Trigger detectors: ageing test at GIF

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• Trigger detectors ageing test at GIF

Francesca Poggio Università degli Studi di
Torino I.N.F.N. sezione di Torino
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ageing requirements (I)
max luminosity (cm-2 s-1)
integrated hits (106/cm2)
max hit rate (Hz/cm2)
months
collision system
heavy-ion program
1027
18
3
6
Pb-Pb
0.6x1029
48
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2
Ar-Ar
1.1x1029
30
15
2
d-Pb
integrated hits in the most irradiated zone of
the most irradiated RPCs is 100 Mhit/cm2, 10
years
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ageing requirements (II)
very different requirements for Pb-Pb wrt p-p.
Pb-Pb
d-Pb
p-p
small Cluster size good position resolution
Rate capability Detector lifetime
Ar-Ar
2 RD lines to fullfill the different requirement
both operating modes work with the same FE
electronic
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outline

• ageing test in streamer mode
• RPC1 (full size g 70x210 cm2), results
• efficiency measurement after ageing (cosmic rays)
• ageing test in avalanche mode
• small prototype 1
• results
• efficiency measurement after ageing (m beam)
• small prototype 23
• efficiency measurement before ageing (m beam)
• ongoing ageing test

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experimental layout at GIF (side view)
g monitor the efficiency of the detection for
cosmic ray under ?-induced counting rate

NOTE effective voltage correction HVeff
HV(p0/p)(T/T0) p0970 mbar, T0
20C current, rate and efficiency continuously
monitored with source on periodical
data-taking with source off dark current rate
current rate in absence of irradiation
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ageing in streamer mode (50.5 Ar, 41.3 C4H10,
7.2 C2H2F4, 1 SF6)
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RPC1 ageing results
see G. Travaglia talk Dimuon Meeting 2004,
Berg-en-Dal A. Musso talk June 1
first ageing test of a full size RPC (RPC1)
differentiated custom shielding to recreate
ALICE-like conditions of irradiation 6-60
Hz/cm2
after 100 Mhit/cm2 (corresponding to 50 mC/cm2)

• dark current 13 mA
• dark rate lt0.4 Hz/cm2
• slight efficiency loss with 60 Hz/cm2
  irradiation due to resistivity increase
• efficiency without irradiation (1 Hz/cm2) stable
  at 95
• rate condition similar to the Pb-Pb operation
• (max 3 Hz/cm2)

RPC1 works satisfactorily up to about 100
Mhit/cm2 fulfilling the requirement for the 10
year heavy-ion program
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RPC1 efficiency measurement
RPC1 tested in the bench test for final RPCs
see M. Gagliardi talk June 6 efficiency for
cosmic rays detection has been measured over the
whole surface of the RPC with 20x20 cm2 cells
(cosmic ray tracked with 2 RPCs)
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RPC1 efficiency radiography
see M. Gagliardi talk June 6
efficiency map at HV8300 V (working point) in
the most irradiated area
uniform and high efficiency (94), after 100
Mhits/cm2
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ageing in avalanche mode(88 C2H2F4, 10 C4H10,
2 SF6)
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small prototype 1 ageing results
see G. Travaglia talk Dimuon Meeting 2004,
Berg-en-Dal A. Musso talk June 1

• after 225 Mhit/cm2 (34 mC/cm2)
• dark current 1 mA and dark rate lt1 Hz/cm2
• no efficiency loss without and with g
  irradiation (120 Hz/cm2)
• efficiency stable at 94
• problem after a first period (100 Mhit/cm2),
  from time to time at high rates (120 Hz/cm2), we
  observe
• a fast increase of the current that gives
  instability
• after HV off the RPC recovers a normal behavior
• (high efficiency, low dark current and low dark
  rate)
• NOTE g gas mixture 88 C2H2F4, 10 C4H10 and 2
  SF6
• working point HV10900 V

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beam test, setup
after the ageing test efficiency plateau
measurement for the detection of muons (m beam
from SPS-X5) scanning the whole surface of the RPC
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small prototype 1 efficiency map

