Hard X-ray Polarimeter for Small Satellite Design, Feasibility Study, and Ground Experiments K. Hayashida (Osaka University), T. Mihara (RIKEN), S. Gunji,

Hard X-ray Polarimeter for Small SatelliteHard X-ray Polarimeter for Small SatelliteDesign, Feasibility Study, Design, Feasibility Study, and Ground Experimentsand Ground Experiments

K. Hayashida (Osaka University),K. Hayashida (Osaka University),

T. Mihara (RIKEN), T. Mihara (RIKEN),

S. Gunji, F. Tokanai(Yamagata University)S. Gunji, F. Tokanai(Yamagata University)

SPIE@GlasgowSPIE@Glasgow 　　 2004/6/222004/6/22

+ Balloon Experiment+ Balloon Experiment

X-ray PolarimetryX-ray Polarimetry

It is still an unexploited field. It is still an unexploited field. http://www-conf.slac.stanford.edu/xray_polar/http://www-conf.slac.stanford.edu/xray_polar/

We are going to make a plan yet has no nWe are going to make a plan yet has no name ame Energy range=Hard X-ray (20-80keV)Energy range=Hard X-ray (20-80keV)Main Targets=Bright compact sourcesMain Targets=Bright compact sourcesOptics=Not to useOptics=Not to usePolarimeter type = Scattering Polarimeter type = Scattering

Targets of X-ray PolarimetryTargets of X-ray Polarimetry Synchrotron Radiation Synchrotron Radiation

SNRSNR （（ Pulsar Nebulae, Shell TypPulsar Nebulae, Shell Typee ））

Clusters of galaxiesClusters of galaxies BlazarsBlazars 、、 QuasarsQuasars

Scattered RadiationScattered Radiation Accretion disk around black holeAccretion disk around black hole Accretion Torus Seyfert galaxiesAccretion Torus Seyfert galaxies

Magnetic field and scatteringMagnetic field and scattering PulsarsPulsars

Pol

ariz

atio

n D

egre

e

©CXC/NASA

Reflection by Accretion Disk

X-ray Energy (keV)

We aim primarily hard X-rays (20-80keV)We aim primarily hard X-rays (20-80keV) Non thermal componentNon thermal component is prominent in the hard X is prominent in the hard X

-ray band.-ray band. Energy dependenceEnergy dependence of polarization is important. of polarization is important. Polarization below 10keV was detected in 1970’ bPolarization below 10keV was detected in 1970’ b

ut has not yet been the hard X-ray band.ut has not yet been the hard X-ray band. Various projects for soft X-ray (AXP, PLEXAS,SXVarious projects for soft X-ray (AXP, PLEXAS,SX

P) polarimetry and gamma-ray polarimetry (POGP) polarimetry and gamma-ray polarimetry (POGO,..) are proposed, though XPE and POGO cover O,..) are proposed, though XPE and POGO cover some part of hard X-rays. some part of hard X-rays.

Balloon experiments prior to a satellite are effectivBalloon experiments prior to a satellite are effective for hard X-ray band. e for hard X-ray band.

(We began this study for the NeXT satellite in whic(We began this study for the NeXT satellite in which hard X-ray super mirrors will be employed.)h hard X-ray super mirrors will be employed.)

Is imaging capability essential for hIs imaging capability essential for hard X-ray polarimetry ?ard X-ray polarimetry ?

Polarization map would be amazing, but diffuse Polarization map would be amazing, but diffuse (>arcmin) sources are estimated to be dim in 20-(>arcmin) sources are estimated to be dim in 20-80keV. Crab is exceptional.80keV. Crab is exceptional. The 2The 2ndnd brightest Crab like= Kes75 3mCrab brightest Crab like= Kes75 3mCrab Tycho, SN1006 1mCrab-2mCrab Tycho, SN1006 1mCrab-2mCrab Coma cluster 2mCrabComa cluster 2mCrab

We should focus on We should focus on bright point-like sourcesbright point-like sources first. first.

1 2

for 1HXT

( ) ~ 400( / 20 )A E Ex keV cm

Collection power of Collection power of super mirror is very super mirror is very attractive, but might be attractive, but might be too expensive for a too expensive for a small satellite.small satellite.

NeXT HXT

Polarimeter TypePolarimeter Type

Scattering Type is better in Scattering Type is better in ththe sensitivitye sensitivity for hard X-ray no for hard X-ray non-imaging polatimetry. n-imaging polatimetry.

