Digitization in EMC simulation Dmytro Melnychuk, Soltan Institute for Nuclear Studies, Warsaw, Poland

General scheme of digitization PWO Preamplifier/ shaper FADC Digi APD ● Conversion from deposited energy to photons ● Signal conversion in APD ● Signal transformation in pre-amplifier/shaper ● FADC ● Extraction of signal amplitude from FADC output (digital filter or simple parabolic fit)

Design parameters which affect digitization ● Noise (preamplifier + APD) ● Photon statistics (photoelectrons per MeV) ● Shaping time (integration, differentiation) ● Scintillation time constant ● FADC frequency Foreseen but not used at the moment: ● Noise dependency on the channel (measured values which will be taken from Condition Data Base (CDB)) ● Non-uniformity of light production

Values of parameters 2 options for read-out electronics: - Quad-preamplifier (developed by Basel group), noise value = 1600 e- at -25 C (0.12 MeV), external shaping = 250 ns - ASIC read-out, noise 4400 e- at -25 C (0.34 MeV), built-in shaping = 100 ns (?) Other parameters: ● APD contribution to noise – excess noise factor F=1.38 at gain M=50, dark current (?) ● 400 photoelectrons per MeV at -25 C, QE=70% ● 80 MHz FADC ● crystal scintillation time 6 ns

Energy resolution dependence on digitization 1) Single gammas with different energies were generated with uniform angular distribution (10, 50, 100, 200, 500, 1000 MeV) 2) Dependence of energy deposited in 1 cluster on parameter of electronics (cluster – group of neighboring crystals) Energy threshold for single crystal = 1MeV

Photon statistic dependence E=10 MeVE=50 MeV RMS (MeV)

Noise dependence RMS (MeV)

Shaping time dependence RMS (MeV)

Summary 1) Energy resolution is sensitive to photon statistic only at lowest energies 2) Noise contribution to energy resolution is on the level of 3% and decrease with growth of energy 3) Energy resolution does not depend significantly on the shaping time but it a little bit worse for smaller values To do: ● Event mixing ● Realistic digi format from DAQ