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

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-rayEmulsion

Plasticbase

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*edetStar camera

Fermi LAT
Angular resolution @100MeV@1GeV

6.0deg (105mrad)

x1/6

GRAINE
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

BackTotal
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 linem-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-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, Converter
e-pair kinematics
Energy reconstruction with MCS
Data-MC comparison+22.1(13x9cm2)(pβ)left=81.4-14.3 MeV/c(pβ)right=68.0+18.4-12.0 MeV/c
Eγ=149+28.7-18.6MeV
θincident=30.6o

g-ray energy distribution
preliminary

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 X

Angle
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 was 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+Attitude

East-west effect (Preliminary)
ENSNW

SEWW

SSNENWE

g-ray plotting on celestial coordinates is ongoing.

GRAINE Scientific observation roadmap
2018

2021-

Alice Springs>~1m2 aperture, >~36hours flight duration<~10g/cm2 altitude
Commissioning flight

Alice Springs
10m2 aperture, >~36hours flight duration<~10g/cm2 altitude
Scientific flight-Scientific model establishment(size, weight)-Flight duration-Performance demonstration-Scientific obs. starting

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 center

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

W44Abdo 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, ns10m2 aperture
5g/cm2 atmospheric depth>1GeV

NsN 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)

5sEnlarging unit size (50x50cm2(3.2cm thick))2 (3.5cm thick),
Baseline (10x12.5cmprecise 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.

Improvements and preparations
for scientific balloon-borne experiments

Emulsion film production
Automatic emulsion gel pouring

Nagoya U

アプリケーターによる自動フィルム成形システム
膜厚相当の隙間を設けたステンレス製のヘッドをフィルム面に沿ってスライドさせ、均質な塗布を実現する

Quite uniform and mass-producible emulsion film production
can be performed.

Next generation
multi-stage shifter

Co-developed with Mitaka Kohki Co., Ltd.

-Larger aperture area
-Longer flight duration
with a higher timing resolution

2~1m<1mm repeatable accuracy(preliminary)Size : 137cm x 116cm x ~20cm
Weight : <~90kg
Electric consumption：~25W
Aperture area : 8550cm2# of stages : 6
Gap between stages : ~0.5mm
Total thickness of aperture area : 5mm

Conventional: 2.6ton/10m2
New: 0.4ton/10m2 (Prospects)
Oct. 2014 Started

Pressure vessel gondola Extended model based on GRAINE 2015
Conceptual designLight
Thin
0.3atm

5m2 (4units) aperture area
w/ a single pressure vessel gondola (~250kg weight)

GRAINE Scientific observation roadmap
2018

2021-

Alice Springs>~1m2 aperture, >~36hours flight duration<~10g/cm2 altitude
Commissioning flight

Alice Springs
10m2 aperture, >~36hours flight duration<~10g/cm2 altitude
Scientific flight-Scientific model establishment(size, weight)-Flight duration-Performance demonstration-Scientific obs. starting

Vela pulsar
Polarization observation (<50%)

Pioneering polarizationobservation 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 center