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 1st try) without these heaters
– Currently, system is stable and producing good tiles

A major maintenance period is coming up soon
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–
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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
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
---
Since
9/1/14
Since
9/8/14
---
(cracked)
Since
Since
9/17/14 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
Remarks: system availability

Tile #20 was started on 7/24, and tile #29 will finish on 9/29
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–
–
–
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
Tile #27
MCP: GEN I, reused from tile #21
produced on 9/17/2014
7
8
9
10
11
Test results of recent tiles
Tile #28
MCP: GEN II (latest, high gain)
produced on 9/24/2014
12
13
QE measurement
Tile 22
Special tile for QE measurement
Produced on 08/08/2014
14
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
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Schedule


System is currently processing tile #29 and #30
Scenario I
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–
–
–

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