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