Applications of High Intensity Proton Accelerators

The following sections are included:

• Organizing Committees

• Preface

• Contents

As the Fermilab Tevatron Collider program draws to a close, a strategy has emerged of an experimental program built around the high intensity frontier. The centerpiece of this program is a superconducting H^- linac that will support world leading programs in long baseline neutrino experimentation and the study of rare processes. Based on technology shared with the International Linear Collider, Project X will provide multi-MW beams at 60-120 GeV from the Main Injector, simultaneous with very high intensity beams at lower energies. Project X also supports development of a Muon Collider as a future facility at the energy frontier.

Rare muon decay experiments to search for charged lepton flavor violation are described. Future prospects of rare muon decay experiments with highly intense proton accelerators are discussed.

The prospects for measuring the ultra-rare decays and are discussed. Several new experiments are being constructed or have been proposed at existing facilities and ideas for reaching very high precision experiments at a future high intensity proton source like Project X ICD2 are under discussion.

Parameters are given of muon colliders with center of mass energies of 1.5 and 3 TeV. Pion production is from protons on a mercury target. Capture, decay, and phase rotation yields bunch trains of both muon signs. Six dimensional cooling reduces the emittances until the trains are merged into single bunches, one of each sign. Further cooling in 6 dimensions is then applied, followed by final transverse cooling in 50 T solenoids. After acceleration the muons enter the collider ring. Ongoing R&D is discussed.

Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture and accelerate O(10²¹) muons/year. This development prepares the way for a new type of neutrino source : a Neutrino Factory. This article reviews the motivation, design and R&D for a Neutrino Factory.

Accelerator driven systems offer the possibility to make nuclear fission energy sustainable and acceptable to society. The Energy Amplifier proposed by Carlo Rubbia at CERN is used to illustrate the potential of ADS, and the resulting R&D activity wave it triggered in Europe and in the world is briefly discussed. ADS must be part of the strategy to provide clean, safe and abundant energy for a harmonious development of society.

Nearly all risks to future generations arising from long-term disposal of used nuclear fuel are attributable to the transuranic elements and long-lived fission products, about 2% of its content. The transuranic elements of concern are plutonium, neptunium, americium, and curium. Long-lived (>100,000-year half-life) isotopes of iodine and technetium are also created by nuclear fission of uranium. We can reduce the problem transuranics through accelerator-based transmutation. Accelerator Driven Systems (ADS) have been proposed for over two decades as one technique to transmute used nuclear fuel. This paper covers the history and some new possible applications of accelerator driven systems.

An Accelerator Driven System (ADS) for transmutation of nuclear waste typically requires a 600 MeV - 1 GeV accelerator delivering a proton flux of a few mA for demonstrators, and a few tens of mA for large industrial systems. This high power accelerator requires an exceptional reliability: because of the induced thermal stress to the subcritical core, the number of unwanted beam-trips should not exceed a few per year, far above usual linac performances. This paper describes the reference solution adopted for such a machine, based on a so-called "fault-tolerant" concept for linear accelerators using superconducting cavities.

The coupling between an accelerator, a spallation target and a subcritical core has been studied for the first time at SCK•CEN in collaboration with Ion Beam Applications (IBA, Louvain-la-Neuve) in the frame of the ADONIS project (1995-1997). ADONIS was a small irradiation facility, based on the ADS concept, having a dedicated objective to produce radioisotopes for medical purposes and more particularly 99Mo as a fission product from highly enriched 235U (HEU) fissile targets. The ad-hoc scientific advisory committee recommended extending the purpose of the ADONIS machine to become a Material Testing Reactor (MTR) for material and fuel research, to study the feasibility of transmutation of the minor actinides and to demonstrate at a reasonable power scale the principle of the ADS. The project, since 1998 named MYRRHA, has then evolved to a larger installation.

