Variation of secondary cosmic gamma ray flux during lunar eclipse
S. Roy* , S. Chatterjee , S. Chakraborty** , S. Biswas , S. Das , S. K. Ghosh , S. Raha Department of Physics (CAPSS), Bose Institute, Kolkata, India. E-mail: [email protected] Introduction Astronomical events such as Solar eclipses and Lunar eclipses provide the opportunity for studying the disturbance produced in the atmosphere and its effect on cosmic ray intensity. There are earlier reports on decrease in secondary cosmic gamma ray (SCGR) flux during solar eclipse and enhancement of the same during lunar eclipse [1-4]. We have measured the variation of SCGR flux during two lunar eclipses that took place in India in the year 2018, one on 31st of January and the other on 27th of July. Both the measurements have been carried out in the Detector laboratory of Bose Institute, Kolkata, India, using NaI (Tl) scintillator detector. We observed slight increment of SCGR during the lunar eclipse of January. We did not observe any significant changes in SCGR during lunar eclipse of July. Experimental Setup ❖ NaI(Tl) scintillator detector is used. Size of the crystal: 5.1cm × 5.1cm ❖ Gamma ray sources used for detector calibration: 137Cs (662 keV), ❖ PMT bias: +600V. Signals are amplified and shaped before sending 60Co (1173 keV and 1332 keV) and 22Na (551 keV) them to MCA for energy spectrum accumulation
ORTEC-556
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Schematic of the signal processing electronics Picture of the experimental setup Gamma ray spectra with different configurations of lead shielding ADC Calibration Curve Lunar Eclipse of January 2018 Observations Lunar Eclipse of July 2018
st ❖ Date: 31 January 2018 ❖ Date: 27th and 28th July ❖ Time: 17:18 hr to 20:41 hr ❖ Time: 22:44 hr (27/07) to 03:49 hr (28/07) ❖ NaI(Tl) detector is used to measure ❖ NaI(Tl) detector is used to measure secondary cosmic gamma ray flux in secondary cosmic gamma ray flux in the the energy range 25 keV to 3 MeV energy range 50 keV to 3 MeV ❖ Increment in gamma count is ❖ Sudden jump in gamma ray count is observed during and after the lunar observed prior to the lunar eclipse eclipse period
Variation of gamma ray count during Variation of gamma ray count during normal days and lunar eclipse day normal days and lunar eclipse day
1.4% increase
Distribution of gamma ray count during Distribution of gamma ray count during Distribution of gamma ray count during Distribution of gamma ray count during a normal day the lunar eclipse day a normal day the lunar eclipse day Discussion ❖ NaI(Tl) detector is used to measure the time variation of secondary cosmic gamma ray flux during two lunar eclipses in the year 2018 which were visible from India. ❖ Local weather parameters like temperature, pressure and humidity were normal during the lunar eclipse [5]. Space weather also was clear according to the SWPC [6]. ❖ Although we observed a mild increase (~1.4%) in the SCGR over the baseline measurement during lunar eclipse in January, no such variation was observed during the eclipse of July 2018. ❖ Measurements must be repeated in future to reach a consensus on the variation of SCGR during lunar eclipses. References Acknowledgement [1] Nayak et al., Astroparticle Physics (2010) Volume 32, Issue 6 [2] Bhaskar et al., Astroparticle Physics (2011) Volume 35, Issue 5 We would like to thank Prof. D. Syam, Dr. Rama Prasad Adak, Dr. Siddhart K. Prasad, Mr. [3] A. Raghav et al. (2013), Journal of Geophysical Research: Space Physics, Vol. 118 Shibnath Shaw and Mr. Rathijit Biswas for their sincere help towards this work [4] S. Roy et al. (2020), Astrophysics and Space Science 365, 172 [5] https://www.timeanddate.com/weather/india/kolkata [6] http://www.spaceref.com/news/viewsr.html?pid=51598
XXIV DAE-BRNS High Energy Physics Symposium 2020
** Now at VECC, Kolkata December 14-18, National Institute of Science Education and Research, Odisha, India