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A high-energy, multiple-pass energy recovery (ER) experiment proposal, using CEBAF, is in preparation by a JLab-BNL collaboration. The experiment will be proposed in support of the electron-ion collider project (EIC) R&D going on at BNL. This new experiment extends the 2003, 1-pass, 1 GeV CEBAF-ER demonstration into a range of energy and recirculation passes commensurate with BNL's anticipated linac-ring EIC parameters. The experiment will study ER and recirculating beam dynamics in the presence of synchrotron radiation, provide opportunity to develop and test multiple-beam diagnostic instrumentation, and can also probe BBU limitations. This paper gives an overview of the ER@CEBAF project, its context and preparations., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

Beamline optics design for recirculatory linear accelerators requires special attention to suppress beam instabilities arising due to collective effects. The impact of these collective effects becomes more pronounced with the addition of energy recovery (ER) capability. Jefferson Lab’s multi-pass, multi-GeV ER proposal for the CEBAF accelerator, ER@CEBAF, is a 10- pass ER demonstration with low beam current. Tighter control of the beam parameters at lower energies is necessary to avoid beam break-up (BBU) instabilities, even with a small beam current. Optics optimizations require balancing both beta excursions at high-energy passes and overfocusing at low-energy passes. Here, we discuss an optics optimization process for recirculatory energy-recovery linacs (ERLs) using multi-objective evolutionary search methods.

The beamline design of recirculating linacs requires special attention to avoid beam instabilities due to RF wakefields. A proposed high-energy, multi-pass energy recovery demonstration at CEBAF uses a low beam current. Stronger focusing at lower energies is necessary to avoid beam breakup(BBU) instabilities, even with this small beam current. The CEBAF linac optics optimization balances over-focusing at higher energies and beta excursions at lower energies. Using proper mathematical expressions, linac optics optimization can be achieved with evolutionary algorithms. Here, we present the optimization process of North Linac optics using multi-objective optimization., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Positron beams would provide new and meaningful probes for the experimental program at the Thomas Jefferson National Accelerator Facility (JLab), including but not limited to future hadronic physics and dark matter experiments. Critical requirements involve generating positron beams with a high degree of spin polarization, sufficient intensity and a continuous-wave (CW) bunch train compatible with acceleration to 12 GeV at the Continuous Electron Beam Accelerator Facility (CEBAF). To address these requirements, a polarized positron injector based upon the bremsstrahlung of an intense CW spin polarized electron beam is considered*. First a polarized electron beam line provides >1 mA of polarized electrons at ~120 MeV to a high-power target for positron production. Next, a second beam line collects, shapes and aligns the spin of positrons for users. Finally, the positron beam is matched into the CEBAF acceptance for acceleration and transport to the end stations with energies up to 12 GeV. An optimized layout to provide positrons beams with intensity >100 nA (polarized) or intensity >3 µA (unpolarized) will be discussed in this poster., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

We present a new ’green energy’ approach to the Energy Recovery Linac (ERL) the future Electron Ion Collider at LHeC using single beam line made of very strong focusing combined function permanent magnets and the Fixed Field Alternating Linear Gradient (FFA-LG) principle. We are basing our design on recent very successful commissioning results of the Cornell University and Brookhaven National Laboratory ERL Test Accelerator-CBETA., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

