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| MO6PFP059 | 4-Coil Superconducting Helical Solenoid Model for MANX | 265 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 Magnets for the proposed muon cooling demonstration experiment MANX (Muon collider And Neutrino factory eXperiment) have to generate longitudinal solenoid and transverse helical dipole and helical quadrupole fields. This paper discusses the 0.4 M diameter 4-coil Helical Solenoid (HS) model design, manufacturing, and testing that has been done to verify the design concept, fabrication technology, and the magnet system performance. The model quench performance in the FNAL Vertical Magnet Test Facility (VMTF) will be discussed. |
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| MO6PFP060 | Studies of the High-Field Section for a Muon Helical Cooling Channel | 268 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-07ER84825 This paper presents the results of design studies of a high field section of a helical cooling channel proposed for the 6D muon beam cooling. The results include the magnet aperture limitations, the tunability of field components, the field correction, the superconductor choice and the magnet operation margin. |
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| MO6PFP062 | RF Integration into Helical Magnet for Muon 6-Dimensional Beam Cooling | 274 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-07ER84825 and by FRA under DOE Contract DE-AC02-07CH11359 The helical cooling channel is proposed to make a quick muon beam phase space cooling in a short channel length. The challenging part of the helical cooling channel magnet design is how to integrate the RF cavity into the compact helical cooling magnet. This report shows the possibility of the integration of the system. |
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| MO6PFP071 | HTS Development for 30-50 T Final Muon Cooling Solenoids | 295 |
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High temperature superconductors (HTS) have been shown to carry significant current density in the presence of extremely high magnetic fields when operated at low temperature. The successful design of magnets needed for high energy physics applications using such high field superconductor depends critically on the detailed wire or conductor parameters which are still under development and not yet well-defined. The HTS is being developed for accelerator use by concentrating on the design of solenoid magnet that will have a useful role in cooling muon beam phase space. A conceptual design of a high field solenoid using YBCO conductor is being analyzed. Mechanical properties of the HTS conductors will be measured along with engineering current densities (JE) as a function of temperature and strain to extend the HTS specifications to conditions needed for low temperature applications. HTS quench properties are proposed to be measured and quench protection schemes developed for the solenoid magnet. |
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| MO6PFP072 | Multi-Purpose Fiber Optic Sensors for High Temperature Superconductor Magnets | 298 |
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Funding: Supported in part by DOE SBIR grant DE-FG02-08ER85024 Optical fibers can be imbedded within new high temperature superconductor (HTS) magnets to monitor strain and temperature, to detect quenches, and, in the case of AgX/Ag/Bi2Sr2CaCu2Ox, (Bi2212) wire magnets, to serve as a heat treatment process monitor for wind-and-react (W&R) manufacturing. The W&R process requires that the optical fibers be installed before the Bi2212 heat treatment, one important issue is whether the fibers survive the 890 oC heat treatment so as to monitor the heat treatment and to serve subsequently as a low temperature monitor. Here, Au-coated optical fibers are attached to Bi2212 wires and processed with the typical reaction cycle. The Bi2212 superconductor is then evaluated for performance degradation due to the presence of the fiber and the fiber is evaluated for performance degradation due to the heat treatment and viability as a heat treatment process monitor. Two approaches to fiber optic sensing are used: a fiber Bragg grating and Rayleigh scattering |
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| MO6RFP036 | H- Ion Sources for High Intensity Proton Drivers | 435 |
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Funding: Supported in part by the US DOE Contract DE-AC05-00OR22725 Spallation neutron source user facilities require reliable, intense beams of protons. The technique of H- charge exchange injection into a storage ring or synchrotron can provide the needed beam currents, but may be limited by the ion sources that have currents and reliability that do not meet future requirements and emittances that are too large for efficient acceleration. In this project we are developing an H- source which will synthesize the most important developments in the field of negative ion sources to provide high current, small emittance, good lifetime, high reliability, and power efficiency. We describe planned modifications to the present external antenna source at SNS that involve: 1) replacing the present 2 MHz plasma-forming solenoid antenna with a 60 MHz saddle-type antenna and 2) replacing the permanent multicusp magnet with a weaker electro-magnet, in order to increase the plasma density near the outlet aperture. The SNS test stand will then be used to verify simulations of this approach that indicate significant improvements in H- output current and efficiency, where lower RF power will allow higher duty factor, longer source lifetime, and/or better reliability. |