MYRRHA is now conceived as a flexible irradiation facility, able to work as an Accelerator Driven (subcritical mode) and in critical mode. In this way, MYRRHA will allow fuel developments for innovative reactor systems, material developments for GEN IV systems, material developments for fusion reactors, radioisotope production for medical and industrial applications and industrial applications, such as Si-doping.

MYRRHA will also demonstrate the ADS full concept by coupling the three components (accelerator, spallation target and subcritical reactor) at reasonable power level to allow operation feedback, scalable to an industrial demonstrator and allow the study of efficient transmutation of high-level nuclear waste.

Since MYRRHA is based on the heavy liquid metal technology, the eutectic lead-bismuth, it will be able to significantly contribute to the development of Lead Fast Reactor Technology. Since MYRRHA will also be operated in critical mode, MYRRHA can even better play the role of European Technology Pilot Plant in the roadmap for LFR.

The cyclotron was invented back in the 1930^th and is one of the first resonant accelerator concepts. Cost effective cyclotrons are used today in a broad variety of industrial applications with low and medium beam-powers. However, the resonant acceleration principle and the continuous wave operation mode also permit the production of very intense beams with cyclotrons. In particular the TRIUMF cyclotron with 200 kW beam power and the PSI Ring Cyclotron that generates 1.3 MW are examples of high intensity cyclotron accelerators. In this article we describe basic aspects of cyclotrons optimized for this purpose as well as practical experience gained in the PSI facility.

Fixed Field Alternating Gradient accelerators(FFAGs) have been developed for various applications recently. Contrary to the ordinary synchrotron, FFAGs have a large capability of accelerating high current beams because of strong beam focusing to have a large beam acceptance and static magnetic field which allows to have very fast beam acceleration and large repetition rate in operation. In this paper I will present the expected characteristics and possible performance of FFAG as the proton drivers for ADSR and muon source, and also show the recent preliminary experiment on ADSR with FFAG proton accelerator complex at Kyoto University Research Reactor Institute (KURRI).

Production rates of kaons and accompanying particles from nuclear targets are modeled with LAQGSM and MARS 15 for low-energy proton beams.

Energy dependence of slow pion yield in proton-nucleus interactions is analyzed. Experimental data of the HARP collaboration is fitted using two-fireball model with χ²/n_d ~ 1 from 3 to 8 GeV/c. It is shown that low momentum negative pion yield rises almost linearly with proton kinetic energy. Normalized low momentum positive pion yield is larger at lower proton energy.

The phase-1 construction of J-PARC was complete by the end of March 2009. Since then all accelerators and experimental facilities have started operations. This paper will summarize the present status of the J-PARC accelerator. Upgrade plans for the Main Ring are discussed.

A recent implementation and verification of consistent modeling of displacements per atom (DPA) in the MARS15 code are described for high-energy particles and heavy ions.

The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon to tau neutrino oscillations. An intense muon-neutrino beam (1E17 muon neutrinos/day) is generated at CERN and directed over 732 km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. CNGS is the first long-baseline neutrino facility in which the measurement of the oscillation parameters is performed by observation of tau-neutrino appearance. In this paper, an overview of the CNGS facility is presented. Highlights on CNGS beam performance since during physics run in 2008 and 2009 are given.

The summary of working group WG1 exploring the discovery science enabled with SRF technology is given here.

Both a Neutrino Factory and a Muon Collider place stringent demands on the proton beam used to generate the desired beam of muons. Here we discuss the advantages and challenges of muon accelerators and the rationale behind the requirements on proton beam energy, intensity, bunch length, and repetition rate. Example proton driver configurations that have been considered in recent years are also briefly indicated.

Muon Colliders [1] need intense, very short, proton bunches. The requirements are presented and a number of possible bunching systems discussed. The best solution uses a small super-conducting buncher ring with 6 bunches that are taken though separate transports and combined on the target.