This work will describe the current status of the FFA@CEBAF energy upgrade feasibility studies. Technical updates are given, but more specific details are left to separate contributions. Specifically, this work will discuss improvements to the FFA arcs, a new recirculating injector proposal, and numerous modifications to the current 12 GeV CEBAF which will be required, such as the spreaders and recombiners architecture, splitters (time-of-flight chicanes), the extraction system, and the hall lines., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Recirculating Linear Accelerators (RLAs) provide an efficient way of producing high-power, high-quality, continuous-wave hadron and lepton beams. However, their attractiveness had been limited by the cumbersomeness of multiple recirculating arcs and by the complexity of the spreader and recombiner regions. The latter problem sets one of the practical limitations on the maximum number of recirculations. We present an RLA design concept where the problem of multiple arcs is solved using the Fixed-Field Alternating gradient (FFA) design as in CBETA. The spreader/recombiner design is greatly simplified using an adiabatic matching approach. It allows for the spreader/recombiner function to be accomplished by a single beam line. The concept is applied to the designs of a high-power hadron accelerator being considered at ORNL and a CEBAF electron energy doubling project, FFA@CEBAF, being developed at Jefferson lab., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The LHeC project studies the design of a future electron-proton collider at CERN that will run in parallel to the standard LHC operation. For this purpose, the existing LHC storage ring will be combined with an Energy Recovery Linac (ERL), to accelerate electrons up to kinetic energy of 50 GeV. This concept - also applicable to the FCC-eh collider and studied at the PERLE project as prototype version - allows a peak luminosity of 10³⁴ cm⁻² s⁻¹. A sophisticated design of the RF structures, linacs, arcs, and interaction region is required. The electrons are accelerated and, after the interaction point, their energy is recovered through the same RF structures. While this energy recovery concept is a very promising approach, severe challenges are set by the layout of the interaction region, the beam separation concept and the design of the linac and arc lattice for the highest possible momentum acceptance. Emittance control and beam-beam effect of both, electron and proton beams, have been studied in front-to-end simulations and will be presented. We summarise the design principles of the ERL, the optimization of the arc lattice, and the main parameters of the project., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Delivery of high charge electron bunches into the main loop of an ERL (energy recovery linac) while preserving the emittance is challenging. This is because at the typical injection momentum, space charge forces still have a significant effect on the beam dynamics. In this work we consider the design of the merger for PERLE, an ERL test facility to be based at IJCLab in France. Previous simulations have shown that the baseline DC gun based injector can achieve the required emittance at the booster linac exit. The quality of the 500 pC bunches must then be preserved with space charge through the merger at total beam energy of 7 MeV keeping the emittance below 6 mm mrad. The beam dynamics in the merger were simulated using the code OPAL and optimised using a genetic algorithm. Three possible merger schemes were investigated. The goal of the optimisation was to minimise the emittance growth while also achieving the required Twiss parameters to match onto the spreader at the main linac exit. A three dipole solution is then examined in more detail., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

An Energy Recovery Experiment at CEBAF (ER@CEBAF) is aimed at demonstrating high energy, low current, multi-pass energy recovery at the existing 12 GeV CEBAF accelerator. The beam break-up instability, limiting the maximum beam current, can be controlled through minimizing beta functions for the lowest energy pass, which gives a preference to strongly focusing optics, e.g. a semi-periodic FODO lattice. On the other hand, one needs to limit beta function excursions, caused by under focusing, at the higher energy passes, which in turn favors weakly focusing linac optics. Balancing both effects is the main objective of proposed multi-pass linac optics optimization. Here, we discuss an optics design process for ER@CEBAF transverse optics using a genetic algorithm., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The Powerful Energy Recovery Linac for Experiments (PERLE) is an accelerator facility for the development and application of the energy recovery technique for an intense 500 MeV electron beam. The paper presents the studies that have been performed to assess the quality of the ERL lattice design and beam optics. The studies include the Coherent Synchrotron Radiation (CSR) emission and wakefields in the superconducting radio-frequency structures of the linacs. The lattice design and optics principles of the ERL structure are discussed, involving the vertical deflection system and the 180° arcs. Finally, the results of the front-to-end tracking simulations that consider the complete multi-turn energy recovery process are presented., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

A multi-pass recirculating superconducting CW linac offers a cost effective path to a multi-user facility with unprecedented scientific and industrial reach over a wide range of disciplines. We propose such a facility as an option for a potential UK-XFEL. Energy Recovery enables multi-MHz FEL sources, for example, an X-ray FEL oscillator or regenerative amplifier FEL. Additionally, combining with external lasers and/or self-interaction would provide access to MeV and GeV gamma-rays via inverse Compton scattering at high average power for nuclear and particle physics applications. An opportunity exists to demonstrate the necessary point-to-parallel longitudinal matches to drive an XFEL and successfully energy recover at the upcoming 5-pass up, 5-pass down Energy Recovery experiment on CEBAF at JLab termed ER@CEBAF. We show candidate matches and simulations supporting the minimal necessary modifications to CEBAF this will require. This includes linearisation of the longitudinal phase space in the injector and a reduction in the dispersion of the arcs, both of which increase the energy acceptance of CEBAF. We expect to commence initial tests of these adaptations on CEBAF during 2021., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