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| MO6RFP080 | Intense Stopping Muon Beams | 560 |
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The study of rare processes using a beam of muons that stop in a target provides access to new physics at and beyond the reach of energy frontier colliders. The flux of stopping muons is limited by the pion production process and by stochastic processes in the material used to slow down the decay muons. Innovative muon beam collection and cooling techniques are applied to the design of stopping muon beams in order to provide better beams for such experiments. Such intense stopping beams will also support the development of applications such as muon spin resonance and muon-catalyzed fusion. |
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| TU5PFP017 | RF Cavities Loaded with Dielectric for Muon Facilities | 846 |
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Funding: Supported in part by FRA DOE contract number DE-AC02-07CH11359 RF cavities below 800 MHz are large, so alternative cavities at low frequencies are needed. Novel dielectric loaded RF cavities will allow smaller diameter cavities to be designed; changing the frequency of a cavity design would be as simple as changing the dielectric cylinder insert material or inner radius of the dielectric in the cavity. This paper discusses RF cavities loaded with dielectric material that could be used in various ways for muon facilities. The examples given are for 400 and 800 MHz cavities. Our initial motivation was to use dielectric to reduce the radial size of gas-filled cavities in helical cooling channels, but dielectric-loading has potential use in vacuum cavities for suppression of dark current emission. We also studied cavities that can be used for the phase rotation channel in the front end of a muon collider or neutrino factory. |
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| TU5PFP018 | Tunable RF Cavities Using Orthogonally Biased Ferrite | 849 |
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Funding: Supported by STTR Grant DE-FG02-07ER86320 and FRA DOE contract number DE-AC02-07CH11359 Originally conceived as a solution for FFAG applications, a new compact RF cavity design that tunes rapidly over various frequency ranges can be used to upgrade existing machines. The design being developed uses orthogonally biased garnet cores for fast frequency tuning and liquid dielectric to adjust the frequency range and to control the core temperature. We describe measurements of candidate ferrite and dielectric materials. The first use of the new cavity concept will be for improvements to the 8 GeV Fermilab Booster synchrotron. |
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| TU5PFP019 | Phase and Frequency Locked Magnetrons for SRF Sources | 852 |
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Funding: Supported in part by USDOE Contract. DE-AC05-84-ER-40150 and by FRA DOE contract number DE-AC02-07CH11359 Magnetrons are low-cost highly-efficient microwave sources, but they have several limitations, primarily centered about the phase and frequency stability of their output. When the stability requirements are low, such as for medical accelerators or kitchen ovens, magnetrons are the very efficient power source of choice. But for high energy accelerators, because of the need for frequency and phase stability–-proton accelerators need 1-2 degrees source phase stability, and electron accelerators need .1-.2 degrees of phase stability–-they have rarely been used. We describe a novel variable frequency cavity technique which will be utilized to phase and frequency lock magnetrons. |
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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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| TU5PFP021 | Traveling Wave RF Systems for Helical Cooling Channels | 858 |
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Funding: supported in part by USDOE STTR Grant DE-FG02-08ER86350 The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation. |
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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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| 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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| WE5PFP009 | RF Breakdown Studies Using a 1.3-GHz Test Cell | 2003 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and FRA DOE contract number DE-AC02-07CH11359 Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator. |
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| WE5PFP042 | Rugged Ceramic Window for RF Applications | 2089 |
