ATUL JAIN (CRL-TIFR, Ooty) on behalf of GRAPES-3 Collaboration 16 Dec, 2010 WAPP-2010

Motivation In past there have been reports of variation in the flux of g-rays during the Total Solar Eclipse (TSE) 16 Dec, 2010 WAPP-2010

g-ray flux during TSE of 24 October 1995 at Kolkata, India 100 cm3 NaI(Tl) detector A. Bhattacharyya et al., Astrop. Space Sci. 250 (1997) 313 16 Dec, 2010 WAPP-2010

g-ray flux during PSE of 11 August 1999, Istanbul, Turkey 16 Dec, 2010 WAPP-2010

Constraints on Earlier Observations Observations were based on measurements from a single detector experiments. Instrumental errors and fluctuations could significantly influence the outcome. 16 Dec, 2010 WAPP-2010

g-ray flux during TSE of 1 August 2008, Novosibirsk, Russia Two Identical NaI(Tl) crystal detectors and signal processing instruments were used for g-ray flux measurements at Novosibirsk Russia. Also carried out concurrent measurements of temperature and humidity. 16 Dec, 2010 WAPP-2010

TSE experiment at BINP, Novosibrisk on 1 August, 2008 16 Dec, 2010 WAPP-2010

Variation in g-ray flux before, during and after the eclipse Integrals counts in the energy region 50-4600 keV. Excellent correlation. Small statistical errors. Just prior to eclipse, a drop in flux of ~4% with subsequent sudden increase in flux of ~9% Throughout eclipse, a steady decline of flux of ~4 % 16 Dec, 2010 WAPP-2010

Comparison with neutron monitor data Neutron monitor data shows a flat distribution, rms spread of ~0.4%. Our data shows rms spread of ~1.5% nearly 4 times larger 16 Dec, 2010 WAPP-2010

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Limitations of all past observations: Single location measurement. Influence of atmospheric and local phenomenon could plays a significant role in generating observed variation. Highlight of Present observation For TSE 2009 measurements were carried out at two widely separated locations along the path of totality with identical detectors and signal processing equipment. 16 Dec, 2010 WAPP-2010

Geomagnetic Cutoff rigidity (GV) Eclipse of the Century The Earth will not see such a long duration TSE in the next century. The TSE began in India, passing through South Asia into China and reaching a maximum duration of 6 minutes and 39 seconds near Japan’s Ryukyu Islands. City of India Average cloud in July (calc. in %ge) Avg. Rainy Days in July Duration of Totality Geomagnetic Cutoff rigidity (GV) Surat 78 19 194 s 18.77 Indore* 16 185 s 17.66 Bhopal 85 20 189 s 17.14 Varanasi 71 > 16 181 s 15.70 Patna 79 224 s 15.36 Siliguri* 84 24 227 s 14.59 Dibrugarh 86 215 s 13.67 Total solar eclipse on 22 July 2009 In view of accessibility and excellent infrastructure facilities at RRCAT, Indore and North Bengal University, Siliguri, it was decided to carry out this experiment at Indore and Siliguri Criteria for selection of the experimental sites

22 July 2009 TSE in India 16 Dec, 2010 WAPP-2010

Experimental Set Up NaI Crystal PMT Pre-Amplifier Spectroscopic LAPTOP NaI Crystal PMT Pre-Amplifier Spectroscopic Amplifier MCA LAPTOP NaI Crystal PMT Pre-Amplifier Spectroscopic Amplifier MCA 16 Dec, 2010 WAPP-2010

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Effect of lead shielding 40K 208Tl 16 Dec, 2010 WAPP-2010

Charged Particle Measurements Plastic Scintillator coupled with PMT through WLS Discriminator INTEGRATED COINCIDENCE UNIT AND SCALER Plastic Scintillator coupled with PMT through WLS Discriminator 16 Dec, 2010 WAPP-2010

Charged Particle Detectors & DAQ 16 Dec, 2010 WAPP-2010

Complete experiment pic 16 Dec, 2010 WAPP-2010

Independent measurements 15th July,2009 16th July,2009 16 Dec, 2010 WAPP-2010

Calibration using Cs137, Co60 661KeV 1173KeV 1332KeV 2505KeV 16 Dec, 2010 WAPP-2010

Daily on site Monitoring 16 Dec, 2010 WAPP-2010

Variation in g-ray flux in three different days 16 Dec, 2010 WAPP-2010

Variation in g-ray flux on 22nd July,2010 16 Dec, 2010 WAPP-2010

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Summary g-ray flux measured during 12-29 July 2009 at Indore and Siliguri including the day of TSE on 22 July 2009. At each location measurements with two identical setup to ensure full redundancy. 1400 km distance between the two sites to exclude local effects Rain just before and after TSE introduced severe g-ray flux variation making it difficult to detect variation due to TSE. 16 Dec, 2010 WAPP-2010

THANKS 16 Dec, 2010 WAPP-2010