A proposal was formulated to increase the CEBAF energy from the present 12 GeV to 20-24 GeV by replacing the highest-energy arcs with Fixed Field Alternating Gradient (FFA) arcs. The new pair of arcs would provide six or seven new beam passes, going through this magnet array, allowing the energy to be nearly doubled using the existing CEBAF SRF cavity system. One of the immediate accelerator design tasks is to develop a proof-of-principle FFA arc magnet lattice that would support simultaneous transport of 6-7 passes with energies spanning a factor of two. We also examine the possibility of using combined function magnets to configure a cascade, six-way beam split switchyard. Finally, a novel multi-pass linac optics based on a weakly focusing lattice is being explored., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The LHeC 60 GeV ERL baseline design features a racetrack composed of two linacs, completed with 6 return arcs, including vertical spreaders and recombines at the arcs ends. Here, we consider a design strategy aiming at ’downsizing’ the ERL e.g. to 50 GeV, while preserving its performance in terms of synchrotron radiation effects. This results in a significant reduction of accelerator components. The optimization explores tuning of each arc, which takes into account the impact of synchrotron radiation at different energies. At the highest energy, it is crucial to minimize the emittance dilution; therefore, the cells are tuned to minimize the dispersion in the bending sections, as in a theoretical minimum emittance lattice. At the lowest energy, one compensates for the bunch elongation with a negative momentum compaction setup which, additionally, contains the beam size. The intermediate energy arcs are tuned to a double bend achromat lattice, offering a compromise between isochronicity and emittance dilution. Finally, a feasibility of a ’dogbone’ ERL is discussed., Proceedings of the 63th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2019, Berlin, Germany

PERLE is a proposed high power Energy Recovery Linac, designed on multi-turn configuration, based on SRF technology, to be hosted at Orsay-France in a col-laborative effort between local laboratories: LAL and IPNO, together with an international collaboration involv-ing today: CERN, JLAB, STFC ASTeC Daresbury, Liverpool University and BINP Novosibirsk. PERLE will be a unique leading edge facility designed to push advances in accelerator technology, to provide intense and highly flexible test beams for component development. In its final configuration, PERLE provides a 500 MeV elec-tron beam using high current (20 mA) acceleration during three passes through 801.6 MHz cavities. This presenta-tion outlines the technological choices, the lattice design and the main component descriptions., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The main thrust of a multi-pass RLA is its very efficient usage of expensive linac structures. That efficiency can be further enhanced by configuring an RLA in a ’dogbone’ topology, which further boosts the RF efficiency by factor of two (compare to a corresponding racetrack). However, the ’dogbone’ configuration requires the beam to traverse the linac in both directions, while being accelerated. This can be facilitated by a special ’bisected’ linac Optics. Here, the quadrupole gradients scale up with momentum to maintain periodic FODO structure for the lowest energy pass in the first half of the linac and then the quadrupole strengths are mirror reflected in the second linac half. The virtue of this optics is the appearance of distinct nodes in the beta beat-wave at the ends of each pass (where the droplet arcs begin), which limits the growth of initial betas at the beginning of each subsequent droplet arc. Furthermore, ‘bisected’ linac optics naturally supports energy recovery in the ’dogbone’ topology. In this paper, we present a-proof-of-principle lattice design of a multi-pass ’dogbone’ ERL., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R, Proceedings of the North American Particle Accelerator Conference, NAPAC2019, Lansing, MI, USA

