Ilhan TAPAN* and Fatma KOCAK Simulation Work on Calorimetric Energy Resolution for the TAC-PF Detector Ilhan TAPAN* and Fatma KOCAK Uludag University Physics Department Bursa-Turkey * on behalf of TAC-PF group Title: Excess Noise Factor of Neutron Irradiated Silicon Avalanche Photodiodes The XVth International Conference on Calorimetry in High Energy Physics, Santa Fe, NM , June 4-8, 2012

- Brief Introduction of TAC project Outline - Brief Introduction of TAC project - Crystals- Photodiode Combination - Calorimetric Energy Resolution - Calculations and Results - Conclusion Motivation: CMS & APDs

Turkish Accelerator Center (TAC) Project The mission of TAC is to design, construct and use high energy particle accelerators for scientific researches in Turkey and in the region and to collaborate with international HEP community.

The ongoing project has three main parts 1) Accelerator Based Light Sources, 2) Proton Accelerator (PA) 3) Particle Factory (PF) An electron-positron collider as a “super charm factory, 1 GeV electron linac and a 3.56 GeV positron ring for linac on ring type collisions and a dedicated detector. Produce charm meson resonantly at the center of mass energy of 3.77 GeV. Motivation: CMS & APDs

TAC super charm factory parameters e--linac e+-ring Energy, GeV 1.00 3.56 Particles per bunch, 1010 2 20  function at IP, mm 80/5 x/y/z, m/m/mm 36/0.5/5 Beam current (A) 0.48 4.8 Circumference, m 600 Crossing angle, mrad 34 Collision frequency, MHz 150 Luminosity, cm-2s-1 1.41035 Motivation: CMS & APDs

Crystals- Photodiode Combination The energy measurement is based on the energy released of the incident particles in the crystal material. An electromagnetic shower is produced by a high-energy electron, positron or photon enters the crystal. The light generated in the shower development is detected by photodetectors. PbWO4 and CsI(Tl) crystals are considered for the construction of the TAC-PF electromagnetic calorimeter. Motivation: CMS & APDs The generated photons in the crystal material are detected by Avalanche photodiodes (APD) or PIN photodiodes placed at the end of the crystal.

PbWO4 Crystal Advantages  Disadvantages  Dense and Radiation hard Short radiation length Fast Disadvantages  Temperature dependence Low light yield Properties of PbWO4 Density 8.28 g/cm3 Radiation length 0.89 cm Interaction length 19.5 cm Moliére radius 2.2 cm Emission peak 420 nm Light yield 120 photons /MeV Radiation hardness 107 rad Lcr = 20 cm = 22.5X0 Motivation: CMS & APDs

CsI (Tl) Crystal Lcr = 30 cm = 16.2X0

Hamamatsu S-8148 silicon APD Advantages  compact and robust very high QE internal gain very good time resolution insensitive to B Produced by epitaxial growth on low resistivite n+-type silicon substrate, followed by ion implantation. Disadvantages  small sensitive areas and noisy gain fluctuations dependence on high radiation Active area; 5x5 mm2

Hamamatsu S2744-08 silicon PIN Photodiode Active area; 1x2 cm2 Photosensitive area: 10mm x 20mm Thickness of Wafer: 300μm Quantum efficiency(560nm): 80% Supplies Reverse Voltage : 70 V Capacitance : 85 PF Dark current: 4 nA Temp. dependence for noise: 10 %/0C

Calorimetric Energy Resolution Energy resolution in the ECAL E : the energy of the incident particle a : stochastic term (photoelectron statistics, shower fluctuations, photo- detector, lateral leakage) b : constant term (non-uniformities, longitudinal leakage) c : noise term Introduction: ECAL Energy Resolution

Calorimetric Energy Resolution The total stochastic term of the energy resolution for crystal- photodiode combination is composed of a contribution from shower containment (lateral leakage contribution) and a contribution from photodiode signal fluctuation (photo-electron statistics). a lateral : Event to event fluctuations in the lateral shower containment a pe : Photoelectron statistics contribution from photodetector F is the avalanche gain fluctuation or excess noise factor Npe is the number of primary photoelectrons Npe = Nph .QE Nph ; photons from crystal, QE ; quantum efficiency

