Electromagnetic Calorimeter for HADES at SIS100:

MAMI and CERN test results

• Lead-glass modules

• Tests

- g beam at MAMI energy resolution

- p-/e- beam at MAMI particle separation

• Outlook

HADES ECAL Workshop, Frankfurt a.M., October 14-15, 2010

A. Krása, F. Křížek, A. Kugler, J. Pietraszko, Y. Sobolev, J. Stanislav, P. Tlustý, T. Torrieri (NPI Řež) ,

M. Golubeva, F. Guber, A. Ivashkin, K. Lapidus, A. Reshetin (INP Moscow),

J. Pietraszko (IKF Frankfurt)

Detector modules Our proposal is to use lead glass modules from OPAL end cap calorimeter.

~ 900 modules needed, at present 1080 modules moved to GSI.

Energy resolution ~ 5%/sqrt(E), E in GeVModule dimensions: 42 x 9.2 x 9.2 cm

Signal Read-out PMT - EMI 9903KB (1.5'') from MIRAC (WA98 hadron calorimeter) ~720 PMT'sdiameter – 38 mm (1.5'')diameter of photocathode – 34 mm

Front-end readout – ADC ADD-ON (Shower)+ TRB

Detector modules

number lightguide, wrapping

glass wrapping PMT

1 lead glass, mylar mylar EMI9903KB

2 lead glass, paper paper EMI9903KB

3 NO mylar EMI9903KB

4 NO paper EMI9903KB

5 NO mylar HAMAMATSU1949

EMI9903KB: 1.5” tube from MIRAC (WA98)H1949: 2.5” tube from HADES Tofino

Lead glass dimensions: 9.2 x 9.2 x 42 cm

Tests – cosmic muons

Source – cosmics muons: energy ≈ 2 GeV, energy deposit in module ≈ 200 MeV, Cerenkov light output corresponds to ≈577 MeV electrons count rate ≈ 20 particles / hour

Measurement of pulse height (ADC) spectra – check of energy resolution

various PMTs, configuration with/without lightguide

July 2009 - test of 5 modules before the MAMI testNovember 2009 - test of 5 modules after the MAMI testDecember 2009 - test of one module with PMTs (same type) with various gains, various wrappingsMarch 2010 – now test of modules produced for one LG HADES sector

cosmics - module No.4

July 2009

Nov. 2009

s = 5.4 ± 0.2 %

s = 5.3 ± 0.2 %

Cosmic tests - results number lightguide,

wrappingglass wrapping

PMT mean (channel)

resolution (%)

1 lead glass, mylar

mylar EMI 356 6.6 ± 0.3

2 lead glass, paper

paper EMI 387 8.8 ± 0.5

3 NO mylar EMI 329 7.0 ± 0.4

4 NO paper EMI 348 5.4 ± 0.2

5 NO mylar H1949 319 6.2 ± 0.3

Cherenkov light from cosmics muons is equivalent to 577 MeV electrons

resolution 6.5% on cosmics corresponds to 5% for electrons at 1000 MeVassuming 5%/sqrt(E), E in GeV

MAMI g beam test conditions

2 days of measurement:1) Ee- = 855 MeV, Ig = 25 kHz2) Ee- = 1508 MeV, Ig = 5 kHz

Beam: - detectors were positioned in the secondary gamma beam with continuous energy distribution from 0 to primary electron beam energy, with intensity exponentially falling with increasing energy - unless stated otherwise, the detectors were hit in the centre of their front side, and the beam proceeded along their longitudinal axis - beam diameter at detector position – 6 mm diameter

Trigger: OR of signals from 8 selected scintillators in electron tagger – giving events with 8 known gamma energies in range from 0 to energy of the electron beam

Purpose: to measure the module energy resolution as a function of g energy

MAMI test setup

Trigger: OR of signals from 8 selected scintillators in electron tagger – giving events with 8 known gamma energies in range from 0 to energy of the electron beam

Beam: detectors were positioned in the secondary gamma beam with continuous energy (intensity exponentially falling with increasing energy)

MAMI test setup

Left up: test setupLeft down: crewRight: detail with detectors, movable table and beam halo (looking in beam direction)

Measured g spectra ALL E= 1399MeV E= 1210MeV

E= 1021MeV E= 831MeV E= 676MeV

E= 261MeV E= 452MeV E= 72.1MeV

Ee=1508 MeV, g energy spread <= 1%, det. module No.1

ADC channel

cou

nts

Energy calibration Ee= 1508 MeV

Resolution vs. Energy Ee= 855 MeV

resolution ~ k . 1/sqrt(E)

Resolution vs. Energy Ee= 1508 MeV

resolution ~ k . 1/sqrt(E)

Resolution vs. Energy Module No.1

resolution ~ k . 1/sqrt(E)

LE: Ee= 855 MeVHE: Ee= 1508 MeVcosmics: cosmics muons

Resolution vs. Energy Module No.4

LE: Ee= 855 MeVHE: Ee= 1508 MeVcosmics: cosmics muons

resolution ~ k . 1/sqrt(E)

