Award Final Technical Report

Abstract

OverviewAs stated above, a broad range of investigations into SASE FELs and high brightness beams were proposed 3 years ago at a preceding grant renewal point. We have accomplished the majority of the stated physics goals, and added other areas of investigation, extending well beyond the scope of the original proposal as the research developed and new opportunities came into view.We review the results in high brightness beam and beam-based radiation physics that have been obtained under this grant's support in the following sections, by topic:Experiments on ultra-short beam creation and coherent radiation generation at UCLAdesigned and built chicane compressor at the BNL ATF. UCLA-performed SASE FEL experiments at VISA, also located at the ATF. Initial velocity bunching experiments at the UCLA Neptune Lab. Velocity bunching experiments performed at the LLNL PLEIADES inverse-Comptonscattering experiment injector. Use of compressed ultra-short beams in ICS experiments. Development and use of high gradient permanent-magnet quadrupole-based final focus systems at PLEIADES, to create ultra-small beam spots for ICS and other applications.These topics will form the background for discussing progress in: computational and theoretical studies, student training, publications, and technology development. We report the progress towards new experimental facilities (advanced injector and diagnostic development at SLAC and INFN), in the context the following section, as lays the groundwork for the discussion of proposed future experiments. BNL Compressor ExperimentsThe chicane compressor at the BNL ATF has been installed in the high-energy beam line after the injector. Significant delays as well as cost increases were encountered in this project because of BNL safety approval demands. The increases in costs were born partially by the DoE BES grant that nominally funds on-campus FEL work, and also by donations of labor and diagnostic equipment from collaborators INFN-LNF (Frascati). Initial data was obtained in late 2004 from this experiment.The compression experiments at ATF have focused on creation of very short (~20-25 micron rms) beam pulses, and on testing the effects of coherent synchrotron radiation (CSR) and of coherent edge radiation (CER) emitted from such short beams. Both of these radiation effects are under investigation for their link to a new form of microbunching instability. The UCLA effort has indeed identified the link between this instability, which may greatly impact the performance of compressors in short wavelength FELs such as the LCLS, and the FEL instability itself. A theoretical study of the comparison between these two instabilities 1 has been published in Physical Review STAB. The microbunching instability is found to have both high gain and low gain regimes which are similar to those corresponding to the FEL, but much stronger. The CSR instability may assert itself in less than a bending period -and can strongly filament the beam's longitudinal phase space.The closely related CER effect 2,3,4 has n...