Four graduate students in the Department of Physics have received fellowships for the 2006-2007 academic year.
Mr. Edward Nissen won a $10,000 graduate scholarship from the Directed Energy Professional Society. Ed received his B.S. degree from Johns Hopkins and is currently interested in working through the nonlinear dynamics of halo formation in high-brightness, high-average-current electron beams, which is likely to be the subject of his Ph.D. dissertation. This is a serious issue for commissioning and operating accelerators of high-average-current beam, such as electron accelerators that would drive high-average-power free-electron lasers (FELs) or ion beams that would drive spallation neutron sources. In such machines, beam loss at just microamp-levels, i.e., just one part in a million of the beam required for future high-power FELs, can damage the accelerator. Here at NIU we have developed the computational tools not only to simulate halo formation with excellent statistics (using a new simulation code based on wavelets), but also to characterize the transient dynamics of the individual electron orbits (using a new “measure of chaos” that is based on pattern recognition in orbits). These tools are ideal for delving into the halo problem and its mitigation (in part, they were designed to do this very task), and Ed intends to use them toward that end.
Mr. Benjamin Sprague is the first person to win a NICADD Accelerator Fellowship. Ben is a new graduate student, and he majored in computer science as an undergraduate at Cedarville University. His initial work is configuring and implementing a parallelized version of the new accelerator simulation code that NIU developed based on multiresolution (wavelet) analysis. Following that, his research is to be determined, but will probably entail making major improvements to the code's capabilities and applying the code to predict the outcome of specific experiments and/or accelerator designs. One example of a major improvement would be to simulate how coherent synchrotron radiation emitted by the beam as it transverses bending magnets acts back on the beam and degrades its quality. This is a notoriously difficult problem, and the new wavelet-based code is designed to offer advantages toward its solution. Mr. Sprague may ultimately capitalize on those advantages.
Mr. Jiong Hua is the first person to win a NIU/ANL Distinguished Graduate Fellowship. Jiong received his M.S. degree in the Department of Electrical Engineering at Northern Illinois University in May 2003. During that time he was involved in research on nanophotonics and co-authored an article published in Nano Letters [5, 1399 (2005)]. Since January 2005 Jiong has been working on his Physics Ph.D. dissertation subject: superconducting films containing arrays of nanoscale holes. This system provides unique platforms to study generic problems appearing in many physical systems, for example, frustration, the interaction between a periodic elastic medium and an array of obstacles. One of the striking phenomena observed in a superconducting film containing a regular array of holes is the so-called matching effect: at temperatures near the superconducting transition, transport measurements show ‘dips’ in the resistance versus magnetic field curves or ‘peaks’ in the field dependence of the critical current at matching fields where the amount of the magnetic flux through each unit-cell is an integer number of the flux quantum. Jiong is currently probing the origins of this intriguing matching effect. He has succeeded in fabricating holes into superconducting niobium films with either direct electron-beam patterning or using substrates containing nanochannels formed during electrochemical anodization which enable him to make holes with diameters down to ~100 nm and 20 nm, respectively. He is also interested in the physics in mesoscopic superconducting crystals with controlled shapes.
Mr. Timothy Maxwell is the recipient of a NIU university fellowship given to outstanding students in a masters program after receiving his B.S. degree from NIU. He has begun research on developing diagnostic techniques to be used at the next generation of linear colliders and or single pass free-electron lasers. These rely on very bright electron bunches which in turn need to be diagnosed with state-of-the-art beam diagnostics. Specifically, Tim will work toward developing an electro-optical imaging technique capable of measuring the electric field of a moving bunch. Based on this measurement one could then develop techniques to reconstruct the bunch distribution. This work will be initially done at NIU, with the newly commissioned femtosecond-class laser, and later the developed diagnostics will be tested at an accelerator facility such as the Argonne Wakefield Accelerator.