Beam and cosmic tests - results

No. lightguidewrapping

glass wrapping

PMT cosmicsresolution

(%)

beam E=579MeVresolution(%)

beam E=1000MeVresolution (%)

1 lead glass, mylar

mylar EMI 6.6 ± 0.3 7.3 ± 0.1 5.4

2 lead glass, paper

paper EMI 8.8 ± 0.5 7.6 ± 0.1 5.8

3 NO mylar EMI 7.0 ± 0.4 9.1 ± 0.1 6.6

4 NO paper EMI 5.4 ± 0.2 8.2 ± 0.1 5.8

5 NO mylar H1949 6.2 ± 0.3 7.2 ± 0.1 5.1

Resolution vs. HV Ee= 1508 MeV, module No.1

resolution ~ k . 1/sqrt(E)

Resolution vs. beam position

reading only module No.1

reading modules No.1+2

Ee= 855 MeV, module No.1

No.1 No.2

01234

CERN p-/e- beam test conditions

Momentum settings: 0.4-2 GeV/c

Beam: - the T10 test beam line of the CERN PS synchrotron was used - pi- with momenta 0.4 – 6 GeV/c with admixture of electrons (increasing at lower momenta) - detectors were positioned in the pion beam - the detectors were hit in the centre of their front side, and the beam proceeded along their longitudinal axis - beam diameter at detector position – 4x4 cm defined by a trigger scintillator - triggered beam intensity: 100-1000 particles/ bunch, 1 bunch per 45 sec.

ID: 2 m long gas Cherenkov in beam, placed 120 cm in front of lead glass, efficiency for electrons 98%

Purpose: to measure the electron/pion separation as a function of momentum to measure the lead glass module time resolution, 5 identical modules tested (glass+optical grease+EMI)

Trigger: OR of signals from 2 scintillators 4x4 cm

Test of lead glass - CERN May2010

Test setup on T10 CERN PS beam lineBeam – pi- with momenta 400-2000MeV/c with admixture of electrons

CERN test setup

Right: T10 beam lineLeft: details with detectors

Measured e/p spectra – CERN May2010

Red – electrons green – pi- separation via gas Cherenkov

ADC channel Electron peaks look worse than gamma peaks at MAMIThe electron peak has long energy tail due to energy lossof electrons in air (~15m) and other detectors in T10 area.

Measured e/p spectra – CERN May2010

Same as before, but e/pi- spectra normalized to the same yield

ADC channel

e/p separation

2 sigma cut set on the electron peak

Ratio of pions outside the cut to all pions is plotted

For “RPC” the time-of-flight is used with assumed resolution of 100 ps (sigma)

SHOWER

Energy resolution – CERN May2010

Looks a little worse than for gamma beam test –The electron peak has long energy tail due to energy lossof electrons in air (~15m) and other detectors in T10 area.

Ee [MeV]

Time resolution – CERN May2010

START signal – quarz detector, resolution < 100 psTDC gain – 50 ps / channel

e- 800 MeV

Summary

detector prototypes tested by cosmic muons

gamma beam pion/electron beam

results optimal detector configuration found detector energy resolution close to 5% at 1 GeV e/p separation better than the SHOWER detector, in combination with RPC excellent separation detector time resolution 215 ps (sigma)

Design • Number of modules 150x6=900• Mass of one module of lead-glass 14 kg• Total mass of cal. 12600

kg

E. Lisowski, TU Krakow

Cosmic test setup

lead glass module

trigger detectors

count rate: ~ 20 particles / hour

σ/Nmean= 5.4 %

our data

Cosmic muon ADC spectra

http://www.e835.to.infn.it/people/gollwitz/thesis/K. Gollwitzer, PhD thesis, University of California at Irvine, 1993

Fermilab E760 Central Calorimeter

σ/Nmean≈ 7 %

OPAL e- 1 GeV Np.e. ≈ 1800 s ≈ 5%

E760 e- 1 GeV Np.e. ≈ 4250 s ≈ 5%

E760 m ≈ 2 GeV Np.e. ≈ 2082 s ≈ 7%

module length 50 cm

PMT Tests

PMT EMI 9903KB (1.5'') ~720 PMTs available 500 PMTs tested

HV dependence of PMT response:

PMT alone at HV=1500 and 1700 V,PMT with a gamma-source 22Na at HV=1200, 1500, and 1700 V;

The results for HV=1500 V: <500 mV 79 pieces of PMTs 16% 500 mV < U < 1500 mV 120 pieces of PMTs1500 mV < U < 2700 mV 191 pieces of PMTs>2700 mV 110 pieces of PMTs

Energy resolution and hadron rejection of the OPAL end cap calorimeter

Energy resolution of the OPAL lead glass modules is 5%/sqrt(E), E in GeV)Hadron rejection below 10 GeV was not measured.

Simulated e/p spectra

K. Lapidus