R K Jain
Articles written in Pramana – Journal of Physics
Volume 72 Issue 1 January 2009 pp 263-267
This is a summary of the activities of the working group on cosmology at WHEPP-X. The three main problems that were discussed at some length by the group during the course of the workshop were (i) canceling a `large' cosmological constant, (ii) non-Gaussianities in inflationary models and (iii) stability of interacting models of dark energy and dark matter. We have briefly outlined these problems and have indicated the progress made.
Volume 75 Issue 6 December 2010 pp 1253-1258 Conributed Papers
In nuclear field, underwater cutting and welding technique is required for post-irradiation examination, maintenance, decommissioning and to reduce storage space of irradiated materials like used zircaloy pressure tubes etc., of nuclear power plants. We have developed underwater cutting technique for 4.2 mm thick zircaloy pressure tubes and up to 6 mm thick steel using fibre-coupled 250 W average power pulsed Nd:YAG laser. This underwater cutting technique will be highly useful in various nuclear applications as well as in dismantling/repair of ship and pipe lines in water.
Volume 78 Issue 3 March 2012 pp 493-498 Brief Report
Fission fragments and other charged particles leave tracks of permanent damage in most of the insulating solids. Damage track detectors are useful for personal dosimeters and for ﬂux/dose determination of high-energy particles from accelerators or cosmic rays. A detector that has its principal response at nucleon energy above 50 MeV is provided by the ﬁssion of Bi-209. Neutrons produce the largest percentage of hadron dose in most high-energy radiation ﬁelds. In these ﬁelds, the neutron spectrum is typically formed by low-energy neutrons (evaporation spectrum) and high-energy neutrons (knock-on spectrum). We used Bi-ﬁssion detectors to measure neutron peak ﬂuence and compared the result with the calculated value of neutron peak ﬂuence. For the exposure to 100 MeV we have used the iThemba Facility in South Africa.
Volume 82 Issue 2 February 2014 pp 211-216 Contributed Papers
Most of today’s industrial Nd:YAG lasers use fibre-optic beam delivery. In such lasers, fibre core diameter is an important consideration in deploying a beam delivery system. Using a smaller core diameter fibre allows higher irradiances at focus position, less degradation of beam quality, and a larger stand-off distance. In this work, we have put efforts to efficiently deliver the laser output of ‘ceramic reflector’-based long pulse Nd:YAG laser through a 200 𝜇m core diameter optical fibre and successfully delivered up to 60 J of pulse energy with 90% transmission efficiency, using a GRADIUM (axial gradient) plano-convex lens to sharply focus down the beam on the end face of the optical fibre and fibre end faces have been cleaved to achieve higher surface damage thresholds.
Volume 84 Issue 4 April 2015 pp 591-608
An analysis of the data based on 924 inelastic interaction events induced by 28 Si nuclei in a nuclear emulsion is presented. The nuclear fragmentation process is studied by analysing the total charge (𝑄) distribution of the projectile spectators for different emulsion target groups along with the comparison of Monte Carlo Glauber model results. Probability distributions for total disintegrated events as a function of different projectile masses are shown and compared with cascade evaporation model results at same energy per nucleon. Further, mean multiplicities of different charged secondaries for different classes of events are presented and for each event, variation of mean multiplicities as a function of total charge (𝑄) is also presented. The pseudorapidity distributions and normalized pseudorapidity distributions of the produced charged particles in nucleus–nucleus collisions at 3.7 A GeV are analysed for total disintegration (TD) as well as minimum-bias events.
Volume 93 | Issue 5
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