雷雲ガンマ線の多地点観測プロジェクト:
可搬型検出器の開発と2016年度冬季の観測成果
Multi-point Observations of Thundercloud Gamma-rays:
Development of Portable Detectors and Results ofFiscal 2016 Winter Observation

和田有希 / Yuuki Wada (東大理 U.Tokyo / 理研 RIKEN)
榎戸輝揚 (京大理), 古田禄大 (東大理), 湯浅孝行 (理研)中澤知洋 (東大理),中野俊男 (理研), 土屋晴文 (原研/理研)
鴨川仁 (学芸大),米徳大輔 (金沢大), 澤野達哉 (金沢大)ほか GROWTHコラボレーション
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Thundercloud Gamma-rays

Cosmic ray・Electron Accerelation in ThundercloudElectronse-- Electric field of 200­300 kV/maccelerates electrons up to ~10 MeV.
- Bremsstrahlung gamma-rays.
- Relativistic Runaway Electron Avalanche Model

Gamma-rays

On-ground Detector(RREA; Grevich 1992, Dwyer+2004)200

shortburst

160
140

Count bin-1

・GROWTH Experiment (2006-)

100
8060

Count Rate(Gamma-Ray Observation of Winter THundercloud)- On-ground remote observation at Niigata- 28 events for 10 years with 1-2 detectors.
・Shortburst (associated with lightning)・Longburst (stable emission)

120

40lightning180

500 ms200−0.1

00.10.2
Second from Shortburst

200.30.4Entries
MeanStd Dev

116

longburst

18161412108(Tsuchiya+2007, 2013, Umemoto+2016 etc.)

6415 min2022 May 2017

−400

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

−300

−200

−1000100200300

400

Questions and Methods
・Characterization of longburst: Big questions- How longburst starts, grows, and disappears?
Key: Total duration, forming condition, time variation.
- Can the conventional RREA model explain longburst mechanism?
Key: Total photon number, size of irradiated area,2D distribution of gamma-ray flux and spectrum.

・Large Area Mapping Observation in Ishikawa (2015-)- Track longburst with gamma-ray detector array.
- Wide area needed to install detector array.
- Started in FY2015 at Kanazawa-> 3 longbursts detected (Enoto+ JpGU 2016).
- Plan to equip ~30 detectors (finally) in Kanazawa.

Important to develop simple, small, low-cost detectors
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Portable Gamma-ray Detector
Configuration
PMTInorganic
Scintillator

Electronics
AmpADC・Inorganic scintillator
for gamma-ray detection
・Photon-by-photon recordto obtain energy and time・Remote-controlled system

PCOutside

FY2016 Detector
・Packed inside water-proof box
・BGO scintillator (25 8 2.5 cm3)
・Compact data acquisition system
・Mobile line (5GB/month)for monitoring and data transfer.

22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Portable Gamma-ray Detector
Configuration
PMTInorganic
Scintillator

Electronics
AmpADC・Inorganic scintillator
for gamma-ray detection
・Photon-by-photon record
to obtain energy and time・Remote-controlled system

PC
InsideFY2016 Detector
・Packed inside water-proof box
・BGO scintillator (25 8 2.5 cm3)・Compact data acquisition system
・Mobile line (5GB/month)for monitoring and data transfer.
Electronics
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Brand-new Compact DAQ Electronics
Including HV supply, amplifier, ADC, data acquisition¥100,000 FPGA/ADC Board
・12 bit ADC 4ch
・Self-trigger photon by photon
data acquisition with Raspberry Pi.

Raspberry Pi 3

Analog Front-end Card
・Coupled with PMT- HV Power Supply- Preamp + Shaper
・GPS receiver・Temperature senser, mini display
・Developed and designed by Wada DAQ Electronics Assembly
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Gamma-ray Spectra
Radiation background- Natural Isotopes (40K, 208Tl, 214Bi etc.)- Cosmic Rays (Gamma-ray, electron, muon etc.)
10310340K (1.46 MeV)

102
10208Tl (2.61 MeV)

(0.609 MeV)
1010・214Bi Lines are variable
Sunny with precipitation
Rainy (Rn wash out)

(1.12 MeV)

-1

Count s MeV-1Counts s-1 MeV-1

211214Bi(1.76 MeV)
(2.20 MeV)

−110-110High BGD region

Low BGD region(variable with precipitation)(cosmic rays)