Calorimetric Energy Resolution Excess Noise; Hamamatsu S8664-55 APD M : avalanche gain : avalanche gain fluctuation The emission weighted excess noise PbWO4 CsI(Tl) Hamamatsu S2744 PD 1 1 Hamamatsu S8664 APD 2.18 3.83 wavelength dependent excess noise and emission

Calorimetric Energy Resolution Quantum efficiencies are wavelength dependent. The emission weighted quantum efficiency wavelength dependent quantum eff. and emission PbWO4 CsI(Tl) Hamamatsu S2744 PD 61 % 80 % Hamamatsu S8664 APD 77 % 84 % Nph : Number of the incident photons collected by the PD Npe : Number of the primary electrons created in the PD

Calculations The contribution to the calorimetric energy resolution from both the shower fluctuations in the crystal and photoelectron statistics in the detectors have been calculated for PbWO4-APD/PIN and CsI(Tl)-APD /PIN combinations. The generated light in the crystals and the number of photons collected from photodiodes have been calculated for 0.25-2 GeV incident photons using the GEANT4 simulation code. PbWO4 same size in PANDA EMC; a length of 20 cm (22.5X0) cross section 2.2x2.2 cm2 CsI(Tl) a truncated-pyramidal shape; a length of 30 cm (16.2X0) front side 5.5x5.5 cm2 rear side 6x6 cm2 Photodiode photon

Calculations: simulation of alateral The contribution to the stochastic term coming from fluctuations in the lateral shower containment has been simulated for 3x3 and 5x5 crystal matrices. CsI(Tl) central 3x3 5x5 PbWO4 Energy responses to 2 GeV photons observed in the central module and the crystal matrices.

Calculations: simulation of alateral Geant4 results of the shower fluctuation ( ) and the leakage out of the crystal. 3x3 : 5x5 : 3x3 : 5x5 :

Calculation of ape The ape photoelectron statistics contribution on the stochastic term has been calculated from; 1.8% for PbWO4-APD, 0.48% for PbWO4-PIN and 0.24% for CsI(Tl)-APD, 0.04% for CsI(Tl)-PIN combinations. Npe = 5100 pe/MeV Simulation Npe = 5000 pe/MeV NIM A 494 (2002) 298–302

Results “a” term indicates shower fluctuations for 5x5 crystal matrices and photoelectron statistics. “a” term and a part of the “b” term originate from the shower-leakage fluctuation.

Conclusion Simulation shows that; PbWO4- photodiodes are not in good combination for lower energies. PbWO4-APD has bigger “a” values then PbWO4-PIN combination. Best choice is CsI(Tl)-PIN combination

Additional slides For the 3x3 matrix IEEE TRANS. on NUCL. SCI, VOL. 55, NO. 3, 2008, p 1298 For the 3x3 matrix NIM A 479 (2002) 117–232

Calorimetric Energy Resolution and Stochastic Term APD contributes to all the terms ECAL energy resolution a sensitive area, quantum efficiency, excess noise b gain sensitivity to operating voltage and temperature, aging and radiation damage c low capacitance, serial resistance and dark current By neglecting the intrinsic resolution, the APD photo-electron statistics contribution to stochastic term is given by Introduction: ECAL Energy Resolution Npe is the number of primary photoelectrons Npe = Nph .QE Nph ; photons from crystal, QE ; quantum efficiency F is the avalanche gain fluctuation or excess noise factor

Calorimetric Energy Resolution and Stochastic Term The relative fluctuation of the APD signal in the proportional mode Npe is the number of primary photoelectrons : S.D. of the number of primary photoelectrons; M : Avalanche gain σM : S.D. of the avalanche gain APD photo-electron statistics contribution to stochastic term

Energy deposition in the crystals- 2 GeV