LAPPD System Status Report Summary

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LAPPD status report
 
6cm system status
 
System up and running  since July
Temperature profile carefully mapped out in sealing and deposition chambers
Vacuum of major chambers are routinely maintained at 10
-9
 – 10
-10
 torr
System routinely produce test/functional devices
Heater issues
1 (out of two) sealing chamber ceramic heater broke: 1 current lead broke off, which is
a know issue with this type of heater
1 (out of two) deposition halogen lamp heater have a back contact after replacing the
light bulbs
Decided to try continue without repairing any of them
Quickly found out running condition (on the 1
st
 try) without these heaters
Currently, system is stable and producing good tiles
A major maintenance period is coming up soon
Install heaters in bake and scrub chamber
Replace sealing chamber ceramic heaters with halogen lamp heaters
Replace contact for deposition heaters
All parts are ready, waiting for system down time
 
2
 
Functional tiles produced so far
 
3
 
Notes:
#22 and #26 are special tiles for QE measurements, with no MCPs in them
#24 and #25 didn’t produce signal at reasonable HV, due to  MCP resistance drop after
     bake (known early GEN I MCP issue), but the seals are good and the photocathodes
     remain light brown up to now (originally thought the seals were bad)
 
Remarks: system availability
 
Tile #20 was started on 7/24, and tile #29 will finish on 9/29
In ~10 weeks we produced 10 tiles with the 6cm system
Only had minor repair/maintenance/bake out, that took ~ 1 week in total
System is available for tile production ~90% of the time
Tile processing time is ~ 1 week
 
4
 
Remarks: sealing
 
In the last 2.5 months, sealed 15 tiles (5 sealing tests + 10 functional tiles)
Other than 5 cracks, all seals are successful
All cracks are understood
3 early ones cracked 1 – 4 days after a good seal was formed: changed fixture
#23 was due to a concaved tile base
#26 top window was accidentally hit by the sealing block too hard
Sealing process is well understood, and carried out with high yield
 
5
 
Remarks: getter activation
 
Found one condition that can activated getter reasonably well (produced tiles with
extended lifetime)
Initially bake/activation at high temperature, but was not successful (1-2 days lifetime)
Switched to low T bake + high T activation, so far successful
Configured separate vacuum system to optimize getter activation
Measure MCP, frit out gas rate
Measure getter pumping speed, capacity under different activation conditions
System is currently ready, we are preparing test samples
 
6
 
Test results of recent tiles
 
7
 
Tile #27
 
 
MCP: GEN I, reused from tile #21
 
produced on 9/17/2014
 
 
 
8
 
 
 
9
 
 
 
 
10
 
 
 
 
11
 
Test results of recent tiles
 
12
 
Tile #28
 
 
MCP: 
GEN II (latest, high gain)
 
produced on 9/24/2014
 
 
 
13
 
QE measurement
 
14
 
Tile 22
 
Special tile for QE measurement
 
Produced on 08/08/2014
 
 
15
 
QE uniformity
 
16
 
QE of tile #28
 
A new method is being developed, in order to estimate QE of functioning tiles
QE is estimated by comparing to a commercial MCP-PMT with known QE
Close to single photon laser pulses are used to illuminate both devices
Tile #28 has QE ~11% (with large uncertainty), which agree with in situ measurement
 
17
 
Schedule
 
System is currently processing tile #29 and #30
Scenario I
Stop tile production after tile #30
Start maintenance period as originally planned
Expect better system performance after maintenance
But down time could be longer than expected, and it also takes time to figure out new
working condition
Scenario II
Continue tile production until having good number of working tiles in hand (or
something significant on the system breaks)
Postpone maintenance period for several weeks
Might be able to secure enough working tiles for testing at early stage
Still need to check part availability for scenario II
Will discuss run plan next Monday (9/29)
 
18
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The LAPPD system has been up and running smoothly since July, with carefully mapped temperature profiles and maintained vacuum levels. Despite minor issues with heaters, the system is stable and producing functional tiles. Maintenance plans include heater replacements and chamber installations. The system has produced functional tiles with varying seal qualities and MCP performances. Repairs and maintenance have been minimal, with the system available for production 90% of the time. Sealing processes have been successful, with a few understood cracks due to specific reasons.


