Cosmic Ray Studies with GRAPES­3 Experiment

Pravata K. Mohanty
Tata Institute of Fundamental Research, Mumbai
ICRR seminar, 8 February 2016

OutlinePART­I
Overview of the GRAPES­3 Experiment
Measurements of Solar Diurnal Anisotropy
Forbush Decrease precursor eventsThundercloud acceleration of muonsPART­IIR&D of scintillator detectors
GRAPES­3 C++/ROOT based data analysis framework

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3

­3ES
AP
GR ASE­3PES
GRA FluxnMuo

1m2 x 400

3 million EAS events /day
4 billion(Energy and Direction)
muons/day(High Statistical Accuracy)

Spectrum and elementalcomposition (1013 – 1016eV)●232 PRC x 16 module
Expansion work in progressfor another 16 modules

Solar phenomena●Thundercloud
acceleration

Diffuse ray studies

4Features of Muon Detector

Cutoff rigidity map

Eµ > 1 GeV sec()Total field of view: 2.3 srNumber of Directions: 13 x 13 (169)
Angular Resolution: 2 to 6oMuon Rate: 5 x 104 / s
Basic time resolution: 10 sStatistical Accuracy (1 h) : 0.01%

14 – 32 GVMedian rigidity map

65 – 140 GV

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Efficiency corrections

7120 x 100 days = 12000 linear
equations to be solved to get 80
coefficients for 16 mod.

Solved using SVD decomposition

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Before correction

Full 2006 data after correction

99.99%
After correction

0.34 counts (0.01%)

Analysis completed from 2004 - 2013

Atmospheric pressure corrections

9Muon rate
β = - 0.075% / hPa

Pressure

β = - 0.128% / hPa

FFT of muon rate

FFT of pressure

Paper Submitted to Astroparticle Physics

Solar Diurnal Anisotropy

Diffusion-Convection Model

GRAPES-3 Muon data10

Harmonics of solar diurnal anisotropy
using FFT (Median Rigidity: 65 – 70 GV)
24h (0.14%)

12h (0.06%)

8h (0.02%)
6h (0.006%)

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Rigidity Spectrum of SDA
First Harmonic

Second Harmonics

A(R) = K R­γ
K = 1.3 ± 0.1, γ = 0.53 ±0.01

γ = 0.45 ±0.02

12Rigidity Spectrum of SDA
Third Harmonic
Before Time offset correction

γ = 1.9 ±0.1

Fourth harmonicγ = 1.8 ±0.4

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Phase of Harmonics

Rigidity dependence
1st2nd
3rd
4th

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Comparison with similar experiment (2006 data)
Harmonic

123
4

Amplitude (%)

Phase (hours)

GRAPES­3 Nagoya

GRAPES­3Nagoya

0.132% 0.105%
0.054% 0.051%
0.014% 0.017%
0.004% ­­­­

12.4 h  0.3 h
12.4 h  0.3 h
12.7 h  0.2 h
12.9 h  0.2 h

12.3 h12.7 h12.7 h­­­­­­

Solar Diurnal Harmonics 2007 - 2010
2007

2008

2009

2010

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Coronal Mass Ejection (CME)17

Strong Southward oriented IMF favors
Forbush decrease (29th October 2003)
magnetic reconnection process which
can trigger severe geomagnetic storm
GRAPES-3 datathat can cause failure of large power grids,
satellite communications, radio blackouts.
Spacecrafts such as ACE, WIND
which are located ~ 1.5 million km(L1 point) can provide advanceintimation of CME of about an hour
T. Nonaka et al., PRD, 74 (2006) 052003

Loss Cone Precursor to an ICME

Intensity deficit
confined in a cone

Precursors detected by muon telescopes can provide
advance warning more than 5 hours.

18Precursor observed by GRAPES-3
on 14 December 200619

Precursor on 14 December 200620

Precursor on 14 December 2006

Muon Rate

Magnetic Field

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Thundercloud acceleration

Thunderclouds may gain
potential ~ Giga-Voltsturning the atmosphere
into a giant natural
particle accelerator

C. T. R. Wilson, the acceleration of beta-particle in strong
electrical fields of thunderclouds, Proc. Cambridge
Philos. Soc. 22, 534, (1925).

Terrestrial Gamma Ray Flashes (TGFs)
First observation by BATSE in CGRO (Fishman,Science, 264 (1994) 5163)
Recent observation by AGILE up to 100 MeV(Tavani, PRL, 106 (2011) 018501)

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30 Sept 2015 Event24

30 Sept 2015 Event25

30 Sept 2015 Event26

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Events during 2006 to 2010

Events from eastern direction: 146/183 = 80%2829PART – IIR&D of scintillator detectors
GRAPES­3 data analysis framework

Old scintillator detector
μ+Low Photo­electron Yield (3­5)(Poor Signal to Noise Separation)
Pedestal

Muon response

Large Non­uniform Response (~ 30%)
Expansion of the Array with abetter detector
Increase photo­electron yield➢
Better spatial uniformity➢
Increase the dynamic range(to several thousands particles / m2)
➢30

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New design

Parallel

Matrixσ

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New design

Parallel

Matrixσ

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Measurement set­up
Muon trigger set­up
Hodoscope

Measurement Parameters
1. Photon yield
2. Uniformity
3. Time Response

Test detector
Hodoscope
PMT

Timing Detector

HodoscopeOld34

OldNewNew

P.K. Mohanty et al. Astropart. Phys. 31 (2009) 24

Monte Carlo simulation: G3sim
1: Generation and propagation of muons

2: Energy loss (dE/dX) calculation using Landau
distribution
3: Generation of photons in scintillator.
4: Propagation of photons in scintillator using basic
laws of reflection and considering attenuation loss andloss due to imperfect surface
5: Capture, trapping and propagation of photons in
WLS fiber considering meridional and skew ray modes
6: Convolution of PMT responses.

