| Paper | Title | Page |
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| MO6RFP079 | Improved DC Gun Insulator | 557 |
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Funding: Supported in part by USDOE Contract No. DE-AC05-84-ER-40150. Many user facilities such as synchrotron light sources and free electron lasers require accelerating structures that support electric fields of 10-100 MV/m, especially at the start of the accelerator chain where ceramic insulators are used for very high gradient DC guns. These insulators are difficult to manufacture, require long commissioning times, and have poor reliability, in part because energetic electrons bury themselves in the ceramic, creating a buildup of charge and causing eventual puncture. A novel ceramic manufacturing process is proposed. It will incorporate bulk resistivity in the region where it is needed to bleed off accumulated charge caused by highly energetic electrons. This process will be optimized to provide an appropriate gradient in bulk resistivity from the vacuum side to the air side of the HV standoff ceramic cylinder. A computer model will be used to determine the optimum cylinder dimensions and required resistivity gradient for an example RF gun application. A ceramic material example with resistivity gradient appropriate for use as a DC gun insulator will be fabricated by glazing using doping compounds and tested. |
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| TU6RFP039 | SNS Laser Stripping for H- Injection | 1629 |
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Funding: Supported in part by USDOE Contract No. DE-AC05-84-ER-40150. Supported in part by USDOE Contract DE-AC05-00OR22725 The ORNL spallation neutron source (SNS) user facility requires a reliable, intense beams of protons. The technique of H- charge exchange injection into a storage ring or synchrotron has the potential to provide the needed beam currents, but it will be limited by intrinsic limitations of carbon and diamond stripping foils. A laser in combination with magnetic stripping has been used to demonstrate a new technique for high intensity proton injection, but several problems need to be solved before a practical system can be realized. Technology developed for use in Free Electron Lasers is being used to address the remaining challenges to practical implementation of laser controlled H- charge exchange injection for the SNS. These technical challenges include (1) operation in vacuum, (2) the control of the UV laser beam to synchronize with the H- beam and to shape the proton beam, (3) the control and stabilization of the Fabry-Perot resonator, and (4) protection of the mirrors from radiation. |
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| WE6PFP097 | Pulsed Magnet Arc Designs for Recirculating Linac Muon Accelerators | 2733 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351 We have previously considered the application of fast pulsing quadrupoles to increase the focusing of muon beams as they gain energy in the linac region of a recirculating linear accelerator (RLA) in order to allow more passes. In this work we consider the use of pulsed magnets, both quads and dipoles, to reduce the number of beam lines needed for the return arcs of the RLA. We investigate the required relationships between the linac parameters (length and energy gain) and the momentum acceptance of the return arcs and consider the optimum strategy for accelerating both muon charge signs. |
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| TH5PFP074 | Putting Space Charge into G4beamline | 3374 |
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Funding: Supported in part by USDOE Contract DE-FG02-6ER86281. The G4beamline program is based on the well-established Geant4 toolkit used to simulate the interactions of particles and photons with matter. Until now, only a single particle at a time could be tracked and there are no interactions between particles. Recent designs for high pressure RF cavities and other novel devices achieving extreme muon cooling require that the effect of space charge be included in the simulations. A new tracking manager in G4beamline propagates a number of particles (typically 1,000-10,000) in parallel, stepping all particles in time. This allows all of the usual Geant4 physics interactions to be applied, plus collective computations. A simple macroparticle-based model is used to represent ~108 charges with an ellipsoidal charge density. At intervals the appropriate macroparticle size and shape are recalculated, the electric and magnetic fields are determined, and an impulse is applied to the simulated particles. Comparisons to standard space charge codes are presented. |
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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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| FR5RFP012 | Epicyclic Helical Channels for Parametric Resonance Ionization Cooling | 4554 |
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Funding: Work supported in part in part by DOE contract DE-AC02-07CH11359 and DOE STTR Grant DE-FG02-05ER86253 In order to achieve cooling of muons in addition to 6D helical cooling channel (HCC) [1], we develop a technique based on a parametric resonance. The use of parametric resonances requires alternating dispersion, minimized at locations of thin absorbers, but maximized in between in order to compensate for chromatic aberrations [2]. These solutions can be combined in an Epicyclic Helical Cooling Channel (EHCC) that meets requirements of alternating dispersion of beam periodic orbit with best conditions for maintenance of stable beam transport in a continuous solenoid-type field [3]. We discuss here basic features and new simulation results for EHCC. |