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A COME & KISS* QDC readout scheme for
the HADES Electromagnetic Calorimeter
DPG-Frühjahrstagung
Frankfurt 2014
* use commercial elements and keep it small & simple
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Adrian Rost
TU Darmstadt
for the HADES collaboration
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 1
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Motivation for a ECAL upgrade for HADES
 Future: HADES at FAIR (SIS100)
 For beam energies between
2 – 40 GeV/u the data base for p0
and h production is not complete
 interpretation of di-lepton data
depends on models!
 Role of ECAL:
o Measurement of p0 and h via ggdecay channel
o Additional improvement of e/p
separation at large momenta
(p > 400 MeV/c)
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 2
Mass vs. momentum distribution
Au+Au at 4 GeV/u (RPC Region)
ECAL for HADES
Detector modules:

Cherenkov lead glass modules from OPAL end
cap calorimeter (163 modules x 6 sectors = 978;
each 14kg)

Module dimensions: 9.4 x 9.4 x 60 cm3

Energy resolution ~ 5%/√E, E in GeV
Signal read out:

PMT-EMI 9903KB (1.5”) (WA98 hadron
calorimeter) ~600 PMT’s

PMT – Hamamatsu R6091 (3“)

PMT – Hamamatsu R8619 (1”)
Digitizing board:

