Lasers for ERL
Lasers for ERL Phase 1 are located in Wilson Lab, Rooms 141A and 143, adjacent to the ERL control room. The laser beam, which undergoes several stages of amplification, shaping, and wavelength shifting on laser tables in the two rooms, is transported through the wall between 141A and 143 and later through the wall to L0 to another laser table, and from there to the electron gun nearby. The lasers range in classification up to class IV (4), and protective measures in both rooms assume the maximum hazard in either. Rooms 141A and 143 both have access restricted to authorized personnel and are signed accordingly. These rooms are protected by keypad entry locks; for unauthorized emergency access (e.g. by fire investigators), the doors can be forced open, and this action shuts down the lasers. A multi-point interlock system is in place, which, depending on where a trip originates, can shut down front-end laser components, close the beam stop between 141A and 143, and/or close the shutter between 143 and L0. Several crash buttons
are located in both rooms.
A laser system is also set up in the rear of Room 128 for the gun/photocathode studies to be conducted there. The laser room is located within the radiation exclusion area and is therefore interlocked to the light beam marking this boundary; in addition the door itself is interlocked to the laser system power. Equipment and required precautions are similar to those in Rooms 141A/143.
In routine operation, light beams and optical elements not on laser tables are completely enclosed in sealed, opaque rigid tubing. On laser tables, beams are frequently transported inside clad optical fibers, and the two L0 laser tables are covered. However, frequent changes on the L0 laser tables occur; hence the table covers are interlocked with microswitches so as to close the shutters from room 143.
Increased hazard exists during modifications to laser setups and alignment, for which a special bypass interlock mode and associated procedures exists. Authorized personnel have the generic EHS
and ERL-specific laser training, and when necessary wear laser safety goggles appropriate for the wavelength and intensity.