Guido Haefeli Lausanne PEBS meeting 10Jan 2011 1 Overview SPIROCA in testbeam 92010 Jean Baptiste Why change from SPIROCA to VATA64 VATA64 measurements Plans for the electronics ID: 221639
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Slide1
ECAL electronics
Guido Haefeli, Lausanne PEBS meeting 10.Jan. 2011
1Slide2
OverviewSPIROCA in
testbeam 9.2010(Jean-Baptiste)
Why change from SPIROCA to VATA64?VATA64 measurementsPlans for the electronics
for testbeam in 2011 2Slide3
Output dependence on the rate
A SiPM is illuminated with stable light pulses produced by a LED
(Light pulses are monitored with a PMT)
3Slide4
Baseline shift (fluctuation)
Pedestal spectra
4
Without common mode correction
After common mode correctionSlide5
SpirocA card problem causing oscillation
The shaping time settings (175ns) make the chip to oscillate, maybe also other settings have a negative effect on the stability. The settings were crosschecked with the Aachen electronics and are correct. Same chip module as on Aachen board used.
no hint where the problem is.
5Slide6
SpirocA
With the use of the high and low gain output on the two sides, 4 measurements for each event are taken.Why are high and low gain measurement required? Noise in high gain mode is too large for small signal measurement!
Difficult to calibrate Large baseline fluctuation for large signal. In the ECAL for large energy showers, order of 9 channels receive large signal, this
gives large baseline fluctuations.Difficult to remove this on the flight!Output dependent on the injection frequencyNo or very limited single photon detection possible with the ECAL detector, would be nice for calibration.
6Slide7
VATA64Very low noise, with one gain the range of 0..100pC can be covered. (see slide on dynamic range)
Therefore only two measurements need to be calibrated! Noise below one photon. Resolution restricted by the 12-bit ADC.No baseline fluctuation for large signals can be observed. Injection of 8 channels with large signal leaves
rms of neighbours unchanged.Single photon detection possible in high gain mode, this is useful for calibration.
Power consumption, some power saved by less drivers (only one gain output) and only half the number of cards. Reduction to current ECAL budget possible.7Slide8
Power consumption measurement
SPIROCA Pch=13mW,
Pcard=428mW, PECAL=51W (120 cards) (
A large fraction not used by the SPIROC but by the other components.High and low gain readout consumes power also in the ADC board (doubles the number of channels).
VATA64
P
ch
=23mW,
P
card
=1.5W, P
ECAL
=75W (50 cards)
Power saving options (shutting down fast shaper has to be implemented first)
Remove additional amp for debugging, power measured on the total card (~10mW/CH for the VA chip only)8Slide9
Dynamic range
Required dynamic range for the ECAL is
0..2000 photons. The number of effective pixels is below 2000, the detectable range should include some margin.
With the nominal gain (0.26Me/PE) this converts in a dynamic range
of
0..
83pC.
Since the
VATA64
offers a dynamic range of
0..50pC
a external current divider must be placed to reduce the signal by a factor 2.
The external
current divider
has only a very small or no impact on the noise and the dynamic range can be extended to
0…100pC
. This will be implemented on the next version electronics.9Slide10
Linearity in lowest gain 0..47pC, (before attenuation)
10Slide11
Baseline change with 8 pulsed channels
11
Rms
=0.75 ADC
Neighbouring channelSlide12
Measurement with high gain and low gain
12
High gain
8 ADC/PE
Low gain
4 ADC/PESlide13
Measurement with high gain and low gain
13
High gain
8 ADC/PE
Measurement with
detector as used by the
t
racker (50umx50um)Slide14
Shaping time settings 50ns to 300ns
Tp
=50ns
Tps
=200ns
Tp
=100ns
Tps
=250ns
Tp
=150ns
Tps
=300ns
Tp
=300ns
Tps
=450ns
Fastest setting is
50ns which corresponds
to a
peaking time
of the slow shaper
Tps
=200ns
Time of maximum measured after the arrival of the input signal (green in the plots)
14Slide15
Testbeam 9.2011
Use VATA64 v2, the chips are available now. The v2 was tested in the lab.Use intermediate PCB for connection of the SiPMs
with the PCB.Separate electronics card with the possibility to read 3x21 channels on the 64 channel readout chip.Card to card connection with small stacking height connectors. Has the advantage that different chips can be used to read the detectors without removing the connections to the
SiPMs.15Slide16
Testbeam 9.2011
Should we also provide a new version of the SPIROC readout? Card could
be plugged instead of the VATA64.
16Slide17
ConclusionWe still need to find the shaping time bug on the
SpirocA cardWe need to decide if we produce a new version SpirocA
card for the next testbeamThe VATA64 chip has clearly advantages over the
SpirocA so we want to use it in the next testbeam17