PERLE (Powerful ERL for Experiments) is a novel ERL test facility, initially proposed to validate choices for a 60 GeV ERL foreseen in the design of the LHeC and the FCC-eh. Its main thrust is to probe high current, CW, multi-pass operation with superconducting cavities at 802 MHz (and perhaps testing other frequencies of interest). With very high virtual beam power (~ 10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERL design; becoming a ‘stepping stone' between present state-of-art 1 MW ERLs and future 100 MW scale applications. PERLE design features Flexible Momentum Compaction lattice architecture for six vertically stacked return arcs and a high-current, 6 MeV, photo-injector. With only one pair of 4 cavity cryomodules, 400 MeV beam energy can be reached in 3 re-circulation passes, with beam currents in excess of 15 mA. The beam is decelerated in 3 consecutive passes back to the injection energy, transferring virtually stored energy back to the RF. This unique facility will serve as a test-bed for high current ERL technologies, as well as a user facility in low energy electron and photon physics., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A multiple-pass, high energy Energy Recovery Linac experiment at the JLab CEBAF will be instrumental in providing necessary information and technology testing for a number of possible future applications and facilities such as Linac-Ring based colliders, which have been designed at BNL (eRHIC) and CERN (LHeC), and also drivers for high-energy FELs and 4th GLS. The project has been submitted to, and has received approval from, JLab Program Advisory Committee (PAC 44) in July 2016. Since it was launched 2+ years ago, it has progressed in defining the experimental goals, including for instance multiple-beam instrumentation, ER efficiency, BBU, and the necessary modifications to CEBAF lattice, including for instance a 4-dipole phase chicane in recirculation Arc A, a dump line, and new linac optics. End-to-end simulations have been undertaken and software tools are under development. A next major objective in demonstrating readiness is a technical review as mandated by PAC 44. This paper gives a status of the project and its context, and presents plans for the near future., Proceedings of the 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2017, Geneva, Switzerland

PERLE (Powerful ERL for Experiments) is a novel ERL test facility, initially proposed to validate design choices for a 60 GeV ERL needed for a future extension of the LHC towards a hadron-electron collider, the LHeC. Its main goal is to test the limits of a high current, CW, multi-pass operation with superconducting cavities at 802 MHz (and perhaps exploring other frequencies of interest). PERLE optics features Flexible Momentum Compaction (FMC) lattice architecture for six vertically stacked return arcs and a high current, 5 MeV photo-injector. With only one pair of 4-cavity cryomodules, 400 MeV beam energy can be reached in three re-circulation passes, with beam currents in excess of 15 mA. This unique quality beam is intended to perform a number of experiments in different fields reaching from uncharted tests of accelerator components via elastic ep scattering to laser-Compton backscattering for photon physics. Following the experiment, the CW beam is decelerated in three consecutive passes back to the injection energy, transferring virtually stored energy back to the RF., Proceedings of the 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2017, Geneva, Switzerland

During the workshop a number of interesting projects were discussed: ERL at KEK, ALICE, PERLE, LHeC, eRHIC, CBETA, ERL for MESA and BERLinPro; a nice mixture of future, existing and past facilities. A rather vigorous development of new ERLs is aggressively pushing the limits: maximizing number of passes, maximizing virtual beam power, opening longitudinal acceptance, mitigation of limiting factors: BBU, CSR/microbunching, diagnostics and Instrumentation for multiple beams, multiparticle tracking studies of dark current and halo formation. A bright future can be expected for the field., Proceedings of the 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2017, Geneva, Switzerland

Optimization of the booster synchrotron design to operate in the extreme space-charge dominated regime is proposed. This study is motivated by the ultra-high luminosity promised by the JLEIC accelerator complex, which poses several beam dynamics and lattice design challenges for its individual components. We examine the effects of space charge on the dynamics of the booster synchrotron for the proposed JLEIC electron ion collider. This booster will inject and accumulate protons and heavy ions at an energy of 280 MeV and then engage in a process of acceleration and electron cooling to bring it to its extraction energy of 8 GeV. This would then be sent into the ion collider ring part of JLEIC. In order to examine the effects of space charge on the dynamics of this process we use the software SYNERGIA., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

