• S K Goel

      Articles written in Pramana – Journal of Physics

    • Experimental study of the variation of the plasma temperature with the laser flux

      B K Sinha N Gopi S K Goel

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      Experiments performed with a 50 MW — 60 nsec ruby laser to estimate the temperature of the plasma produced on the planar targets of carbon as well as polyethylene are reported. Temperatures were estimated by two foil ratio technique. The temperatures of carbon and polyethylene plasma show aφ2/9 dependance on flux in the flux regime of 1010 W/cm2 to 5 × 1011 W/cm2. The comparatively slower dependance is explained on the basis of purely collisional absorption, the effect being enhanced due to relatively long duration of the laser pulses. Scaling laws of plasma temperature against laser flux obtained by different workers in different flux regimes have been analysed on the basis of collisional and non-collisional absorption.

    • Development of an experimental facility for studying atomic-field, bremsstrahlung from keV electrons interacting with atoms and molecules

      S K Goel M J Singh R Shanker

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      A dedicated working setup for studying the process of atomic-field bremsstrahlung and its dependence on various parameters for keV electrons incident on a solid or a gaseous target has been indigenously developed. The setup consists of a high vacuum scattering chamber attached with a rotatable X-ray photon detector, a home-built high voltage electron gun with a replaceable tungsten-filament cathode, an isolated floating high voltage system, high vacuum pumping units, various signal processing electronic modules and an IBM PC/XT based 4K-multichannel analyzer. A brief description of the facility is presented. The performance of the facility has been tested by recording the bremsstrahlung spectra from 7.0 keV electrons on thin Ag, Au and 7.5 keV electrons on Hf targets; the corresponding spectra are presented and discussed. The gun can operate in the range of 0–8.0 kV accelerating voltage in the present configuration. Other feasible experiments that can be performed on the setup are also briefly mentioned.

    • SCORPION: A system for coincidences between recoil and projectile ions at NSC, New Delhi

      M J Singh S K Goel R Shanker D O Kataria N Madhavan P Sugathan J J Das D K Avasthi A K Sinha

      More Details Abstract Fulltext PDF

      An on-line facility to measure coincidences between the recoil ions and the scattered projectiles (SCORPION) has been designed, fabricated and commissioned at Nuclear Science Centre (NSC), New Delhi. The facility consists of a four jaw slit assembly, a time of flight (TOF) spectrometer, a parallel plate electrostatic charge analyser and a one dimensional position sensitive parallel plate avalanche counter (PPAC). Details of the design and working principles of various components and the test results obtained for the Siq+-Ar collision system are presented to highlight the performance of the system. A multiple loss of up to four electrons has been observed for 60 MeV Si4+ ions colliding with argon atoms in a single collision condition. Spectra of recoil ions detected in coincidence with a particular charge state of the scattered projectile show a bell shaped distribution as a function of the recoil charge state (r) for the electron loss events. However, the yield of recoil ions drops asr increases for the direct ionization channel. Also for electron loss, the peak of the recoil ion distribution is seen to shift to a higher recoil charge state as the number of lost electrons from the projectile increases.

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