We report the status of two-color high intensity laser-plasma interaction experiments on the UT³ laser system at the University of Texas at Austin. After an outline of the experimental apparatus, an overview of the motivating theoretical work, and a characterization of the performance of our Chirped Pulse Raman Amplification system (CPRA) we report the status of our most recent experiment. We have attempted to seed the growth of the Raman Forward Scattering (RFS) instability in order to produce electrons at lower driving pulse power than is conventionally needed. We have been unsuccessful, and provide reasons why and recommendations for future modifications to the experimental apparatus. The most significant conclusion is that the CPRA system as it is now is not appropriate for this experiment because the observed RFS spectrum is at higher wavelength than our system. Possible future changes include either amplifying a separate barium nitrate sideband at 938 nm through the CPRA system or using a different Raman active medium after the main 800 nm UT³ pulse is compressed. The feasibility study of these possible modifications is not yet complete. / text

<p>The PAMELA space experiment is scheduled for launch towards the end of 2004 on-board a Russian Resurs DK1 satellite, orbiting Earth at an altitude of 300– 600 km. The main scientific goal is a study of the antimatter component of the cosmic radiation. The semipolar orbit (70.4◦) allows PAMELA to investigate a wide range of energies for antiprotons (80 MeV–190 GeV) and positrons (50 MeV– 270 GeV). Three years of data taking will provide unprecedented statistics in this energy range and will set the upper limit for the ratio He/He below 10−7. PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield built at KTH. The anticounter scintillators are used to aid in the rejection of background from particles not cleanly entering the acceptance of the tracker. Information from the anticounter system will be included as a veto in a second level trigger, to exclude the acquisition of events generated by false triggers.</p><p>An LED-based monitoring system has been developed for the anticounter system. The LEDs mimic the light signal produced in the scintillator by an ionising particle. This allows the functionality of the AC system to be verified in-orbit. The development and testing of the monitoring system are presented and comparisons have been made with independent radioactive source-based calibration methods. The anticounter system has also been extensively tested with cosmic rays and particle beams. Most of these tests have been performed with the anticounters integrated with the other PAMELA subdetectors in a flight-like configuration.</p>

The tabu search particle filter is proposed in this research based on the integration of the modified tabu search metaheuristic optimization and the genetic particle filter. Experiments with this algorithm in real time human tracking applications in unconstrained environments show that it is more robust, accurate and faster than a number of other existing metaheuristic filters, including the evolution particle filter, particle swarm filter, simulated annealing filter, path relink filter and scatter search filter. Quantitative evaluation illustrates that even with only ten particles in the system, the proposed tabu search particle filter has a success rate of 93.85% whereas the success rate of other metaheuristic filters ranged from 68.46% to 17.69% under the same conditions. The accuracy of the proposed algorithm (with ten particles in the tracking system) is 2.69 pixels on average, which is over 3.85 times better than the second best metaheuristic filters in accuracy and 18.13 times better than the average accuracy of all other filters. The proposed algorithm is also the fastest among all metaheuristic filters that have been tested. It achieves approximately 50 frames per second, which is 1.5 times faster than the second fastest algorithm and nineteen times faster than the average speed of all other metaheuristic filters. Furthermore, a unique colour sequence model is developed in this research based on a degenerated form of the hidden Markov model. Quantitative evaluations based on rigid object matching experiments illustrate that the successful matching rate is 5.73 times better than the widely used colour histogram. In terms of speed, the proposed algorithm achieves twice the successful matching rate in about three quarters of the processing time consumed by the colour histogram model. Overall, these results suggest that the two proposed algorithms would be useful in many applications due to their efficiently, accuracy and ability to robustly track people and coloured objects.

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