10 -210−20.5

1123Energy (MeV)
Energy (MeV)・Strength of 40K & 208Tl
Lines are constant- Use for energy calibration

51010・＞3 MeV region mainly
consists of cosmic rays- stable- high S/N ratio forthundercloud gamma-rays

Use ＞3 MeV region for Thundercloud Gamma-ray search
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

FY2016 Campaign - Location
・We operated 8 portable detectors and 2 conventional detectors.
- From October 2016 to March-April 2017
Suzu

1Kashiwazaki

Kanazawa
Komatsu

432(c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus, Data SIO, U.S. Navy, NGA, GEBCO

22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

FY2016 Campaign - Location
・We operated 8 portable detectors and 2 conventional detectors.
- From October 2016 to March-April 2017

FY2016 Campaign - Installation
Kanazawa Univ HS

Izumigaoka HS

Suzu(c) Google, ZENRIN, Data Japan Hydrographic Association, Landsat/Copernicus,SIO, U.S. Navy, NGA, GEBCO
KanazawaData
Univ

Kashiwazaki

Kashiwazaki

Sci. Hills Komatsu

22 May 2017

22JpGU+AGU
May 2017Meeting2017 大気電気学
MIS18-05
JointJpGU+AGU
Meeting Joint
2017
大気電気学
MIS18-05

Komatsu HS

Results of FY2016
We detected 10 longbursts and 2 shortbursts.
DateTime (JST)

LocationType

20161208

00:14

Kanazawa Univ.

long

02:56

Komatsu HS

long

02:58

Science Hills Komatsulong

20161209

16:29

Kanazawa. Univ. HS

long20170113

01:43

Kanazawa Univ.

long

05:05

Kanazawa Univ.

long

20170115

05:31

Kanazawa Univ.

long

20170116

12:19

Kashiwazaki

short20170206

05:07

Kanazawa Univ.

long

05:10

Kanazawa Univ.

long

17:34

Kashiwazaki

short

17:10Suzu

long20170211

28 event / 10 years / 1-2 detectors (2006-2015)-> 12 events / year / 10 detectors (FY2016)

Five times improvement
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Results of FY2016
We detected 10 longbursts and 2 shortbursts.
DateTime (JST)

LocationType

20161208

00:14

Kanazawa Univ.

long

02:56

Komatsu HS

long

02:58

Science Hills Komatsulong

20161209

16:29

Kanazawa. Univ. HS

long20170113

01:43

Kanazawa Univ.

long

05:05

Kanazawa Univ.

long

20170115

05:31

Kanazawa Univ.

long

20170116

12:19Kashiwazaki

short20170206

05:07

Kanazawa Univ.

long

05:10

Kanazawa Univ.

long

17:34

Kashiwazaki

short

17:10

Suzu

long

20170211

28 event / 10 years / 1-2 detectors (2006-2015)-> 12 events / year / 10 detectors (FY2016)

Five times improvement
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Longbursts on 20161208 at Komatsu・Count rate history of 2 longbursts- Brighter at “Science Museum” then “High School”.
- Symmetric in time (＞3 MeV)・112 sec time lag- Gamma-rays from the same thundercloud
passing above the 2 detectors?
505045Counts s-1

Count Rate (count/sec)

4040

NScience Museum
High School

High School

35303025112 sec

202015Longburst
moved withthundercloud?

1010
500

02:54 02:55 02:56 02:57 02:58 02:59 03:00
2:56
2:54
2:58
3:00
Date (JST)Time (JST)22 May 2017

03:01

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

MuseumLongbursts on 20161208 at Komatsu
・Dynamics of thundercloud with JMA Weather Radar
10 km

Science MuseumKomatsu
High School
High School
ScienceHills Komatsu

60

4030

20

10

2016/12/08 02:40 (JST)22 May 2017(c) Google, ZENRIN

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-050Precipitation (mm/h)

50

Longbursts on 20161208 at Komatsu
10 km

Science MuseumKomatsu
High School
High School
ScienceHills Komatsu
Just before detection

605040302010

2016/12/08 02:50 (JST)22 May 2017(c) Google, ZENRIN

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-050Precipitation (mm/h)

・Dynamics of thundercloud with JMA Weather Radar

Longbursts on 20161208 at Komatsu
10 km

Science MuseumKomatsu
High School
High School
ScienceHills Komatsu
Just after detection

605040302010

2016/12/08 03:00 (JST)22 May 2017(c) Google, ZENRIN

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-050Precipitation (mm/h)

