Data Acquisition System of

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Data Acquisition System of the PoGOLite Balloon
Experiment
Hiromitsu TAKAHASHI (Hiroshima University) hirotak
a_at_hep01.hepl.hiroshima-u.ac.jp
M. Matsuoka, Y. Umeki, H. Yoshida, T. Tanaka, T.
Mizuno, Y. Fukazawa (Hiroshima University), T.
Kamae, G. Madejski, H. Tajima (SLAC and KIPAC),
M. Kiss, W. Klamra, S. Larsson, C. Marini
Bettolo, M. Pearce, F. Ryde, S. Rydström (Royal
Institute of Technology), K. Kurita, Y. Kanai, M.
Arimoto, M. Ueno, J. Kataoka, N. Kawai (Tokyo
Institute of Technology), M. Axelsson, L.
Hjalmarsdotter (Stockholm University), G. Bogaert
(Ecole Polytechnique), S. Gunji (Yamagata
University), T. Takahashi (JAXA/ISAS), G. Varner
(University of Hawaii), T. Yuasa (University of
Tokyo)
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Network Topology Utilized in PoGOLite
- As a part of studying the SpaceWire capability,
we are constructing the data acquisition system
(DAQ) of PoGOLite with Tree structure, since
PoGOLite is a scalable detector (the number of
signal inputs changes from 91 to 271). - Once the
function in one tree is established with the
smaller number of the inputs, we easily expand
the system.
Final version
Current
2010
CPU
Router
Router
Router
Router
Router
DIO
FADC
FADC
FADC
FADC
FADC
FADC
FADC
FADC




- This system is developed as a part of the JAXA
project "Shin-Concept Project in JAXA".
3
Polarized Gamma-ray Observer (PoGOLite)
- The Polarized Gamma-ray Observer, PoGOLite, is
a balloon experiment with the capability of
detecting 10 polarization from a 200 mCrab
celestial object in the energy-range 2580 keV. -
The project is international collaboration
including Japan, Sweden and US. - Its pathfinder
flight is scheduled in 2010 from Esrange facility
(Sweden).
217 detector units of plastic scintillators ?
Measuring the azimuthal angle anisotropy of
Compton-scattered photons. Well-type phoswich
detector ? Large effective area, lower background
SAS
PDCs
Polarized vector
1 m
Slow plastic scintillator

Distribution of scattered photon
Fast plastic scintillator
PMTs
Bottom BGO
4
Pathfinder Flight in 2010 from Sweden
- 61 well-type phoswich detector cells (PDCs)
with plastic and BGO. - 30 side anti-coincidence
shields (SASs) with BGO.
Total 91 units
? Observing Crab nebula and Cyg X-1 etc.
- All the detectors units have been already
constructed and the install to the housing is
now started.
30 SASs with Housing
PDC units
Slow plastic scintillator(t 300ns)
Fast plastic scintillator (t 2ns)
Detecting photoabsorbed orCompton-scattered
photons
BGO crystal (t300ns)
PMT low-noise high Q.E.
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SpaceWire-Based Data Acquisition System
- To measure polarization, we need to measure
waveforms of both Compton-scattered and
photoabsorbed events from some PDC units.
- PMT signals from PDCs and SASs are acquired
with the DAQ system consisting six parts with
four components.

• Front-end electronics
• Waveform digitizer
• Trigger logic
• Global event logic
• Microprocessor
• Storage system
• Routing

Waveform digitizer (FADC) board(Shimafuji/JAXA)
Digital I/O board (Shimafuji/JAXA)
SpaceCube1 (Shimafuji/JAXA)
Router board (NEC/JAXA)
Router board
Waveform digitizer board
Digital I/O board
SpaceCube1
5cm
All the components are operated with 5V input.
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KEK Beam Test (2008 Feb)
- To verify the performance of the detector units
and the flight-version DAQ system, 90 polarized
X-ray bema (50 keV) was irradiated at the center
PDC. - This setup is identical to that of the
61-unit pathfinder instrument, apart from the
number of the waveform digitizer boards.
Experimental setup (19 PDCs 1 SAS total 20
units)
Flight DAQ system
4 x FADC Boards (3 for PDCs, 1 for SAS)
Rotate every 30 deg
19 PDCs
1 SAS
50 keV X-ray (90 polarized)
1 x DIO Board
1 x SpaceCube
1 x Router Board
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Network Topology Utilized in PoGOLite
- As a part of studying the SpaceWire capability,
we are constructing the data acquisition system
(DAQ) of PoGOLite with Tree structure, since
PoGOLite is a scalable detector (the number of
signal inputs changes from 91 to 271). - Once the
function in one tree is established with the
smaller number of the inputs, we easily expand
the system.
Current
CPU
- Logical Addressing - RMAP access
Router
DIO
FADC
FADC

