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At least 271 records · Page 15

Phase space density as a measure of cooling performance for the international muon ionization cooling experiment

The International Muon Ionization Cooling Experiment (MICE) is an experiment to demonstrate ionization cooling of a muon beam in a beamline that shares characteristics with one that might be used for a muon collider or neutrino factory. I describe a way to quantify cooling performance by examining the phase space density of muons, and determining how much that density increases. This contrasts with the more common methods that rely on the covariance matrix and compute emittances from that. I discuss why a direct measure of phase space density might be preferable to a covariance matrix method. I apply this technique to an early proposal for the MICE final step beamline. I discuss how matching impacts the measured performance.

43 PARTICLE ACCELERATORS↗

A space-time tracking algorithm for high occupancy events at future colliders

We propose to explore the potential advantages of a newclass of tracking algorithms loosely inspired by the Hough transformconcept and where we include the time of arrival of each hit as anadditional coordinate to be treated in the same way as a spatialcoordinate. A remarkable property of this algorithm is that theexecution time is proportional to the total number of hits to beprocessed, making it particularly attractive for high occupancysituations expected at future colliders. The particular structureof the algorithm also lends itself naturally to parallel hardwareimplementations which, combined to its intrinsic flexibility, shouldprovide a powerful tool for triggering at future colliders. To probethe effectiveness of the algorithm, we apply it to a quasi-realisticsimulated environment of a possible future muon collider experimentand report the performance.

Casarsa, Massimo [INFN, Trieste; Royal Inst. Tech.↗

Pulsed-focusing recirculating linacs for muon acceleration

Since the muon has a short lifetime, fast acceleration is essential for high-energy applications such as muon colliders, Higgs factories, or neutrino factories. The best one can do is to make a linear accelerator with the highest possible accelerating gradient to make the accelerating time as short as possible. However, the cost of such a single linear accelerator is prohibitively large due to expensive power sources, cavities, tunnels, and related infrastructure. As was demonstrated in the Thomas Jefferson Accelerator Facility (Jefferson Lab) Continuous Electron Beam Accelerator Facility (CEBAF), an elegant solution to reduce cost is to use magnetic return arcs to recirculate the beam through the accelerating RF cavities many times, where they gain energy on each pass. In such a Recirculating Linear Accelerator (RLA), the magnetic focusing strength diminishes as the beam energy increases in a conventional linac that has constant strength quadrupoles. After some number of passes the focusing strength is insufficient to keep the beam from going unstable and being lost. In this project, the use of fast pulsed quadrupoles in the linac sections was considered for stronger focusing as a function of time to allow more successive passes of a muon beam in a recirculating linear accelerator. In one simulation, it was shown that the number of passes could be increased from 8 to 12 using pulsed magnet designs that have been developed and tested. This could reduce the cost of linac sections of a muon RLA by 8/12, where more improvement is still possible. The expense of a greater number of passes and corresponding number of return arcs was also addressed in this project by exploring the use of ramped or FFAG-style magnets in the return arcs. A better solution, invented in this project, is to use combined-function dipole-quadrupole magnets to simultaneously transport two beams of different energies through one magnet string to reduce costs of return arcs by almost a factor of two. A patent application was filed for this invention and a detailed report published in Physical Review Special Topics. A scaled model using an electron beam was developed and proposed to test the concept of a dog bone RLA with combined-function return arcs. The efforts supported by this grant were reported in a series of contributions to particle accelerator conferences that are reproduced in the appendices and summarized in the body of this report.

43 PARTICLE ACCELERATORS↗

High-Field Magnets for Future Hadron Colliders

Recent strategy updates by the international particle physics community have confirmed strong interest in a next-generation energy frontier collider after completion of the High-Luminosity LHC program and construction of a e + e - Higgs factory. Both hadron and muon colliders provide a path toward the highest energies, and both require significant and sustained development to achieve technical readiness and optimize the design. For hadron colliders, the energy reach is determined by machine circumference and the strength of the guiding magnetic field. To achieve a collision energy of 100 TeV while limiting the circumference to 100 km, a dipole field of 16 T is required and is within the reach of niobium–tin magnets operating at 1.9 K. Magnets based on high-temperature superconductors may enable a range of alternatives, including a more compact footprint, a reduction of the cooling power, or a further increase of the collision energy to 150 TeV. The feasibility and cost of the magnet system will determine the possible options and optimal configurations. In this article, I review the historical milestones and recent progress in superconducting materials, design concepts, magnet fabrication, and test results and emphasize current developments that have the potential to address the most significant challenges and shape future directions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