We propose a novel use of Fixed Field Altrenating Gradient beam line (FFAG) to replace multiple beam lines in existing ERL’s (4-pass at Novosibirsk, ERL of CEBAF, ERL at KEK, etc.) with a single FFAG beam line connected with spreaders and combiners to the linac. We present two designs for the Electron Ion Colliders one at CERN LHeC and one at Brookhaven National Laboratory to be placed in the tunnel of the existing Relativistic Heavy Ion Collider (RHIC) called eRHIC. The proof of principle electron accelerator with the FFAG arc is to be built at Cornell University Wilson Hall where there are already available injector, superconducting linac accelerator and the dump. There are very new developments in the FFAG design never accomplished before: arc-to straight adiabatic matching with merged multiple orbits into one, permanent magnet design for the arc and straights with ability of four times in energy, etc., Proceedings of the 21st Int. Conf. on Cyclotrons and their Applications, Cyclotrons2016, Zurich, Switzerland

Baseline design of the JLEIC booster synchrotron is presented. Its aim is to inject and accumulate heavy ions and protons at 285 MeV, to accelerate them to about 7 GeV, and finally to extract them into the ion collider ring. The Figure-8 ring features two 260 deg. achromatic arcs configured with negative momentum compaction lattices, designed to avoid transition crossing for all ion species during the course of acceleration. The arc optics is based on a lightly perturbed 90 deg. FODO, with missing dipoles every fourth half-cell, where the horizontal dispersion is driven partly negative for the inward bending arc leading to negative momentum compaction. The lattice also features a specialized high dispersion injection insert optimized to facilitate the transverse phase-space painting in both planes for multi-turn ion injection. Furthermore, the lattice has been optimized to mitigate magnet error sensitivity and to ease chromaticity correction with two families of sextupoles in each plane. The booster ring is configured with super-ferric, 3 Tesla bends. We are presently launching optimization of the booster synchrotron design to operate in the extreme space-charge dominated regime., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Here, we summarize current state of concept for muon acceleration aimed at future Neutrino Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance through exploring interplay between complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival of the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to initially low RF frequency, e.g. 325 MHz, and then increased to 650 MHz, as the transverse size shrinks with increasing energy. High-gradient normal conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. Here, we considered two cost effective schemes for accelerating muon beams for a stagable Neutrino Factory: Exploration of the so-called 'dual-use' linac concept, where the same linac structure is used for acceleration of both H⁻ and muons and alternatively, the SRF efficient design based on multi-pass (4.5) 'dogbone' RLA, extendable to multi-pass FFAG-like arcs., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The LHeC aims at delivering an electron beam for collision with the LHC proton beam. The current baseline design consists of a multi-pass superconductive energy recovery linac operating in a continuous wave mode. Here, we describe the overall layout of such ERL complex located on the LHC site. We present an optimized multi-pass linac optics enabling operation of the proposed 3-pass RLA in the Energy Recovery mode. We also describe emittance preserving return arc optics architecture; including layout and optics of the arc switch-yard. High current (>100 mA) beam operation in the linacs excites long range wake-fields between bunches of different turns, which induce instabilities and might cause beam losses. The impact of long-range wake-fields, synchrotron radiation, and beam-beam effects has been assessed in this paper., Proceedings of the 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2015, Stony Brook, NY, USA

The LHeC study aims at delivering an electron beam for collision with the LHC proton beam. The current baseline design consists of a multi-pass superconductive energy-recovery linac operating in a continuous wave mode. The high current beam (~100 mA) in the linacs excites long-range wake-fields between bunches of different turns, which induce instabilities and might cause beam losses. PLACET2, a novel version of the tracking code PLACET, capable to handle recirculation and time dependencies, has been employed to perform the first LHeC end-to-end tracking. The impact of long-range wake-fields, synchrotron radiation, and beam-beam effects has been assessed. The simulation results and recent improvements in the lattice design are presented and discussed in this paper., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The baseline electron accelerator for LHeC and one option for FCC-he is an Energy Recovery Linac. To prepare and study the necessary key technologies, CERN has started – in collaboration with JLAB and Mainz University – the conceptual design of an ERL Test Facility (ERL-TF). Staged construction will allow the study under different conditions with up to 3 passes, beam energies of up to about 1 GeV and currents of up to 50 mA. The design and development of superconducting cavity modules, including coupler and HOM damper designs, are also of central importance for other existing and future accelerators and their tests are at the heart of the current ERL-TF goals. The ERL-TF could also provide a unique infrastructure for several applications that go beyond developing and testing the ERL technology at CERN. In addition to experimental studies of beam dynamics, operational and reliability issues in an ERL, it could equally serve for quench tests of superconducting magnets, as physics experimental facility on its own right or as test stand for detector developments. This contribution will describe the goals and the concept of the facility and the status of the R&D;.

