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– 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

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Functional tiles produced so far

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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 1-2days

1-2days

4 days(cracked)

--- Since 9/1/14

Since9/8/14

--- 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)

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

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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

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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

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Test results of recent tiles

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Tile #27

MCP: GEN I, reused from tile #21produced on 9/17/2014

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10

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Test results of recent tiles

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Tile #28

MCP: GEN II (latest, high gain)produced on 9/24/2014

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QE measurement

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Tile 22Special tile for QE measurementProduced on 08/08/2014

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QE uniformity

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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

– 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)

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