Fermilab, Batavia
Muons, Inc, Batavia
Voss Scientific, Albuquerque, New Mexico
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.
BNL, Upton, Long Island, New York
CEA, Gif-sur-Yvette
ESS-S, Lund
Fermilab, Batavia
CERN, Geneva
Funding: ESS-S Scandinavia Consortium
The conceptual design of the European Spallation Source-Scandinavia (ESS-S) is presented. The accelerator system baseline draws heavily on state-of-the-art mature technologies that are being employed in the CERN Linac4 and SPL projects, although advances with spoke resonator and sputtered superconducting cavities are also being evaluated for reliable performance. Irradiation damage due to proton beam losses is a key issue for linac and target components. Their optimized design is performed from an engineering perspective, using the last updated versions of mechanical design codes which were already qualified for irradiated components. Finally, future upgrades of power and intensity of the proton linac are considered, including the design optimization of the Target Station (proton/neutron convertor), with the possibility of increasing the average pulsed power deposition up to 7.5 MW. All possible upgrades will be taken into account for the final design review, in the frame of the costs and constraints given with the site decision.
Old Dominion University, Norfolk, Virginia
Muons, Inc, Batavia
Fermilab, Batavia
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
BNL, Upton, Long Island, New York
Fermilab, Batavia
The University of Texas at Austin, Austin, Texas
An AC dipole magnet produces a sinusoidally oscillating dipole field with frequency close to betatron frequency and excites large sustained oscillations of beam particles circulating in a synchrotron. Observation of such oscillations with beam-position-monitors allows direct measurements of a synchrotron's nonlinear parameters. This paper presents experimental studies to measure effects of sextupole and octupole fields, such as tune dependence on amplitude and resonance driving terms, performed in the Fermilab Tevatron using an AC dipole.
Fermilab, Batavia
Funding: Work supported by the United States Department of Energy under Contract No. DE-AC02-07CH11359
Over the past year Tevatron has been routinely operating at initial luminosity over 3·1032. The high luminosity regime highlighted several issues that became the focus for operational improvements. In this report we summarize the experience in such areas as mitigation of particle losses, maintaining orbit and optics stability, and identification of aperture restrictions.