Data Acquisition System of the PoGOLite Balloon Experiment Hiromitsu TAKAHASHI (Hiroshima University) 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)

Network Topology Utilized in PoGOLite CPU DIOFADC … Router - 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. - This system is developed as a part of the JAXA project "Shin-Concept Project in JAXA". Router FADC … … … Final versionCurrent2010

Polarized Gamma-ray Observer (PoGOLite) 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 Distribution of scattered photon PMTs Fast plastic scintillator Slow plastic scintillator Bottom BGO - 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 25–80 keV. - The project is international collaboration including Japan, Sweden and US. - Its pathfinder flight is scheduled in 2010 from Esrange facility (Sweden). 1 m

Pathfinder Flight in 2010 from Sweden - 61 well-type phoswich detector cells (PDCs) with plastic and BGO side anti-coincidence shields (SASs) with BGO. → Observing Crab nebula and Cyg X-1 etc. Slow plastic scintillator (τ~ 300ns) Fast plastic scintillator (τ~ 2ns) BGO crystal (τ~300ns) PMT : low-noise & high Q.E. PDC units - All the detectors units have been already constructed and the install to the housing is now started. 30 SASs with Housing Detecting photoabsorbed or Compton-scattered photons Total: 91 units

SpaceWire-Based Data Acquisition System - 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 - To measure polarization, we need to measure waveforms of both Compton- scattered and photoabsorbed events from some PDC units. Waveform digitizer board Digital I/O board SpaceCube1 Router board Waveform digitizer (FADC) board (Shimafuji/JAXA) Digital I/O board (Shimafuji/JAXA) SpaceCube1 (Shimafuji/JAXA) Router board (NEC/JAXA) 5cm All the components are operated with +5V input.

KEK Beam Test (2008 Feb) 19 PDCs 1 SAS 4 x FADC Boards (3 for PDCs, 1 for SAS) 1 x SpaceCube 1 x Router Board 1 x DIO Board - 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) 50 keV X-ray (~90% polarized) Rotate every 30 deg Flight DAQ system

Network Topology Utilized in PoGOLite CPU DIOFADC … - 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. - This system is developed as a part of the JAXA project "Shin-Concept Project in JAXA". Router FADC Current - Logical Addressing - RMAP access

Block Diagram of DAQ System Between SpaceCube and (waveform digitizer, digital I/O, router boards) - SpaceWire : Setting (Threshold, HV, …) & Data reading by SpaceCube (pulse-shape discriminator, upper discriminator) - LVCMOS/LVDS : Trigger, Data acquisition, Vetos Between wavefrom digitizar and Digital I/O boards Waveform digitizer board Digital I/O board SpaceCube1 Router board Waveform digitizer board

Waveforms of a Gamma-ray Event Ch 4 Ch 0 Ch 5 Ch 1 Ch 6 Ch 2 Ch 7 Ch 3 - One photon has Compton-scattered in channel 0 and subsequently been photo-absorbed in channel 4 of the same waveform digitizer board. - Signals from the remaining six channels were not stored due to the zero- suppression setting. → Determine the azimuthal angle anisotropy of Compton-scattered photons

Results of Polarization Measurement Measured MF for each group % % % Inner 6 units Outer 12 units 19 PDC units Measured Modulation curves (depending on distances from the center unit) There are 3 groups according to the distances from the center. Combined MF over 3 groups % - 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%. ()()

Data-Acquisition Rate with the previous SpaceCube1 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 The current SpaceCube1 has >10 times higher data-acquisition speed than the previous one, and we are testing with this current version.

Network Topology Utilized in PoGOLite CPU DIOFADC … Router - 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. - This system is developed as a part of the JAXA project "Shin-Concept Project in JAXA". Router FADC … 2010

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). Base-line subtraction Normal PHA Am + Cs(20kHz) Am + Cs(15kHz) Am + Cs(9kHz) Am only(6kHz) Huge signal by charged particle Undershoot Signal by gamma-ray background on the undershoot True PH Base-line - 60 keV peak ( 241 Am) is clearly seen even with the irradiation of strong 137 Cs. 60 keV peak Base-line subtractionPHA spectra of 241 Am with 137 Cs

RCNP Beam Test (July 2006) Cs + proton(15kHz) Cs + proton(6.5kHz) Cs + proton(930Hz) Cs only 392 MeV Proton beam Waveform digitizer board SpaceCube Gamma-ray from radio isotope BGO crystal for SAS - SAS PHA spectra of 662 keV gamma-rays from 137 Cs were obtained in a background from 392 MeV protons. - UD events were discarded 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 ~40 km). Experimental Setup PHA spectra of 137 Cs with 392 MeV protons 1 x Waveform digitizer board 1 x SpaceCube

Conclusions ACKNOWLEDGMENTS The SpaceWire-based I/O and boards were developed in JAXA’s program ”Research and Development for Future Innovative Satellite.” - 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.