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Development of a very small satellite “ Tsubame ” for Hard X-ray polarimetry of GRBs. ○ T. Toizumi , T. Enomoto , Y. Yatsu, N. Kawai, S. Matsunaga (Tokyo Tech), T. Nakamori , J. Kataoka ( Waseda Univ.), & S. Kubo (Clear Pulse .co). Contents. The “ Tsubame ” Project
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Development of a very small satellite“Tsubame”for Hard X-ray polarimetry of GRBs ○T. Toizumi, T. Enomoto, Y. Yatsu, N. Kawai, S. Matsunaga (Tokyo Tech), T. Nakamori, J. Kataoka (Waseda Univ.), & S. Kubo (Clear Pulse .co)
Contents • The “Tsubame” Project • Description of Hard X-ray Polarimeter (HXCP) • Results of X-ray Beam Test • Summary
Cube-Sat Project in Tokyo Tech • We have been working on cube sat projects since 2001~ Now Developing In Operation In Operation Re-Entered Tsubame CUTE I(2003) Cute1.7+APD(2006) Cute1.7+APD II (2008) Tsubame is the 4th very small satellite in Tokyo Tech. ・ Dimension:50 x 50 x 50 cm3 ・ Total Mass: 50 kg ・ Attitude Control: 4 CMGs (6 degrees/s) ・ Launch:Early 2013~
Science Instruments of the Tsubame Wide-field Burst Monitor • For “Real time” and “Automatic” polarimetry, • Two detector systems are onboard. • Wide-field Burst Monitor (FoV: 2π str) • → Detection and Localization • Hard X-ray Compton Polarimeter • → Polarimetry at 30-200 keV energy band Hard X-ray Compton Polarimeter Observation Sequence Trigger and Localization 2. High Speed Pointing 3. Observation (<15 s after the trigger)
η Polarized direction Hard X-ray Compton Polarimeter APD MAPMT MAPMT APD CsI(Tl) scintillator Plastic scintillator ・Detection principle : anisotropy of the Compton scattering ・Performance Effective area: 7 cm2@ 100 keV(Physical area: 36cm2) Modulation Factor: 47.8 ±0.9 % Minimum Detectable Pol.(3σ): 6.2% (3.2x10-5 erg/cm2/s @25-100keV)
Development of prototype polarimeter Plastic array CsI array CsI Plastic array MAPMT APD plastic CsI array CsI array Geometry of the Detector ASIC for PMT ASICfor APD MAPMT APD APD ~20 cm trigger trigger data data hold hold ASIC for APD ASIC for APD ADC ADC ASIC for PMT IFC Interface Card(IFC) Data bus (outside) Prototype polarimeter for beam test ・ Plastic 16units, CsI 16units (Partial model of 1 PMT + 16 APDs) ・Two types of ASIC ・ADCs triggered by coincidence
Polarized Beam Test @KEK-PF Polarized direction ・2009/Dec/20th ~ Dec/24th ・(KEK @ Tsukuba, Japan) Photon Factory (PF) BL 14A Polarized X-ray beam Rotated per 45degree Polarized direction 90 % polarized 82.5 keV X-ray beam Equatorial mount Attenuator (Tungsten-foil) Polarimeter Setup Image
Obtained Spectra Spectrum of the recoil electrons detected by Plastic (PMT) Spectrum of Scattered photons detected by CsI(Tl) (APD) Coutns Coutns Deposit Energy [keV] Photon Energy [keV] Compton 10 Total energy (keV) Total energy (keV) Photo- electric abs. Compton event Extracting Compton events 1 noise Deposit Energy [keV] Deposit Energy (keV)
Making the modulation curve of polarization All data are combined Reducing systematic error 0° Beam test MF = 72.3 ± 5.4 % Simulation MF = 68.7 ± 1.2 % Polarized direction Counts Counts Azimuth Angle [deg] Azimuth Angle [deg] The beam test result seems consistent with the simulation
We are now developing Engineering Model Passive Shield CsI APD Plastic Data processing boards PMT • HV module • Data processing boards • Lighter (~4 kg/unit) HVmodule • ASIC for APDs • Passive Shield (W, Sn, Pb)
Summary • We are now developing the small satellite Tsubame to be launched after 2013 • To measure the polarization of GRBs • Expecting significant detection of X-ray polarization for 6 GRBs/yr. • Evaluation of the performance of the polarimeter by irradiating polarized X-ray beam@KEK-PF • The results are consistent with the simulation • Manufacturing the EM of polarimeter based on prototype