PANDA electromagnetic calorimeters Pavel Semenov IHEP, Protvino on behalf of the IHEP PANDA group INSTR08 28 Feb - 05 Mar 2008

PANDA electromagnetic calorimeters

Pavel Semenov IHEP, Protvinoon behalf of the IHEP PANDA group

INSTR08 28 Feb - 05 Mar 2008

3 March 2008 Pavel Semenov, INSTR08@BINP, Novosibirsk 2

Outline

• PANDA detector setup

• Target Spectrometer EMC– PANDA gamma irradiation facility at IHEP

– Light output at -20°C

– Radiation hardness measurements at -20°C

• Forward Spectrometer EMC– EMC prototype module parameters

– Prototype testbeam results for energy and position resolution

– MC studies to find optimal parameters


PANDA EM Calorimeters placement

FS EMCTS EMC


Target spectrometer EMC

• Requirements – Geometrical coverage close to 4π– Compact size– Fast signal, good time resolution– Low energy threshold (10 MeV) of photon detection– Excellent position and energy resolutions

• PbWO4 (PWO) crystal as a good candidate for the TS EMC– 21 mm x 21 mm x 20 cm barrel cell size (front), 25 mm x 25 mm x 20

cm endcap cell cize – ~17000 crystals (96 % of 4 π)

• Improved light output is needed to reach excellent resolution and low threshold– Calorimeter operates at low temperature (about -200C, factor of 3 increase

of light output) – PWO-II: enhanced light output PWO (~20 phe/MeV)

• PWO radiation hardness at room temperature is not a problem for PANDA (dose rates not more then a few rad/hour). But there were no data for PWO radiation hardness properties at -20 0C


PANDA-IF at IHEP features

• Crystal holder (Cu plate with heat-exchanging system) for 5 crystals

• Cryothermostat (LAUDA RC6CP) capable of temperature stabilization in the region of -35 °C --- +200 °C

• LED system to monitor PMT gain and crystals transparency in blue and red part of the visible spectrum

• Cs137 gamma source gives irradiation dose rate 100 rad/h and below

• Monitoring of temperature sensors ( Pt100 and Pt1000 class A ) at 6 points (2 on crystals)


PANDA-IF picture

Cryothermostat

Crystal box


PWO properties studies at low temperatures

Crystal # S(-19.4) / S(+18.5)

b4 2.83

b16 2.80

b17 2.75

b24 2.78

b30 2.84

Light output change before the irradiation with temperature change from +18.5 0C to -19.4 0C

Radiation hardness studies of PWO-II at PANDA dose rates (max 2 rad/hour) and -20 0C showed 20%-35% drop of DC output signal after 300-400 hours of irradiation


PWO light transmittance recovery at -200C

Published at NIM A Vol 582/2 pp 575-580

Paper:First study of radiation hardness of lead tungstate crystals at low

temperatures


Radiation hardness studies of PWO-II (high dose rate)

Still factor 1.4 enhancement of light output


Forward Spectrometer EMC

• 7 meters from the interaction point

• Covers 3 m2

• Fine segmented sampling calorimeter with light collection by optical WLS fibers passing through holes in the scintillator and lead layers (shashlyk type)

• Not in magnetic field (PMT as photodetector)

• Working energy range 10 MeV – 10 GeV


Testbeam setup

DC1M14 DC2DC3

DC4ECAL prototype Beam

• Spectrometer consisted of 4 drift chamber stations and a magnet to measure beam particle momentum precisely

• Calorimeter prototype installed on a movable platform


Shashlyk prototype module parameters

9 modules assembled in matrix 3x3• 380 layers of 0.3-mm lead and 1.5-mm scintillator,

total length 680 mm• Transverse size 110x110 mm2

• Effective Moliere radius: RM=59 mm

• Effective radiation length: X0=34 mm

• Total radiation length: 20X0

• Light collection: 144 (1212) fibers BCF-91A (1.2 mm)

• PMT Hamamtsu R5800 as photodetectors


Shashlyk modules production


Shashlyk prototype pictures

3x3 matrix of shashlyk modules and PMT attached to the modules


Minimum ionizing particle peak


Energy Resolution dependence on energy


Energy Resolution parameterization

σE /E = a/E b/√E c [%], E in GeV

Experiment data fit: MC data fit:

a = 3.5 ± 0.3 a = 0.0

b = 2.8 ± 0.2 b = 3.0 ± 0.3

c = 1.3 ± 0.04 c = 1.1 ± 0.7

Good agreement with MC without noise term.

Good agreement with previous studies of similar sampling modules at lower energies (2.9%/ √E at 220-370 MeV: Test beam study of the KOPIO shashlyk calorimeter prototype, G.Atoian, S.Dhawan,V.Issakov et al. CALOR-2004 Proceedings )


Measured S-curve at 19 GeV

Real Position, cm

Xcog,au


Position resolution (center) dependence on energy


Position resolution parameterization

σx = a/√E b [mm], E in GeV

Experiment data fit: MC data fit:

a = 17.6 ± 0.9 a = 14.2 ± 0.6

b = 4.6 ± 0.9 b = 5.5 ± 0.9

Worst case – resolution at the module center.

Resolution near the module edge is 3 times better


Shashlyk 8x8 cells prototype

• We plan to have another shashlyk testbeam run in 2008 with prototype of 8x8 cells

• Now prototype with 55mm x 55mm module sizes is under construction

• Testbeam studies includes prototype energy and position resolution as well as test of π0 reconstruction capabilities in the energy range up to 15 GeV


Conclusions

• PWO-II radiation hardness at -200C studies showed deep light transmission drop (20%-35% at 2rad/hour) and low light transmission recovery rate

• Testbeam studies of energy and position resolution of shashlyk prototype (110x110mm cell) results:

– Energy σE /E = 3.5/E 2.8/√E 1.3 [%] – Position (at the cell center) σx = 17.6/√E 4.6 [mm] – Good agreement with MC results

• Further improvement of shashlyk parameters includes prototype with 55x55 mm cell size testbeam study


Backup slides


Radiation hardness temperature dependence


MC shashlyk parameters

• Shashlyk module geometry including holes

• Tile att. length 70 cm

• Fiber att length 400 cm

• Reflection from tile edges diffusive

• Tot. internal reflection 0.97

• Tile light output 100 eV/photon

• Reemission probability in fiber 0.1

• Refraction in tiles and fibers 1.59


S-curve MC (0.5 – 10 GeV)


PANDA-IF electronics

• Based on i7k (ICP DAS) modules with RS485 interface

• Short connections (0.5 m) from PMT and temperature sensors to read-out electronics

• Temperature measurements with an accuracy better than 0.03 °C

• DC current measurements accuracy up to nA

• LED signals in DC mode – measurement of the mean current thru 10 kΩ generated by a bunch of pulses

• HV for PMTs: LeCroy1440 system


PANDA-IF electronics diagram

7013PT1000

CAMAC

RS485 bus

Irradiation facilityControlroom

7017ADC

7042DO

LED generator

HV

Crystal Box

Shutter

LRS1440HV system

VME

Shutter digital control lines

RS232

DAQ computerLinux

RS485/RS232converter

LAUDA

PT1000

7 signal lines

Opt. fibers

RS232-CL

Cs137

Documents

PANDA electromagnetic calorimeters Pavel Semenov IHEP, Protvino on behalf of the IHEP PANDA group INSTR08 28 Feb - 05 Mar 2008