and close beamline pneumatic valves. All crucial information pertaining to the interlock operation is shown on the unit's front panel. In normal operation, the lights on the front panel should all be green (all is well), with the exception that some may be yellow (safe operation, but proceed with caution). If any lights are red, the beamline is either in a condition where no X-rays will make it down the beamline (e.g., mask/shutter is closed) or vacuum safety interlocks are being overridden (leaving the beamline and possibly the synchrotron vulnerable to severe damage).

To open a valve, press its ``open'' button. If a valve does not open, it is because vacuum interlocks dictate otherwise. Note that the indicator lights display the actual status of the valve; if neither the green ``open'' nor the yellow ``close'' lights are on, the valve is in an undetermined state. To close a valve, press its ``close'' button.

As a general rule, the only time an override switch should ever be on is during vacuum system maintenance or modification work. If an override switch is on, it is not possible to open the next valve upstream or the mask/shutter.

Note that all the VAT pneumatically-driven valves must be in the manually closed position for them to be able to be opened remotely by the interlock.