LINAC

NEED PROOF READING

Power Outage Procedure

When the building power is interrupted the Helium liquefier will stop along with its associated compressors. After this happens the linac boil off will begin to vent through a 1” pressure relief valve located behind the liquefiers. Do not be alarmed by this as it is designed to operate in this manner.

The linac chart recorder auto dialer will activate and someone on the linac list will be “beeped”. He will usually call the lab on the 644-6763 line before coming in. If no one calls within 15 minutes, call someone of the call list (see notice by phone in the control room).

Of the following procedure, item 1 should be done immediately after the emergency power comes on. Items 2 and 3 within 30 minutes or so, items 5 and 6 only if necessary.

1. Open vacuum valves between the cryostats by switching the valve controllers FV5 thru FV8 to the manual open position. This allows the entire linac to be pumped by the turbomolecular and rotary pumps which are on emergency power.
2. Make sure the turbo pumps on the buncher, cryostats B, C and D and the rebuncher have restarted. If not follow procedure posted by each pumping stations electronics rack.
3. Close the J. T. valve on the liquefier (this is the micrometer handled valve) a fraction of a turn clockwise until you feel resistance.
4. Now wait and monitor:
   1. Pressures: 1K dewar, linac and compressor return.
   2. Vacuums in all cryostats.
   3. LN2 and LHe levels in the 1K dewar and cryostats.
   4. Resonator and solenoid temperatures.
5. As each cryostat runs out of LHe and its resonators (and solenoids) start to warm up:
6. Pump the helium out of the slow tuners.
7. Run down the persistent currents in the solenoids.

Helium Refrigerator Restart Procedure

1. Turn on the load 2 RS compressors (look in the log book for information on which 2 were being used) using compressor start buttons on the liquefier.
2. Defrost o-rings on relief valves as required.
3. Start the appropriate liquefier:
4. Push the liquefier start button.
5. Turn the flywheel c.c.w. until the machine starts to run.
6. Open the J. T. valve to 0.085.
7. Return FV5 thru FV8 to auto position.
8. Restart the turbopumps just upstream from the 90◦ magnet and on the switching magnet (note: before starting the tumbopumps, make sure the foreline pumps are running and the ball valves to the turbos have been re-opened with foreline vacuum < 50 m.)

Super Fast Valve Reset Procedure

The super fast valve operates with the spark-gap vacuum protection system on the beamlines to the various experimental stations. If vacuum is lost downstream of the switching magnet this valve will quickly close to prevent vacuum loss in the Linac cryostats. Once this valve has fired it must be “rearmed” using the following procedure:

1. Switch the S.F.V. controller (located in the vacuum protection rack) to disarmed.
2. Disconnect the cable from the back panel of the controller labeled to valve.
3. Using a 7/64 allen wrench loosen the two hex head bolts that attach the trigger mechanism to the top of the valve body.
4. Using a pair of vise-grips remove the spent squib from the trigger device and replace it with a new one from the can located on switching magnet.
5. Make sure there is good contact between the pin on the squib and the connector on the cable from the controller.
6. Hook up the air line (nylon tubing with nu-pro valve next to the valve) to the swagelok fitting on the side of the valve body and open the nupro valve. The valve stem should emerge from the hole in the top of the valve body after this occurs, close the nupro valve and remove the air line.
7. Hook up the cable on the controller marked “to valve” again and then switch the control unit to the “Test” position. Push the reset button and then switch the controller to the armed position.

Troubleshooting Linac out of Lock Problems

If the L.E. Bunching system and the Linac resonators are ‘in-lock’, the % in-lock meter in the control room should read 100%. If the reading is zero or unsteady, the following should be checked:

1. Is the L.E. buncher phase lock O.K.? see 43.3.1.
2. Are any of the resonators “out of lock”? See 43.3.2.
3. If several resonators are simultaneously out of lock (their LED’s on the resonator display panel are flickering), one or more cryostats are probably filling with the LN2.
4. Go to the LINAC Hall and check the status of the “fill” indicator lights on the LN2 controllers which are located on the instrumentation racks hanging from the blue radiation shield wall. If one or more of these indicator lights is illuminated, you will have to wait for all of them to stop filling before further diagnosis can be made.

5.5 Troubleshooting Loss of Beam Phase Lock

Look at the oscilloscope labeled “PHASE LOCK STATUS” in the LINAC electronics rack in the control room. If operating properly there should be a trace – the beam phase error signal – 1 division above ground, at the position marked ‘buncher’ on the scope. If this trace is a straight line at zero, or the top of the screen, or is very jumpy, the beam phase lock is not working properly. Check the following:

• Is there beam going through the phase detector, that is, is there beam on BS-2? See 2.
• Is the L.E. buncher “PHASE LOCK” phase set properly? See 3.
• Is the chopper phase set properly? See 4.