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  1. LAPPD status report

  2. 6cm system status System up and running since July Temperature profile carefully mapped out in sealing and deposition chambers Vacuum of major chambers are routinely maintained at 10-9 10-10torr System routinely produce test/functional devices Heater issues 1 (out of two) sealing chamber ceramic heater broke: 1 current lead broke off, which is a know issue with this type of heater 1 (out of two) deposition halogen lamp heater have a back contact after replacing the light bulbs Decided to try continue without repairing any of them Quickly found out running condition (on the 1sttry) without these heaters Currently, system is stable and producing good tiles A major maintenance period is coming up soon Install heaters in bake and scrub chamber Replace sealing chamber ceramic heaters with halogen lamp heaters Replace contact for deposition heaters All parts are ready, waiting for system down time 2

  3. Functional tiles produced so far Serial # 20 21 22 23 24 25 26 27 28 Seal Good Good Good/ Cracked Cracked Good Good Cracked Good Good MCP Gen I Gen I (none) --- Gen I (bad) Gen I (bad) (none) Gen I Gen II Getter Bad Bad Better --- Good Good --- Good Good lifetime 1-2 days 1-2 days 4 days (cracked) --- Since 9/1/14 Since 9/8/14 --- Since 9/17/14 Since 9/24/14 Notes: #22 and #26 are special tiles for QE measurements, with no MCPs in them #24 and #25 didn t produce signal at reasonable HV, due to MCP resistance drop after bake (known early GEN I MCP issue), but the seals are good and the photocathodes remain light brown up to now (originally thought the seals were bad) 3

  4. Remarks: system availability Tile #20 was started on 7/24, and tile #29 will finish on 9/29 In ~10 weeks we produced 10 tiles with the 6cm system Only had minor repair/maintenance/bake out, that took ~ 1 week in total System is available for tile production ~90% of the time Tile processing time is ~ 1 week 4

  5. Remarks: sealing In the last 2.5 months, sealed 15 tiles (5 sealing tests + 10 functional tiles) Other than 5 cracks, all seals are successful All cracks are understood 3 early ones cracked 1 4 days after a good seal was formed: changed fixture #23 was due to a concaved tile base #26 top window was accidentally hit by the sealing block too hard Sealing process is well understood, and carried out with high yield 5

  6. Remarks: getter activation Found one condition that can activated getter reasonably well (produced tiles with extended lifetime) Initially bake/activation at high temperature, but was not successful (1-2 days lifetime) Switched to low T bake + high T activation, so far successful Configured separate vacuum system to optimize getter activation Measure MCP, frit out gas rate Measure getter pumping speed, capacity under different activation conditions System is currently ready, we are preparing test samples 6

  7. Test results of recent tiles Tile #27 MCP: GEN I, reused from tile #21 produced on 9/17/2014 7

  8. 8

  9. 9

  10. 10

  11. 11

  12. Test results of recent tiles Tile #28 MCP: GEN II (latest, high gain) produced on 9/24/2014 12

  13. 13

  14. QE measurement Tile 22 Special tile for QE measurement Produced on 08/08/2014 14

  15. 15

  16. QE uniformity 16

  17. QE of tile #28 A new method is being developed, in order to estimate QE of functioning tiles QE is estimated by comparing to a commercial MCP-PMT with known QE Close to single photon laser pulses are used to illuminate both devices Tile #28 has QE ~11% (with large uncertainty), which agree with in situ measurement 17

  18. Schedule System is currently processing tile #29 and #30 Scenario I Stop tile production after tile #30 Start maintenance period as originally planned Expect better system performance after maintenance But down time could be longer than expected, and it also takes time to figure out new working condition Scenario II Continue tile production until having good number of working tiles in hand (or something significant on the system breaks) Postpone maintenance period for several weeks Might be able to secure enough working tiles for testing at early stage Still need to check part availability for scenario II Will discuss run plan next Monday (9/29) 18

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