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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