The new physics case for beam-dump experiments with accelerated muon beams

As the field examines a future muon collider as a possible successor to the LHC, we must consider how to fully utilize not only the high-energy particle collisions, but also any lower-energy staging facilities necessary in the R&D process. An economical and efficient possibility is to use the accelerated muon beam from either the full experiment or from cooling and acceleration tests in beam-dump experiments. Beam-dump experiments are complementary to the main collider as they achieve sensitivity to very small couplings with minimal instrumentation. We demonstrate the utility of muon beam-dump experiments for new physics searches at energies from 10 GeV to 5 TeV. We find that, even at low energies like those accessible at staging or demonstrator facilities, it is possible to probe new regions of parameter space for a variety of generic BSM models, including muonphilic, leptophilic, L μ − L τ , and dark photon scenarios. Such experiments could therefore provide opportunities for discovery of new physics well before the completion of the full multi-TeV collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Muon Tracking Studies in a Skew Parametric Resonance Ionization Cooling Channel

Skew Parametric-resonance Ionization Cooling (SPIC) is an extension of the Parametric-resonance Ionization Cooling (PIC) framework that has previously been explored as the final 6D cooling stage of a high-luminosity muon collider. The addition of skew quadrupoles to the PIC magnetic focusing channel induces coupled dynamic behavior of the beam that is radially periodic. The periodicity of the radial motion allows for the avoidance of unwanted resonances in the horizontal and vertical transverse planes, while still providing periodic locations at which ionization cooling components can be implemented. A first practical implementation of the magnetic field components required in the SPIC channel is modeled in MADX. Dynamic features of the coupled correlated optics with and without induced parametric resonance are presented and discussed.

43 PARTICLE ACCELERATORS↗

Workshop on a future muon program at FNAL

The Snowmass report on rare processes and precision measurements recommended Mu2e-II and a next generation muon facility at Fermilab (Advanced Muon Facility) as priorities for the frontier. The Workshop on a future muon program at FNAL was held in March 2023 to discuss design studies for Mu2e-II, organizing efforts for the next generation muon facility, and identify synergies with other efforts (e.g., muon collider). Topics included high-power targetry, status of R&D for Mu2e-II, development of compressor rings, FFA and concepts for muon experiments (conversion, decays, muonium and other opportunities) at AMF. This document summarizes the workshop discussions with a focus on future R&D tasks needed to realize these concepts.

43 PARTICLE ACCELERATORS↗

MULTIPASS MUON RLA RETURN ARCS BASED ON LINEAR COMBINED-FUNCTION MAGNETS

Recirculating Linear Accelerators (RLA) are an efficient way of accelerating short-lived muons to the multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. In this paper we present a design of a two-pass RLA return arc based on linear combined function magnets, in which both charge muons with momenta different by a factor of two are transported through the same string of magnets. The arc is composed of 60{sup o}-bending symmetric super cells allowing for a simple arc geometry closing. By adjusting the dipole and quadrupole components of the combined-function magnets, each super cell is designed to be achromatic and to have zero initial and final periodic orbit offsets for both muon momenta. Such a design provides a greater compactness than, for instance, an FFAG lattice with its regular alternating bends and is expected to possess a large dynamic aperture characteristic of linear-field lattices.

43 PARTICLE ACCELERATORS↗

MICE: the Muon Ionization Cooling Experiment. Step I: First Measurement of Emittance with Particle Physics Detectors

The Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Novel Application of Density Estimation Techniques in Muon Ionization Cooling Experiment

The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate muon beam ionization cooling for the first time and constitutes a key part of the R&D towards a future neutrino factory or muon collider. Beam cooling reduces the size of the phase space volume occupied by the beam. Non-parametric density estimation techniques allow very precise calculation of the muon beam phase-space density and its increase as a result of cooling. These density estimation techniques are investigated in this paper and applied in order to estimate the reduction in muon beam size in MICE under various conditions.

43 PARTICLE ACCELERATORS↗

Simulation of RF Cavity Dark Current In Presence of Helical Magnetic Field

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of RF cavity with beryllium windows in solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to RF electric field significantly modifies the performance of RF cavities. However, magnetic field in Helical Cooling Channel has a strong dipole component in addition to solenoidal one. The dipole component essentially changes electron motion in a cavity compare to pure solenoidal case, making dark current less focused at field emission sites. The simulation of dark current dynamic in HCC performed with CST Studio Suit is presented in this paper.

43 PARTICLE ACCELERATORS↗

Bunch Coalescing in a Helical Channel

A high-luminosity Muon Collider requires bunch recombination for optimal luminosity. In this paper, we take advantage of the large slip factor attainable in a helical transport channel (HTC) to coalesce bunches of muons into a single one over a shorter distance than can be achieved over a straight channel.

