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The HMPID performance
during the LHC run period
2010-2013
Detector stability and PID
performance
(with the contribution of: G. Volpe, S. Bansal, A Franco, L. Olah)
HMPID Plenary meeting
19/07/2013
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Summary as outlines of the
presentation
•
September 2006, the HMPID installed on the cradle was slide in the ALICE magnet;
•
The detector performance has been stable except some concerns with:
–
–
the tightness of the C6F14 trays: 4 out 21 trays have shown leakages ;
3 HV sectors out of 42 are off.
•
Combining faulty systems, they have gradually reduced the detector acceptance down to 72%.
Nevertheless this has not prevented the detector to carry out successfully its PID task!
•
The long term stability and Q.E. of the CsI Photocathodes is confirmed. In principle no
degradation will be observed up to the end of the 2021(RUN3), during the HL LHC period ;
•
During the LHC run period 2010-2013 the HMPID has efficiently collected data in p-p, p-Pb and PbPb collisions;
•
A Technical Internal note with all the details is being prepared, its temporary title is: The HMPID
performance during the LHC run period 2010-2013 ;
•
On the same subject a contribution to the RICH 2013 workshop is ready to be submitted;
Thanks to you all for the excellent results and for the efforts in building, operating the detector up to
now and for analyzing data!
HMPID Plenary meeting
19/07/2013
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Sept 2006: HMPID, the first detector sliding
in the empty ALICE magnet
HMPID Plenary meeting
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2013: Leaking C6F14 trays and faulty HV sectors
Leaking 8/2006
Leaking radiator
5
6
Faulty HV sector
Leaking 6/2012
4
Leaking 10/2010
3
Leaking 6/2010
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0
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The detector
performance have been
stable.
There have been some
concerns with:
• the tightness of the
C6F14 trays: 4 out 21
trays have shown
leakages ;
• 3 HV sectors out of
42 are off.
Combining faulty
systems, they have
gradually reduced the
detector acceptance
down to 72%.
Nevertheless this has
not prevented the
detector to carry out
successfully its PID
task!
4
NEOCERAM-quartz trays for the liquid C6F14
Cherenkov radiator
Fixations
1.4 m
1.4 m
Liquid C6F14 inlets
HMPID Plenary meeting
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Details of the C6F14 Inlet
Delicate connection
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Possible main causes of the C6F14
leakages and perspective!
1.
Detachment of pieces on the C6F14 inlet (inox-NEOCERAM
contact surfaces)?
2.
Glue etching (or ageing) with consequent separation of the
quartz-NEOCERAM plates?
3.
On thermal dilatations (mechanical stress) difficult sliding of the
radiators in the fixation with consequent cracking of the plates?
4.
5.
?…………….
Perspective: difficult to say, more care in filling/empting phase of
the trays; hope to keep the situation stable at least up to the end
RUN2 ( dec 2017);
HMPID Plenary meeting
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Monitoring of MWPC Gas gain stability
Ao in ADC channels
•
•
11_c run period
2010
2011
2012
HMPID Plenary meeting
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Monitoring of the CH4 Gas gain stability and uniformity
in the seven RICH modules up to the end 2012. Its
stability can affected by variations of the gas density in
the MWPC r(T,P).
An equalization of the 42 HV setting values has been
done during the run period 11_c (coordinated by
Antonello). An optimal gas gain value (Ao~35) is reached
where the ratio of resolved Č ph.e. over ph. feedback is
maximised.
2010
2011
2012
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CsI photocathodes: long term
performance and ageing effects
• The long term stability refers to the Q.E. stability of the
300nm thick CsI layer on the pad-photocathode, since its
production time, in “normal” storage conditions, not
necessarily exposed to the radiation;
• Ageing effects are those caused on the CsI photocathode by
the ion-bombardment produced in the CH4 MWPC by both
the ionizing particles and photons (Cherenkov and
feedback);
• In two works (mainly carried out by H. Hoedelmoser and lead by F. Piuz NIM A 553
(2005)187-195 and NIM A 574 (2007) 28-38)[ref.1-2], these two effects have
been carefully analyzed and today let us to know in
advance the possible effects on the CsI photocathodes due
to the integrated charge dose during the LHC operation.
