# Presentation: 559257

## HBD upgrade status.

**HBD upgrade status.**

***Sasha Milov***
***Nov 09, 2005***

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Progress:

** ****Photocathode production and measurement**
** ****Glove Box modification**
** ****GEMs testing**
** ****Electronics status**
** ****LEGS beam test**

**Progress:**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Mechanical assembly.

** ****Some delays of order of a week were experienced in production of ... **
** ****Not critical for the current scheduler. **
** ****A modification to eliminate divider boxes is considered.**
** ****Allows to reduce material close to the active volume  **
** ****Reduces number of cables from 7 to 2 per module**
** ****Reduces mechanical stress on the box**
** ****Does not cause any delay **
** ****Target day to complete the mechanical part of the cage is Dec,XX 2005**

**Mechanical assembly.**

**Itzhak, please verify**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Photocathodes.

** ****vacuum down to 8E-8 mbarr**
** ****capable to produce 4 full size at a time**
** ****Q.E. control works inside the vessel**
** ****Residual Gas Analyzer works inside the vessel**
** ****Produced several 10x10 cm****2 ****photocathodes on GEMs (previously used and washed, but fully operational) **

**Photocathodes.**

** ****Q.E. of the photocathodes is as in the proposal (as good as it can be) controlled at SUNYSB and measured at BNL**
** **_**This is a major milestone, we were trying to achieve since a while. Now we have it!**_

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Glove Box modification.

** ****Possible choice of playgrounds for the main assembly can be:**
** ****INFN Glove Box, currently at SUNYSB, which would require upgrade for much less money well within MRI available budget. It would not provide all luxury we expected and may require changing in the assembly procedure. A reasonable one.**
** ****A new glove box from a company for less money and with less options.**
** ****Company representatives (first of them) visited SUNYSB yesterday to meet Tom and Rich. A decision is likely to be know by the end of the week.**
** ****Glove Box will require attention in next several weeks, but it will be on time for the main assembly.**

**Glove Box modification.**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## GEM testing.

*** *****First 18 GEM foils arrived at the WIS. 16 were successfully framed.**
** ****one had low resistance in one sector, one was damaged in operation**
** ****6 frames were soldered with resistors.**
** ****6 were successful, 1 failed HV test, 9 were not yet soldered**
** ****2 stack of 3 GEMs were tested with ****55****Fe in CF****4 ****for uniformity. Results are worse than reported by COMPASS.**
** ****50% gain variation is seen in both**
** ****expected 25% or less**
** ****investigation in on its way**

**GEM testing.**

*** *****Test box, the same as used at WIS was shipped to SUNYSB this week.**
** ****It will be used here to test GEMs after evaporation**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Electronics status.

** ****It is currently is used by Chi at NEVIS.**
** ****More boards are expected by the end of the week, worst case early next week. They will be tested a.s.a.p.**
** ****No more results on that. Electronics remains critical item for HBD.**

**Electronics status.**

*** *****Backplane will be separate PCB (not a part of HBD panel) that doesn’t cost too much in the radiation length, but allows a lot of flexibility both in time and in design.**
** ****First prototype was produced. It had too much Cu deposited on it. Bo Yu was contacted to look into that. **

**FEM**

**FEE**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## LEGS beam test.

** ****We have new (old cleaned and re-evaporated) GEM with very good photocathode (see plot above) and a stack of 3 GEMs in the vessel ready to go.**
** ****The prototype to be installed in LEGS this weekend and put under gas flow.**
** ****We might be given beam time on Monday.**
** ****Unfortunately the NSLS magnet which was recently repaired was not yet powered on.  In case it fails our time will be revoked.**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Summary:

** ****Very good news from INFN evaporator, best Q.E. curve in vacuum was reached. Some issues remain with that in CF****4****. Is under study now.**
** ****Glove Box price is way above what we can spend. A modification of INFN box is considered with a new box of lower parameters as an alternative.**
** ****GEMs testing started with the first bunch of CERN GEMs. Gas gain non-uniformity was observed. The reason is investigated**
** ****Electronics remains critical**
** ****LEGS beam test may happen next week.**

**Summary:**

- Sasha Milov                    DC meeting                  Nov 9, 2005

## BACKUPS

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Cathode Production Parameters

- CsI Source:
- INFN group uses “pre-melted” full boats.
- Changed to “broken crystal” chunks (ala D. Anderson)
- Heating:
- System uses heating of vacuum vessel to eventually heat the cathode (60o C).
- Cylinder heated, not Nose.
- New procedure:
- Bake during pump down (heats all including cathode)
- Turn off external heat prior to shot.
- Cathode remains hot longer...shoot!
- Vacuum Quality:
- Run the residual gas analyzer DURING shot.
- If “puff” of contamination seen during boat heat-up...wait.
- Vacuum Value:
- 8x10-7 mbar (1 mbar = 0.76 torr) at shot.
- After weekend... 8x10-8 mbar!! (NOTE:  CsI on walls helps)