18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 3
HADES Trigger and Readout Board v3 (TRBv3)
The COME & KISS Charge measurement
principle
 Fast signal: leading edge (fast_LE), trailing edge (fast_TE)  timing
 Slow signal: slow_LE, slow_TE  charge-to-width (Q2W) ~ charge
 TRBv3 used as FPGA-TDC (time precision ~ 20 ps) and DAQ
(developed at GSI see: http://trb.gsi.de/)
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 4
From theory to reality:
The new PaDiWa-AMPS frontend board for TRBv3
 Fast signal: leading edge (fast_LE), trailing edge (fast_TE)  timing
 Slow signal: slow_LE, slow_TE  charge-to-width (Q2W) ~ charge
 TRBv3 used as FPGA-TDC (time res. ~ 16 ps???) and DAQ
 Proper thresholds settings are important
 near to the baseline as possible, to get a high dynamic range
 to near at baseline, problems with noise can appear
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 5
PaDiWa-AMPS response to signals generated
by LED pulses
 Green: analogue
integrated signal
 Orange: slow
charge-to-width
(Q2W) signal
 Blue: fast timing
signal
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 6
40 ns
Time resolution for pulser measurements
Trigger signal (NIM)
 PMT like pulser signal as input into
PaDiWa-AMPS, pulser sync. was
used to trigger TRBv3
 Measured was the jitter between
fast_LE and TRBv3 trigger signal
 Up to now a time resolution of
about ~ 83 ps / 𝟐 = 58 ps can be
achieved
 Can still be improved with a proper
calibration of FPGA-TDCs of TRBv3
and better pulser
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 7
TRBv3
Test signals
fast signal
slow signal
PaDiWa-AMPS
Charge resolution for pulser measurements
(without walk correction)
 Charge-to-width (Q2W) measurement
for different signal widths (~ charges)
generated by pulser
 Absolute charge resolution ~ 4.5 pC
 Relative charge resolution depends on
attenuation resistor, for expected ECAL
signals its below 0.5%
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 8
Motivation for a beam-time at MAMI in Mainz
1 inch Hamamatsu R8619
1. Measure energy resolution
of modules with different
PMT types (1 inch
Hamamatsu, 1.5 inch EMI,
and 3 inch Hamamatsu)
+ price
- collect less light than EMI
1.5 inch EMI 9903KB
- not enough pieces
3 inch Hamamatsu R6091
Lead glass module from
OPAL experiment
2. Test new PaDiWa Amps
front-end board with
TRB3
3. Measure pulse shapes and compare
them with pulse shapes from cosmic
muons and LED light
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 9
+better light collection than EMI
- price
Test conditions at MAMI in Mainz
 Used secondary beam of g from MAMI facility at
Johannes Gutenberg-Universität Mainz
 g produced on Cu-target irradiated by 1508.4
MeV electron beam
 g beam intensity ~ 5 kHz (100 Hz in trigger-rate)
Tagger
 Used tagger to select 8 known g energies (100 1400 MeV)
 8 different trigger signals – 8 energies measured
in one measurement
 Beam collimated by Ø 2 mm lead collimator
placed 1.5 meters upstream
 Beam size in front of the modules ~ 6 mm
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 10
The experimental setup in hall A2
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 11
MAMI beam-time setup for PaDiWa-AMPS
Master Trigger
OR of Delayed Triggers
Plastic scintillator
8 beam energies
separated by time
delay
TRBv3
ECAL modules
fast signal
slow signal
PaDiWa-AMPS
Online analysis tools:
dabc+Go4 as flexible stand-alone live monitoring and analysis package
 developed by PaDiWa group
Hydra2 based offline analysis:
 DST production and hydra macro
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 12
Energy calibration for the different PMT types
 Results consistent with
reference measurements,
i.e. CAEN ADC
 All detectors at nominal voltage
(1 inch Hamamatsu close to
maximal – saturation effects)
 at this HV saturation effects starts
to appear – non-linear behavior!
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 13
1 inch 1300V
(nominal)
1 inch 1100V
1 inch 900V
Relative energy resolution
1 inch PMT does not follow
expected energy dependence
1 inch Ham.
Resolution [%]
1.5 inch EMI
3 inch Ham.
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 14
 Best energy
resolution for 3″ PMT
 integration
parameters
optimized for this
PMT
Summary
 PaDiWa-AMPS COME and KISS Q2W principle is working:
 In laboratory conditions
 In beam conditions
 Energy resolution of different ECAL modules at 1 GeV g beam measured with
PaDiWa-AMPS comparable with reference measurement:
 3″ PMT: 4.76% (PaDiWa-AMPS optimized to this PMT)
 1.5″ PMT: 5.76%
 1″ PMT: 7.78%
 Timing measurements of ECAL modules are in progress
 measurements with rotated modules show similar energy resolution as with nonrotated modules
 See also talk of A. Neiser on simulations for the PaDiWa AMPS (HK 6.3)
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 15
Thank you for you attention!!!
1GSI
Helmholtzzentrum, Darmstadt,
Germany;
2Institute
for Nuclear Research, Moscow,
Russia;
3
Institut für Kernphysik, Goethe-Universität,
Frankfurt, Germany;
4Nuclear
Physics Institute of ASCR, Rez,
Czech Republic;
5
Institut für Kernphysik, TU Darmstadt,
Darmstadt, Germany;
6Smoluchowski
Institute of Physics,
Jagiellonian University of Krakow, Poland;
7Institut
für Kernphysik, Johannes
Gutenberg-Universität, Mainz, Germany
The HADES ECAL team: 1S. Linev, 2O. Petukhov, 1W. König, 3B. Kardan, 4O. Svoboda,
4P. Tlustý, 5A. Rost, 1J. Pietraszko, 4P. Ramos, 6G. Korcyl, 1M. Traxler, missing: 5T. Galatyuk,
3J. Michel, 1C. Ugur
Special Thanks to the MAMI facility in Mainz for providing excellent beam conditions and their
help with this measurements: 7A. Thomas, 7P. Ott, 7P. Otte, 7P. Skott, 7A. Neiser
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 16
Backup
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COME & KISS: Charge Measurement with an
FPGA
 Idea: Modified Wilkinson ADC
 Integrate input signal with a capacitor
 Discharge via a current source
 fast crossing of zero
 Q2W: Measure time to reach zero
~Q using an FPGA-TDC
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 18
Walk correction via leading edges
 Q2W measured for different
signal widths (~ charges)
 Jitter of the slow discriminator
width (charge) can be corrected
offline using jitter between
leading edges of fast & slow
signal (walk)
 Q2W resolution still can be
improved
18/03/2014 | DPG-Frühjahrstagung 2014, Frankfurt | Adrian Rost | 19

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