Muon-based facilities offer unique potential to provide capabilities at both the Intensity Frontier with Neutrino Factories and the Energy Frontier with Muon Colliders. They rely on a novel technology with challenging parameters, for which the feasibility is currently being evaluated by the Muon Accelerator Program (MAP). A realistic scenario for a complementary series of staged facilities with increasing complexity and significant physics potential at each stage has been developed. It takes advantage of and leverages the capabilities already planned for Fermilab, especially the strategy for long-term improvement of the accelerator complex being initiated with the Proton Improvement Plan (PIP-II) and the Long Baseline Neutrino Facility (LBNF). Each stage is designed to provide an R&D platform to validate the technologies required for subsequent stages. The rationale and sequence of the staging process and the critical issues to be addressed at each stage, are presented., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

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 superconducting 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 discuss 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 and arc magnets to allow the maximum number of passes. The design will include the optics for the multi-pass linac and droplet-shaped return arcs., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Within the Neutrino Factory Project the muon acceleration process involves a complex chain of accelerators including a (single-pass) linac, two recirculating linacs and an FFAG. The linac consists of RF cavities and iron shielded solenoids for transverse focusing and has been previously designed relying on idealized field models. However, to predict accurately the transport and acceleration of a high emittance 30 cm wide beam with 10 % energy spread requires detailed knowledge of fringe field distributions. This article presents results of the front-to-end tracking of the muon beam through numerically simulated realistic field distributions for the shielded solenoids and the RF fields. Real and phase space evolution of the beam has been studied along the linac and the results will be presented and discussed., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The proposed electron collider lattice exhibits low β- functions at the Interaction Point (IP) (βx∗100mm − βy∗ 20 mm) and rather large equilibrium momentum spread of the collider ring (δp/p = 0.00158). Both features make the chromatic corrections of paramount importance. Here the chromatic effects of the final focus quadruples are cor- rected both locally and globally. Local correction features symmetric sextupole families around the IP, the betatron phase advances from the IP to the sextupoles are chosen to eliminate the second order chromatic aberration. Global interleaved families of sextupoles are placed in the figure-8 arc sections, and non-interleaved families at straight sec- tion making use of the freely propagated dispersion wave from the arcs. This strategy minimizes the required sex- tupole strength and eventually leads to larger dynamic aper- ture of the collider. The resulting spherical aberrations induced by the sextupoles are mitigated by design; the straight and arc sections optics features an inverse identity transformation between sextupoles in each pair., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

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. 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. We present a combination of the non-scaling NS-FFAG RLA placed in a straight section. Orbit offsets of different energy muons are kept small in the NS-FFAG arcs during multiple passes. The NS-FFAG, made of densely packed FODO cells, allows momentum acceptance of dp/p=±60%. This solution would reduce overall cost and simplify the operation. Difference in a muon path length for corresponding energies is corrected with a chicane. We will also discuss 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., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

A unique design feature of a polarized Medium Energy Electron-Ion Collider (MEIC) based on CEBAF is its ’Figure-8’ storage rings for both electrons and ions, which significantly simplifies beam polarization maintenance and manipulation. While electron (positron) polarization is maintained vertical in arcs of the ring, a stable longitudinal spin at four collision points is achieved through solenoid based spin rotators and horizontal orbit bends. The proposed MEIC lattice was developed in order to preserve a very high polarization (more than 70%) of the electron beams injected from the CEBAF machine. The otherwise coupled beam trajectory due to solenoids used in the spin rotators was decoupled by design. Aspin matching technique needs to be implemented in order to enhance quantum self-polarization and minimize depolarization effects., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan