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      Articles written in Pramana – Journal of Physics

    • Development of a zero-cost multichannel analyser based on digital signal processing for $\gamma$ -ray spectroscopy using the PC sound card

      A JANA S K SINGH A GUPTA S DAS K BASU S SAMANTA R RAUT S S GHUGRE A K SINHA

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      A zero-cost multichannel analyser (MCA) system based on the digital signal (pulse) processing (DSP) convenient for $\gamma$ -ray spectroscopy with conventional detectors such as scintillators and high-purity germanium (HPGe) has been implemented. The in-built high-performance analog-to-digital converter (ADC) in the sound card, an integral component of the present day personal computers, was used to digitise the signals from the radiation detectors. These pulses were then shaped using the established digital signal processing recursive algorithms. The filtered data were then displayed as histograms which then could be subjected to the traditional analysis to obtain peak parameters and the associated quantities were deduced. The developed system combines the performance of the sound card hardware with the flexibility allowed by the DSP to achieve a versatile MCA.

    • Stability study and time resolution measurement of straw tube detectors

      S ROY S JAISWAL S CHATTERJEE A SEN S DAS S K GHOSH S RAHA V M LYSAN G D KEKELIDZE V V MYALKOVSK S BISWAS

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      Straw tube detectors are single wire proportional counters that are widely used as tracking devices. We have carried out R&D activity with a straw tube detector prototype. The aim of this work is to study the stability of the performance in terms of gain and energy resolution of these types of detectors under high rate of radiation. The gain and energy resolution of the detector are studied along with its variation with ambient temperature and pressure. X-rays from a radioactive source are used to irradiate the detector and to monitor the energy spectra simultaneously for calculating the gain. The method followed here is unique as the ageing measurements have been performed without using an accelerated particle beam or any radiation generator. The performance of a straw tube detector has been studied in a laboratory for more than 800 h at a stretch using a single sealed radioactive X-ray source with high intensity. Variation of gain and energy resolution of the straw tube detector under X-ray irradiation in Ar/CO$_2$ gas mixture (volume ratio 80/20) is discussed in this article. The gain of an aged straw depends on gas flow rate. We have estimated the time required for the gain of a straw tube detector under ageing tests to recover on increasing the gas flow rate. We have also estimated the time resolution of the straw tube detectors by using cosmic rays as the trigger for the Ar/CO$_2$ gas mixture in 70/30 volume ratio (different gas mixture was used for the measurement of the time resolution). This type of ageing and time resolution measurements in Ar/CO$_2$ gas mixture has not been reported earlier. The details of the measurement process and the experimental results are presented in this article.

    • Cosmic ray flux and lockdown due to COVID-19 in Kolkata – Any correlation?

      A SEN S CHATTERJEE S ROY R BISWAS S DAS S K GHOSH S BISWAS

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      Cosmic ray muon flux is measured by the coincidence technique using plastic scintillation detectors in the High Energy Physics Detector Laboratory at Bose Institute, Kolkata. Due to the COVID-19 outbreak and nationwide complete lockdown, the laboratory was closed from the end of March 2020 till the end of May 2020. After lockdown, although the city is not in its normal state, we still were able to take data on some days. The lockdown imposed a strict restriction on the transport service other than the emergency ones and also most of the industries were shut down in and around the city. This lockdown has significant effect on the atmospheric conditions in terms of change in the concentration of air pollutants. We have measured the cosmic ray flux before and after the lockdown to observe the apparent change if any, due to change in the atmospheric conditions. In this article, we report the measured cosmic ray flux at Kolkata (22.58°N 88.42°E and 11 m above the Sea Level) along with the major air pollutants present in the atmosphere before and after the lockdown.

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