- This system is developed as a part of the JAXA
project "Shin-Concept Project in JAXA".
8
Block Diagram of DAQ System
Waveform digitizer board
Router board
SpaceCube1
Digital I/O board
Waveform digitizer board
- SpaceWire Setting (Threshold, HV, ) Data
reading by SpaceCube
Between SpaceCube and (waveform digitizer,
digital I/O, router boards)
- LVCMOS/LVDS Trigger, Data acquisition, Vetos
(pulse-shape discriminator, upper discriminator)
Between wavefrom digitizar and Digital I/O boards
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Waveforms of a Gamma-ray Event
- One photon has Compton-scattered in channel 0
and subsequently been photo-absorbed in channel 4
of the same waveform digitizer board.
? Determine the azimuthal angle anisotropy of
Compton-scattered photons
- Signals from the remaining six channels were
not stored due to the zero-suppression setting.
Ch 0
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Ch 6
Ch 7
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Results of Polarization Measurement
- All the 20 detector units and the DAQ system
worked well, and the data were acquired as we
assumed. - The obtained modulation factors (MFs)
are consistent with those predicted by our
GEANT4-based simulation within 5.
Measured MF for each group
Measured Modulation curves (depending on
distances from the center unit)
19 PDC units

• Inner 6 units

31.3 - 0.4

• Outer 12 units

37.9 - 0.7
40.2 - 0.8
There are 3 groups according to the distances
from the center.
Combined MF over 3 groups
(p)
34.1 - 0.3
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Data-Acquisition Rate with the previous
SpaceCube1

• One waveform event is 110 bytes
• Waveform 100 bytes (12 bits 4 bits (dummy) )
  x 50 clocks
• - Header 10 bytes Data ID, Board ID, TIME,
  Hit-pattern, Vetos

(15 pre-trigger and 35 post-trigger samples)
More than 32 events are stored in one waveform
digitizer board, SpaceCube reads 3520 bytes (
110 bytes x 32 events) at once via SpaceWire.
- we obtained a maximum data-acquisition rate of
about 400 waveforms per second, corresponding to
340 Kbps with the previous SpaceCube1. - This
rate is sufficient for the 61-unit pathfinder
flight planned in 2010. - The current SpaceCube1
has gt10 times higher data-acquisition speed than
the previous one, and we are testing with this
current version.
12
Network Topology Utilized in PoGOLite
- As a part of studying the SpaceWire capability,
we are constructing the data acquisition system
(DAQ) of PoGOLite with Tree structure, since
PoGOLite is a scalable detector (the number of
signal inputs changes from 91 to 271). - Once the
function in one tree is established with the
smaller number of the inputs, we easily expand
the system.
2010
CPU
Router
Router
Router
DIO
FADC
FADC
FADC
FADC


- This system is developed as a part of the JAXA
project "Shin-Concept Project in JAXA".
13
Background Monitoring by SAS Units
- As well as storing hit-pattern information for
background events coincident, the waveform
digitizer board for the SAS continuously records
a Pulse Height Analysis (PHA) histogram with a
12-bit resolution.
? Studying the in-flight background environment
- The pulse height of each trigger is obtained
with subtracting the base-line (pre-trigger pulse
height).
- 60 keV peak (241Am) is clearly seen even with
the irradiation of strong 137Cs.
Base-line subtraction
PHA spectra of 241Am with 137Cs
Am Cs(20kHz) Am Cs(15kHz) Am Cs(9kHz) Am
only(6kHz)
Huge signal by charged particle
Base-line subtraction
Normal PHA
Signal by gamma-ray background on the undershoot
60 keV peak
True PH
Base-line
Undershoot
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RCNP Beam Test (July 2006)
- SAS PHA spectra of 662 keV gamma-rays from
137Cs were obtained in a background from 392 MeV
protons. - UD events were discarded. - 662 keV
peak was unaffected even with a proton intensity
of up to 6.5 kHz. This rate is higher than that
expected in flight (1 kHz _at_ 40 km).
PHA spectra of 137Cs with 392 MeV protons
Experimental Setup
392 MeV Proton beam
BGO crystal for SAS
Cs proton(15kHz) Cs proton(6.5kHz) Cs
proton(930Hz) Cs only
Gamma-ray from radio isotope
Waveform digitizer board
SpaceCube
1 x Waveform digitizer board
1 x SpaceCube
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Conclusions
- To study one of the SpaceWire performances, we
established the DAQ system of PoGOLite with Tree
structure. - The DAQ system consists of the
four components waveform digitizer board,
digital I/O board, SpaceCube1 and router
board. - The maximum data-acquisition rate is
obtained as 340 Kbps (400 waveforms) with the
previous SpaceCube1, and this rate is already
sufficient for the pathfinder flight scheduled in
2010 from Sweden. - Through the beam tests at
KEK and RCNP, the functions of the polarization
measurement by PDC and the background monitor by
SAS were also verified.
ACKNOWLEDGMENTS The SpaceWire-based I/O and
boards were developed in JAXAs programResearch
and Development for Future Innovative Satellite.