Future Work: LAPPD 6cm system and device Lei Xia

Work items for the 6cm system and device  “Maintenance period” for 6cm system  Baking and scrubbing studies  Development of new tile design  Other tests/studies 2

Maintenance period: overview  The current 6cm system is actively producing tiles, but has some issues –Bake/scrub chamber heater is completely mission Currently bake/getter activation done in deposition chamber Not a great idea to keep deposition chamber clean LTA (with activated getter) need to sit in sealing chamber for ~24hrs, waiting for cathode –Current sealing heater is the last ceramic heater we have, can break at any time This type of ceramic heater has a very weak contact lead, which break off very easily We designed strain relief mechanism to avoid pulling off lead, but it still happens –Deposition heater got a bad contact on one of the halogen lamp Contact will be disconnected at high temperature Both lamps only works constantly at low power (OK for low temperature bake) But only work for short time at high power (limit the possibilities for high temperature bake) Have a modified top window fixture, but don’t have temperature measurement for it  We plan to address all the above issues during maintenance period –We are currently processing tile #33 in the system, which will be done on 10/24 –Starting Monday, 10/27, we will start the maintenance period –Work should be done < 1 month 2 weeks installation/testing + 1 week baking + 1 week contingency 3

Maintenance period: bake/scrub chamber  New Tungsten Filament Heater in hand for the bake/scrub chamber –Tested by vender to be able to heat up LTA to 400 C –New copper LTA fixture machined and cleaned –All other parts ready –Heater partially assembled and ready to go in  Testing –Need to map out heater temperature as a function of input power –Need to carefully map out the relationship between heater temperature and LTA/getter temperature 4 Tungsten Filament Heater Lower Tile Assembly

Maintenance period: deposition chamber  Fixing deposition chamber heater –New heater contacts machined with more heat resistant material –Taking out/installing heater is not easy, but we’ve done it several times –Effusion cells will be re-charged –Inner walls of the chamber will be cleaned  Testing –Heaters will be tested with high power for 24+ hrs –Need to re-map the platen temperature as a function of heater power –Need to re-map the relationship between platen temperature and LTA/getter temperature –Need to re-map the relationship between platen temperature and top window temperature, with different top window fixtures 5

Maintenance period: sealing chamber  Replacing sealing heater –Take out the current ceramic heaters and strain relief parts –Install new halogen lamp heaters with light shade –All parts are in hand and cleaned  Testing –Need to re-map the lower/upper platen temperature as a function of heater power –Probably don’t need to re-map relationship between lower/upper platen temperature and Indium seal temperature –Sealing test 6 Current ceramic heater Halogen lamp heater to be installed

Maintenance period: re-commissioning system  Test part transfers throughout the system  Check part alignment, especially in the sealing chamber  Perform sealing tests  System bake out 7

Baking/getter activation studies  The balance between getter activation and capacity preservation seems to be the key issue here –Getter have to be baked together with MCPs, which outgas a lot at high temperature –Some capacity lost is unavoidable, but need to stop baking as soon as activation is done  Current low-high bake scheme seems promising –Will continue to try along this line and explore the optimal activation condition –New heaters will provide new ways to try things out  At the same time, we will do a series of measurements, and provide guideline to optimize the baking / getter activation –System was used for out-gas measurement –Modified to do getter activation studies 8

Scrubbing studies  Electron gun coverage, uniformity study –Could be studied by loading a small phosphor screen into the scrubbing chamber –Would like to do it some time after the maintenance period  MCP gain study –Requires connection to the top of MCP/spacer stack –Need some modification to the current scrubbing system –Not clear how/when we are going to do it  Hope to get some advice on how to proceed 9

Beside thinking of how to produce functional devices Since we do make them It is time to start thinking of what kind of devices we want to make now! 10

Development of new tile design (I)  Pros of current ‘resister chain’ design –No electrical contact that goes through the glass package is needed –Only a single HV needed to operate the device  Cons of current design –The two MCPs need to have matching resistance at ~10% level –All grid spacers need to have resistive coating (which can NOT be precisely controlled) –Grid spacer resistance need to match that of the MCPs to 20-50% level –Can’t vary voltage between cathode/MCP/anode –Can’t measure Q.E. of photocathode  Start thinking of a new design that can individually control MCP potentials –Bringing electrical contact into the tile should not be a problem: the existing silver strips on anode plate pass through the frit on tile base without any problem –Difficulty would be an electrical connection from the silver strips to, for example, a metal shim that sits in the MCP stack and touches the MCP surface –Any suggestion/advice would be really appreciated 11

Development of new tile design (II)  For many applications, a pad readout is preferred than strip readout –Had a discussion recently on how to implement pad readout on LAPPD device  Idea 1: resistive coating on anode plate inside tile, pad readout capacitive coupled on the outside of the LAPPD device –No technical barrier foreseen –Might be the quickest/easiest way to implement pad readout –Unavoidable rate limitation, due to resistive coating (maybe not too bad to start with)  Idea 2: pads on ceramic anode plate with through going via’s –Main concern is technical feasibility –Cost is another concern  Idea 3: pads on silicon with integrated readout system –Main concern is the tile processing temperature (but might have a chance)  Any new ideas? Suggestions? Advices? 12

What are the key features of the device, that we should optimize?  Time resolution  Position resolution  Photocathode Q.E.  Overall acceptance of the device  …  Are our current tests sufficient? What are we missing?  It is very important to get feedback from users (next talk)  Again, Suggestions? 13 Device design Processing condition Operating condition

Summary  We are now at an exciting time, as the first functional tiles are being produced  6cm tile production system will continue to improve  We will optimize the processing procedure, and hopefully in the near future, tile production becomes a routine work with high yield  Looking into the future, things will be even more exciting: we are entering a new phase to develop better detectors –New tile design –Pad readout –Performance optimization –… 14