A block coil geometry is appealing in the body of particle accelerator dipole or quadrupole magnets, but less so in the ends of conventional designs, because conductors near the midplane of the beam tube must be bent in the hard direction to cross over to the other side of the tube. To avoid damage to brittle conductors such as Nb3Sn or HTS, the bend must be very gradual, resulting in undesirably long magnet ends. An alternative design - “overpass/underpass” or “cloverleaf” - can ramp the conductor within a short length with bending only in the easy direction. Described here is a proof-of-principle design and analysis of an “overpass/underpass” coil geometry for a block coil dipole of 11 T or more.

Mu*STAR is a superconducting accelerator-driven, subcritical, molten-salt reactor designed to consume the spent nuclear fuel (SNF) from today's commercial fleet of light water reactors. In the process of doing so it will: 1) generate electricity in a cost-competitive manner, 2) significantly reduce the waste-stream volume per Gigawatt-hour generated, 3) greatly reduce the radio-toxic lifetime of the waste stream. As many states and countries now prohibit licensing of new nuclear plants until a national strategy has been established for the long-term disposal of their nuclear waste, Mu*STAR can be an important enabler for new nuclear facilities. This is especially important in the light of climate change, as nuclear energy is the only carbon-free technology for a base-load generation that is readily expandable.

This paper presents work under a Small Business Innovation Research Phase I grant to Particle Beam Lasers, Inc. and Brookhaven National Laboratory to develop a passive superconducting shield as an alternative to the present design of an active shield with superconducting coils. This shielding provides a nearly field-free region for the electron beam near the high-gradient quadrupole for the proton beam in the interaction region (IR) of the proposed electron ion collider. Several materials are being examined for this shielding-tubes of low- or high-temperature superconductors (LTS or HTS), LTS sheets, and HTS tapes. Supplementing this shielding is an iron ring between the superconducting shield and beam tube to counter any decay in shielding currents. If successfully developed, demonstrated, and shown to be compatible with the magnet designs of all the IR magnets, this technique will provide an economical and technically excellent solution that reduces the need to operate IR magnets at higher current. This paper will summarize the latest design studies and test results both at 77 K for the shielding by the bulk-HTS tube and at 4 K for the shielding by tubes of HTS or LTS.

The proposed electron-ion collider (EIC) needs high-gradient, large-aperture quadrupole magnets in the interaction region (IR). This paper presents the work under a Small Business Innovation Research Phase I grant to Particle Beam Lasers, Inc., and Brookhaven National Laboratory (BNL) to develop a novel modular design for EIC quadrupoles based on racetrack coils, which need no expensive tooling to build. It also enables the same coils to be used in Nb3Sn magnets of a range of apertures. Such a modular program may greatly facilitate R&D and reduce its costs, which often dominate the total cost of magnets that are one-of-akind or produced in limited numbers. For the EIC IR, the same coils are used in four R&D quadrupoles: one Nb3Sn quadrupole as proposed for the BNL eRHIC and three Nb3Sn quadrupoles as proposed by Jefferson Laboratory for JLEIC. This paper will present the basic magnetic and mechanical design of the several IR quadrupoles for the proposed EIC.

High gradient superconducting cavities (SRF) will be needed for future accelerators. The higher gradient can achieve the high energy with fewer cavities. However, the accelerating field of niobium cavities is limited by the peak magnetic field on the cavity surface. Cavities coated with Nb 3 Sn have a significantly larger H c2 , allowing the cavity to achieve a larger gradient. Measurements of Nb 3 Sn coated cavities have achieved about half the theoretical predicted gradient. It is possible to improve Nb 3 Sn plated cavity performance.

The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only injection phase locking but also amplitude modulation to compensate for the cavity’s microphonics, which cause the cavity voltage to change, and for the variation of the beam current. To be able to do a fast and efficient modulation and to compensate the frequency pushing effect due to the anode current change, the magnetron’s magnetic field has to be trimmed by an external coil [1]. To facilitate this, a low eddy current magnetron body has been designed and built [2-4]. This paper will present the analytical prediction, simulation and experimental results of a conventional 2.45 GHz magnetron on the test stand. In addition, the progresses on the injection lock to a matched load, copper cavity, new 1497 MHz magnetron prototype, and the 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported.

In many applications dipole magnets with coils having significant curvature are needed. This is particularly challenging for high temperature superconductors (HTSs) as they are brittle. One possible application for curved HTS coils was the fragment separator dipole magnets for the Facility for Rare Isotope Beams (FRIB). For this application these magnets would operate in a high radiation environment and would be subject to a high heat load. Removal of heat generated in magnets in this environment using conventional Ni–Ti and Nb 3 Sn superconductors, which generally operate at ∼4.5 K, is difficult. However, an HTS conductor can be used to permit operation at 40 K where heat removal is significantly more efficient. As these coils are curved, one side of the coils has a reverse curvature requiring the development of special technology to wind the coils. As part of an STTR grant to develop and demonstrate a super-ferric design for a 2.2 T magnet, two curved coils were fabricated with a 12-mm-wide SuperPower ReBCO conductor and first tested in liquid N 2 at 77 K. Afterwards the coils were installed into a cryostat and cooled to the design temperature of 48 K with cryocoolers. This paper presents the construction details and test results for these coils.