ScatteringScattering Photo-electron-trackPhoto-electron-trackAnistropy 1-sin2cos2 sin2cos2

Photon: travel straightPhoton: travel straight Electron: scatteredElectron: scattered

M >0.9 is possible, 0.5 is easy 0.4-0.5 was obtained

M 0.6 is max, 0.2-0.3 is easy Max ~0.07@20keV

- E>5keV + Imaging capability

Pacciani et al. 2002 SPIE

M: Modulation contrast … modulation observed against 100% polarized beam: Efficiency … the ratio of number of photons employed in the polarimetry to that incident to the polarimeter.

Mη

1/2

MinimumDetectablePolarization

Polarimetry using scattering target : Polarimetry using scattering target : employed in beam polarization calibrationemployed in beam polarization calibration

Ｅ

0

200

400

600

0 90 180 270 360

Ex=10keV

cou

nts

rotation angle

KEK-PF 10keV beam by Hayashida et al.

Spring8 20keV beam by Tokanai et al.

MM1/21/2 x f x f1/21/2

M~1 <<1

M~0.5 ~0.6

M~0.25 ~0.6

f<<1

f~1/4

f~1

f: effective area of scatter /total area

GAPOMMihara et al.

Top view Side view

Scattering target

Detector

M should be higher to reduce systematics

Segmented/Active Scatter PolarimeterSegmented/Active Scatter PolarimeterScatter=Plastic Scintillator(e.g. 2mmx2mmx40mm x 54)

Absrber=CdTe (e.g.2mmx0.5mmx40mmx32)(or CSI)

Multi-Anode Position sensitive PMT

18mm

Whole detector is actrively Whole detector is actrively Shielded by BGO or CsIShielded by BGO or CsI

X-ray

Plastic CdTe or CSI

Efficiencyηfor three kinds of eventsEfficiencyηfor three kinds of events

Double eventAbsorped eventSingle event

Compton recoil not detected 　 Compton recoil

detected 　 　

Photo Absorption

EfficiencyEfficiency and Modulation Contrast and Modulation Contrast ＭＭX-rays are irradiated uniformly on the plastic scintillator

Double hit events

Single hit events

M~0.55

M~0.28

Double hit events

Single hit events

Experiment on the groundExperiment on the groundTop View

CsI(Tl)plastic scintillator

52 mm

6 mm

H8500 (52 x 52 x 28 mm3) is verycompact. The uniformity of anodesis fairly good.

Balloon Experiment by Yamagata Balloon Experiment by Yamagata Group (Gunji et al.)Group (Gunji et al.)

Collimator

Scinti

Balloon Flight on 2004June3rdBalloon Flight on 2004June3rdfrom Sanriku-Balloon Centerfrom Sanriku-Balloon Center

Altitude (km)

Raw Counting Rate not filtered with ANTI

Detectors functioned properly.Did it detect Crab ? How about its polarization degree?

Polarization SensitivityPolarization Sensitivity

0.1

1

10

100

10 100 1000

Flux (mCrab)

40-80keV (double)

0.1

1

10

100

10 100 1000

Flux (mCrab)

20-40keV (single)

100ksWithout BGD

Considering BGD

1Ms

100ks

1Ms

Double Hit Events 40-80keV Single Hit Events 20-40keV

25 units of Balloon experiments ->Satellite

Low energy extensionLow energy extension

0.1

1

10

100

10 100 1000

Flux (mCrab)

5-20keV (Li)

Top View

CsI(Tl)plastic scintillator

52 mm

6 mm

Li target

Ti filter

Single Hit (Li) Events 5-20keV

SummarySummary Scattering type is better for hard X-ray non-imagiScattering type is better for hard X-ray non-imagi

ng polarimeterng polarimeter To optimize M,h,f, we propose to use segmentedTo optimize M,h,f, we propose to use segmented

/active scatter as a target. /active scatter as a target. Ground experiments / balloon experiments are in Ground experiments / balloon experiments are in

progress.progress. Low energy extension is possible by inserting Li Low energy extension is possible by inserting Li

target at the center. Increase the PMT sensitivity target at the center. Increase the PMT sensitivity will also lower the energy threshold.will also lower the energy threshold.

Electric power and circuits is the issue we have tElectric power and circuits is the issue we have to consider. (Heritage of Astro-E2 HXD, NeXT So consider. (Heritage of Astro-E2 HXD, NeXT SGD may be useful) GD may be useful)

Next step: Name the project. Next step: Name the project.