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.