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Residual Gas Analyzer Observations:

- The vacuum has been mostly water!!!
- Initially a surprise since the cryo pumps water MUCH faster than N2 or O2 (other major components).
- Assumption:  Walls are a source of water.
- Only cylinder region heated (not rectangular nose)
- Test:  Leave pump going for the weekend monitor RGA
- BINGO: Overnight Friday water dropped by 3 orders!!
- Present vacuum is mostly H2 (8x10-8 mbar)
- All present shots done PRIOR to complete elimination of water.
- Good vacuum means little water even when its mostly water.
- We can only improve from previous shots.
- We KNOW at all times our exact status (driving a Cadillac)

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Cathode History

- SS:
- Old CsI + air exposure (mis-wired of QE device).
- Bad.
- GEM:
- Old CsI/no air exposure.
- Bad (local system and Bob).
- SS:
- New CsI, no air, good vacuum (unknown composition).
- Good (local only).
- GEM: (pictures are from here)
- New CsI, no air, good vacuum, mostly water.
- Good (local and Bob).
- GEM:
- New CsI, no air, good vacuum, mostly water.
- Good (local...send to Bob soon)

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Latest result

- Causes for celebration:
- Equally as good as Amos Breskin.
- Equal to assumptions for successful GEM.
- Reproducible.
- Shot onto GEM.
- GEM was cleaned and held voltage prior to shot.
- Vacuum value and quality have only improved since this result!

- I told you so!

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Worries about QE are over...now what?

- How do we MAINTAIN the good QE?
- Minor transfer box improvements:
- Presently gravity-driven Ar fill (2” hole).
- Replace hole with electrical feedthrough.
- No cadillac for the glove box:
- Bids came in $100,000 – $200,000.
- Budget $40,000
- How to survive w/ lesser quality Glove Box?
- DUH!!!  Vacuum is MUCH better than any Glove Box!
- Change procedure to minimize the exposure of cathodes to Glove Box air.
- “Upgrade” INFN Glove box to make it good enough.

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Procedural Modifications:

- Old procedure:
- New cathodeGB;  Cathode rejoins full stack; Gain test in GB; Stack  HBD....repeat...
- Multiple openings w/ cathodes already on HBD.
- Air Lock...excellent atmosphere ALWAYS required.
- New procedure:
- New cathodeGB; Cathode rejoins full stack;  Gain test in GB; Stack  HIGH VACUUM STORAGE (HVS)
- When vacuum storage is full, all GEMSHBD in a single short term operation.
- Maybe don’t need airlock?
- INFN Box begins to look attractive.
- How to implement:
- Use fraction of original GB money to make HVS.
- Work on INFN Glove Box to make it good enough.

- Sasha Milov                    DC meeting                  Nov 9, 2005

## INFN Glove Box

- IT STINKS (quite literally).
- Latex gloves...overpowering smell when opened.
- Butyl or Hypalon material ($200/pair...16 pairs).
- Re-pressurizing Dewar
- Special LN2 dewar uses internal bubbling regulator to maintain head pressure ~150 psi.
- One fill lasts ~1 week.
- Large Oxysorb canister...excellent gas supply.
- ROUGH measurement = 30-40 ppm water after weekend (with latex gloves).
- Want to borrow better water/oxygen meters...

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Summary

- The required QE is achieved and almost certainly reproducible.
- The QE achievement era is over.
- The QE maintenance era begins.
- We can lessen requirements on GB by changing procedure:
- Use high vacuum storage of GEMS.
- Assemble GEMS into HBD as single task.
- We can redirect some original GB funds to:
- Establish high vacuum storage facility.
- Upgrade INFN glove box.

- Sasha Milov                    DC meeting                  Nov 9, 2005

## The procedure

- The first step of the test is done before framing checking each HV segment of the foil. This step passed 17 out of 18 foils.
- The second step is testing HV segments after framing. This step passed 16 out of 17 foils, one GEM was damaged.
- The third step is again testing each HV segment after soldering SMD resistors. This step passed 6 out of 7 foils.
- The last step is testing the assembled module (triple GEM detector) in the SS vessel in CF4 with nominal voltage and measuring the signal on each of 56 pads. So far we tested two modules.
- Since the two tested modules showed a big gain variations (see next slide) we paused the production in order to investigate the possible reason (s) for it.

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Gain measurements

- Gain was measured on two modules on all 56 pads.
- The gain variations are quite large (~2 from min to max).
- Does not seem to be a mounting problem.
- We will measure the holes diameter under microscope. The gain strongly depends on the metal hole diameter.
- We will measure the gain variations on the single GEM in Ar/CO2 using collimated source.

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Q.E. in CF4

- Q.E. in CF4

- Sasha Milov                    DC meeting                  Nov 9, 2005

## Q.E. in CF4

- Q.E. in CF4

- Sasha Milov                    DC meeting                  Nov 9, 2005