We describe a Project-X proton driver based on a CW Superconducting RF Linac with final energy as high as 8 GeV. This machine would have the potential to produce multi-MW H^- beams to drive the Fermilab neutrino programs, rare kaon and muon decay experiments, muon cooling R&D programs, neutrino factories, and muon colliders. Keys to a CW machine to suit these uses include ways to generate the desired bunch trains and ways to accumulate many protons in an intermediate storage ring before they are bunched and directed to a target. Enhanced carbon foil techniques can allow accumulation of intense proton beams from a CW linac, which we propose to be extended from 3 GeV to as much as 8 GeV for the most efficient muon production for colliders and neutrino factories and to replace the Booster for improved Main Injector operation.

This paper presents an 8 GeV Rapid Cycling Synchrotron (RCS) option for Project X. It has several advantages over an 8 GeV SC linac. In particular, the cost could be lower. With a 2 GeV 10 mA pulsed linac as injector, the RCS would be able to deliver 4 MW beam power for a muon collider. If, instead, a 2 GeV 1 mA CW linac is used, the RCS would still be able to meet the Project X requirements but it would be difficult for it to serve a muon collider due to the very long injection time.

A Neutrino Factory Proton Driver based on a superconducting proton linac has been designed in the CERN context. The 5 GeV/4 MW H^- beam from the linac is accumulated using charge exchange injection in a fixed-energy synchrotron and afterwards transferred to a compressor ring, where bunch rotation takes place. The lattices of the accumulator and compressor are described, as well as magnet technology and RF manipulations. Critical issues related to charge-exchange injection, space-charge effects in the compressor and beam stability in the accumulator, are addressed. The analysis is focused on the baseline scenario, which provides 6 bunches on the target. Results of preliminary analysis of options with less bunches (three and one) are also presented.

Optimization of pion and muon production/collection for neutrino factories and muon colliders is described along with recent developments of the MARS15 code event generators and effects influencing the choice of the optimal beam energy.

The paper discusses main limitations on the beam power and other machine parameters for a 4 MW proton driver for muon collider. The strongest limitation comes from a longitudinal microwave instability limiting the beam power to about 1 MW for an 8 GeV compressor ring.

Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture, accelerate and collide high intensity beams of muons. At present, a high-luminosity multi-TeV muon collider presents a viable option for the next generation lepton-lepton collider, which is believed to be needed to fully explore high energy physics in the era following LHC discoveries. This article briefly reviews the needs and possibilities for a Muon Collider beam test facility to carry out the R&D program on the collider front-end and 6D cooling demonstration experiment.

The summary of working group WG2 exploring the Muon Collider and Neutrino Factory cience enabled with SRF technology is given here.

Steady development in SRF accelerator technology combined with the success of large scale installations such as CEBAF at Jefferson Laboratory and the SNS Linac at ORNL gives credibility to the concept of very high average power CW machines for light sources or Proton drivers. Such machines would be powerful tools for discovery science in themselves but could also pave the way to reliable cost effective drivers for such applications as neutrino factories, an energy-frontier muon collider, nuclear waste transmutation or accelerator driven subcritical reactors for energy production. In contrast to machines such as ILC that need maximum accelerating gradient, the challenges in these machines are mainly in efficiency, reliability, beam stability, beam loss and of course cost. In this paper the present state of the art is briefly reviewed and options for a multi-GeV, multi-MW CW linac are discussed.

We describe accelerator R&D being pursued in Indian (mainly DAE) labs for Accelerator Driven Sub-critical system (ADS) applications. Currently design and prototype development of most subsystems is on, that should pave the way for a construction of full system in future.

VECC has developed excellent infrastructure for advanced research and development in the field of accelerator technology particularly in the superconducting magnet technology. The main activities are focused on development and operation of the K130 cyclotron, K500 superconducting cyclotron and the ECR ion sources. We have recently commissioned the superconducting cyclotron with internal ion beam and subsequently beam extraction program has been taken up. This large superconducting magnet (1.42 m pole diameter) operates at 4.8T average magnetic field. This cyclotron will be used to accelerate a variety of heavy ion beams for basic nuclear physics and allied experiments. In this paper, details of the design, construction and operation experience of various systems of this superconducting cyclotron will be presented.