• in all position the plateau reaches 0.95-0.97 of
  efficiency
• the mean efficiency at HV10900 V (working point)
  is 0.95?0.001

low efficiency due to geometrical problems
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small prototype 1 instability problem (I)

• hp local discharge g the temperature in
  correspondence of the discharge point should
  increase appreciably
• RPC without external
• mechanics, with the
• ground side fully covered
• by thermosensitive adhesives

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small prototype 1 instability problem (II)
mean T ?25 C over the whole surface (measured
with an IR thermometer)
RPC
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• the instability is given by a local discharge
• the current trend during the instability seems to
  have a strict correlation with the high rates and
  also with the high voltage
• NOTE g gas mixture 88 C2H2F4, 10 C4H10 and 2
  SF6
• working point HV10900 V
• we try to decrease the SF6 percentage to lower
  the working point
• beam test to check the performances of RPCs with
  the gas mixture 90 C2H2F4, 10 C4H10 0.3
  SF6
• working HV10100 V
• performances no significant differences wrt 2
  SF6 gas mixture
• tested 2 small prototypes

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small prototypes 23 efficiency plateaux
small prototype 2
small prototype 3

• in all position the plateau reaches 0.95-0.96 of
  efficiency
• the mean efficiency at HV10100 V (working point)
  is 0.94?0.01

• in all position the plateau reaches 0.95 of
  efficiency
• the mean efficiency at HV10100 V (working point)
  is 0.94?0.01

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small prototype 2 efficiency map

• small
• prototype 2

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current vs int.hits small prototype 2

• after 170 Mhit/cm2 (corresponding to 25.5
  mC/cm2)
• dark current 6 mA
• dark rate lt4 Hz/cm2

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efficiency vs int.hits small prototype 2

• after 170 Mhit/cm2 no efficiency loss, both with
  and without irradiation,
• (HV 10050 V, effective voltage)

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current vs int.hits small prototype 3

• after 145 Mhit/cm2 (corresponding to 22 mC/cm2)
• dark current 1-2 mA
• dark rate lt1 Hz/cm2

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efficiency vs int.hits small prototype 3

• after 145 Mhit/cm2 no efficiency loss, both with
  and without irradiation
• (HV 10010 V, effective voltage)

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ageing in avalanche mode conclusions

• small prototype 2 g after 170 Mhit/cm2
• dark current 6 mA and dark rate lt4 Hz/cm2
• no efficiency loss without and with g
  irradiation (100 Hz/cm2)
• efficiency stable at 93-95
• small prototype 3 g after 145 Mhit/cm2
• dark current 1-2 mA and dark rate lt1 Hz/cm2
• no efficiency loss without and with g
  irradiation (80 Hz/cm2)
• efficiency stable at 93-95
• the 2 prototypes work satisfactorily up to about
  145-170 Mhit/cm2
• fulfilling the requirement
• for 1.5 years of the p-p program for the most
  irradiated RPC
• for 8 years of the p-p program for other RPCs
• the test is going on

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the ageing problem

• the RD program to understand the RPCs ageing
  problems was focused on two aspects
• effects due to flowing the RPCs with dry gas
• g increase of bakelite resistivity
• effects due to long-term operation of the
  detector in condition of high counting rates
• g increase of bakelite resistivity and a surface
  damaging due to the streamer discharge

ageing proportional to integrated current per
surface unit (mC/cm2), i.e. to the integrated
hits per surface unit (Mhit/cm2) g increase of
the current drawn by the detector, a (minor)
increase of the single rate and a possible
efficiency decrease.
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beam test small prototype 2

• in all position the plateau reaches 0.95-0.96 of
  efficiency
• the mean efficiency at HV10100 V (working point)
  is 0.94?0.01

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beam test small prototype 3

• in all position the plateau reaches 0.95 of
  efficiency
• the mean efficiency at HV10100 V (working point)
  is 0.94?0.01

low efficiency due to geometrical problems