96 research outputs found
A table-top laser-based source of short, collimated, ultra-relativistic positron beams
No full textAn ultra-relativistic electron beam passing through a thick, high-Z solid target triggers an electromagnetic cascade, whereby a large number of high energy photons and electron-positron pairs are produced. By exploiting this physical process, we present here the first experimental evidence of the generation of ultra-short, highly collimated and ultra-relativistic positron beams following the interaction of a laser-wake field accelerated electron beam with high-Z solid targets. Clear evidence has also been obtained of the generation of GeV electron-positron jets with variable composition depending on the solid target material and thickness. The percentage of positrons in the overall leptonic beam has been observed to vary from a few per cent up to almost fifty per cent, implying a quasi-neutral electron-positron beam. We anticipate that these beams will be of direct relevance to the laboratory study of astrophysical leptonic jets and their interaction with the interstellar medium.</p
Nuclear physics merely using a light source
No full textThe interaction of ultra-intense focused laser beams with solid targets is a new field of research resulting in the production of exotic plasma conditions similar to the conditions which exist in the interior of some stellar objects. The lasers generate very high energy electrons and ions which can subsequently produce γ-rays, positrons, neutrons and pions. The results obtained from these studies have major implications to fundamental plasma physics and high energy accelerator physics as well as important technological potential for the production of compact sources of neutrons, positrons and isotopes
Performance assessment using remote sensing
No full textPresented at Irrigated agriculture responds to water use challenges - strategies for success: USCID water management conference held on April 3-6, 2012 in Austin, Texas.The Krishna delta irrigation system, one of the earliest major irrigation projects in southern India was designed by Sir Arthur Cotton during in the middle of 19th century on river Krishna near Vijayawada. The project irrigates an ayacut of 5.14 lakh hectares covering West Godavari, Krishna, Guntur and Prakasam districts of Andhra Pradesh. Using multi-date satellite data of Krishna Western Delta (KWD), flow information, crop cutting experiment (CCE) plot data of the State Department of Agriculture (SDA) and AP Water Management (APWAM) Project obtained during kharif 2005-06, performance indicators were computed and performance of irrigation system was assessed. Paddy was the major crop gown in KWD. Hence paddy yield model was developed using ground obtained CCE plot yield data and satellite derived normalized difference vegetative index (NDVI). Very good correlation (r = 0.7) was obtained between these parameters. Hence, it was extrapolated to the entire KWD belt. The average yield of KWD derived based on NDVI observations was closely matched with the yield data of APWAM and SDA. Highest efficiency (85%) was obtained in high-level canal command. The lower efficiency obtained in Kommamur was due to poor condition of the canal, high conveyance losses and release of excess rain water in to the sea through the canal. The productivity of water was varying from 0.7 to 1.0 kg m-3 across KWD except in Kommamur which had only 0.5 kg m-3. The information on nature, extent and distribution of salt affected soils and waterlogged areas in KWD was generated based on visual interpretation of FCC imageries obtained from space-borne remote sensing satellites. It was computed that about 18,102 and 4,675 hectares of area was salt affected and waterlogged, respectively
Kinetic treatment of radiation reaction effects
No full textModern accelerators and light sources subject bunches of charged particles to quasiperiodic motion in extremely high electric fields, under which they may emit a substantial fraction of their energy. To properly describe the motion of these particle bunches, we require a kinetic theory of radiation reaction. We develop such a theory based on the notorious Lorentz-Dirac equation, and explore how it reduces to the usual Vlasov theory in the appropriate limit. As a simple illustration of the theory, we explore the radiative damping of Langmuir waves
Ion source development and radiobiology applications within the LIBRA project
No full textNext generation intense, short-pulse laser facilities require new high repetition rate diagnostics for the detection of ionizing radiation. We have designed a new scintillator-based ion beam profiler capable of measuring the ion beam transverse profile for a number of discrete energy ranges. The optical response and emission characteristics of four common plastic scintillators has been investigated for a range of proton energies and fluxes. The scintillator light output (for 1 MeV > Ep < 28 MeV) was found to have a non-linear scaling with proton energy but a linear response to incident flux. Initial measurements with a prototype diagnostic have been successful, although further calibration work is required to characterize the total system response and limitations under the high flux, short pulse duration conditions of a typical high intensity laser-plasma interaction
Applications for nuclear phenomena generated by ultra-intense lasers
No full textThe amplification of laser light to generate powers large enough to affect the nucleus has been the desire of scientists since the invention of the laser 40 years ago. Many lasers, including tabletop varieties, now have pulse powers greater than the electrical power generated by all the world's power plants combined. When this power is focused to dimensions of a few microns, laser-driven nuclear phenomena can occur. Here we review the developments in this research field and describe the potential of laserproduced proton, neutron, and heavy ion beams, together with isotope and isomer production
The radiative self-force and charged fluids
No full textWe develop a new fluid model of a warm plasma that includes the radiative self-force on each plasma electron. Our approach is a natural generalization of established methods for generating fluid models without radiation reaction. The equilibrium of a magnetized plasma is analysed, and it is shown that the thermal motion is confined to the magnetic field lines. A dispersion relation is deduced for electric waves in a magnetized plasma, and it is shown to agree with our recently established relativistic kinetic theory derived from the Lorentz-Abraham-Dirac equation
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