・Dynamics of thundercloud with JMA Weather Radar

Longbursts on 20161208 at Komatsu
10 km

Science MuseumKomatsu
High School
High School
ScienceHills Komatsu
Just after detection

6050

40302010

2016/12/08 03:00 (JST)22 May 2017(c) Google, ZENRIN

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-050Precipitation (mm/h)

・Dynamics of thundercloud with JMA Weather Radar

Longbursts on 20161208 at Komatsu
N1 km

High SchoolScience Museum
High School50112 sec

Count Rate45Count Rate (count/sec)

4035302520
1510ScienceMuseum

5002:54(c) Google

22 May 2017

02:55

02:56

02:57
02:58
Date (JST)

02:59

03:00

2:54 2:56 2:58 3:00
Time (JST)JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

03:01

Longbursts on 20161208 at Komatsu
N1 km

High School

Science MuseumHigh School50

112 sec

Count Rate

45

Count Rate (count/sec)

40
35
30
25
20
15
10ScienceMuseum

50

02:54

02:55

02:56

02:57
02:58
Date (JST)

02:59

03:00

2:54 2:56 2:58 3:00
Time (JST)(c) Google“Electron accelerator“ moved at least 1.2 km
with the thundercloud.
22 May 2017JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

03:01

Spectral Analysis
Longburst at Science Museum
・We generated background subtracted spectrum.

1040K~15000 photons detected(0.8-14.0 MeV)

2208Tl1010

Count s-1 MeV-1

Counts s-1 MeV-1

310−21010-3

BGD

45

4040
35

3030

11010-1−1

Source5050 BGDCountRate
Count Rate (count/sec)

10103

252020Source
BGD
Subtracted

Is cutoff real?

22 May 2017

1010
5−3

1115

2 Energy (MeV) 5
Energy (MeV)

101000 02:52
2:52

02:54

02:56

2:56

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

02:58
03:00
Date (JST)

3:00

03:02

03:04

3:04

Spectral Analysis
Longburst at Science Museum
・We generated background subtracted spectrum.
・Detector response is removed by Geant4 Monte Carlo Simulation.
10103

10105

5208Tl1010
11010-1−1

10−2

1010-3Source
BGD
Subtracted−31
1

22 May 2017

2 Energy (MeV) 5
Energy (MeV)

101010104-1

2

4Monte Carlo Simulation(1)Input photon ( f (E) ∝ E-1)
(2)Energy deposit at
BGO Scintillator-2~15000 photons detected(0.8-14.0 MeV)Count cm MeV

40K

Counts cm-2 MeV-1

10Count s-1 MeV-1

Counts s-1 MeV-1

31010331020.5

115
Energy (MeV)JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Energy (MeV)

1010

Spectral Analysis
Longburst at Science Museum
・We generated background subtracted spectrum.
・Detector response is removed by Geant4 Monte Carlo Simulation.
10103

11208Tl

1010
11010-1−1

10−21010-3

Source
BGD
Subtracted−3

Response removed

F(E) ∝ E-Γ exp(-E/Ecutoff)

1010-1−1Photons cm-2 s-1 MeV-1~15000 photons detected(0.8-14.0 MeV)

Photons cm-2 s-1 MeV-140K

102Count s-1 MeV-1

Counts s-1 MeV-1

31010-2−21010-3−31010-4

Resembles Bremsstrahlung
from 20 MeV electrons.
Flux =0.65 ± 0.05 cm-2 s-1(0.4-10.0 MeV)

−41
1

2 Energy (MeV) 5
Energy (MeV)

1010112 Energy (MeV) 5
Energy (MeV)1010

The response-resolved spectrum consists ofa powerlaw continuum with cutoff.
22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05

Conclusion and Future Prospects
・We deployed 10 detectors in FY2016 winterand detected 10 longbursts and 2 shortbursts.
・Detectors in Komatsu successfully tracked a longburst
moving with thundercloud.
・Spectrum was apparently consistent with Bremsstrahlung
from 20 MeV electrons.
Kanazawa
10 km

Future array will reveal
・“Life of longbursts” by tracking
from “birth” to “death”.
・Acceleration mechanism (RREA?)
by measuring fluxes and spectra.

10 km

We will answer
the questions of longburst(c) Google, ZENRIN, DATA SIO, NOAA, US Navy, NGA, GEBCO, Landsat

22 May 2017

JpGU+AGU Joint Meeting 2017 大気電気学 MIS18-05