| Paper | Title | Page |
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| TU5PFP020 | Doped H2-Filled RF Cavities for Muon Beam Cooling | 855 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86350 and and FRA DOE contract number DE-AC02-07CH11359 RF cavities pressurized with hydrogen gas may provide effective muon beam ionization cooling needed for muon colliders. Recent 805 MHz test cell studies reported below include the first use of SF6 dopant to reduce the effects of the electrons that will be produced by the ionization cooling process in hydrogen or helium. Measurements of maximum gradient in the Paschen region are compared to a simulation model for a 0.01% SF6 doping of hydrogen. The observed good agreement of the model with the measurements is a prerequisite to the investigation of other dopants. |
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| WE5PFP008 | RF Breakdown of Metallic Surfaces in Hydrogen | 2000 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86350 Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and in part by FRA DOE contract number DE-AC02-07CH11359 In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown |
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| FR5PFP018 | Experimental Studies of Random Error Effects in High-Intensity Accelerators Using the Paul Trap Simulator Experiment (PTSX) | 4344 |
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Funding: Research supported by the U.S. Department of Energy. Understanding the effects of random errors in machine components such as quadrupole magnets and RF cavities is essential for the optimum design and stable operation of high-intensity accelerators. The effects of random errors have been studied theoretically, but systematic experimental studies have been somewhat limited due to the lack of dedicated experimental facilities. In this paper, based on the compelling physics analogy between intense beam propagation through a periodic focusing quadrupole magnet system and pure ion plasma confined in a linear Paul trap, experimental studies of random error effects have been performed using the Paul Trap Simulator Experiment (PTSX). It is shown that random errors in the quadrupole focusing strength continuously produce a non-thermal tail of trapped ions, and increases the rms radius and the transverse emittance almost linearly with the amplitude and duration of the noise. This result is consistent with 2D WARP PIC simulations. In particular, it is observed that random error effect can be further enhanced in the presence of beam mismatch. |
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| FR5PFP018 | Experimental Studies of Random Error Effects in High-Intensity Accelerators Using the Paul Trap Simulator Experiment (PTSX) | 4344 |
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Funding: Research supported by the U.S. Department of Energy. Understanding the effects of random errors in machine components such as quadrupole magnets and RF cavities is essential for the optimum design and stable operation of high-intensity accelerators. The effects of random errors have been studied theoretically, but systematic experimental studies have been somewhat limited due to the lack of dedicated experimental facilities. In this paper, based on the compelling physics analogy between intense beam propagation through a periodic focusing quadrupole magnet system and pure ion plasma confined in a linear Paul trap, experimental studies of random error effects have been performed using the Paul Trap Simulator Experiment (PTSX). It is shown that random errors in the quadrupole focusing strength continuously produce a non-thermal tail of trapped ions, and increases the rms radius and the transverse emittance almost linearly with the amplitude and duration of the noise. This result is consistent with 2D WARP PIC simulations. In particular, it is observed that random error effect can be further enhanced in the presence of beam mismatch. |