13 Readout Electronics

A First Look

28-Jan-2004

January 28, 2004 J. Pilcher2

Requirements

Digitize charge seen by each PMT Energy reconstruction

Provide timing of signal for each PMT Position reconstruction

Provide trigger for DAQ Physics triggers

Neutrinos (prompt EM energy, delayed neutron energy) Backgrounds (to study and subtract) Muons

Electronic calibration triggers (test pulses) Source/laser/LED calibration triggers Random triggers

January 28, 2004 J. Pilcher3

Comparisons KamLAND is important reference point

Same reaction channel Scintillator-based detector Recent design But much larger target volume

~20 times larger

KamLAND resolutions Energy

7.5% / Sqrt[E(MeV)] 2% 5.7% at 2 MeV Position

25cm 5 cm– timing resolution 2.0 ns RMS after charge correction

January 28, 2004 J. Pilcher4

KamLAND Electronics Berkeley Analog Waveform

Transient Digitizer (AWTD) For 1325 PMTs (32%

coverage) Sample every 1.5ns

For signals above 1/3 pe 3 gain ranges (0.5, 4, 20) Store analog samples in

switched capacitor arrays until trigger

128 samples deep (200 ns) 10-bit ADC

~15 bit dynamic range Converts 128 samples in 25s.

January 28, 2004 J. Pilcher5

Channel Response CharacteristicsSensitivity Full Scale

Charge pe Energy Charge pe Energy(cnts/pC) (cnts/pe) (cnts/KeV) (pC) (pe) (KeV)

High Gain 247 186 55.7 4.14 5.5 18.4

Medium Gain 49.4 37 11.1 20.7 27.5 91.8

Low Gain 6.18 4.6 1.39 166 220 734

0.752 pC/pe

300 pe/MeV

Readout Resolution

0.10

1.00

10.00

100.00

0.10 1.00 10.00 100.00 1000.00

Single PMT Energy (KeV)

Percentage Resolution

January 28, 2004 J. Pilcher6

KamLAND Signals128 samples of 1.5ns3 gain scales(most events just use 20X

scale)

Gain 1/2

Gain 4X

Gain 20X

January 28, 2004 J. Pilcher7

KamLAND Vertex Reconstruction Calibrate timing of individual

PMT channels with variable laser pulses at center of detector

Time offsets T vs Q

Measure performance for physics with sources along z-axis

January 28, 2004 J. Pilcher8

KamLAND Vertex Reconstruction Mean reconstructed

position depends on photon energy

Apply energy dependent correction

January 28, 2004 J. Pilcher9

KamLAND Energy Reconstruction Set gains of PMTs using LEDs Equalize 1 pe peaks to 184 counts

Must correct for variations in storage capacitors All signals converted to equivalent photoelectrons Convert to energy using calibration sources

January 28, 2004 J. Pilcher10

KamLAND Energy Reconstruction

January 28, 2004 J. Pilcher11

Fresh look at Readout Electronics Avoid ASICs if possible (local bias)

Long development time Not cost effective in small volume Do not profit from evolution of chips in the

commercial sector Main advantage size and possibly performance

and functionality Continued performance growth in commercial

ADCs and FPGAs (PLD) Popular building blocks for many applications

January 28, 2004 J. Pilcher12

Fresh look at Readout Electronics Does one need detailed pulse shape for E and t?

Pulse shape discrimination can resolve photons from neutrons

Depends on scintillator Some exhibit this property and some do not May depend on light collection from target

– Reflections could obscure the effect

Much simpler if one can do shaping of input signal Output amplitude proportional to input charge Can be done with passive elements (no noise

added)

January 28, 2004 J. Pilcher13

ATLAS TileCal Approach For ATLAS TileCal 20 ns PMT signals converted

into 50-ns-wide standard shape Amplitude proportional to input charge Slower signal can be handled by commercial

ADCs (+40 megasamples per second) Analysis process fits shape to extract amplitude

and time

January 28, 2004 J. Pilcher14

Performance of TileCal System

Time reconstruction is excellentamplitude independent

January 28, 2004 J. Pilcher15

Alternatives Use LBNL AWTD

Likely if they join the collaboration Possibly an updated version

Build a system based on a flash ADC Eg. Maxim MAX1151

8 bit flash 750 MHz (sample every 1.3 ns) Power 5.5W each

Need 3 per PMT for dynamic range Use 40 MHz “system” clock à la LHC

Easy to distribute on optical fiber if LHC hardware used Generate local vernier clock synced to system clock Tale 16 samples for every 25 ns period of system

January 28, 2004 J. Pilcher16

Alternatives Build integrating system as in TileCal

The next steps Test LHC system reading out scintillator test cell Look at pulse shape discrimination with test cell Continue to think about electronics

Trigger– Can it be derived from digital data, thereby avoiding a second

signal branch

Consult with Harold