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ALICE-HMPID testbeam at T10 285-186

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					      ALICE-HMPID testbeam at T10
              28/5-18/6
                           Antonello Di Mauro


• The ALICE HMPID (High Momentum Particle ID) detector is a RICH
(Ring Imaging Cherenkov) using C6F14 liquid radiator and MWPC coupled
to CsI photocathodes as photodetector
• Tests related to upgrade to higher momenta PID capability (VHMPID)
• Two users:
    • Budapest University: Thick-GEM based detector for high pt trigger
    • Mexico City University: Cherenkov radiation readout in an aerogel
    counter with Fresnel lens
     TGEM test measurements

• Thick GEM based small-scale prototype test
  for a High PT Trigger Detector (HPTD) for the
  VHMPID in ALICE
• PS-T10 beam area
• Budapest VHMPID/HPTD group :
  A.G.Agócs, G.G.Barnaföldi, G.Bencze,
  L.Boldizsár, Z.Fodor, E.Futó, G.Hamar,
  L.G.Kovács, P.Lévai, L.Molnár, D.Varga
      Geometry of the test chamber




   TGEM size: 10cmx10cm
   Padwidths [mm] : 2.5, 5.0 mm;   length : 50 mm
   Gas : Ar/CO2 : 80%/20%, 90%/10%, 95%/5%
Test Beam Setup
              Main Studies
• Two chambers with padwidths: 2.5 mm and
  5.0 mm, cross-talk between the neighbouring
  pads
• New 1-bit digitized multiplexed readout
• Efficiency vs High Voltage
• Track incidence angle (from 0o to 60o)‫‏‬
• Spark limit vs. Rate and HV
• Gas mixture study (gas: Ar with 20%, 10%
  and 5% CO2)‫‏‬
              Analogue signals
                             • Pre-amplified signals from
                               the analogue readout




• The Landau distribution
  appears on the histogram
  of the analogue signals.
                    Digital readout
• Offline analysis in progress!
• Preliminary results:

   – Efficiency around 95-98 %,
   comparable to analogue readout
   – Strong rate dependence in HV
   spark limit
    TEST OF AEROGEL for Cherenkov
          Threshold detector
• Ruben Alfaro, Alex Sokolov, Guy Paic -
  Universidad Nacional Autonoma de Mexico
 Aim of the test of aerogel with Fresnel lens

• Investigate the possibilities of using a Fresnel
  lens design in conjunction with an aerogel
  detector to concentrate the photons on a
  smaller PMT instead of using a “integration box”
  design which necessitate 2 PMTs with large
  diameter.
• The test has been performed with 1-1/2” PMT
  which can be used in a magnetic field (not
  possible with traditional larger size PMT)
             Aerogel Cherenkov Counter
            Beam Test @ T10, June 2008
Setup:
• Light-tight container box,
• 2 types of the aerogel:
  n=1.008 (Novosibirsk),
  n=1.015 (Matsushita)
• Fresnel Lens + Mirror OR Light Integration Box ,
• Photomultiplier (PMT),
• Triggers.




   Light Int. Box                         Fresnel Lens
                                                          Signal Spectra
 3
          Detector signal, run091 P(0)=0.086483, Mean=2.1967 p.e.                 3
                                                                                           Detector signal, run090 P(0)=0.38725, Mean=1.5772 p.e.
10                                                                               10
                                                    Data, 19990 events                                                                 Data, 9997 events


 2                                                                                2
10                                                                               10



 1                                                                                1
10                                                                               10



 0                                                                                0
10                                                                               10



 -1                                                                               -1
10                                                                               10



 -2                                                                               -2
10                                                                               10
      0          100        200         300      400        500          600           0         100        200         300      400         500           600
                       Aerogel signal, QADC channels                                                   Aerogel signal, QADC channels




Aerogel n=1.008, Fresnel Lens                                                  Aerogel n=1.008, Fresnel Lens,
Beam 6 GeV negative                                                            Beam 1 GeV negative, below pion
Mean=2.2 p.e.                                                                  Cherenkov threshold.
8.6% in the pedestals (zero signal)                                            Mean=1.6 p.e.
                                                                               39% in the pedestals (zero signal)
                                                                               → signal from electrons in the beam

				
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