Decay Ring Research Articles

Racetrack FFAG muon decay ring for nuSTORM with triplet focusing

The neutrino beam produced from muons decaying in a storage ring would be an ideal tool for precise neutrino cross section measurements and the search for sterile neutrinos due to its precisely known flavour content and spectrum. In the proposed nuSTORM facility, pions would be directly injected into a racetrack storage ring, where the circulating muon beam would be captured. In this paper we show that a muon decay ring based on a racetrack scaling FFAG (Fixed Field Alternating Gradient) with triplet focusing structures is a very promising option with potential advantages over the FODO based solution. We discuss the ring concept, machine parameters, linear optics design, beam dynamics and the injection system.

Overview of the Neutrinos from Stored Muons Facility - nuSTORM

Neutrino beams produced from the decay of muons in a racetrack-like decay ring (the so called Neutrino Factory) provide a powerful way to study neutrino oscillation physics and, in addition, provide unique beams for neutrino interaction studies. The Neutrinos from STORed Muons (nuSTORM) facility uses a neutrino factory-like design. Due to the particular nature of nuSTORM, it can also provide an intense, very pure, muon neutrino beam from pion decay. This so-called "Neo-conventional" muon-neutrino beam from nuSTORM makes nuSTORM a hybrid neutrino factory. In this paper we describe the facility and give a detailed description of the neutrino beams that are available and the precision to which they can be characterized. We then show its potential for a neutrino interaction physics program and present sensitivity plots that indicate how well the facility can perform for short-baseline oscillation searches. Finally, we comment on the performance potential of a "Neo-conventional" muon neutrino beam optimized for long-baseline neutrino-oscillation physics.

A FODO racetrack ring for nuSTORM: design and optimization

The goal of nuSTORM is to provide well-defined neutrino beams for precise measurements of neutrino cross-sections and oscillations. The nuSTORM decay ring is a compact racetrack storage ring with a circumference of ∼ 480 m that incorporates large aperture (60 cm diameter) magnets. There are many challenges in the design. In order to incorporate the Orbit Combination section (OCS), used for injecting the pion beam into the ring, a dispersion suppressor is needed adjacent to the OCS . Concurrently, in order to maximize the number of useful muon decays, strong bending dipoles are needed in the arcs to minimize the arc length. These dipoles create strong chromatic effects, which need to be corrected by nonlinear sextupole elements in the ring. In this paper, a FODO racetrack ring design and its optimization using sextupolar fields via both a Genetic Algorithm (GA) and a Simulated Annealing (SA) algorithm will be discussed.

Neutrinos from STORed Muons, nuSTORM

Neutrino beams produced from the decay of muons in a racetrack-like decay ring (the so called Neutrino Factory) provide a powerful way to study neutrino oscillation physics and, in addition, provide unique beams for neutrino interaction studies.The Neutrinos from STORed Muons (nuSTORM) facility is a neutrino factory-like facility designed for short baseline neutrino oscillation and neutrino interaction studies. However, due to the particular nature of nuSTORM, it can also provide an intense, very pure, muon neutrino beam from pion decay, which is possibly suitable for long-baseline neutrino oscillation searches as well. This so-called “Neo-conventional” muon neutrino beam from nuSTORM makes nuSTORM a hybrid neutrino factory.In this paper, the facility is described and a description of the neutrino beams and the precision to which they can be determined is given. Sensitivity plots are presented that indicate how well the facility can perform for short-baseline oscillation searches and show its potential for a neutrino interaction physics program. Finally, the concept of the “Neo-conventional” muon neutrino beam available at the nuSTORM facility is briefly discussed.

NuSTORM and a Path to a Muon Collider

This article reviews the current status of the nuSTORM facility and shows how it can be utilized to perform the next step on the path toward the realization of a μ+μ−collider. This review includes the physics motivation behind nuSTORM, a detailed description of the facility and the neutrino beams it can produce, and a summary of the short-baseline neutrino oscillation physics program that can be carried out at the facility. The basic idea for nuSTORM (the production of neutrino beams from the decay of muons in a racetrack-like decay ring) was discussed in the literature more than 30 years ago in the context of searching for noninteracting (sterile) neutrinos. However, only in the past 5 years has the concept been fully developed, motivated in large part by the facility's unmatched reach in addressing the evolving data on oscillations involving sterile neutrinos. Finally, this article reviews the basics of the μ+μ−collider concept and describes how nuSTORM provides a platform to test advanced concepts for six-dimensional muon ionization cooling.

