observations by balloon-borne emulsion telescope with a high
GRAINE project g-ray
angular resolution, polarization sensitivity and large-aperture-area

Satoru Takahashi (Kobe Univ.)for GRAINE collaboration, PI: S. Aoki (Kobe Univ.)
Aichi University of education, ISAS/JAXA, Kobe University, Nagoya
University, Okayama University of science, Utsunomiya University

SNR W44
Simulation
gEmulsion g-ray telescope
Microscopic view of an emulsion filme- e+

BG photo： GRAINE2011, JAXA scientific ballooning (taken by NHK)

Fermi's Five-year View of the Gamma-ray Sky (>1GeV)

Image credit: NASA/DOE/Fermi LAT Collaboration>3000 sources (3FGL)

Morphology

Un-ID

SNR W44
Abdo et al., Science, 2010
Color : 2-10GeV gamma-ray (Fermi LAT)
Contour : IR(Spitzer)

Energy spectrum(Eg>1GeV)

Unknown
31%
M. Ackermann et al. Science, 2013

Polarization
CrabTransient
GRB
Yonetoku et al., ApJ, 2011

Dark matter
Galactic Center
1.0-3.16GeV
Total flux

A. J. Dean, et al., Science, 2008
INTEGRAL

2.5°0 -2.5°
Crab nebula flare

ResidualBuehler et al., ApJ, 2012

T.Daylan et al., arXiv:1402.6703v1

高エネルギーガンマ線の検出原理
光子と物質との相互作用
電子対生成が主要な領域

原子番号 Z

光電効果が主要な領域

47Ag
35Br

コンプトン散乱が主要な領域
0.010.1

1hn10100 MeV

http://www.nuclear-power.net

電子対生成の概念図

到来方向、到来時刻、エネルギー、偏光Nuclear emulsion

Microscopic view
10micron

Intrinsic position accuracy ~60nme+/-Gamma-raye-/+Cross sectional view of an emulsion film

Powerful tracking device>High spatial resolution : <1micron>Small radiation length : 0.002Xo

Gamma-ray
Emulsion

Plastic
base

Emulsion

e-e+

0.3mm
(0.002Xo)High angular resolution for gamma-ray
Sensitive to gamma-ray polarization

GRAINE

Gamma-Ray Astro-Imager with Nuclear Emulsion
gConverter

e- e+Emulsion + Copper foilTimestamper
Multi-stage shifter

Calorimeter
Emulsion + metal plate

Attitude monitor* 10m2*etrans*econv*edet

Star camera

Fermi LAT
Angular resolution @100MeV@1GeV

6.0deg (105mrad)

x1/6GRAINE
1.0deg (17mrad)

0.90deg (16mrad) x1/9 0.1deg (1.7mrad)

Energy range

20MeV - 300GeV

10MeV - 100GeV

Polarization sensitivity---Yes

Effective area @ 100MeV

0.25m2@ 1GeV
Dead time

0.88m226.5μsec(readout time)

x8x3

2.1m2 *2.8m2 *Dead time freeAngular resolution
LEPS/SPring-8 (Dec. 2004)
UVSOR (Mar. 2008)
New SUBARU (Nov. 2013)
GRAINE2011 (June 2011)

UVSOR(Zenith : 0-47deg)

New SUBARUGRAINE 2011

Fermi-LAT (2008- )(P7SOURCE_V6)

SPring-8

1mrad

Back
Total
Front

GRAINE (MC)emulsion film(70,180,70)

1arcmin

1film
2films3films100MeV

1GeV

10GeV

100GeVPolarization sensitivity
LEPS/SPring-8 (Dec. 2004)
Eg, Max.=2.4GeV

N ( )  p 0 1  p1  cos 2(  p 2  90 )Significant and consistent result was obtained.

<P>=66%, modulation factor=0.21+0.11-0.09
K. Ozaki, S. Takahashi et al., NIMA (2016)

Energy range

Atmospheric g-ray @Mt. Norikura (July, Sep. 2007, July 2013), et al.

