| Paper | Title | Page |
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| MOPD053 | Conceptual Design of the ESS LINAC | 804 |
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A three year design update for the European Spallation Source (ESS) linac is just starting and a full review of this work will be presented. The acceleration in the medium energy part of the LINAC using the spoke cavities have been optimized and the rest of the machine has been redesigned to incorporate this optimization. The ESS LINAC will deliver an average power of 5~MW to the target in the nominal design and the possibility to upgrade to 7.5~MW has been included in all the design steps. Acknowledgments to all the people in the ESS LINAC Reference Group. |
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| WEPE066 | Beam Test of a High Pressure Cavity for a Muon Collider | 3494 |
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To demonstrate the feasibility of a high pressure RF cavity for use in the cooling channel of a muon collider, an experimental setup that utilizes 400-MeV Fermilab linac proton beam has been developed. In this paper, we describe the beam diagnostics and the collimator system for the experiment, and report the initial results of the beam commissioning. The transient response of the cavity to the beam is measured by the electric and magnetic pickup probes, and the beam-gas interaction is monitored by the optical diagnostic system composed of a spectrometer and two PMTs. |
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| WEPE067 | Beam-induced Electron Loading Effects in High Pressure Cavities for a Muon Collider | 3497 |
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Ionization cooling is a critical building block for the realization of a muon collider. To suppress breakdown in the presence of the external magnetic field, an idea of using an RF cavity filled with high pressure hydrogen gas is being considered for the cooling channel design. In the high pressure RF cavity, ionization energy loss and longitudinal momentum recovery can be achieved simultaneously. One possible problem expected in the high pressure RF cavity is, however, the dissipation of significant RF power through the electrons accumulated inside the cavity. The electrons are generated from the beam-induced ionization of the high pressure gas. To characterize this detrimental loading effect, we develop a simplified model that relates the electron density evolution and the observed pickup voltage signal in the cavity, with consideration of several key molecular processes such as the formation of the polyatomic molecules and ions, excitation, recombination and electron attachment. This model is expected to be compared with the actual beam test of the cavity in the MuCool Test Area (MTA) of Fermilab. |
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| WEPE069 | Study of Electron Swarm in High Pressure Hydrogen Gas Filled RF Cavities | 3503 |
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A high pressurizing hydrogen gas filled RF cavity has a great potential to apply for muon colliders. It generates high electric field gradients in strong magnetic fields with various conditions. As the remaining demonstration, it must work under high radiation conditions. A high intensity muon beam will generate a beam-induced electron swarm via the ionization process in the cavity. A large amount of RF power will be consumed into the swarm. We show the recent non-beam test and discuss the electron swarm dynamics which plays a key role to develop a high pressure RF cavity. |
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| WEPE081 | Wedge Absorber Design for the Muon Ionisation Cooling Experiment | 3536 |
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In the Muon Ionization Cooling Experiment (MICE), muons are cooled by ionization cooling. Muons are passed through material, reducing the total momentum of the beam. This results in a decrease in transverse emittance and a slight increase in longitudinal emittance, but overall reduction of 6D beam emittance. In emittance exchange, a dispersive beam is passed through wedge-shaped absorbers. Muons with higher energy pass through more material, resulting in a reduction in longitudinal and transverse emittance. Emittance exchange is a vital technology for a Muon Collider and may be of use for a Neutrino Factory. Two ways to demonstrate emittance exchange in the straight solenoidal lattice of MICE are discussed. One is to let a muon beam pass through a wedge shaped absorber; the input beam distribution must be carefully selected to accommodate chromatic aberrations in the solenoid lattice. Another approach is to use the input beam for MICE without beam selection. In this case no polynomial weighting is involved; however, a more sophisticated shape of the absorber is required to reduce longitudinal emittance. |
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| THPEA046 | The MuCool Test Area and RF Program | 3780 |
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TThe MuCool RF Program focuses on the study of normal conducting RF structures operating in high magnetic field for applications in muon ionization cooling for Neutrino Factories and Muon Colliders. This paper will give an overview of the program, which will include a description of the test facility and its capabilities, the current test program, and the status of a cavity that can be rotated in the magnetic field which allows for a more detailed study of the maximum stable operating gradient vs. magnetic field strength and angle. |
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| THPEA054 | Rectangular Box Cavity Tests in Magnetic Field for Muon Cooling | 3795 |
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Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown significant drop in accelerating field performance for the case of parallel electric and magnetic fields. It has been suggested that having the magnetic field perpendicular to the electric field should provide magnetic insulation and suppress breakdown. An 805-MHz Cu rectangular box cavity was built for testing with the fields perpendicular. It was mounted on an adjustable support to vary the angle between the rf electric and external magnetic field. We report on design and operation of the rectangular box cavity. |