Design and simulation of the nuSTORM pion beamline

The nuSTORM (neutrinos from STORed Muons) proposal presents a detailed design for a neutrino facility based on a muon storage ring, with muon decay in the production straight section of the ring providing well defined neutrino beams. The facility includes a primary high-energy proton beam line, a target station with pion production and collection, and a pion beamline for pion transportation and injection into a muon decay ring. The nuSTORM design uses “stochastic injection”, in which pions are directed by a chicane, referred to as the Orbit Combination Section (OCS), into the production straight section of the storage ring. Pions that decay within that straight section provide muons within the circulating acceptance of the ring. The design enables injection without kickers or a separate pion decay transport line. The beam line that the pions traverse before being extracted from the decay ring is referred to as the pion beamline. This paper describes the design and simulation of the pion beamline, and includes full beam dynamics simulations of the system.

Optimization of the magnetic horn for the nuSTORM non-conventional neutrino beam using the genetic algorithm

This paper describes the strategy for optimizing the magnetic horn for the neutrinos from STORed Muons (nuSTORM) facility. The nuSTORM magnetic horn is the primary collection device for the secondary particles generated by bombarding a solid target with 120GeV protons. As a consequence of the non-conventional beamline designed for nuSTORM, the requirements on the horn are different from those for a conventional neutrino beamline. At nuSTORM, muons decay while circulating in the storage ring, and the detectors are placed downstream of the production straight so as to be exposed to the neutrinos from muon decay. nuSTORM aims at precisely measuring the neutrino cross sections, and providing a definitive statement about the existence of sterile neutrinos. The nuSTORM horn aims at focusing the pions into a certain phase space so that more muons from pion decay can be accepted by the decay ring. The paper demonstrates a numerical method that was developed to optimize the horn design to gain higher neutrino flux from the circulating muons. A Genetic Algorithm (GA) was applied to the simultaneous optimization of the two objectives in this study. The application of the technique discussed in this paper is not limited to either the nuSTORM facility or muon based facilities, but can be used for other neutrino facilities that use magnetic horns as collection devices.

Design of a neutrino source based on beta beams

“Beta beams” produce collimated pure electron (anti)neutrino beams by accelerating beta active ions to high energies and having them decay in a racetrack shaped storage ring of 7 km circumference, the decay ring. EUROnu beta beams are based on CERN infrastructures and existing machines. Using existing machines may be an advantage for the cost evaluation, but will also constrain the physics performance. The isotope pair of choice for the beta beam is He6 and Ne18. However, before the EUROnu studies one of the required isotopes, Ne18, could not be produced in rates that satisfy the needs for physics of the beta beam. Therefore, studies of alternative beta emitters, Li8 and B8, with properties interesting for a beta beam have been proposed and have been studied within EUROnu. These alternative isotopes could be produced by using a small storage ring, in which the beam traverses a target, creating the Li8 and B8 isotopes. This production ring, the injection linac and the target system have been evaluated. Measurements of the cross section of the reactions to produce the beta beam isotopes show interesting results. A device to collect the produced isotopes from the target has been developed and tested. However, the yields of Li8 and B8, using the production ring for production of Li8 and B8, is not yet, according to simulations, giving the rates of isotopes that would be needed. Therefore, a new method of producing the Ne18 isotope has been developed and tested giving good production rates. A 60 GHz ECRIS prototype, the first in the world, was developed and tested for ion production with contributions from EUROnu. The decay ring lattices for the Li8 and B8 have been developed and the lattice for He6 and Ne18 has been optimized to ensure the high intensity ion beam stability.43 MoreReceived 15 April 2014DOI:https://doi.org/10.1103/PhysRevSTAB.17.071002This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society