The conceptual design of a prototype S-band pulsed, 9.5 MeV compact microtron with type-II injection is described. Estimates of parameters such as beam current and cathode lifetime, and comparisons with X-band and C-band parameters are presented. The electron beam can be extracted at various energies up to 9.5 MeV. Estimated yields of gammas produced at 6.5 MeV operation and estimated yields of gammas and neutrons produced at 9.5 MeV are presented.

A compact microtron can be an effective gamma source that can be transported to locations outside the laboratory. As part of a Phase I study we have studied a portable microtron that can accelerate electrons with energies of 6 MeV and above as a source for gamma and neutron production. The mass of the magnet is a significant contribution to the overall mass of the system. This paper will discuss conceptual designs for both permanent magnet and electromagnet systems. The choice of microtron RF frequency range is determined by the application requirements. The RF frequency band influences the size of the microtron magnet and consequently its weight. We have looked at how the design would vary with the different frequency configurations.

A helical cooling channel (HCC) consisting of a pressurized gas absorber imbedded in a magnetic channel that provides solenoid, helical dipole and helical quadrupole fields has been shown to provide six-dimensional phase space reduction for muon beams. Such a channel can be implemented by a helical solenoid (HS) composed of short solenoid coils arranged in a helical pattern. The magnetic channel will provide the desired B$_{\phi}$, B$_z$, and dB$_{\phi}$/dr along the reference path. The channel must allow enough space for RF cavities which replace energy lost in the absorber material present for the cooling process. The study will describe how to achieve the desired field while allowing sufficient space for the cavities. The limits to this design imposed by the achievable current density in the coils will be discussed.

Muon accelerators bear unique potential for the high energy physics community supporting the US Intensity Frontier research program and when relying on the infrastructure developed the Energy Frontier using one or more muon colliders as a subsequent stage [1]. Muon beam ionization cooling is deemed the only solution to provide the very high beam intensities required for a neutrino factory or muon collider. Cooling channels generally demand strong magnetic fields enclosing RF cavities that compensate for the energy loss due to ionization. Co o achieve this reduction for a 250 MeV/c muon beam necessitates about seven times that much energy loss, which means an equivalent accelerator of about 1.75 GeV. This represents a multi-billion dollar expense based on large diameter superconducting magnets, pillbox-like cavities, and present RF power source technology. The HCC is considered a cost-saving solution for muon cooling, though its engineering design remains challenging. After briefly introducing the HCC concept and the benefit of gaseous absorbers, the paper focuses on the development of RF cavity concepts.

Magnets in the fragment separator region of the Facility for Rare Isotope Beams (FRIB) would be subjected to extremely high radiation and heat loads. The critical elements of FRIB are the dipole magnets, which are used to select the desired isotopes. Since conventional NiTi and Nb 3 Sn superconductors must operate at ~ 4.5 K, the removal of the high heat load generated in these magnets using these superconductors would be difficult. High-temperature superconductors have been shown to be radiation resistant and can operate in the 40 K temperature range where heat removal is an order of magnitude more efficient than at 4.5 K. The coils of this magnet must accommodate the large curvature from the 30° bend that the magnet will subtend. This paper will describe the magnetic and conceptual design for these magnets.

Muon colliders are considered to be an important future energy frontier accelerator. It is possible to build a large muon collider as a circular machine, even at multi-TeV energies, due to the greatly reduced synchrotron radiation expected from muons. In addition to the same physics processes present in an electron collider, a muon collider will have the potential to produce s-channel resonances such as the various Higgs states at an enhanced rate. For a muon collider with 750GeV/c μ+μ− with 2×1012 muons per bunch we would expect 8.6×105 muon decays per meter for the two beams. The energetic electrons from muon decays will produce detector backgrounds that can affect the physics. These backgrounds include electrons from muon decays, synchrotron radiation from the decay electrons, hadrons produced by photo-nuclear interactions, coherent and incoherent beam-beam pair production and Bethe-Heitler muon production. In this paper we will discuss these processes and calculate particle fluxes into the detector volume from these background processes.

Multipole correction insert coils with significant field strength are required inside the large aperture superconducting quadrupole magnets in the fragment separator section of the Facility for Rare Isotope Beams (FRIB). Correction coils made with copper do not create the required field and conventional low temperature superconductors are not practical in the fragment separator magnets which will operate at 40-50 K. The correction coils for this application should be made of HTS as are the main quadrupole coils in this magnet. There is a significant advantage to using HTS in these coils as it can withstand the high radiation and heat load that will be present. This paper will describe the innovative design suitable for coils with the complex end geometry of cylindrical coils. We will look at the forces in the corrector coils from the main quadrupole fields and anticipate possible coil distortions.