HMPID Plenary meeting
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CsI Q.E. by particles at saturated Č
angle 2010-2012
RICH 5
RICH 6
2010
2011
2012
2010
2011
RICH 4
2010
2011
Monitoring of the average number of
reconstructed Č photons by particles at
the saturation. It depends on the CsI
Q.E. and it doesn’t show any loss during
the LHC run RUN1.
2012
RICH 3
2012
2010
2011
RICH 2
2012
2010
RICH 1
2010
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2011
2011
2012
RICH 0
2012
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2010
2011
2012
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CsI Q.E. by particles at saturated Č
angle 2013
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CsI Q.E. by particles at saturated Č
angle 2010-2013
•
The average number of about10 photons/ring is less than the about fifteen measured during
the photocathode characterization in dedicated beam tests (2004-2006).
•
Unfortunately the available statistics in the LHC data set doesn’t allow a particle selection for
reproducing the same experimental conditions as in the beam tests. So, a direct comparison
is not yet possible.
•
Nevertheless, due to the absence of any CsI Q.E. loss we are convinced that also the long
term stability of the photocathodes has not been affected.
•
These results are also consistent with the measurement of the average dose of the integrate
charge of 0.013 mC/cm2, which is less than the charge threshold value of 0.2 mC/cm2, where
ageing effects of CsI photocathodes resulting in a Q.E. loss may appear[ref1-2].
HMPID Plenary meeting
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The integrated charge dose on the CsI
photocathodes
•
•
A bit of history: 2002, on request of F. Piuz, a dedicate HV board with 1 nA of current resolution was
developed: (in the CAEN catalogue A1821PH where H is for HMPID!);
Below as an example, the Io values 2010-2013 of the six HV sectors of the RICH0 (each HV sector covers
two halves photocathodes): the black curves refer to the HV channel rampup/down , the red curves show
the Io values when the operational HV values were set and particle collisions were taking place in IP2.
RICH0 HV-S0-5
RICH0 HV S0
RICH0 HV S5
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Some comparisons p-p, Pb-Pb and p-Pb
p-p 2010
p-p 2012
Pb-Pb 2010
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p-Pb2013
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Integrated Charge dose
Integrated charge dose
RICH0 HV S0-5
RICH0 HV S0
2010 2011
2012
2013
RICH0 HV S5
RICH0 HV S3=lowHV
How much of this current flown trough the CsI fotocathodes?
A simple model (to be refined) suggests that a conservative value of 2/3 of the anodic Io,
(in details: ½Io from ionizing particles + IČ photons assumed equivalent to ½ Io since on
the average, there are 10 Č ph./radiating particle)
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Summary of the integrated charge dose
From this analysis there are no concerns about the CsI Q.E. during RUN2 (2015-2017).
In principle the detector can be operational also during the full RUN3 period, with HL LHC up to 2021. This
has been possible thanks to the fortunate condition of the measured particle multiplicity (~1 Kparticles/h in
Pb-Pb) a factor 6 less than what expected from the simulation (~6 Kparticles/h in Pb-Pb).
HMPID Plenary meeting
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HMPID PID performance
•
•
•
The PID performance have already been presented several times during the weekly meetings where more
details can be found;
To summarize the excellent PID performance of the detector, I have just put the scatter plot of Č angles vs.
momentum at 7 TeV and the K/p and p/K separation in p-p @2.76 TeV (newest); for the protons up to 6
GeV/c at 2 sigmas (REM: measured Č angle resolution ~ 4 mrad);
Refined method for the background subtraction and track-by-track ID algorithm, as already shown in the
previous presentations, are permitting the HMPID to provide interesting physics results in p-Pb and Pb-Pb
collisions as well.
HMPID Plenary meeting
19/07/2013
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Backup
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Number of photons for LHC 10b
* Number of photons for LHC 10b
We have used a strip of 10 cm in the ydirection
* p>4GeV
HMPID Plenary meeting
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