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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)
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Contents
The “Tsubame” Project Description of Hard X-ray Polarimeter (HXCP) Results of X-ray Beam Test Summary
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Tsubame is the 4th 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) TsubameRe-EnteredIn Operation In Operation
・ Dimension: 50 x 50 x 50 cm3 ・ Total Mass: 50 kg・ Attitude Control: 4 CMGs (6 degrees/s)・ Launch: Early 2013~
Now Developing
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Observation Sequence
1. Trigger andLocalization
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 30-200 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 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)
MAPMT
MAPMT
APD
APD
η
Polarized direction
6Development of prototype polarimeter
・ Two types of ASIC・ ADCs triggered by coincidence
Plasticarray
MAPMT
IFC
APD
CsIarray
ASIC for PMT ADC ADC
Plasticarray
CsIarray
MAPMT APD
trig
ger
trig
ger
data
data
hold
hold
ASIC forPMT
ASIC forAPD
Interface Card(IFC)
Prototype polarimeter for beam test・ Plastic 16 units, CsI 16 units(Partial model of 1 PMT + 16 APDs)
CsIarray
APD
ASICfor APD
Geometry of the Detector
plastic
CsI
~20
cm
ASICfor APD
Data bus (outside)
7Polarized Beam Test @KEK-PF
・ 2009/Dec/20th ～ Dec/24th ・ (KEK @ Tsukuba, Japan) Photon Factory (PF) BL 14A
Polarimeter
Equatorialmount
90 % polarized 82.5 keV X-ray
beam Attenuator(Tungsten-foil)
Setup Image
Polarized X-ray beam
Rotated per 45 degree
Polarized direction
Polarized direction
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Obtained SpectraSpectrum of the recoil electrons
detected by Plastic (PMT)Spectrum of Scattered photons
detected by CsI(Tl) (APD)
Deposit Energy [keV]
Deposit Energy [keV]
Tota
l ene
rgy
(keV
)
Compton event
Deposit Energy (keV)
Tota
l ene
rgy
(keV
)
Extracting Compton events
Photon Energy [keV]
Cout
ns
Cout
nsCompton
Photo-electric abs.
noise
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9Making the modulation curve of polarization
Beam testMF = 72.3 ± 5.4 %
The beam test result seems consistent with the simulation
Azimuth Angle [deg]Azimuth Angle [deg]
Coun
ts
Coun
ts SimulationMF = 68.7 ± 1.2 %
Polarized direction
0°All data are combined
Reducing systematic error
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Plastic
CsIAPD
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)
11Summary
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
