CB1@GSI 1 Results on glass timing RPC aging P. Fonte LIP/ISEC Coimbra, Portugal. 15 October 2002 GSI...
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Transcript of CB1@GSI 1 Results on glass timing RPC aging P. Fonte LIP/ISEC Coimbra, Portugal. 15 October 2002 GSI...
CB1@GSI 1
Results on glass timing RPC aging
P. FonteLIP/ISEC
Coimbra, Portugal.
15 October 2002GSI Darmstadt/Germany
CB1@GSI 2
Aging in streamer mode glass RPCs (BELLE)
[Kub
o et
al,
RP
C20
01, H
.Sak
ai e
t al.,
NIM
A48
4, 1
53]
Problemwater+freon+streamers
Fluoridric acid
DepositsGlass corrosion
Dark current
Inefficiency
Freonless gas
Freon gasEff
icie
ncy
(%)
Sin
gles
rat
e (H
z/cm
2 )
Days
Wet (1000ppm)
Dry
CB1@GSI 3
Aging in streamer mode glass RPCs (BELLE)
[Kub
o et
al,
arX
iv: h
ep-
ex/ 0
2110
20 v
1]
Anode Cathode
Freon
Freonless
New glass
Depositsmay be removed
by scrubbing with alcohol
AFM pictures
~ 50 nm ~80 nm
~ 5 nm ~5 nm
CB1@GSI 4
Aging in avalanche mode glass RPCs
• 6 counters with single 0.3 mm gap, irradiated with an UV lamp.• One glass electrode and one aluminium electrode.• 3 glass-cathode and 3 aluminium-cathode counters.• Gas: (85% C2H2F4+10% SF6 +5%C4H10 ) + 10% rel. humidity.• Currents measured continuously + temp., press. and lamp intensity.• 20 hours irradiation + 2 hours rest for dark current measurement.
Test in progress
UV lamp
Aluminium
Glass
CB1@GSI 5
Glass cathode
Aluminium cathode
Da
rk c
urr
ent (
nA)
Days
Integrated charge (mC108 avalanches)
Chambers2 and 6cleaned
Corrected fortemperaturevariations
Aging in avalanche mode glass RPCsResults after 200 days
Equivalent to ~900 days @200Hz/cm2.
No measurable aging, but...
CB1@GSI 6
Ageing in avalanche mode glass RPCsAfter 180 days Glass: SCHOTT Athermal (dark glass for welding masks)
Aluminium electrodes absolutely clean!
Localiseddry
deposit
Removable by
scrubbing
Diffuse dry
deposit
Diffusewet
deposit(anode only)
Anode Cathode
UVUV
Hypothesis:Polymerisation from gas?Ion extraction from glass?
Elemental analysis soon(glass heavy elements)
CB1@GSI 7
• Bad news
• There is some material deposition after an equivalent of 900 days of operation at 200 Hz/cm2 (but only 18 days @ 10 kHz/cm2).
• Good news
• The deposit seems have no influence so far on the chamber operation(but at high rates situation may be worse due to Malter effect).
• The gas was heavily polluted with water + other stuff (glues, rubbers, etc.) very unfavourable situation
• Further research
• Origin of deposit?
• Gas: unavoidable at high rates gas must be cleaner.
• Glass: probably absent in electron-conductive materials may not appear in low resistivity materials/high-rate
counters.
• Repeat in reasonably clean conditions.(but present test should progress until chambers show measurable
effects)
Conclusions