PSFC Diborane Discharge Cleaning Checklist

Plasma Science and Fusion Center

Office of Environment, Safety, and Health

190 Albany Street, NW21 2nd floor
617-253-8440 (Catherine Fiore)
617-253-8917 (Matt Fulton)
617-253-5982 (Bill Byford)
617-258-5473 (Nancy Masley)
Fax 617-252-1808

Be Safe or Die

Reviewed and Approved By:

PSFC Supervisor--Gary Dekow

PSFC Supervisor—Andy Pfeiffer

PSFC Supervisor--Jim Irby

PSFC Safety Officer--Catherine L. Fiore

As in Version 6.6

Alcator C-Mod

Checklist for Diborane Gas System Discharge Cleaning





NOTE: Steps a-h must be done at any time prior to the search and lock of the cell. The vacuum system setup, item k may be done simultaneously.



Prior to closing the cell, turn off the RGA filament from the RGA PC in the control room.

Cell preparations:

The following items are done on the upper level of the cell:

_____b. ______Turn off the two RGA filament Ametek power supplies.  One is locate at H-port horizontal on top of the pumping system and the other is located on top of the Torvac rack.

______Turn off the Ametek Data logger located int the Torvac rack, middle shelf

_______At H-port right side and left side close the gate valves for the RGA and torque them.


Close the shutters at A, C and F port.

_____MSE Shutter

_____CXRS Shutter (under control of Bruce Lipschultz)

_____CXRS Shutter (under control of Bob Granetz)

At this time, the MSE and CXRS shutters are under the direct control of Bob Granetz and Bill Rowan, and will not be open or shut during setup for boronization.   Check with them to see that they have taken care of the shutter.


_____Jim Terry's A port shutter.

Proceed to the B-port-side of A port. The status of shutter will be given by the red plate velcro'ed to the igloo between A and B ports. The plate says ``A port shutter is... '', with ``OPEN'' or ``CLOSED'' indicated by the appropriate side of the red, velcro'ed plate. It should indicate ``OPEN''.

If the indicator says ``OPEN'', then locate the rotary motion feedthrough located at the bottom left corner of the reentrant A-port-side flange. This feedthrough controls the position of the shutter. It is a Aluminum cylinder about 3.5" long, at the end of which is a knurled knob with a metal-colored locking screw. (Even if the indicator says ``CLOSED'', this position should be verified by executing step 3 and feeling that the knurled head of the rotary motion feedthrough is turned fully clockwise.)

Unscrew the locking screw about one turn to free the feedthrough for rotary motion. It will be difficult to reach your arm into the A side flange area, but do so without damaging %the Thomson scattering mirrors or the microwave waveguide. To ``CLOSE'' the shutter, rotate the head of the rotary motion feedthrough approximately 1 full turn CLOCKWISE. If it resists strongly or if you feel that you are using anything more than ``finger strength'', then stop and do not force it. Try to return it to the fully counter-clockwise (OPEN) position. Notify Jim Terry (ext. 3-8637 or at home 323-6597).

Tighten the feedthrough locking screw.

Switch the red plate indicator to show that the A port shutter is ``CLOSED''


Close the NPA gate valve at F-port top:  The valve is closed manually by rotating fully clockwise. 


Start the flow from the vaporizer into the diborane vent work and the vacuum pump outlet by opening ball valve MV5 (mezzanine level, North Wall). The regulator should be opened to at least 5 PSI but no more than 12 PSI.



Open the valve going to the torus roughing pump. The regulator should be opened to at least 5 PSI but no more than 12 PSI.



Verify that MV4 (mezzanine level, on igloo at AB) is open.


_____h.  Polarimeter shutter:   Verify that the helium tank supplying the polarimeter shutter is above 1000 psi, and that the regulator              pressure is at least 15 psi.  Verify that the polarimeter shutter vacuum pump on top of the igloo above k-hor is pumping.                   Remove the cover from the polarimeter mirror housing at k-hor.  Shine in a light and verify that the polarimeter inner wall               shutter is closed.

_____i. Surface Science Station: Close the Turbo pump gate valve, then open the manual gatevalve on the beam line for probe insertion.     Set the N2 purge flow meter on the exhaust of the secondary seal pump to 6-8 SLM to dilute the pump exhaust into the cell           exhaust system. Verify that the N2 purge is active at the turbo pump exhaust. 

