Transcript Slides - Indico

Testing GEM foils
A. Cardini / INFN Cagliari
Cagliari, May 5th, 2006
The Procedure
• GEM foils are produced at CERN EST/DEM Atelier by Rui de
Oliveira
• The delivery of 20-30 GEM foils takes place approximately
once per month
• GEM foils are electrically tested by us before leaving the
production atelier
• The GEM foils are then taken to an optical microscope
facility located in a clean room to perform a visual inspection
• Rejection criteria are defined in agreement with Rui de
Oliveira
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
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The Electrical Test
•
It is performed in a clean room with controlled temperature (~20-23
Celsius) and humidity (30%-40% R.H.)
•
GEMs are supplied at 500V by means of a CAEN NIM 2 channels HV
Power Supply through a 100 MW protection resistor
•
Each sector is tested and the leakage current measured on the module
should not exceed 1-2 nA
•
Good GEM foils should have small (< 5nA, but this limit depends very
strongly on humidity) sector leakage current. The asymptotic current
value should be reached in a short time (<10 sec). Leakage currents on the
sectors should be uniform. No important sparking should be found.
•
Bad GEM foils have non-constant current, non-uniform leakage current on
sectors, large sparking rate, …
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
3
The Visual Inspection
•
The foils are at first observed by eye
under a uniform illumination
– Find non-uniformities of hole sizes on
the GEM area
– Find small defects (a single non-etched
hole is visible!)
•
Defects are then observed at the
optical microscope and a picture is
taken
•
A general picture of the GEM area
(under small magnification) is also
kept for reference
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
4
Some mechanical defects…
All these GEM foils have obviously been rejected
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
5
The GEM Production Today
Batch # GEM
ok
1st
choice
2nd
choice
1
30
0
0
0
2
9
6
4
2
3
12
12
11
1
4
24
21
15
6
5
30
27
24
3
6
21
15
11
4
Total
126
81
65
16
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
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Conclusion
• We have established a very detailed and careful
procedure to test GEM foils after the production
• A strong effort was done in order to be able to
perform the test directly at CERN (some GEM can
be “repaired” immediately by Rui de Oliveira)
• A detailed report on the test is written after each
GEM delivery to keep track of every single GEM
foil installed in our detectors
Cagliari, 05-May-2006
A. Cardini / INFN Cagliari
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