Transcript transparencies - Indico

HV tests, leak test,uniformity test
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HV training of anode planes
Uniformity chamber test
High radiation test
Chamber leak test
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HV tests
•HV anode plane test is a preassembling test. Test preparation
includes visual inspection, check of the integrity, the
presence of the capacitors and resistors…
•Test is being done with the wire plane without the second
(upper) cathode in dry air (hum <40%) or in a closed box
filled with dry air
( or CO2)
•HV is being applied gradually in a range 2-3.3 kV with steps
100, 50 V. Plane cleaning (ionized nitrogen, alcohol) is
foreseen. To localize the dirty pad (wire strip) the
measurements of the voltage drops or signals from scope can
be used.
•Adoptable dark current limit is ~20 nA at max voltage. The
plane is being kept at max voltage one hours to see current
behavior and provoke sparking. The current limitation should
be set to 200 nA per plane in order to not damage the wire.
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HV tests
Test example. The planes have 1.5 mm pitch and area 560 cm2
2 mm pitch plane training
18.10.02
I (nA)
100
10
1
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
HV (kV)
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HV tests
(Pre) Assembled chamber HV test includes:
•Preliminary check with dry air (CO2) the quality of the
assembly.The voltage is <2 kV (to see probable short circuits etc).
•Training with working gas mixture. HV is being gradually
increased from 2 to 3.0 kV (with steps of 100,50 V). The
procedure can include the training with the negative polarity (range
1.5-2.1 kV) for additional wire cleaning. Gas flow ~ 1 vol/hour.
•Chamber is left under the max voltage (3.0 kV) for 8 h’s. The
common training duration is ~5 days per chamber.
•Trained chamber is left with the gas flushing and voltage for one
week. The voltage will be increased in 100 V from 2.7 till 3 kV
after each two days. The last voltage 3 kV will be one day. The
dark current, P,T, humidity, gas flow (~1 vol/day) should be fixed.
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Uniformity test
241Am
source inspection
•For each source position the average values and variances of the
anode ( or cathode pad ) are being measured.
•Aims:
(1) check of the gain variations over the chamber area
(2) estimation of the gain difference between the individual
chambers or the gaps of one chamber.
(3) check the chamber border in the vicinity of the field wires
and wire fixation bars (probable gap deformation influence).
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Uniformity test
Example of
source
investigations
of the two
gaps of the
chamber used
in aging test
2001
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Uniformity test
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Uniformity test
• Cosmic uniformity test is based on the count rate
measurements from wire strips or cathode pads. These
rates are consisted from noise and cosmic particle
signals.The comparison of the counts when the cosmic
particles are dominating will characterize the chamber
uniformity.
• Count rate dependencies on voltage will give not only
the chamber uniformity but estimation the plateau limit
(PNPI production center).
• Special test station is now being developed in CBPF
(Brazil) for the CERN.
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High radiation test
•Test using Gamma irradiation facility (GIF) at CERN (based on
137Cs source with strength 740 GBq (1997))
•The high rate chambers (CR’s> 10 kHz/cm2 ) and randomly chosen
low rate chambers (CR’s<10 kHz/cm2 ) will be tested with the GIF
beam.
Aims:
(1) to see the gain differences between the gaps and their
behavior with voltage increase (probable instabilities at high
irradiation)
(2) to measure the gain differences between the chambers
(3) to test quality of the cathodes (Malter current ?)
(4) to test with high gamma flux the chamber border and HV parts
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High radiation test
1.5&2 mm pitch gap current vs HV
14.11.02
1.00E+03
I (nA)
1.00E+02
1.00E+01
1.00E+00
1.9
2.1
2.3
2.5
2.7
2.9
3.1
3.3
3.5
HV (kV)
The current (gain) differences between the inner and outer gaps
(~2 times) of the chamber used in the aging test 2001.
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Leak test
•Leak rate is determined from the pressure drop after
5 mbar over pressure have been applied to the
chamber.
•Procedure, the parameters and devices to be used are
the same for all the production centers.
•Leak limit: decay < 2 (4->2) mbar/hour<
corresponding to a leak rate of about 3*10-5 vol/min
(at T, P, V=const dP/P~dV/V ).
•Leak rate limit will be less strong for the chambers in
the station M1 and the inner regions of the stations
M2,M3 due to
•larger gas flow rates requested by larger particle
flux and •more complicated design
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Leak test
•small total volume (~8%)
•Parameters measured: differential pressure,
absolute pressure, temperature, an accuracy ~(23)*10-4
•Procedure will be automated.
•Leak rate should be done after the final chamber
closing.
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Devices under test are equipped with the serial
interfaces to be connected to a computer
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Conclusion
• Backbone of the tests listed before is ready.
•These procedures will be updated after
construction and test the modules 0 from the
different production sites.
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