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2 Contents The “Tsubame” Project Description of Hard X-ray Polarimeter (HXCP) Results of X-ray Beam Test Summary

3 Tsubame is the 4 th very small satellite in Tokyo Tech. Cube-Sat Project in Tokyo Tech We have been working on cube sat projects since 2001~ CUTE I(2003) Cute1.7+APD(2006) Cute1.7+APD II (2008) Tsubame Re-Entered In Operation ・ Dimension: 50 x 50 x 50 cm 3 ・ Total Mass: 50 kg ・ Attitude Control: 4 CMGs (6 degrees/s) ・ Launch: Early 2013~ Now Developing

4 Observation Sequence 1.Trigger and Localization 2. High Speed Pointing 3. Observation (<15 s after the trigger) Hard X-ray Compton Polarimeter Wide-field Burst Monitor Science Instruments of the Tsubame 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 keV energy band

5 Hard X-ray Compton Polarimeter Plastic scintillator CsI(Tl) scintillator ・ Detection principle : anisotropy of the Compton scattering ・ Performance Effective area ： 7 cm 100 keV （ Physical area: 36cm 2 ） Modulation Factor: 47.8 ±0.9 % Minimum Detectable Pol.(3σ): 6.2 % (3.2x10 -5 erg/cm 2 MAPMT APD η Polarized direction

6 Development of prototype polarimeter ・ Two types of ASIC ・ ADCs triggered by coincidence Plastic array MAPMT IFC APD CsI array ASIC for PMT ADC Plastic array CsI array MAPMTAPD trigger data hold ASIC for PMT ASIC for APD Interface Card(IFC) Prototype polarimeter for beam test ・ Plastic 16 units, CsI 16 units (Partial model of 1 PMT + 16 APDs) CsI array APD ASIC for APD Geometry of the Detector plastic CsI ~20 cm ASIC for APD Data bus (outside)

7 Polarized Beam ・ 2009/Dec/20th ～ Dec/24th ・ Tsukuba, Japan) Photon Factory (PF) BL 14A Polarimeter Equatorial mount 90 % polarized 82.5 keV X-ray beam Attenuator (Tungsten-foil) Setup Image Polarized X-ray beam Rotated per 45 degree Polarized direction

8 Obtained Spectra Spectrum of the recoil electrons detected by Plastic (PMT) Spectrum of Scattered photons detected by CsI(Tl) (APD) Deposit Energy [keV] Total energy (keV) Compton event Deposit Energy (keV) Total energy (keV) Extracting Compton events Photon Energy [keV] Coutns Compton Photo- electric abs. noise 10 1

9 Making the modulation curve of polarization Beam test MF = 72.3 ± 5.4 % The beam test result seems consistent with the simulation Azimuth Angle [deg] Counts Simulation MF = 68.7 ± 1.2 % Polarized direction 0° All data are combined Reducing systematic error

10 Plastic CsI APD Data processing boards HV module Passive Shield PMT We are now developing Engineering Model ASIC for APDs Passive Shield （ W, Sn, Pb ） HV module Data processing boards Lighter ( ～ 4 kg/unit)

11 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 The results are consistent with the simulation Manufacturing the EM of polarimeter based on prototype