SLACINJECTOR-PROC-002
Rev. 1
31 Oct 2007
PROCEDURES TO CHANGE CATHODE IN THE ITF
Opening up the gas
vessel
1. Contact Cryo Techs to turn off Dry-air/SF6 system
2. Lock off and tag off of HV power supply for the gun
3.
Close gun nose valve?
4. Detach gas lines for Dry-air/SF6, and covers the gas lines with foil
5. Prepare to move the top SF6 vessel:
- Remove
nuts between gun body and the top half of SF6 vessel
- Remove
the nuts and bolts between the top half and bottom half of SF6 vessel
-
Lift top half a few inches, using grounding hook, discharge any remaining
stored energy
- Remove
the top half of SF6 vessel, and store it in hallway
6. Prepare to move the bottom SF6 vessel
- Detach
HV cable from clam shell, and also loosen locking nuts (external SF6 vessel),
and eventually pull out the cable.
- Remove nuts between gun body
and SF6 vessel bottom
- Remove the bottom SF6 vessel and store it in
hallway
7. Remove clam shell
- Install jack stand under the bottom of clam shell with Kimwipes between jack and shell
- Remove screws from gun body
to the top half of clam shell
- Remove two screws between
the top and bottom half of clam shell
- Remove the top half of clam shell
and store it in hallway (clean surface)
- Remove screws from gun body
to the bottom half of clam shell
- Hold
the bottom half of clam shell up, remove jack, and remove the bottom clam shell
and store it hallway (clean surface)
Old cathode
retraction from gun
8. Strongback support preparation
- Roll
in and install load-lock strongback support; align strongback support with
washer and c-clamps
- Move
in movable mechanism and bolt bellows to movable mechanism
9. Preparation for emitter tube
- Disconnect emitter tube supports from back
of bellow flange
- Install heater and o-ring with cooling
tube on the top
- Attach light on the top window of prep
chamber
10. Retract old cathode into prep chamber
11. Close vacuum valve between load-lock and gun
Remove puck tray
with old cathode and/or heat shield
12. Change ion pump power supply from optically isolated diode laser powered supply to local Varian supply
13. Install puck elevator driver
- Remove one support from puck elevator
- Install elevator drive
- Remove the other support from puck
elevator
14. Store heat shield into puck tray from prep chamber/emitter tube
- Lower elevator until forks are below the
level of puck tray
- Move
in puck tray to position #2 to hang the heat shield
- Lower
fork
- Back
out puck tray
15. Store old cathode into puck tray from emitter tube
- Raise fork to capture cathode on emitter tube
- Back
out emitter tube from cathode
- Lower
fork with cathode below puck tray
- Move
puck tray in to store old cathode to the position (as listed on the traveler
form)
- Raise
fork to position cathode in front of “nose cylinder” and “roller”
- Move
puck tray to insert nose cylinder” and engage roller
- Lower
fork
- Back
out puck tray
16. Remove puck tray
- Close
valve between puck tray and elevator
-
Punch and vent copper tube with dry N2?
