1. SPIROC Readout in PEBS PEBS - Positron Electron Balloon Spectrometer
Orsay, March 2009
Waclaw Karpinski
I. Physikalisches Institut B
RWTH Aachen

2. Outline Introduction PEBS detector concept
Description of the Prototype Board for a PEBS ScFi-module with 128 channels
First measurements
Summary
Waclaw Karpinski

3. PEBS
PEBS is a project in Research & Development phase The purpose of the experiment is a precision
measurement of the electron & positron cosmic ray
flux in the energy range from 1 to 2000 GeV.
Superconducting magnet, B-Field: 0.8 Tesla
4 ScFi-Outer Tracker Planes
single Point resolution mm
6 Si-Inner-Tracker Planes
single Point resolution mm
2 TRD‘s, each with 12 layers
Proton Rejection 100 GeV
11 X0 ECAL, Weight 650 kg
Key parameters: Acceptance: ~3000 cm2 sr Weight: ~2000 kg Power: ~900 Watt
R&D Phase: – 2009 Construction Phase: – PEBS-1
2012 – PEBS-2
Waclaw Karpinski

4. Proposal for PEBS-1 & PEBS-2 submitted to NASA in March 2009 by:
PEBS Collaboration
Proposal for PEBS-1 & PEBS-2 submitted to NASA in March 2009 by:
Prof. J. Beatty, Ohiho State University PEBS ToF, Gondula
Prof. G. Dissertori, ETH Zuerich, Switzerland PEBS ECAL
Prof. Dr. T. Nakada, EPF Lausanne, Switzerland PEBS ECAL
Prof. Dr. S. Schael, RWTH Aachen, Germany PEBS Magnet, TRD, Tracker
Prof. Dr. S. Swordy, University Chicago, USA PEBS Trigger, DAQ, RICH
Decision expected by September 2009 4
Waclaw Karpinski

5. PEBS
PEBS is planned to be a part of NASA`s Scientific Ballooning Program
Two flights :
Arctic : in 2012
Antarctica: in 2014
Why go to Arctic or Antarctica?
Because the Sun never sets
during summer!
And stratospheric wind pattern
is circular around pole.
CREAM ~42 days
Waclaw Karpinski

6. THE ELEMENTAL COMPOSITION OF HIGH ENERGY COSMIC RAYS:
BALLOON
PAYLOAD
Solar
Panel
PARACHUTE
HELIUM
LAUNCH VEHICLE
DESCENT ON PARACHUTE
AT FLOAT
40 km altitude
(3 mbar) 6

7. Outer-Tracker Module 250 µm
Module support: 10 mm Rohacell foam between two 100 µm thin carbon fiber skins
five layers of scintillating fibers, 250 µm, glued to top and bottom of support structure
8 SiPm arrays on each module end
SiPM arrays:
- 32 channels 0.25 x 1.1mm2
- 80 pixels/channel
256 readout channels per module-end
250 µm
Waclaw Karpinski

8.
Waclaw Karpinski

9. Readout Boards Outer Tracker: 8 Spiroc1 chips per board
Spirocs mounted on BGA carriers
256 channels per board
For PEBS-1 and PEBS-2 in total
1700 Spiroc1 chips needed
ECAL:
One Spiroc1 chip per board
144 boards needed
Waclaw Karpinski

10. Prototype Board HPE-SPIROC-128
analogue, multiplexed readout of 128 channels
4 Spiroc chips, 32 channels per chip used
chips mounted on a pluggable chip carrier
differential analogue data transfer at 5 MHz
to higher DAQ
download of slow control parameters
via USB or SPI interface
SPIROC
16 mm
SPI Interface
13 mm
Interface to higher DAQ
USB Interface
Waclaw Karpinski

11. First results The readout board is operating satisfactory
32 chips assembled on the chip carriers
Chip yield ~60%
some chips might have been damaged by us during commissioning of the readout board
SPIROC
Digital Part
Analogue Part
SR Output
DACs
Output 1 ok
ch15: Vmin=VRef 2 3
ch0: Vmin=VRef 4 5
error 6 7
Vmin ~ 1.1V 8
broken 9 10
b r o k e n 11
ch10: low gain 12 13 14 15 16 17 18 19 20 21 22 23
21 channels bad 24 25 26 27 28 29 30 31 32
Waclaw Karpinski

12. Single photoelectron spectrum
Aachen prototype board
Spectra taken with Aachen prototype and
Orsay test board under the same
conditions:
High gain, Cfb=100fF, T=25ns
Hamamatsu SiPm S C
Vbias =70.2V, I=0,60µA
good S/N ratio ~ 8
no significant differences in gain and
noise performance between the
readout boards
Orsay test board
Waclaw Karpinski

13. SPIROC vs.VA32_75
Measurements performed with SiPms from Hamamatsu MPPC
Readout at 5 MHz multiplexing
Spiroc: High Gain, Feedback Cap.=100pF, Shaping Time=25ns
VA damping 300 x on the input
SPIROC much better performance
HamHamamatsu amatsu MPPC 71V
SPIROC Readout
VA32 – 75 Readout
SpiRoc
S/N: 7.9
VA32_75
S/N: 3.3
Waclaw Karpinski

14. Power consumption
Unlike the operation in ILC, in PEBS it is not possible to use the power pulsing method to reduce the power consumption of the SPIROC chips
The total power consumption amouts to~ 390 mW/chip →10.8mW/ch
Not acceptable for PEBS-Tracker !
For PEBS maximal power consumption allowed:
< 2.5 mW/channel at multiplexer frequency of 5 MHz
Breakdown of the power consumption:
preamplifier+shaper = 4 mW/channel
SCA = 5.6 mW/channel
auxiliary parts (not needed in our application ) =2.2 mW/channel
Waclaw Karpinski

15. Reduction of Power Consumption
Turn off Preamplifier LG
Pin 222, ibi_pa_lg directly to GND vdda_pa : mA → mA
vdd_pa: mA → mA
Turn off  Gain Selection    - on pin 192, ibo_gs , directly  to VDD vdd_gs: mA → 9.3 mA    - on pin 193, ibm_gs, directly  to VDD → 9.0 mA    - on pin 194, ibi_gs, directly  to GND → 7.9 mA
Turn off ADC
on pin 191, ib_adc_discri, directly to GND vdd_adc : mA → 0 mA
Reduce SCA power
pin 212 ib_SCA , kOhm to Vdd vdd_sca:
510 kOhm to GND ( 5 MHz readout ): mA → 13 mA
68 kOhm to GND (1 MHz readout) : mA → mA
Turn on output buffer only for reading vdd_ gs: mA → mA
After reduction the total power consumption decreases to :
2.5 mW / channel at 1 MHz readout frequency
3.4 mW / channel at 5 MHz readout frequency , Still too much !
Waclaw Karpinski

16. Analog Output Impedance
SPIROC does not have a high impedance analog output
unlike the digital outputs, the analog outputs cannot be directly
connected in a daisy chain
Waclaw Karpinski

17. Summary So far the optimal chip does not exist. Two options: SPIROC
VA64 from Gamma Medica-Ideas
Spiroc show better performance
SPIROC has an excellent S/N performance
The DAC operates very well
The power consumption however is too high
Waclaw Karpinski

18. Summary Requirements for the new SPIROC optimized for PEBS
64 channels (32 channels version not excluded)
analogue functionality only
Power consumption < 2.5 mV channels
Additional power shut down for following stages :
preamp low gain
preamp high gain
gain selection
SCA
Daisy chain of analogue outputs
Differential current output which is turned on for reading only
Quantity: ~ 1000 chips with 64 channels
Waclaw Karpinski