Validation of electro-thermal simulation with experimental data to prepare online operation of a molten salt target at ISOLDE for the Beta Beams

The main objective of the Beta Beams is to study oscillation property of pure electrons neutrinos. It produces high energy beams of pure electron neutrinos and anti-neutrinos for oscillation experiments by beta decay of 6He and 18Ne radioactive ion beams, stored in a decay ring at γ=100. The production of 6He beam has already been accomplished using a thick beryllium oxide target. However, the production of the needed rate of 18Ne has proven to be more challenging. In order to achieve the requested yield for 18Ne a new high power target design based on a circulating molten salt loop has been proposed. To verify some elements of the design, a static molten salt target prototype has been developed at ISOLDE and operated successfully. This paper describes the electro-thermal study of the molten salt target taking into account the heat produced by Joule effect, radiative heat exchange, active water cooling due to forced convection and air passive cooling due to natural convection. The numerical results were compared with the available experimental data in order to validate the model. This approach allows one to improve the reliability of the model, which will help to predict the thermo-mechanical impact of the required targets for future facilities such as HIE-ISOLDE and the Beta-Beams.

Strategies for Future Accelerator Neutrino Physics

Accelerator neutrino (ν) physics has come back to the forefront, with the discovery of ν transitions, our first and unique window beyond the standard model. The experimental program to provide a complete map of the ν mixing matrix, including its far reaching CP violation sector, and test its unitarity constraints is likely to extend over several future decades, as it has been for quark mixing. So far, conventional ν beams based on pion (π) decay have been used and more are already being planned, at higher power (superbeams), in Japan and the US, in conjunction with larger or novel detectors. Superbeams have limited potential, however. Novel very intense beams of ν parents, longer lived than πʼs, accelerated and then coasted in a decay storage ring replacing the π decay tunnel, promise the ultimate reach. R&D for muon decay ring (ν factory) and ion decay ring (betabeam) experiments is thus a decisive task today.

Conceptual design report for a Beta-Beam facility

The Beta-Beam is a concept of large-scale facility that aims at providing pure electronic neutrino and antineutrino beams for the measurement of $ \nu_{e}^{}$ $ \rightarrow$ $ \nu_{\mu}^{}$ oscillations. Beta-decaying nuclides are produced in large amounts in a facility of the scale of EURISOL, and are then post-accelerated and stored at large $ \gamma$ in a racetrack decay ring. We present here a conceptual design of the accelerator chain of a Beta-Beam based at CERN.

Neutrino Factory Downstream Systems

We describe the Neutrino Factory accelerator systems downstream from the target and capture area. These include the bunching and phase rotation, cooling, acceleration, and decay ring systems. We also briefly discuss the R&D program under way to develop these systems, and indicate areas where help from CERN would be invaluable.

Radiation Shielding of a Beta-Beam Rapid Cycling Synchrotron

In a future beta-beam facility, radioactive ions (namely, 6He and 18Ne) are produced, accelerated, and then stored in a large decay ring, where they eventually produce neutrino beams through beta decay. Radiation protection is of great concern for this facility because decay products are present at all energies along the accelerator chain.Experimental data on radioactivity produced by ion accelerators are still poor, and few Monte Carlo codes can transport ions. All present calculations are performed with the Monte Carlo code FLUKA. The radiation environment generated by ion beam losses is compared with the available experimental data. The attenuation length of radiation in concrete is calculated for 6He and 18Ne at four different energies, from 100 to 1650 MeV/u.A preliminary shielding design for the Rapid Cycling Synchrotron, purpose-designed for a beta-beam accelerator chain at CERN, is proposed.

Accelerator design concept for future neutrino facilities

This document summarizes the work of the Accelerator Working Group (AWG) of the International Scoping Study (ISS) of a Future Neutrino Factory and Superbeam Facility. The main goal of the activity was to reach consensus on a baseline design for a Neutrino Factory complex, including proton driver parameters, choice of target, front-end design, acceleration system design, and decay ring geometry. Another goal was to explore the commonality, if any, between the proton driver for a Neutrino Factory and those for a Superbeam or Beta Beam facility. In general, the requirements for either of the latter facilities are less stringent than those for a Neutrino Factory. Here, we discuss concepts, parameters, and expected performance of the required subsystems for our chosen baseline design of a Neutrino Factory. We also give an indication of the main R&D tasks — many of which are already under way — that must be carried out to finalize facility design approaches.