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Funding: Supported in part by USDOE SBIR Grant DE-FG02-08ER85171 High-current RF cavities that are needed for many accelerator applications are often limited by the power transmission capability of the pressure barriers (windows) that separate the cavity from the power source. Most efforts to improve RF window design have focused on alumina ceramic, the most popular historical choice, and have not taken advantage of new materials. Alternative window materials have been investigated using a novel Merit Factor comparison and likely candidates have been tested for the material properties which will enable construction in the self-matched window configuration. Window assemblies have also been modeled and fabricated using compressed window techniques which have proven to increase the power handling capability of waveguide windows. Candidate materials have been chosen to be used in fabricating a window for high power testing at Thomas Jefferson National Accelerator Facility. |
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| WE6PFP064 | Achromatic Interaction Point Design | 2649 |
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Designers of high-luminosity energy-frontier muon colliders must provide strong beam focusing in the interaction regions. However, the construction of a strong, aberration-free beam focus is difficult and space consuming, and long straight sections generate an off-site radiation problem due to muon decay neutrinos that interact as they leave the surface of the earth. Without some way to mitigate the neutrino radiation problem, the maximum c.m. energy of a muon collider will be limited to about 3.5 TeV. A new concept for achromatic low beta design is being developed, in which the interaction region telescope and optical correction elements, are installed in the bending arcs. The concept, formulated analytically, combines space economy, a preventative approach to compensation for aberrations, and a reduction of neutrino flux concentration. An analytical theory for the aberration-free, low beta, spatially compact insertion is being developed. |
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| WE6PFP089 | Muon Capture, Phase Rotation, and Precooling in Pressurized RF Cavities | 2712 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86252 and FRA DOE contract number DE-AC02-07CH11359 Gas-filled RF cavities can provide high-gradient accelerating fields for muons, and can be used for simultaneous acceleration and cooling of muons. In this paper we explore using these cavities in the front-end of the capture and cooling systems for neutrino factories and muon colliders. We consider using gas-filled RF cavities for the initial front end cooling systems. We also consider using them for simultaneous phase-energy rotation and cooling in a front-end system. We also consider using lower-density RF cavities, where the gas density is primarily for RF breakdown suppression, with less cooling effect. Pressurized RF cavities enable higher gradient rf within magnetic fields than is possible with evacuated cavities, enabling more options in the front-end. The status of designs of the capture, phase rotation, and precooling systems of muon beams in pressurized cavities is described. |
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| WE6PFP090 | MANX, A 6-D Muon Beam Cooling Experiment for RAL | 2715 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 and by FRA under DOE Contract DE-AC02-07CH11359 MANX is a six-dimensional muon ionization cooling demonstration experiment based on the concept of a helical cooling channel in which a beam of muons loses energy in a continuous helium or hydrogen absorber while passing through a special superconducting magnet called a helical solenoid. The goals of the experiment include tests of the theory of the helical cooling channel and the helical solenoid implementation of it, verification of the simulation programs, and a demonstration of effective six-dimensional cooling of a muon beam. We report the status of the experiment and in particular, the proposal to have MANX follow MICE at the Rutherford-Appleton Laboratory (RAL) as an extension of the MICE experimental program. We describe the economies of such an approach which allow the MICE beam line and much of the MICE apparatus and expertise to be reused. |
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| WE6PFP093 | Reverse Emittance Exchange for Muon Colliders | 2721 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86253 Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Six-dimensional cooling schemes now being developed will reduce the longitudinal emittance of a muon beam so that smaller high frequency RF cavities can be used for later stages of cooling and for acceleration. However, the bunch length at collision energy is then shorter than needed to match the interaction region beta function. New ideas to shrink transverse beam dimensions by lengthening each bunch (reverse emittance exchange and bunch coalescing) will help achieve high luminosity in muon colliders with fewer muons. Analytic expressions for the reverse emittance exchange mechanism are derived, including a new resonant method of beam focusing. Correction schemes for the aberrations were explored, and a lattice to implement them was proposed. To mitigate space charge detuning and wake field effects, a scheme was invented to coalesce smaller intensity bunches after they are cooled and accelerated to high energy into intense bunches suitable for a muon collider. |
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| WE6PFP094 | Quasi-Isochronous Muon Capture | 2724 |
