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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-a-kind 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.

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.

This paper presents the design, construction, and test results of a hybrid dipole magnet. The inner coils were of second generation (2G) high-temperature superconductor (HTS) ReBCO tape and the outer coils were of low-temperature superconductor (LTS) Nb3Sn Rutherford cable. The HTS and LTS coils were independently powered and protected using different power supplies. The HTS coils were quenched many times with no degradation in performance observed. The hybrid field reached ∼8.6 T, which is believed to be a record for a hybrid dipole. The maximum field was limited by the stable operation of the leads in the LTS coil at 8000 A. The HTS coils were independently ramped to 800 A, and the LTS coils to 10 000 A. With improved leads and instrumentation, this hybrid dipole is expected to produce over 13 T when the ReBCO tape in the HTS coil is aligned nearly parallel to the field. One major purpose of this program was to perform magnetization studies in the coils made with the HTS tape. Magnetization-induced field errors are expected to be small when the field is nearly parallel to the wide face of the tape. The magnetization measurements were performed at 77 K with the two racetrack coils in two orientations, with field predominantly either parallel or perpendicular to the wide face of the HTS tape. In addition, measurements were also performed at 4 K in different background fields provided by the outer Nb3Sn coils. This paper will summarize the magnetization measurements and present the quenching experience of the HTS coils in this hybrid magnet system.

This paper presents several magnetic designs for a 16-T 50-mm aperture Nb 3 Sn dipole based on the common coil design for a future circular collider. It has an aperture-to-aperture spacing of 250 mm, a yoke outer diameter of 700 mm, and uses a similar or less conductor amounts than cosine theta or block designs. All field harmonics are about an order of magnitude better than specified at the design field and well below the specification in the entire range of operation. Initial results of mechanical design and analysis are also encouraging. They indicate that the proposed structure is able to support the pole coil blocks against the vertical Lorentz forces and that the maximum stresses in all coils remain generally below 150 MPa. Given several inherent advantages of the common coil design, the development presented here should make this approach a leading candidate for very high field magnets in future colliders.

Next-generation particle accelerators, such as the proposed Large Hadron Collider (LHC) energy upgrade (highenergy LHC), will require very-high-field (> 20 T) superconducting magnets. This paper describes the progress toward this goal made to date as a part of a collaborative work between Particle Beam Lasers, Inc., and Brookhaven National Laboratory. To reduce the cost, high-temperature superconductors (HTSs) are used in a hybrid design with conventional low-temperature superconductors (LTSs) Nb3Sn and NbTi. The focus of this paper is on using a second generation (2G) ReBCO HTS tape in cosine-theta coil geometry. The complex ends of the cosine-theta geometry are particularly challenging for a brittle HTS tape. We report the construction and 77-K test results, one with a 4-mm and another with a 12-mm ReBCO tape, neither showing measurable degradation. This paper also presents the first successful use of Kapton CI on an HTS tape, which offers many advantages. Future plans include the construction and 4-K testing of a full cosine-theta HTS coil (first in a stand-alone mode and then in a hybrid structure with LTS coils) and the modeling and measurements of magnetization. This paper is a part of comprehensive research and development toward eventually building a high-field accelerator-quality dipole magnet.

A potential future muon collider requires high field solenoids ( 30 T) for the final cooling stage; the Magnet Division at Brookhaven National Laboratory is undertaking the task of demonstrating feasibility using high-temperature superconductors (HTS). The aim is to construct an all-HTS dual-coil system capable of delivering more than 20 T. Recently, a new record for an all-HTS solenoid has been established with a field of 15 T on-axis. In coil tests, it was noticed that during a fast energy extraction, the current in the solenoids decays faster in comparison to the expected exponential decay. This paper describes the effect and shows how it can be simulated using commercial finite element code. The faster current decay helps to lower the integral current density squared with time by about 10% and is therefore beneficial for quench protection.

The proposed muon collider requires very high field solenoids in the range of 30-50 T. The use of High Temperature Superconductors (HTS) operating at low temperature (~ 4 K) is essential for achieving such high fields in a superconducting magnet. As a part of this program, we have built and successfully tested a 25 mm aperture HTS insert generating 16 T peak field (the highest field ever achieved in an all-HTS magnet), a 100 mm aperture HTS midsert generating 9 T peak field, and designed an outsert with a conventional Low Temperature Superconductor (LTS) to provide additional field. In addition to presenting the test results and progress made in support technologies, we will also discuss a number of challenges associated with the high field HTS magnets. Finally, we present a set of strategies to overcome some of those challenges.

This paper demonstrates the capabilities of a computer program to design magnets with exquisite field homogeneity and minimal fringe field. The program adjusts magnet parameters to reduce (typically to zero) selected coefficients cn in the power series expansion Bz(z) = Σcnzn, with n ranging from -21 to +16 ( n ≠ - 2 or -1) and cn evaluated by multiple differentiations of the on-axis field of a solenoid. Presented are illustrative MRI magnets of 1-m I.D. with field homogeneity of 12th order and fringe field annulled through order as high as 21st. ΔB/B(0) is 0.1-0.2 ppm within a 30-cm sphere. The volume of the OSHA “hazard zone” (|B| > 5 is as little as 0.5% that of an uncompensated magnet.

We have designed and optimized the uniform-field magnet system of two dozen, one-meter-bore, one-tesla, MRI, and Magnetic Resonance Therapy (MRT) systems with a minimum axial gap between the coils of one meter. These magnet systems include not only mirror-symmetric systems, but also ergonomic, non-mirror-symmetric systems. These super-open systems are ideal for MRI-guided surgery and image-guided radiotherapy, as well as for diagnosis, particularly if the patient suffers from claustrophobia. By iterating between three computer programs, one can also design optimum uniform-field magnet systems that include permanent magnets and/or magnetizable iron.

This paper presents the goal and status of the high field High Temperature Superconductor (HTS) solenoid program funded through a series of SBIRs. The target of this R&D program is to build HTS coils that are capable of producing fields greater than 20 T when tested alone and approaching 40 T when tested in a background field magnet. The solenoid will be made with second generation (2G) high engineering current density HTS tape. To date, 17 HTS pancake coils have been built and tested in the temperature range from 20 K to 80 K. Quench protection, high stresses and minimization of degradation of conductor are some of the major challenges associated with this program.

The muon collider is a new idea for lepton colliders. The ultimate energy of an electron ring is limited by synchrotron radiation. Muons, which have a rest mass that is 200 times that of an electron can be stores at much higher energies before synchrotron radiation limits ring performance. The problem with muons is their short life time (2.1 /spl mu/s at rest). In order to operate a muon storage ring large numbers of muons must be collected, cooled and accelerated before they decay to an electron and two neutrinos. As we see it now, high field superconducting solenoids are an integral part of a muon collider muon production and cooling systems. This report will describe the design parameters for superconducting and hybrid solenoids that are used for pion production and collection, RF phase rotations of the pions as they decay into muons and the muon cooling (reduction of the muon emittance) before acceleration.

Superconducting solenoids are integral part of the proposed muon collider and Higgs factory. Superconducting solenoids that produce inductions up to 15 T will be used to capture pions that are produced by a proton beam impinging on a target contained within the solenoid. After the pions are captured they are phase rotated and allowed to decay to muons. The phase rotation and pion decay channel keeps the pions and muons captured in a 1.25 T rotation system. Superconducting solenoids will also be integral part of the muon cooling system. Within the muon cooling channel, which is projected to be up to 300 meters long, solenoidal fields up to 30 T are needed. This report presents the latest thoughts on how superconducting solenoids will be used as part of the muon collider.