Momentum measurement accuracy w/MCS
35MeV electron LINAC@Tokai-mura (Aug. 2012)

35.2+6.5-7.4 [MeV/c]
Absolute:1.8% (34.6MeV/c@incidence)
Relative:20% (15films)
14%@Eg=70MeV (even case)
20%@Eg=35MeV (uneven case)

Energy measurement accuracy
NewSUBARU(Nov. 2013)

Data: 70.8MeV(+30%-19%)
MC: 70.4MeV(+26%-17%)

Timestamper
Multi-stage shifter
June 2007–
S.Takahashi et al.,NIMA(2010)

Flatness study
J-PARCn beam line
m-pit (Nov. 2014)

RMS<1.8mrad(0.10deg)~sea level
12hours
2stages

RMS

1.5s

Efficiency

98%

Reliability

97%

GRAINE 2011

JAXA scientific ballooning
First balloon-borne emulsion g-ray Taiki Aerospace Research Field(Hokkaido, Japan)
telescope experiment

June 8th, 2011
4.3 hour flight duration(1.6 hours @34.7km)

12.5cm×10cm apertureFirst balloon-borne experiment
Feasibility testGRAINE 2011 Flight data analysis
Angular resolution
1deg@100MeVFeasibility demonstration
S. Takahashi et al., PTEP 043H01 (2015); H. Rokujo et al., NIM A 701, 127 (2013)

GRAINE6:33
2015 放球
5/123780cm2 aperture (x30)~millisecond timing resolution (1/10)

Flight duration: 14hour22min(11hour32min(x7)@36.0-37.4km)
almost covered
Vela w/in 45deg zenith
image©JAXA

Launched, 6:33 12th May 2015
Design, various improvements & preparations
Establishment of a scheme & flow of the experiment in Australia
Demonstration of overall performance

Image©JAXA

S. Takahashi et al., PTEP 073F01 (2016); K. Ozaki et al., JINST 10 P12018 (2015)

GRAINE 2015, Flight data analysis

Emulsion track read-out

After film development, surface treatment, thickness tuning, scanning parameter tuning

Emulsion read-out system
Hyper Track Selector @ Nagoya U

Scanning progress
All area (37.6cmX24.5cm/film)|qproj|<53deg (|tanqproj|<1.35)

HTS update

First practical scanning

Completed for all films(432films, 41m2(film area basis))-Converter 100 films x 4units-Timestamper 8 films x 4units

GRAINE 2015, Flight data analysis, ConverterGRAINE 2015, Flight data analysis, Converter

Reconstructed tracks with 8 films

GRAINE 2015, Flight data analysis, Converter

GRAINE 2015, Flight data analysis, Converter

GRAINE 2015, Flight data analysis, Converter

Achieved improvements-Emulsion film S/N ratio X~20, data size ~1/20-Track finding inefficiency in a single film ~1/10-Data reduction load for g-ray event detection ~1/200

g-ray event detection

Completed for 75% (2830cm2/3780cm2(aperture basis))(~30m2/40m2(film area basis))g-ray event detection can be performed for a large area.

GRAINE 2015, Flight data analysis, Timestamper
Altitude

Altitude & Track rate
15 min.

Hadron event on spike structure

Simultaneity of hadron event tracks

s=4.9mm w/ 500mm/sec operation

Position Y

Time resolution 9.8msec

Position XAngle
scale

10cm

Phase-resolved analysis for pulsars is capable.

e.g. 89msec period of Vela pulsar

GRAINE 2015, Flight data analysis, Converter+Timestamper

Measurement of atm. g-ray flux

GRAINE 2015, Flight data analysis, Converter+Timestamper

Eg>130MeV, tanqg, zenith<0.5Preliminarysproj = 0.5deg (8mrad)

Angular resolution 0.7deg

Calibration sorce(direction, timing, energy, polarization, efficiency)

High g-ray imaging performance is being obtained.

