Data Acquisition System of the Po GOLite Balloon

Data Acquisition System of the Po. GOLite Balloon Experiment Hiromitsu TAKAHASHI (Hiroshima University) hirotaka@hep 01. 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)

Network Topology Utilized in Po. GOLite - As a part of studying the Space. Wire capability, we are constructing the data acquisition system (DAQ) of Po. GOLite with Tree structure, since Po. GOLite 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 2010 Final version Router DIO FADC … FADC Router FADC … FADC - This system is developed as a part of the JAXA project "Shin-Concept Project in JAXA".

Polarized Gamma-ray Observer (Po. GOLite) - The Polarized Gamma-ray Observer, Po. GOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 m. Crab celestial object in the energy-range 25– 80 ke. V. - 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 PDCs SAS Slow plastic scintillator Fast plastic scintillator PMTs Bottom BGO f n o on ti o hot ibu d p e str Di atte r sc 1 m Po l ed z i ar r o t c ve

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 (τ~ 300 ns) Fast plastic scintillator (τ~ 2 ns) Detecting photoabsorbed or Compton-scattered photons BGO crystal (τ~300 ns) PMT : low-noise & high Q. E.

Space. Wire-Based Data Acquisition System - To measure polarization, we need to measure waveforms of both Comptonscattered 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 (FADC) board • Waveform digitizer (Shimafuji/JAXA) • Trigger logic • Global event logic Digital I/O board (Shimafuji/JAXA) • Microprocessor Space. Cube 1 (Shimafuji/JAXA) • Storage system Router board (NEC/JAXA) • Routing Router board Waveform digitizer board Digital I/O board Space. Cube 1 5 cm All the components are operated with +5 V input.

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 ke. V) 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) Rotate every 30 deg Flight DAQ system 4 x FADC Boards (3 for PDCs, 1 for SAS) 19 PDCs 50 ke. V X-ray (~90% polarized) 1 SAS 1 x DIO Board 1 x Space. Cube 1 x Router Board

Network Topology Utilized in Po. GOLite - As a part of studying the Space. Wire capability, we are constructing the data acquisition system (DAQ) of Po. GOLite with Tree structure, since Po. GOLite 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".

Block Diagram of DAQ System Waveform digitizer board Router board Space. Cube 1 Digital I/O board Waveform digitizer board - Space. Wire : Setting (Threshold, HV, …) & Data reading by Space. Cube Between Space. Cube 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

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 zerosuppression setting. Ch 0 Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 Ch 6 Ch 7

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 GEANT 4 -based simulation within ~5%. 19 PDC units Measured Modulation curves (depending on distances from the center unit) Measured MF for each group • 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%

Data-Acquisition Rate with the previous Space. Cube 1 One waveform event is 110 bytes: -Waveform 100 bytes : (12 bits + 4 bits (dummy) ) x 50 clocks (15 pre-trigger and 35 post-trigger samples) - Header 10 bytes: Data ID, Board ID, TIME, Hit-pattern, Vetos More than 32 events are stored in one waveform digitizer board, Space. Cube reads 3520 bytes (= 110 bytes x 32 events) at once via Space. Wire. - we obtained a maximum data-acquisition rate of about 400 waveforms per second, corresponding to ~340 Kbps with the previous Space. Cube 1. - This rate is sufficient for the 61 -unit pathfinder flight planned in 2010. - The current Space. Cube 1 has >10 times higher data-acquisition speed than the previous one, and we are testing with this current version.

Network Topology Utilized in Po. GOLite - As a part of studying the Space. Wire capability, we are constructing the data acquisition system (DAQ) of Po. GOLite with Tree structure, since Po. GOLite 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. CPU 2010 Router DIO FADC … FADC Router FADC … FADC - This system is developed as a part of the JAXA project "Shin-Concept Project in JAXA".

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

RCNP Beam Test (July 2006) - SAS PHA spectra of 662 ke. V gamma-rays from 137 Cs were obtained in a background from 392 Me. V protons. - UD events were discarded. - 662 ke. V peak was unaffected even with a proton intensity of up to 6. 5 k. Hz. This rate is higher than that expected in flight (~1 k. Hz @ ~40 km). Experimental Setup 392 Me. V Proton beam BGO crystal for SAS Gamma-ray from radio isotope Waveform digitizer board Space. Cube 1 x Waveform digitizer board 1 x Space. Cube PHA spectra of 137 Cs with 392 Me. V protons Cs + proton(15 k. Hz) Cs + proton(6. 5 k. Hz) Cs + proton(930 Hz) Cs only

Conclusions - To study one of the Space. Wire performances, we established the DAQ system of Po. GOLite with Tree structure. - The DAQ system consists of the four components: waveform digitizer board, digital I/O board, Space. Cube 1 and router board. - The maximum data-acquisition rate is obtained as ~340 Kbps (~400 waveforms) with the previous Space. Cube 1, 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 Space. Wire-based I/O and boards were developed in JAXA’s program ”Research and Development for Future Innovative Satellite. ”