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Intense muon beams have many potential applications. However, muons originate from a tertiary process that produces a diffuse swarm. To make useful beams, the swarm must be rapidly collected and cooled before the muons decay. A promising new concept for the collection and cooling of muon beams to increase their intensity and reduce their emittances is investigated: the use of a nearly isochronous helical cooling channel (HCC) to facilitate capture of the muons into a few RF bunches. Such a distribution could be cooled quickly and then coalesced efficiently into a single bunch to optimize the luminosity of a muon collider. An analytical description of the method is presented followed by simulation and optimization studies. Practical design constraints and integration into a collider, neutrino factory or intense beam scenario are discussed and plans for further studies are addressed. |
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| WE6PFP095 | Integrating the MANX 6-D Muon Cooling Experiment with the MICE Spectrometers | 2727 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 The MANX experiment is to demonstrate the reduction of 6D muon phase space emittance using a continuous liquid absorber to provide ionization cooling in a helical solenoid magnetic channel. The experiment involves the construction of a short two-period long helical cooling channel (HCC) to reduce the muon invariant emittance by a factor of two. The HCC would replace the current cooling section of the MICE experiment now being setup at the Rutherford Appleton Laboratory. The MANX experiment would use the existing MICE spectrometers and muon beam line. This paper shall consider the various approaches to integrate MANX into the RAL hall using the MICE spectrometers. This study shall discuss the matching schemes used to minimize losses and prevent emittance growth between the MICE spectrometers and the MANX HCC. Also the placement of additional detection planes in the matching region and the HCC to improve the resolution will be examined. |
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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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| WE6PFP098 | Multipass Arc Lattice Design for Recirculating Linac Muon Accelerators | 2736 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351 Recirculating linear accelerators (RLA) are the most likely means to achieve the rapid acceleration of short-lived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. One problem is that in the simplest schemes, a separate return arc is required for each passage of the muons through the linac. In the work described here, a novel arc optics based on a Non Scaling Fixed Field Alternating Gradient (NS-FFAG) lattice is developed, which would provide sufficient momentum acceptance to allow multiple passes (two or more consecutive energies) to be transported in one string of magnets. With these sorts of arcs and a single linac, a Recirculating Linear Accelerator (RLA) will have greater cost effectiveness and reduced losses from muon decay. We will develop the optics and technical requirements to allow the maximum number of passes by using an adjustable path length to accurately control the returned beam phase to synchronize with the RF. |
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| WE6PFP100 | Pulsed-Focusing Recirculating Linacs for Muon Acceleration | 2742 |
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Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351 Neutrino Factories and Muon Colliders require rapid acceleration of short-lived muons to multi-GeV and TeV energies. A Recirculating Linear Accelerator (RLA) that uses International Linear Collider (ILC) RF structures can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the RF cavities, leading to greater cost effectiveness. We discus the optics and technical requirements for RLA designs, using RF cavities capable of simultaneous acceleration of both μ+ and μ- species, with pulsed Linac quadrupoles to allow the maximum number of passes. |
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| TH5RFP095 | Fiber Bragg Optical Sensors for YBCO Applications | 3675 |
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Magnetic confinement fusion reactors (tokamaks) require the development of magnets capable of generating large fields under stringent structural constraints. High temperature superconducting magnets which are well suited to this application are however vulnerable to quench occurrence during operation. Temperature and strain sensors based on fiber optics are being developed as a countermeasure to this contingency. Optical fibers with Bragg gratings are amenable to embedding within superconducting magnets to monitor temperature, strain, irradiation, and to detect quench occurrence. In a length of YBCO tape where quench propagation velocities are slow, we show that it is possible to detect the event occurrence using fiber optic sensors even with a sampling rate as low as 1 Hz. This preliminary result demonstrates the feasibility of using fiber optic sensors to monitor the temperature and strain condition along the length within a coil. These sensors could be used to provide feedback to or trigger magnet protection systems. This would be an invaluable method for mitigating damage to superconducting magnets and increasing up-time for reactors. |
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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. |