Accelerator Handbook

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====== Cesium Sputter Source Target Change ======
===== (Revised 4/15/2009; Rev. 17 Aug 2011; Rev. 26 April 2016) =====


   - Obtain proper target.  Wear clean gloves when handling target and target holder. Determine if target is new or used. Used will have a blackened and scared tip.
   - Turn off DEL HIGH VOLTAGE POWER SUPPLY  (Main Extractor Power) 
   - Record present value and decrease Cesium Reservoir Current by 50%, usually to about 0.125 amp.
   - Decrease Ionizer Current by 50%, to ~11 amp.
   - Decrease Target Voltage to zero.
   - Decrease Extractor Voltage to zero.
   - At gate in vault, open gate - the orange lights on the Glassman supplies should go off.  If not, stop and get help.
   - Hang large ground hook at red arrow on power platform.
   - At the source, hang small ground hook on the target plane of source head.
   - Close gate valve between source and inflection magnet. Controller on source base below gate valve.
   - Check that the source box Ion gauge is on and controller display can be seen from the source head area.  You will need to see the pressure in the source box during later steps.  You may have to rotate the controller to see it from the source.
   - In the steps 13 through 16, if source pressure increases to 2x10E-6, you are leaking too much and should tighten the silver O-ring collar.
   - Back off BRASS target positioner and set it aside. 
   - Remove the red banana plug (white wire) from the end of the target holder.
   - Slowly pull back target holder until it clears the hand gate valve on the source, the target can be seen thru the clear plastic ring.  Source pressure may rise to mid 10E-6 pressure during this step, this is OK.
   - Close hand gate valve by pushing down on the black knob firmly.  You should hear or feel a click at the bottom of the motion.
   - Open the small green roughing valve (on plastic hose) at the target air lock to vent the target area. 
   - (Wear gloves) Loosen the silver O-ring collar and slowly remove target holder. 
   - (Wear gloves) Remove the used target.  Wrap the used pellet in a small Kimwipe and store in appropriate container.
   - (wear gloves) Install new target; thread on finger tight (Al foil is no longer used). 
   - Re-insert target holder and tighten the silver O-ring collar snugly (by hand only).
   - Close the small valve labeled “VENT” on the roughing line on the left side of the source.  
   - Open the other small valve labeled “VAC’M” in the same area.  
   - Watching the TC gauge on top of the source, rough on the target air lock until the vacuum falls back to <30 microns (a couple minutes).  Source vacuum should fall back to 10E-7 once roughing starts.
   - Close the small green valve at the target air lock 
   - Watch the ION GAGE DISPLAY FOR NEXT STEP.
   - SLOWLY open hand gate value.   Vacuum will rise and then should quickly return to <10E-7 range. 
   - Hold the brass positioner in place on its bracket and allow the assembly to slide forward. Begin threading the brass positioner when it contacts the rod and stop when it reaches the jam nuts.   It does not have to be tight.
   - Reattach red banana plug (white wire) on target holder.
   - Pressure may rise slightly as the pellet heats up.
   - Re-tighten the silver O-ring collar by hand.
   - Close the small valve labeled “VAC’M” on the left side of the source.  
   - Open the small valve labeled “VENT”  to vent the roughing line.
   - Remove the small ground hook from the source head.
   - Open gate valve between source and inflection magnet.
   - Remove large ground hook from power platform and close both gates.  The orange lights on Glassman power supplies should light up, if not, try pushing the boost button on the wall.   If this still does not make the lights come on, wait a few minutes and try again (leave gate open while waiting to let the actuator cool).
   - Press the doorbell button on top the Pelletron AC Power Center. The Extractor and Target Glassman supplies should indicate Voltage Control with red lights.
   - In control room, turn on Del Main Extractor supply to the previous value.
   - Return ionizer to 21 A.
   - Slowly raise the extractor voltage to 12.5 KV.  If you see twitching in the voltage or current meters, stop at that point and wait a few minutes for stability before going higher, until extractor is at 12.5 KV. The twitching will most likely happen if the target pellet was previously used.
   - Slowly raise the target voltage to 6.5 KV.  If you see twitching in the voltage or current meters, stop at that point and wait a few minutes for stability before going higher, until target is at 6.5 KV.  The twitching will most likely happen if the target pellet was previously used.
   - Return the Cesium reservoir to the previous value.

====  Two hours should produce beam with a previously used pellet.   New pellets may take longer. ====
Accelerator Handbook

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