- Remove puck tray
Install and
bake-out puck tray with new cathode
17. Install puck tray with new cathode and bake out
- Replace
gas kit and attach it to flange
- Pump down the puck tray with a turbo pump
- Place thermocouples at both ends of puck
tray
- Place 3rd thermocouple on the
venting valve
- Wrap puck tray and its small valve using
two special blankets
- Connect the heating blankets to Variacs
- Bring up temperature: within half hour,
adjust Varaics from 0 to 90; and keep baking 4 hours at 250 deg, and then
switch all off to zero for cooling down
- Remove blankets
18. Cool down puck tray before moving new cathode to emitter
tube
- Pinch
the copper tube to seal off the turbo pump when temperature below 100 deg,
- Open the valve between the
puck tray and prep chamber
- Cool down puck tray
overnight before the 1st cathode activation
Move new cathode from puck tray to emitter tube
19. Install puck tray drive
- Remove
the lower supporting bracket
- Install
puck tray drive
- Remove
the upper supporting bracket along with thermocouples
20. Transport the new cathode from puck tray to emitter tube
- Lower fork
- Move puck tray to position
new cathode above fork
- Raise fork to lift cathode
- Retract puck tray to
disengage nose cylinder and roller
- Lower fork and cathode below
puck tray
- Back out puck tray
- Raise fork and cathode
- Insert emitter tube nose and
rollers to hold cathode
- Lower forks below puck tray
Move heat shield from puck tray to emitter tube
21. Transport the heat shield from puck tray to emitter tube
- Move in puck tray to
position heat shield above forks
- Raise forks to engage bottom
of heat shield
- Move in puck tray a little
to straighten heat shield as raising forks
- With forks up, move puck
tray in to free heat shield
- Lower forks below puck tray
- Retract puck tray all the
way
- Raise
forks to position heat shield in front of cathode such that the ceramic inlays
in fork will be against cathode when it will later be removed against
forks
Heat treating for new cathode
22. Preparation of heat treating
- Install c-clamp to hang N2 bucket at end of
load lock movable bellows support
- Connect Cu o.25’’ tubing
coil to end of heater
- Connect the other end to N2
source and set flow to 20SCFH hang bucket
- Connect thermocouple
connector from heater to “PEG load lock” TC readout box and
- Connect x2 transformer to
heater plug
- Connect Variac to
transformer with Variac off and at zero
- Connect Variac AC
- Connect 6A DC power supply
to cesiator with current knob all the way down and switch off
- Close other two vacuum
valves until resistance, then a little farther but not enough to click
- Tie-wrap
ion-pump cable such that it relieves torque on feedthroughs.
23. Heat treating
- Turn Variac to 140V and knob
to 80
- Record: time, variac
setting, temp, N2 flow, pressure in load lock
- Ensure micrometer stage is
loose – note the needle value
- When
TC at 800c, move cathode into contact with forks by: slightly tap long bellows
to make cathode bounce; move it forward until oscillation stops abruptly
- Look
at micrometer again. If the delta is bigger than 41lbs, back cathode out and
repeat.
- Emitter tube should be dull orange and
cathode dull red at 800c
- Take
data every 10-15 minutes for 1 h at the temperature
24. Preparation of cathode cesiation
- Run cesiator up to 2A for 30s, then 3A for 30s, 3.8A for 30s, then back to 2A and leave it at 2 A (use local power supply).
Preparation of
cathode activation
25. Setup pickup-device
- Install
laser and warm it up
- Roll
in activation cart with chart recorder, Keithley ammeter, and variable voltage
battery box.
- Connect
battery box to keithley ammeter and prep chamber (positive bias to electron collector
ring).
- Connect
keithley ammeter output to charter recorder
- Connect
ion pump current monitoring output to handheld digital multimeter
26. Cool down
- Turn
Variac off
- Turn
up N2 purge to max (50 SCFM)
- Fill
LN2 bucket to further cool N2
- Take
data at 600c, 400c, and 200c.
- At
400c, lower heat shield enough for cathode to move in
- Move
cathode in to cesiate position
- Remove
LN2 at 135c, and cool it down to 300c.
Cathode activation
27. Start 1st cesiation
- Turn
on both lamp and diode laser
- At
300c, bring up cesiator current to 3.7A
- Turn
on Keithley ammeter and chart recorder to record photocurrent
- When
photocurrent generated from laser is observed, turn off the lamp and cover view
ports.
- When
photocurrent starts to roll over, add NF3 and photocurrent should go up.
- Monitor
the vacuum pressure by watching the ion pump current (via handheld digital
multimeter).
- Increase
NF3 flow when photocurrent starts to roll over, repeatedly increase NF3 flow
until photocurrent cannot be increased further. Note that the handheld digital
multimeter reading, which represents ion pump current, should not exceed 60 mV.
- Write
down photocurrent on chart
- Close
NF3
- Turn
off cesiator
28. 1st activation is finished; 2nd activation can’t start until vacuum is recovered. Repeat the procedure.
29. Finish all activations
- Remove
transformer, chart recorder, diode laser
- Uncover ports
- Open valves to gun
- Move cathode into gun
Close up the clam shell and gas vessel
30. Undo cathode retraction
- Attach emitter-tube bellow
support
- Remove heater
- Switch local ion-pump power
supply to optically powered supply
- Install support on elevator
bellow and remove screw drive
- Remove load lock strongback
support
31. Close up the clam shell
32. Close up the gas vessel
33. Hook up gas lines on the top and bottom of gas (SF6) vessel