High intensity proton accelerators have two important applications in China in recent years: Accelerator Driven Sub-critical System for nuclear waste transmutation and China Spallation Neutron Source. This paper focuses on the R&D activities of the key technology of high intensity proton accelerators in China, including the normal conducting and superconducting accelerator technologies. Chinese efforts in ADS basic research will also be outlined.

A review is given of present and planned involvement in ADSR research in the UK, and the activities of the ThorEA association.

Accelerator driven nuclear transmutation system has been pursued to have a clue to the solution of high-level radioactive waste management. The concept consists of super conducting linac, sub-critical reactor and the beam window. Reference model is set up to 800MW thermal power by using 1.5GeV proton beams with considerations multi-factors such as core criticality. Materials damage is simulated by high-energy particle transport codes and so on. Recent achievement on irradiation materials experiment is stated and the differences are pointed out if core burn-up is considered or not. Heat balance in tank-type ADS indicates the temperature conditions of steam generator, the beam widow and cladding materials. Lead-bismuth eutectics demonstration has been conducted. Corrosion depth rate was shown by experiments.

We seek to develop accelerator-driven subcritical (ADS) nuclear power stations operating at more than 5 to 10 GW in an inherently safe region below criticality, generating no greenhouse gases, producing minimal nuclear waste and no byproducts that are useful to rogue nations or terrorists, incinerating waste from conventional nuclear reactors, and efficiently using abundant thorium fuel that does not need enrichment. First, the feasibility of the accelerator technology must be demonstrated. Fermilab is developing concepts for Project X, which would use a superconducting RF (SRF) linear proton accelerator to provide beams for particle physics at the intensity and energy frontiers. We propose to extend this linac design to serve as a prototype for a practical accelerator that can drive several ADS reactors at once and also provide beams for reactor development.

We describe the power production process in Accelerator Driven Sub-critical systems employing Thorium-232 and Uranium-238 as fuel and examine the demands on the power of the accelerator required.

An experimental neutron source facility has been developed for producing medical isotopes, training young nuclear professionals, providing capability for performing reactor physics, material research, and basic science experiments. It uses a driven subcritical assembly with an electron accelerator. The neutrons driving the subcritical assembly were generated from the electron interactions with a target assembly. Tungsten or uranium target material is used for the neutron production through photonuclear reactions. The neutron source intensity, spectrum, and spatial distribution have been studied to maximize the neutron yield and satisfy different engineering requirements. The subcritical assembly is designed to obtain the highest possible neutron flux intensity with a subcriticality of 0.98. Low enrichment uranium is used for the fuel material because it enhances the neutron source performance. Safety, reliability, and environmental considerations are included in the facility conceptual design. Horizontal neutron channels are incorporated for performing basic research including cold neutron source. This paper describes the conceptual design and summarizes some of the related analyses.

This paper presents a brief summary of the objectives of transmutation mission and relevant fuel cycle strategies and transmutation systems, including a short comparison of the main characteristics of fast reactor and accelerator-driven systems for actinide transmutation.

This paper identifies the basic safety functions in nuclear reactor design, and the safety design issues for accelerator-driven subcritical reactors.

A design methodology for the lead-bismuth eutectic (LBE) spallation target has been developed and applied. This methodology includes the target interface with the subcritical assembly and the different engineering aspects of the target design, physics, heat-transfer, hydraulics, structural, radiological, and safety analyses. Several design constrains were defined and utilized for the target design process to satisfy different engineering requirements and to minimize the time and the cost of the design development. Target interface requirements with the subcritical assembly were defined based on performance parameters and material damage issues to enhance the lifetime of the target structure. Different structural materials were considered to define the most promising candidate based on the current database including radiation effects.

This paper briefly discusses the design objectives of accelerator transmutation of waste systems and important design parameters and constraints to be considered.