# of g-ray events / (0.003)2

g-ray imaging performancew/ hadron induced g-ray events

GRAINE 2015, Flight data analysis, Converter+Timestamper 検出器外部光源

放球プレート撮像 w/ g-ray
検出器水平面投影図
放球プレートsx: 6.43cm
0.84deg(14.6mrad)

sy: 8.11cm
1.05deg(18.4mrad)

unit1

Flight, >100MeV
Extrapolated to 4.4m
Running bin(半径5cm円)

88mm

・放球プレート位置にexcessを検出(ずれ1.7cm→0.22deg(3.9mrad))・放球プレートの大きさ程度のJAXA大気球実験室より広がりが見えている・結像性能<1.2deg(20.6mrad)(cf. 角度分解能1.0deg@100MeV)・ユニットごとの結像重心のばらつき<0.06deg(1mrad)

GRAINE 2015, Flight data analysis, Converter+Timestamper+Attitude

East-west effect (Preliminary)
EN

S

N
W

E

N

S
E

N
W

S

W
W
S

E
全系を総合した精度が確認できつつある。
処理面積や時間を増やす、時間幅を狭くするなど、精度の改善を図る。
緯度、経度、高度を考慮した東西効果について本田守弘氏(東大宇宙線研)に相談中。

Current summary of GRAINE 2015
• 3780cm2 aperture (x30, new-type emulsion films, total 48m2)• 14.4hour flight duration (11.5hour(x7)@36.0–37.4km)• Establishment of a scheme & flow of the experiment in Australia• Emulsion track read-out, total 41m2 w/ HTS• Emulsion film S/N ratio x~20, data size ~1/20• Track finding inefficiency in a single film ~1/10• Data reduction load for g-ray event detection ~1/200• Data processing of all effective area, 2830cm2 aperture (total 30m2)• g-ray angular resolution, 0.7deg >130MeV• Time resolution, 9.8 msec (1/10)• Star camera sensitivity, magnitude of 6.1  7.5• Limited g-ray yield from Vela pulsar

GRAINE Scientific observation roadmap
2018, Demonstration

2021–, Scientific flight

Alice Springs~0.4m2 aperture~18hours flight duration<~5g/cm2 altitude

Alice Springs
10m2 aperture>~36hours flight duration<~10g/cm2 altitude

Vela pulsar detection, Imaging,phase resolved analysis
Galactic diffuse & Geminga
detection/indication

Vela pulsar
Polarization observation (<50%)

Pioneering polarization
observation for highenergy g-rays

SNR W44 (<200MeV, >200MeV)
Precise spectrum measurement
High resolution imaging

Studying cosmic raysources

Galactic CenterObs. with ~arcmin resolution

Resolving GeV g-rayexcess at galactic centerTransient sources
Obs. w/ high sensitivity& high photon stats

Studying transient
sources & w/ ones

Observation of transient sources Large collection area, 10m2
[Effective area@100MeV, 2.1m2 (3.6 x Fermi LAT, cf. 0.58m2 (P8R2_TRANSIENT020_V6) ) ] Wide field of view, >2.2sr (17.5% of all sky) High angular resolution, 1.0deg(17mrad)@100MeV Polarization sensitive Dead time freeHigh sensitivity incl. “Unexplored region”
High photon statistics-Energy spectrum-Light curve-Polarization observation
Good localization ~0.1deg @100photons
 Not continuous survey
 Not real time

1 week

1 day

1 hourFlux [cm-2s-1]

Sensitivity to transient sources
Fermi LAT observed
638 transient/year(614 flares/year
16 GRBs/year
7 solar flares/year) 1.7 transient/day

