| Paper | Title | Page |
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| MO6RFP045 | Photocathode Studies for Ultra-Low Emittance Electron Sources | 458 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Future x-ray light sources such as FELs and ERLs impose requirements on emittance and bunch repetition rate that are very demanding on the electron source. Even if perfect compensation of space-charge effects could be attained, the fundamental cathode emission properties determine a lower bound on achievable source emittance. Development of ultra-low-emittance sources is a rapidly evolving area of R&D with exciting new results measured for low bunch charge, but it is very difficult to compare different results and quantify what works. The study of photocathodes, with the goal of optimizing for low emittance, is limited in scope. In this paper, we describe an R&D effort to systematically measure and design the fundamental properties of photocathodes suitable for an FEL or ERL. We plan to apply surface analysis lab techniques to characterize photoemission, and then correlate material properties with emittance. On the theory side, we plan to calculate electron band structure for crystal surfaces, correlate with lattice parameters and work function, and then estimate the transverse momentum using the three-step model. The status and results to date of this effort will be reported. |
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| TH5PFP076 | Particle Tracking in Matter Dominated Beam Lines | 3380 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86281 Most computer programs that calculate the trajectories of particles in accelerators assume that the particles travel in an evacuated chamber. The development of muon beams, which are needed for muon colliders and neutrino factories and are usually required to pass through matter, is limited by the lack of user-friendly numerical simulation codes that accurately calculate scattering and energy loss in matter. Geant4 is an internationally supported tracking toolkit that was developed to simulate particle interactions in large detectors for high energy physics experiments, and includes most of what is known about the interactions of particles and matter. Geant4 has been partially adapted in a program called G4beamline to develop muon beam line designs. The program is now being developed and debugged by a larger number of accelerator physicists studying muon cooling channel designs and other applications. Space-charge effects and muon polarization are new features that are being implemented. |
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| FR5RFP069 | Intensity Dependent Beam Dynamics Studies in the Fermilab Booster | 4692 |
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Funding: This work supported by NSF grant No. 0237162, and DOE SCIentific Discovery through Advanced Computing: Accelerator science and simulation DE-PS02-07ER07-09 The FNAL Booster is a combined-function proton synchrotron with a bunch intensity of ~6·1010 protons; significantly greater than expected in the original design. The injection energy is 400 MeV (gamma factor 1.4), low enough for space charge forces to play a role in beam dynamics. The magnets are used directly as vacuum tanks, so the laminated pole surfaces contribute significantly to impedance. A study of the transverse coupling dependence on beam intensity is presented here. Experimental results are being analyzed using Synergia, a high-fidelity, parallel, fully 3D modeling code that includes both space charge and impedance dynamics. Previously, Synergia has always shown good agreement with experimental data. Our initial studies show that the direct space charge contribution to beam dynamics is too small to account for the increase in the coupling seen experimentally, corroborating analytic results. Parametric studies of the impedance needed to match the measured coupling are being done. Agreement between simulation and experiment should provide an independent measure of the Booster impedance, which has been analytically modeled and calculated elsewhere. |