The Japan Atomic Energy Agency (JAEA) has been proceeding with the research and development on accelerator-driven system (ADS) for the transmutation of long-lived radioactive nuclides. The ADS proposed by JAEA is a lead-bismuth eutectic (LBE) cooled fast subcritical core with 800 MW_th. Various activities were conducted to investigate the feasibility of the ADS from viewpoints of the accelerator, LBE handling technology, minor actinide bearing fuel and subcritical core design. The design study and discussion of effective application on the Transmutation Experimental Facility (TEF) was also continued under a framework of J-PARC (Japan Proton Accelerator Research Complex) project.

Plutonium recycle in fast reactors, as well as utilization/transmutation of minor actinides and long-lived fission products in hybrid reactor systems (e.g. accelerator driven systems, ADS) offer promising nuclear fuel backend management options. Several R&D programs in various IAEA Member States are actively pursuing these options, along with the energy production and breeding mission of fast reactor systems. The paper presents an overview of the major national and international R&D programs in the area of ADS for transmutation of spent nuclear fuel. It also describes IAEA's ongoing and planned activities in this field.

Significant high-current, high-intensity accelerator research and development have been done in the recent past in the US, centered primarily at Los Alamos National Laboratory. These efforts have included designs for the Accelerator Production of Tritium Project (APT), Accelerator Transmutation of Waste (ATW), and Accelerator Driven Systems (ADS), as well as many others. A 6.7-MeV, 100-mA, CW proton demonstration accelerator was operated successfully as a proof-of-principle for the APT Project that also showed promise as the front-end of a GWth-class ADS driver. This past work and some specific design principles that were developed to optimize linac designs for ADS and other high-intensity applications will be discussed briefly.

The summary of working groups WG3 and WG4 SRF linacs and Accelerator driven subcritical systems (ADS) is given here.

The science of cancer research is currently expanding its use of alpha particle emitting radioisotopes. Coupled with the discovery and proliferation of molecular species that seek out and attach to tumors, new therapy and diagnostics are being developed to enhance the treatment of cancer and other diseases. This latest technology is commonly referred to as Alpha Immunotherapy (AIT). Actinium-225/Bismuth-213 is a parent/daughter alpha-emitting radioisotope pair that is highly sought after because of the potential for treating numerous diseases and its ability to be chemically compatible with many known and widely used carrier molecules (such as monoclonal antibodies and proteins/peptides). The object of this effort is to refine the simulations for producing actinium-225 at proton beam energies of 400 MeV and above up to about 8 GeV. Once completed, the simulations will be experimentally verified using 400 MeV and 8 GeV protons available at Fermi National Accelerator Laboratory. Targets will be processed at Argonne National Laboratory to separate and purify the actinium-225 that will subsequently be transferred to NorthStar laboratory facilities for product quality testing and comparison to the product quality of ORNL produced actinium-225, which is currently the industry standard. The test irradiations at FNAL will produce 1-20 mCi per day which is more than sufficient for quantitative evaluation of the proposed production process.

The nuclear Schiff moment and its resulting atomic electric dipole moment (EDM) are signatures of time-reversal and parity violation. They represent an important window onto physics beyond the Standard Model. We are developing a next generation experiment to search for the Schiff moment and EDM of ²²⁵Ra (t_1/2 = 15 d) based on laser-cooled and –trapped radium atoms. Due to octupole deformation of the nucleus, ²²⁵Ra is predicted to be 2-3 orders of magnitude more sensitive to T-violating interactions than ¹⁹⁹Hg (stable), which currently sets the most stringent limits in the nuclear sector. At present, ²²⁵Ra samples at the level of a few mCi (~ 10¹⁴ atoms) are available from the decay of the long-lived ²²⁹Th in stock. A future ISOL facility driven by a high-intensity accelerator could deliver 4-5 orders of magnitude more ²²⁵Ra. It holds the potential to further improve the EDM search sensitivity.

The summary of working group WG15 exploring topics in material science and medicine enabled by SRF technology is given here.

The following sections are included:

• List of Participants

• Author Index