Digitization in EMC simulation

Dmytro Melnychuk, Soltan Institute for Nuclear Studies, Warsaw, Poland

General scheme of digitization

APD PWO Preamplifier/ shaper FADC Digi ● ● ● 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 Energy threshold for single crystal = 1MeV crystals)

Photon statistic dependence

E=10 MeV E=50 MeV s im p le d ig it iza t io n n o is e (0 .1 2 M e V) n o is e (0 .1 2 M e V) + p h o t o n s t a t is t ic RMS (MeV)

1 0 M e V

0 .6 2 5 0 .6 3 7 0 .7 1

5 0 M e V

3 .2 3 3 .3 0 3 .3 0

1 0 Me V 5 0 Me V 1 0 0 Me V 2 0 0 Me V 5 0 0 Me V 1 0 0 0 Me V

Noise dependence

RMS (MeV)

S im p le d ig it iz a t io n 0 . 1 2 M e V 2 5 0 n s ( Q u a d -p r e a m )

0 .6 2 5 0 .7 1 1 3 .2 3 4 .3 8 5 .9

3 .3 1 4 .5 4 5 .9 1 8 .7

1 6 .8

8 .7 1 1 6 .7

0 . 3 4 M e V 1 0 0 n s ( AS IC )

0 .7 5 9 3 .3 1 4 .5 4 5 .9 1 8 .7 7 1 6 .8

Shaping time dependence

RMS (MeV) 1 0 M e V 5 0 M e V 1 0 0 M e V 2 0 0 M e V 5 0 0 M e V 1 0 0 0 M e V

0 . 3 4 M e V 1 0 0 n s

0 .7 5 9 3 .3 1 4 .5 4 5 .9 1 8 .7 7 1 6 .8

0 . 3 4 M e V 2 5 0 n s

0 .7 2 1 3 .3 0 4 .4 7 5 .9 3 8 .7 2 1 6 .7

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