1 sasha milov dc meeting nov 9, 2005 hbd upgrade status. sasha milov nov 09, 2005

1Sasha Milov DC meeting Nov 9, 2005

HBD upgrade status.HBD upgrade status.

Sasha Milov

Nov 09, 2005


Mechanical assembly

Photocathode production and measurement

Glove Box modification

GEMs testing

Electronics status

LEGS beam test

Progress:Progress:


Mechanical assembly is on its way.

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.Mechanical assembly.Itzhak, please verify


INFN evaporator from JLab is at SUNYSB 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 cm2 photocathodes on GEMs (previously used and washed, but fully operational)

Photocathodes.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!


Glove Box bids came out “slightly” (x2.5-x5) higher than originally planned. These options are not considered.

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.Glove Box modification.


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 55Fe in CF4 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.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


Out of 5 boards required for HBD 1 came out of production.

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.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


LEGS beam test.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.


Mechanical assembly is on its way and is likely to be finished on time.

Very good news from INFN evaporator, best Q.E. curve in vacuum was reached. Some issues remain with that in CF4. 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:Summary:


BACKUPSBACKUPS


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)


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)


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)


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!


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.


Procedural Modifications:

• Old procedure:– New cathodeGB; 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 cathodeGB; Cathode rejoins full stack; Gain test in GB; Stack

HIGH VACUUM STORAGE (HVS)– When vacuum storage is full, all GEMSHBD 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.


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…


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.


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.


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.


Q.E. in CF4

1 sasha milov dc meeting nov 9, 2005 hbd upgrade status. sasha milov nov 09, 2005

Documents

sasha milov dc meeting

test box

infn glove box

glove box bids

new glove box

main assembly

evaporation slide

assembly procedure