Radiation issues in a radioactive ion decay ring

In a beta-beam facility, a pure beam of electron neutrinos, or their antiparticles, are produced by the decay of fully stripped radioactive ions (6He and 18Ne) circulating in a storage ring. Since the beam is not extracted from the ring, all the particles will eventually be lost somewhere in the machine and thus activate the accelerator components and the surrounding concrete and rock. In particular, as nuclei change their charge in beta-decay, a large part of the particles will be lost in the arcs of the decay ring and mainly irradiate the magnets. The density of inelastic interactions of hadrons in the magnets, concrete and rock and the track-length distribution of secondary hadrons were calculated by means of the FLUKA Monte Carlo code. These values were used to estimate the induced radioactivity in the facility, the dose rates expected in the decay ring and the consequences for the environment.

A novel scheme for injection and stacking of radioactive ions at high energy

In the so-called “beta-beam” route to accelerator-driven neutrino experiments, it is proposed to accumulate radioactive ions at high energy in a large decay ring. Stacking is essential to reach the intensities required, but none of the established beam cooling methods can be applied to counter the inflation of beam emittance with the addition of each fresh shot. A new stacking scheme which exploits the fact that the ions are radioactive is proposed to prevent a runaway growth of emittance.

The acceleration and storage of radioactive ions for a beta-beam facility

The term beta-beam has been coined for the production of a pure beam of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. This concept requires radioactive ions to be accelerated to as high Lorentz gamma as 150. The neutrino source itself consists of a storage ring for this energy range, with long straight sections in line with the experiment(s). Such a decay ring does not exist at CERN today, nor does a high-intensity proton source for the production of the radioactive ions. Nevertheless, the existing CERN accelerator infrastructure could be used as this would still represent an important saving for a beta-beam facility.

Ionization cooling in FFAGs: progress since NuFact'01

Although Japan's unique FFAG scenario for a neutrino factory does not rely on ionization cooling of the muon beam, moderate cooling in the first FFAG could be beneficial for the overall muon yield and, perhaps even more important, reduce the final emittances in the decay ring. Using basic cooling theory, one can show that this appears possible. In the Nufact'01 contribution on ‘ionization cooling in FFAGs’ [1], the addition of absorbers into the superconducting 0.3–1 GeV/c Japanese FFAG was investigated. The cooling absorbers were 7 mm beryllium sheets in the median plane of the RF cavities. Beryllium was chosen because Be windows are a known design to increase field strength and quality of large aperture cavities. Obviously metallic lithium or a sandwich of lithium hydride between thin metallic Be sheets is preferable to the cooling viewpoint. We have thus complemented the results for Be by equivalent inserts of pure lithium and lithium hydride. For each material two thicknesses were compared.

The acceleration and storage of radioactive ions for a neutrino factory

The term beta-beam has been coined for the production of a pure beam of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. This concept requires radioactive ions to be accelerated to a Lorentz gamma of 150 for 6He and 60 for 18Ne. The neutrino source itself consists of a storage ring for this energy range, with long straight sections in line with the experiment(s). Such a decay ring does not exist at CERN today, nor does a high-intensity proton source for the production of the radioactive ions. Nevertheless, the existing CERN accelerator infrastructure could be used as this would still represent an important saving for a beta-beam facility. This paper outlines the first study, while some of the more speculative ideas will need further investigations.

A 40–80 MHz system for phase rotation and cooling

In this note a scheme for the collection, phase rotation and cooling of muons for a neutrino factory is reported. The scheme is sufficiently generic to be site independent also if some particular choices are influenced by the CERN design. The system discussed in this note is worked on as a possible alternative to the induction linac scheme. The results presented assume the following overall set-up: the proton driver is constituted by a 2.2GeV superconducting linac followed by an accumulator and compressor ring; the muon re-circulator and decay ring are assumed as described in PJK scenario.