GRAINE sensitivity(10m2, 5g/cm2, 5s, >5photons
BG: Kinzer et al. (1974), Staib et al. (1973), 4.5GV)>100MeV, 0deg
45deg
>200MeV, 0deg
45deg
Fermi-LAT observed○ GRB (ApJS 209 11 (2013), 2008 Aug – 2011 Aug, 100MeV–10GeV, T90, LAT)
△ Solar Flare (ApJ 787 15 (2013), 2008 Aug – 2012 Aug, 100MeV–10GeV)□ Nova (Science 345 6196 (2014), >100MeV)■ Flare (arXiv:1612.03165v2, 100MeV–800MeV)

2FAV
7.4 year4547 flares(518 sources)

Duration [sec.]Pioneering polarization observation
for high energy g-rays
Approaching emission mechanism

Model prediction
Polarization characteristicof the curvature radiationin the outer gap

Pulsars, AGNs, Flares, GRBs

Crab pulsar

T. Saito, PhD thesis (2010)

J.Takata and H.-K.Chang, ApJ, 670:677-692, 2007

Minimum Detectable Polarization (3s)Vela pulsar, polarization sensitivity
MDP 

3a Fse eff  FBG MFse eff

Aeff Teff

10m2 aperture
5g/cm2 atmospheric depth
Signal: Vela pulsar (3FGL)
BG: Atmospheric gamma-rays
Kinzer et al. (1974), 4.5GV, 11.5 GV
Staib et al. (1973), 4.5GV, 12 GV
2

10x12.5cm (3.5cm thick),
Baseline (>100MeV,
45deg zenith, precise measurements)
Optimizing pol. sens. eval
Enlarging FoV (60deg zenith)
Optimizing energy band (>200MeV)
Enlarging unit size (50x50cm2(3.2cm thick))

Alice Springs# of crosses of a source in a field of view of the telescope
Apr. 15th, 19:39(ACST) culmination, 21.6deg zenith with diurnal rotation (roughly corresponding to flight days)
16:24–22:54 (6.5h/cross) w/in 45deg zenith, 14:58 – 24:20(9.4h/cross) w/in 60deg zenith

Minimum Detectable Polarization (3s)

Polarization sensitivity

0.5MDP 

Optimizing kinematical cut→MF↑
Precise measuring→
Scattering suppressed→MF↑
Recoil momentum correlation→MF↑3 Fse eff  FBG 2 RFse eff

Aeff Teff

Aperture area : 10m2
Modulation factor : R=0.1
BG : Staib et al. (1973), 4.5GV, 12GV

7days
flight x10

0.1

4.5GV
12GV
12GV, Grain by Grain
5x10-6Flux (>100MeV) Fs [cm-2s-1]

12FGL, 2Monitored Source List Light Curves0 emission: Direct evidence ofproton acceleration

60MeV-2GeV

SNRs
200MeV

Sys. error

Spatial structure:
Emission mechanism
M. Ackermann et al., Science 339, 807 (2013)<200MeV, precise spectrum measurementswith suppressed systematic errors>200MeV, investigating spatial structure

W44
Abdo et al., Science, 2010
Color : 2-10GeV gamma-ray(Fermi LAT)
Contour : IR(Spitzer)

W44
200MeV● GRAINE(Simulation)(10m2, 7crossX10, 5g/cm2,Incl. atm g-rays)

Sys. errors

GRAINE(Simulation)
10m2, 100hours (41.7m2day),5g/cm2>1GeV, Incl. atm g-rays

0.5deg

W44
Abdo et al., Science, 2010
Color : 2-10GeV gamma-ray (Fermi LAT)
Contour : IR(Spitzer)<200MeV
Precise spectral measuringwith suppressed systematic errors>200MeV
Investigating spatial structure
deconvolved

Smearing IR(Spitzer) distribution with 0.08deg(1.4mrad)
Considering atmospheric gamma-ray(>1GeV) as BG

Detection significance, ns

W44 detection sensitivity

ns NsN BG

Optimizing energy band (>200MeV)
Reviewing BG
Enlarging unit size (50x50cm2(3.2cm thick))
Enlarging FoV (60deg zenith)(>100MeV, 10x12.5cm2 (3.5cm thick),
Baseline 45deg zenith, precise measurements)