Probability distributions and uniform random
numbers (0 to 1) used to model each process

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Photon Trapping in Fiber

Core: 0.94mm
Refractive index = 1.59
Inner clad: 0.03mm
Refractive index = 1.49
Outer clad: 0.03mm
Refractive index = 1.42

Meridional rays
Incident, normal and reflected raylie in the same plane

Skew Rays
do not lie in the same plane

Ref: N.S. Kapany, Fiber Optics: Principles & Applications,
Academic Press London & New York (1967)

Axial angle distribution of trapped photons

Meridional rays

Skew Rays

Trapping Efficiency of meridional rays = 3.2 %With inclusion of skew rays, trapping efficiency = 4.8%

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Input parameters

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Photon Statistics (50 cm x 50 cm x 2cm)

10%

0.4%

parallel

Photo-electron Yield

paralleldatamatrix

Time Response

parallelsimmatrix

matrixσσσ

Uniformity

39Summary of groove comparisons
RMS non­uniformity (%)

Photo­electron yield
GrooveParallel
Matrixσ

Fiber­length(cm) Photo­electrons

900
900656

20.5
21.7
17.9

GrooveParallel
Matrixσ

Experiment Monte Carlo
2.7
2.0
2.1
1.6
3.5
3.3

Time Response (ns)
GrooveParallelMatrix
σExperiment
2.5
2.4
2.4

Monte Carlo
2.3
2.3
2.4

Parallel groove design selected for final configuration
because of ease in fabrication

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Attenuation

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200cm

Self Absorption

150cm
100cm
50cm

Photon­electron with number of fibers

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G3sim configuration file

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RunNumber
1
NumberOfEvents
50000
PhotonConversionEnergyeV
100
PathLengthStepcm
0.01
ETIRScintillator
0.93
G3sim consists of 1200
ReflectivityFiber
0.9999lines of C++ code.
ReflectivityDiffuseReflector
0.9
RefractiveIndexScintillator
1.59
G3sim code is available
RefractiveIndexFiberCore
1.59
on request
RefractiveIndexFiberInnerClad
1.49(contact: pkm@tifr.res.in)
RefractiiveIndexFiberOuterClad
1.42
AttenuationLengthScintillatorcm
100
AttenuationLengthFibercm
350
ScintillatorDecayTimens
1.5
FiberDecayTimens
6.1
PMTQuantumEfficiencySpectrumFileOption1
PMTQuantumEfficiencySpec.dat
PMTPeakQuantumEfficiencyOption2­1
PMTSinglePhotoElectronDistributionWidth
0.2
PMTTransitTimeJitterns
1.0
PMTWindowTransmissionCoefficient
0.93
FiberEmissionWaveLengthSpectrumFileOption1
WLSFiberEmissionSpec.dat
FiberPeakEmissionWaveLengthnmOption2­1
GeometrySpecificationFile
GeometrySpecification.dat
OutputfileDirectoryWithPath/home/grapes/g3simpaper_work/program/version2
P.K. Mohanty et al. Rev. Sci. Instrum. 83 (2012) 043301.

Number of showers

Enhanced dynamic range with two PMT design

Low Gain PMTHigh Gain PMTMore details:“Measurement of some EAS properties using new scintillator detectors
developed for the GRAPES­3 experiment",
P. K. Mohanty et al., Astropart. Phys. 31 (2009) 24.

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PRC

22 GB/dayData Analysis Framework
An object oriented software framework was created for theGRAPES­3 data using popular graphics and analysis tool ROOT
with the following philosophy­

Efficient storage and access of various data streams using ROOT tree­

Efficient monitoring of data quality­

Portability of data to the collaboration.

­

Adaptation to the data system with short learning curveand more time devoted for detailed analysis for a new member­ Involvement of more people in parallel development

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~ 1 00 000 lines of code
Effort spread over 5 years

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ROOT Tree structure for scintillator data

10 GB RAW DATA => 1.5 GB ROOT DATA per day
Inbuilt compression, no explicit uncompression while retrieval

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ADCDA
TA

ScmainDAQ

TDC DATAScRateWeather
DAQ

SCRATEDATA

ScmainDAQ

All monitoring plots generated inautomated way before 9 AMMuon calibration

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Summary53

1. Unique measurement of diurnal anisotropy. Demonstration ofunprecedented sensitivity of GRAPES-3 detector
2. Exploiting the GRAPES-3 sensitivity for space weather studies
3. Continuing our effort to understand atmospheric acceleration
4. GRAPES-3 has now efficient shower detectors and expected toprovide better measurement of shower parameters
5. The new data analysis frame work made the analysis
convenient and fast. Inclusion of more people for analysis

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THANK YOU