The following items are done on the lower level of the cell:

_____j. Dust Injection System:  Close hand valve on A-port bottom inside.  Aaron Bader and Bob Granetz are responsible.


Prior to closing the cell, check that the controller unit for the ECDC microwave source has been placed in Analog control mode (center switch on front panel of Lab Power Supply located between D and E port.



Prior to closing the cell, check that the camera on the diborane cabinet has a clear view and can be seen on channel 27 in the control room.



Verify that:

_____Manual valves MV1 and MV3 are open.

_____The diborane regulator (REG1) is set to 30 PSI (this is normally set at the first boroniztion and left set).

_____The venturi regulator (REG3) is set to 100 PSI.

_____The helium purge gas regulator (REG2) is set to 30 PSI (PV3 and PV4 and manual valve MV2 will have to be open to set the diborane regulator pressure.)



Prepare vacuum system and diagnostics

____n. Verify that the lower hybrid wave guide has been pulled back.  This can be done by switching the  encoder from remote to local by flipping the switch up. Check and record that the reading is 1902 (+- 2 counts). Finally return the encoder switch to remote (flip switch down).



 _____Go into the TORVAC PLC. Turn off all filaments specified (IGT, IGP1, IGP2)

_____Verify that all of the diagnostic gate valves are closed.

_____Close GV3.

_____Turn off the Ratiomatic (make sure the Ratiomatic has been taken out of Auto mode.)

_____Close the Z Bolo Shutter from Torvac.

_____Close the HIREX III  gate valve.



Prepare the boronization system


Search and lock the cell, power room and diagnostic labs.

______Secure and check the ACCESS permissive on the DIBORANE PLC.


Activate the purge procedure from the PLC:

_____Enable the AUTO switch on the DIBORANE PLC.

_____Reset PV5.

_____Enable PURGE60. (This will not work unless the DIBORANE MV CLSD bit is enabled. Do not change this bit without verification of the bottle valve status.)


Verify that the PURGE60 cycle is working. Make sure that PV5 is open, and that TR4 is cycling between vacuum and pressure.


Open the diborane gas bottle valve:

_____Two persons should don the SCBA. (Two more SCBA qualified persons must be standing by.)

_____The persons wearing SCBA should enter the cell under controlled access, taking 2 walkie-talkies with them.

_____One of the two should don the welding glove and open the diborane bottle while the other watches the toxic gas detector on the cabinet.

_____Exit the cell and remove the SCBA.

_____Enable the DIBORANE MV OPN bit on the PLC.

_____Return the cell access system to a secured state.


Set up for the discharge cleaning cycle:

_____Enable the FILL ENABLE on button on the DIBORANE PLC.

_____Go into the AFILL screen of TORVAC and clear the fault, even if no fault is indicated.

_____Go into the ECDC screen of TORVAC and enter requested scan settings for PEI sweep.


Set the pressure by entering 35 Mtorr into the DIBORANE PLC and enable the fill request. 


if a higher pressure is desiered, raise the pressure in increments of 10 mTorr not to exceed 90 mTorr.


Activate the diborane discharge cleaning mode from TORVAC.

_____Verify that a discharge has formed in the machine.

_____Enable the pulser"on" button on the lower right hand side of the diborane PLC screen.

_____Set pulser .3 s off, .7 s on.

_____Verify that the discharge is flashing on and of on the TV screen.

Start up is now complete: Maintain discharge cleaning for the desired period.


Shut down discharge cleaning.

_____Verify that the Piezo-electric valve has been asked to close. If it does not close, toggle the Fill request.

_____Toggle the ``FILL ENABLE OFF'' bit.


Evacuate the gas line:

_____On the DIBORANE PLC enable AUTO.

_____Enable PURGE5.


Don the SCBA and enter the cell under access control. Don the welding glove and close the valve on the diborane bottle. Exit the cell.


Enable the DIBORANE MV CLSD switch on the DIBORANE PLC.

_____Secure and check the ACCESS permissive on the DIBORANE PLC.

_____On the DIBORANE PLC enable AUTO and initiate the PURGE60 cycle.



At completion of the purge cycle verify that all automatic valves are shut.


Release the access control system unless setting up for a run later in the day.


When the vacuum vessel has been pumped out (1 to 1.6 mTorr on TC3):

_____Turn on IGT.

_____Turn on IGP2.

_____Reopen The diagnostic valves which were closed at the beginning of this procedure


_____If the surface science station was used, reopen the S3 gate valve and close the gate valve to the machine.



This page maintained by Catherine L. Fiore FIORE@PSFC.MIT.EDU