PEPPo Weekly Meeting February 23, 2011 PEPPo Electromagnetic Calorimeter First measurements...
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Transcript of PEPPo Weekly Meeting February 23, 2011 PEPPo Electromagnetic Calorimeter First measurements...
PEPPo Weekly Meeting February 23, 2011
PEPPo Electromagnetic PEPPo Electromagnetic CalorimeterCalorimeter
First measurementsFirst measurements
Jean-Sébastien Réal, Eric Voutier
Laboratoire de Physique Subatomique et de CosmologieGrenoble, France
Experimental setup
Light tight crystal boxOptical coupling with gel or silicon cookie
• Crystals are illuminated with 22Na or 137Cs radioactive sources for the measurement of their energy resolution in self-triggering mode.
• The influence of the wrapping material and of the optical coupling are of interest, as well as a relative comparison of the crystals performance.
Sodium source spectra
Pedestal
0.511 MeV
1.275 MeV
Discriminator threshold effect
HV = 1200 V t = 2.0 µs Th. = 7 mV
Cesium source spectra
Compton edge region
0.662 MeV
HV = 1200 V t = 2.0 µs Th. = 7 mV
Experimental data
CsI Crystal Resolution
0.250.20LocationPedestalLocationPeak
WidthPeak%
E
ΔE
HV = 1200 V Th. = 7 mV
Crystal 5
Background correction
Statistics + Background Systematics
Crystal 3
Original Tyvek wrapping gives 4.01%Mylar wrapping gives 7.90%
Optical gel coupling gives 3.82%Opical cookie coupling gives 4.18%
Operating time gate
The E166 wrapping configuration (Tyvek+Copper) will be preserved.
Experimental data
CsI Crystal Resolution
Source data from E166
Source data from PEPPo
16527.0Ampeak-Photo
Copeak-Photoph/MeVPY
241
60
The observed resolution dispersion for the PEPPo configured crystals is ±8%, as compared to ±9% for the photon yield
measured by E166.
HV = 1200 V t = 2.0 µs Th. = 7 mV
Experimental prospects
Experimental Plan
Visual characterization (optical transmission) and carefull cleaning (optical coupling) of each crystal for final measurements
of the resolution.
Evolution of the resolution along the crystal (optical transmission).
Characterization of each PMT (quality check).
Integration and test of the LED monitoring system.
To be done with radioactive sources
Data collection and analysis by the end of march
Cosmic Bench Test
Experimental prospects
A new cosmic trigger is under construction for the complete characterization of the crystals in Grenoble, and will also be used at
JLab.
The characterization of the final assembly (crystals + PMTs + custom bases) with cosmic will be the last measurement before
shipping.
• The combination of an up-down coincidence with a crystal raw and the anti-coincidence of the other crystals define a track.
• At JLab, additionnal lead shielding between cosmic scintillators and the crystals will select minimum ionizing muons with a well-defined energy deposit.