10m2 aperture
5g/cm2 atmospheric depth

5sSignal: W44
3FGL 5.48x10-7cm-2s-1(>100MeV)
BG: Atmospheric gamma-rays
Thompson, (1974), 4.5GV (5-10g/cm2)
Kinzer et al. (1974), 4.5GV, 11.5 GV
Staib et al. (1973), 4.5GV, 12 GV

Alice Springs# of crosses of a source in a field of view of the telescope
Apr. 15th, 6:04(ACST) culmination, 25.1deg zenith with diurnal rotation (roughly corresponding to flight days)
3:27–8:42 (5.25h/cross) w/in 45deg zenith, 2:19 – 9:49(7.5h/cross) w/in 60deg zenith

GeV g-ray excess at galactic center region
Galactic Center
1.0-3.16GeV
Total flux

2.5°

Residual0-2.5°

T.Daylan et al., arXiv:1402.6703v1

GeV g-ray observations at galactic center region
with ~arcmin resolution

10m2, 420hours, >1GeV

Dark matter scenario

Millisecond pulsar scenario

dNg/dV∝r-2.4

Luminosity function: Hooper et al. (2016)
dNsource/dV∝r-2.4
0.1deg@68%

Energy spectrum: Daylan et al. (2016)
0.1deg@68%

Counts/(0.05deg)-2

Simulation of GeV g-ray excess at galactic center region
w/ high angular resolution

Galactic center region, detection sensitivity
ns 

Detection significance, ns

10m2 aperture
5g/cm2 atmospheric depth>1GeVNsN BG

Signal: 3FGL J1745.3-2903c & 3FGL J1745.6-2859c (0.1deg distance)
3FGL J1745.3-2903c, 3.87x10-8cm-2s-1
3FGL J1745.6-2859c, 2.18x10-8cm-2s-1
BG: Atmospheric gamma-rays
bCALET-2 (Taiki, 35km, 2009)5s

Enlarging unit size (50x50cm2(3.2cm thick))2 (3.5cm thick),
Baseline (10x12.5cm
precise measurements)

Alice Springs# of crosses of a source in a field of view of the telescope
Apr. 15th, 4:53(ACST) culmination, 5.3deg zenith with diurnal rotation (roughly corresponding to flight days)
1:31–8:16 (6.75h/cross) w/in 45deg zenith
Nsignal=132, NBG=78 @ 6 crosses

Test of fundamental symmetries
beyond the Planck scale
IKAROS-GAP (70keV-300keV)

Yonetoku et al., ApJ, 2011

Scale of CPT violation (rotation angle of pol. vector)𝑑𝜃 ≃ 𝜉𝑝2 𝑑𝑡/𝑀𝑃𝑙
Constraint from GRB pol. obs. by GAP𝜉 < 𝑂(10−15 )K.Toma et al., PRL 109, 241104 (2012)

By polarization observation for high energy grays (e.g. > 100 MeV) from distant AGNs andGRBs by emulsion g-ray telescope, much strict(five order of magnitude better) validation of
CPT symmetry can be performed.

GRAINE Scientific observation roadmap
2018, Demonstration

2021–, Scientific flight

Alice Springs~0.4m2 aperture~18hours flight duration<~5g/cm2 altitude

Alice Springs
10m2 aperture>~36hours flight duration<~10g/cm2 altitude

Vela pulsar detection, Imaging,phase resolved analysis
Galactic diffuse & Geminga
detection/indication

Vela pulsar
Polarization observation (<50%)

Pioneering polarization
observation for highenergy g-rays

SNR W44 (<200MeV, >200MeV)
Precise spectrum measurement
High resolution imaging

Studying cosmic ray
sources

Galactic Center
Obs. with ~arcmin resolution

Resolving GeV g-rayexcess at galactic centerTransient sources
Obs. w/ high sensitivity& high photon stats

Studying transient
sources & w/ ones