43 PARTICLE ACCELERATORS↗

Lepton-flavor-violating ALP signals with TeV-scale muon beams

We explore the feasibility of using TeV-energy muons to probe lepton-flavor-violating (LFV) processes mediated by an axion-like particle (ALP) a with mass O(10 GeV). We focus on µτ LFV interactions and assume that the ALP is coupled to a dark state χ, which can be either less or more massive than a. Such a setup is demonstrated to be consistent with χ being a candidate for dark matter, in the experimentally relevant regime of parameters. We consider the currently operating NA64-µ experiment and proposed FASERν2 detector as both the target and the detector for the process µA → τA a, where A is the target nucleus. We also show that a possible future active muon fixed-target experiment operating at a 3 TeV muon collider or in its preparatory phase can provide an impressive reach for the LFV process considered, with future FASERν2 data providing a pilot study towards that goal. The implications of the muon anomalous magnetic moment (g - 2) µ measurements for the underlying model, in case of a positive signal, are also examined, and a sample UV completion is outlined.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Multiple Scattering Measurements in the MICE Experiment

The international Muon Ionization Cooling Experiment (MICE), under construction at RAL, will test a prototype cooling channel for a future Neutrino Factory or Muon Collider. The cooling channel aims to achieve, using liquid hydrogen absorbers, a 10% reduction in transverse emittance. The change in 4D emittance will be determined with an accuracy of 1% by measuring muons individually. Step IV of MICE will make the first precise emittance-reduction measurements of the experiment. Simulation studies using G4MICE, based on GEANT4, find a significant difference in multiple scattering in low Z materials, compared with the standard expression quoted by the Particle Data Group. Direct measurement of multiple scattering using the scintillating-fibre trackers is found to be possible, but requires the measurement resolution to be unfolded from the data.

43 PARTICLE ACCELERATORS↗

Numerical Studies of Optimization and Aberration Correction Methods for the Preliminary Demonstration of the Parametric Ionization Cooling (PIC) Principle in the Twin Helix Muon Cooling Channel

Muon colliders have been proposed for the next generation of particle accelerators that study high-energy physics at the energy and intensity frontiers. In this paper we study a possible implementation of muon ionization cooling, Parametric-resonance Ionization Cooling (PIC), in the twin helix channel. The resonant cooling method of PIC offers the potential to reduce emittance beyond that achievable with ionization cooling with ordinary magnetic focusing. We examine optimization of a variety of parameters, study the nonlinear dynamics in the twin helix channel and consider possible methods of aberration correction.

43 PARTICLE ACCELERATORS↗

A Staged Muon-based Facility to Enable Intensity and Energy Frontier Science in the US

Muon-based facilities offer a unique potential to provide capabilities at both the Intensity Frontier with Neutrino Factories and the Energy Frontier with Muon Colliders ranging from the Higgs energy to the multi-TeV energy range. They rely on novel technology with challenging parameters, for which the feasibility is currently being assessed by the U.S. Muon Accelerator Program (MAP) [1]. 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 at Fermilab, especially Project X and LBNE. Each stage is defined in such a way as to provide an R&D platform to validate the technologies required for subsequent stages. The rationale and sequence of a realistic staging process are presented.

Delahaye, Jean-Pierre↗

Progress towards the Facility for Rare Isotope Beams

Muon-based facilities offer a unique potential to provide capabilities at both the Intensity Frontier with Neutrino Factories and the Energy Frontier with Muon Colliders ranging from the Higgs energy to the multi-TeV energy range. They rely on novel technology with challenging parameters, for which the feasibility is currently being assessed by the U.S. Muon Accelerator Program (MAP) [1]. 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 at Fermilab, especially Project X and LBNE. Each stage is defined in such a way as to provide an R&D platform to validate the technologies required for subsequent stages. The rationale and sequence of a realistic staging process are presented.

Wei, J.↗

Design of Accumulator and Compressor Rings for the Project-X Based Proton Driver

A Muon Collider (MC) and a Neutrino Factory (NF) - which may be considered as a step towards a MC - both require a high-power ({approx}4 MW) proton driver providing short (<1 m r.m.s. length) bunches for muon production. However, the driver repetition rates required for these two machines are different: {approx}15 Hz for MC and {approx}60 Hz for NF. This difference suggests employing two separate rings: one for accumulation of the proton beam from the Project-X linac in a few (e.g. 4) long bunches, the other for bunch compression - one by one for NF or all at a time for MC with simultaneous delivery to the target. The lattice requirements for these two rings are different: the momentum compaction factor in the accumulator ring should be large (and possibly negative) to avoid the microwave instability, while the compressor ring can be nearly isochronous in order to limit the required RF voltage and reduce the dispersion contribution to the beam size. In the present report we consider ring lattice designs which achieve these goals.

43 PARTICLE ACCELERATORS↗