1 sasha milov dc meeting... march 7, 2007 hbd status sasha milov march 7, 2007

1Sasha Milov DC meeting... March 7, 2007

HBD statusHBD status

Sasha Milov

March 7, 2007


Detector statusDetector status All gems in all modules were tested individually with external power supply.

54 out of 72 GEMs were found problematic.most GEMs have 1 or 2 problems.this is ~60% more then 2monts agothere are more problems on West then on the East. two modules on the West have more severe problems and are likely not recoverable. most problems are curable on expense of loosing ~3.5% of single module area per problem.

Rest of the detector was brought to 3600V (~1/3 of operational gain) and several to 3720V (full gain). We saw cosmic signals from more than one module

We found the reason and fixture to the most severe problem hitting us for long time: the massive trips on the detector


Detector gain snapshot:Detector gain snapshot:


Massive trip solutionMassive trip solution We found a problem in the voltage divider not adequately responding to the LeCroy trips. That would cause a detector to spark Spark produces enough light to cause modules at HV to trip We fixed 3 modules yesterday and ran a conclusive test.

not at full Vdidn’t triptrippedinduced trip

When we induced trip in fixed modules there was no follow up, except ES0ES1, but ES1 is one with high current. When we did in unfixed modules there was 100% follow up, or none except EN5. When we induced trip in both fixed and unfixed modules in a different way, such that a spark occurs, we saw 100% follow up.

Right now Mike Lenz is fixing all modules on both HBDs

es en

0 1

2 3

4 5


• Peripheral events (60-100%)

– An alternate of p+p collisions• Many basic features can be checked• Single particle efficiency can be used

(no embedding is needed)

– Run4 data: ~250Mevts out of 700Mevts(MB)

• ~100-200 phi’s in PHENIX acceptance

– If we have fake pair rejection of ~100, We can see the peak at ~25Mevts out of 70Mevts.

– We may want to have 2-3 times of it as an initial check?

Peripheral event filteringPeripheral event filtering


cell1-input to HBD

ce

ll/m

on

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ell'

/mo

n'

0.4

0.6

0.8

1.0

1.2

fri pm / fri am (vacuum)fri pm / fri am (HBD CF4) - 30 min after switchfri pm' / fri am (HBD CF4) - 2.5h after switchmon am / fri am (HBD CF4)mon pm / fri am (HBD CF4)

cell2- West HBD output

ce

ll/m

on

/ c

ell'

/mo

n'

0.4

0.6

0.8

1.0

1.2

cell3- East HBD output

wavelength (nm)

120 130 140 150 160 170 180

ce

ll/m

on

/ c

ell'

/mo

n'

0.4

0.6

0.8

1.0

1.2

CF4 Scans from HBD Gas Transparency Monitor. 3/02/07

1.2

1.9 2.52.0

2.2

2.0

2.20.4

~20%Loss

~23%Loss

2.0slpm 3.5slpm

30-40% 20% in photon loss

27pe 31pe in primary electron statistics

CF4 IN

HBD W

HBD E

Input Gas is flat as always

Transmittance @ 3slpmTransmittance @ 3slpm


Next steps.Next steps. Fix modules and continue conditioning to full operational voltage

Do one more gem-by-gem test to adjust currents in modules where they are different from nominal by more then 0.3%.

We expect that after fixing the trip problem detector will be not only more stable but will significantly slow deterioration.

Start look at cosmic and noise at full HV (was very good so far).

Continue work on monitoring.

If we do not bump in more problems, the detector has a good chance (full East and most of West) to be in working condition when the beam comes.


BACKUPSBACKUPS


Divider again…Divider again…


Floating MeshFloating Mesh

MT only happen between the two modules sitting at high enough voltage? our killer question from Friday studies (!)

MT are confined to one arm, and have no other patterns

Prototype was more stable, then real detector

More short problems in top GEMs

Two modules with mesh-gem shorts

0.0s 0.1s 0.2s 0.3s 0.4s 0.5s 0.6s 0.7s 0.8s 0.9s 1.0s-3.6KV

-3.3KV

-3.0KV

-2.7KV

-2.4KV

-2.1KV

-1.8KV

-1.5KV

-1.2KV

-0.9KV

-0.6KV

-0.3KV

0.0KVV(n014) V(n020)


SolutionsSolutions

1 sasha milov dc meeting... march 7, 2007 hbd status sasha milov march 7, 2007

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