[Show abstract][Hide abstract] ABSTRACT: The Mu2e experiment at Fermilab will search for charged lepton flavor
violation via the coherent conversion process mu- N --> e- N with a sensitivity
approximately four orders of magnitude better than the current world's best
limits for this process. The experiment's sensitivity offers discovery
potential over a wide array of new physics models and probes mass scales well
beyond the reach of the LHC. We describe herein the preliminary design of the
proposed Mu2e experiment. This document was created in partial fulfillment of
the requirements necessary to obtain DOE CD-2 approval.
[Show abstract][Hide abstract] ABSTRACT: Large aperture superconducting solenoid magnets are needed for the production and capture of pions, which decay to create intense muon beams in future experiments to search for direct muon to electron conversion. The COMET experiment in Japan and the Mu2e experiment in the U.S. are jointly conducting research into the design of capture solenoid coils made from aluminum-stabilized NbTi superconductor that is cooled by conduction to a supply of liquid helium. A prototype coil of 1.3-m inner diameter, having four layers of eight turns each, has been wound with pure aluminum interlayer fins for the conduction cooling. The test coil includes two types of welded splices, two film heaters for quench studies, and extensive instrumentation to evaluate strain, temperature profiles, and coil voltages. Details of the cryogenic conduction cooling scheme, test systems design, and test program plans will be discussed.
[Show abstract][Hide abstract] ABSTRACT: The Fermilab Mu2e experiment seeks to measure the rare process of direct muon to electron conversion in the field of a nucleus. The magnet system for this experiment is made of three warm-bore solenoids: the Production Solenoid (PS), the Transport Solenoid (TS), and the Detector Solenoid (DS). The TS is an “S-shaped” solenoid set between the other bigger solenoids. The Transport Solenoid has a warm-bore aperture of 0.5 m and field between 2.5 and 2.0 T. The PS and DS have, respectively warm-bore aperture of 1.5 m and 1.9 m, and peak field of 4.6 T and 2 T. In order to meet the field specifications, the TS starts inside the PS and ends inside the DS. The strong coupling with the adjacent solenoids poses several challenges to the design and operation of the Transport Solenoid. The coil layout has to compensate for the fringe field of the adjacent solenoids. The quench protection system should handle all possible quench and failure scenarios in all three solenoids. The support system has to be able to withstand very different forces depending on the powering status of the adjacent solenoids. In this paper, the conceptual design of the Transport Solenoid is presented and discussed focusing on these coupling issues and the proposed solutions.
[Show abstract][Hide abstract] ABSTRACT: The Mu2e experiment at Fermilab has been approved by the Department of Energy to proceed with the development of the preliminary design. Integral to the success of Mu2e is the superconducting solenoid system. One of the three major solenoids is the detector solenoid that houses the stopping target and the detectors. The goal of the detector solenoid team is to produce detailed design specifications that are sufficient for vendors to produce the final design drawings, tooling and fabrication procedures and proceed to production. In this paper we summarize the reference design of the detector solenoid.
[Show abstract][Hide abstract] ABSTRACT: A superconducting quadrupole magnet with splittable yoke has been designed for use in ILC Main Linac (ML) cryomodules. The splittable yoke allows assembly around the beam pipe, to avoid potential contamination of the superconducting RF cavities. The magnet is cooled by conduction and covers the full range of required ML field gradients. A critical requirement is stability of the magnetic center, at the level of 5 μm, for a 20% variation of the operating field. We report here the results of thermal, quench, and magnetic performance tests of a prototype splittable quadrupole, that were made up to the maximum design operating gradient in a conduction-cooled test cryostat.
[Show abstract][Hide abstract] ABSTRACT: In preparation for the high luminosity upgrade of the Large Hadron Collider (LHC), the LHC Accelerator Research Program (LARP) is developing a new generation of large aperture high-field quadrupoles based on Nb3Sn technology. One meter long and 120 mm diameter HQ quadrupoles are currently produced as a step toward the eventual aperture of 150 mm. Tests of the first series of HQ coils revealed the necessity for further optimization of the coil design and fabrication process. A new model (HQ02) has been fabricated with several design modifications, including a reduction of the cable size and an improved insulation scheme. Coils in this magnet are made of a cored cable using 0.778 mm diameter Nb3Sn strands of RRP 108/127 subelement design. The HQ02 magnet has been fabricated at LBNL and BNL, and then tested at Fermilab. This paper summarizes the performance of HQ02 at 4.5 K and 1.9 K temperatures.
[Show abstract][Hide abstract] ABSTRACT: Large-aperture, high-field, Nb3Sn quadrupoles are being developed by the U.S. LHC accelerator research program (LARP) for the High luminosity upgrade of the Large Hadron Collider (HiLumi-LHC). The first 1 m long, 120 mm aperture prototype, HQ01, was assembled with various sets of coils and tested at LBNL and CERN. Based on these results, several design modifications have been introduced to improve the performance for HQ02, the latest model. From the field quality perspective, the most relevant improvements are a cored cable for reduction of eddy current effects, and more uniform coil components and fabrication processes. This paper reports on the magnetic measurements of HQ02 during recent testing at the Vertical Magnet Test Facility at Fermilab. Results of baseline measurements performed with a new multilayer circuit board probe are compared with the earlier magnet. An analysis of probe and measurement system performance is also presented.
[Show abstract][Hide abstract] ABSTRACT: The U.S. LHC Accelerator Research Program has been developing Nb3Sn quadrupole magnets of progressively increasing performance and complexity for the High-Luminosity LHC project. The magnets are wound with Rutherford cables following the wind-and-react process. The resulting inter-strand coupling can generate strong field distortions during current ramp. The latest series of 120 mm aperture magnets (HQ) are designed and built for high field quality, offering an opportunity for detailed studies of these effects. Magnetic measurements of first-generation HQ magnets showed strong ramp-rate dependence. A stainless-steel core was introduced for the second generation of magnet coils to control the inter-strand coupling currents and the resulting dynamic multipoles. We report the observed dynamic effects and compare with calculations taking into account the coil geometry and cross-contact resistance in the Rutherford cable. In particular, the dependence of field quality on width and position of the stainless steel core is discussed.
[Show abstract][Hide abstract] ABSTRACT: A new test stand for testing large superconducting solenoid magnets at the Fermilab Central Helium Liquefier (CHL) has been designed, installed, and operated. This test stand is being used to test a coupling coil for the Muon Ionization Cooling Experiment (MICE), and future uses include solenoids for the Fermilab μ2e experiment. This paper describes the test stand design and operation including controlled cool-down and warm-up. Overviews of the process controls system and the quench management system are also included.
[Show abstract][Hide abstract] ABSTRACT: A systematic series of measurements of the time decay of the scxtupole component of the magnetic field in a full-length SSC dipole magnet prototype was carried out in order to characterize the mechanisms involved. At least two mechanisms have been isolated. The first is a slow logarithmic decay which is independent of the excitation history of the magnet. This component is stopped by a decrease of the magnet temperature and is identified with flux creep. The second component, which is not yet fully understood, only appears when the magnet is pre-cycled to a high level of current, and cannot be stopped by decreasing the magnet temperature.
[Show abstract][Hide abstract] ABSTRACT: Development of a high-current proton linac at FNAL went through many stages, starting from a pulsed 8 GeV linac, then to the HINS linac front end R&D, and now toward the ProjectX CW linac. For different parts of the accelerator front end in each of these linacs, the design requires solenoid-based focusing lenses that can provide the needed transverse focusing on a very tight real estate environment. The multiple, often contradictory, design requirements of focusing lenses include the need for high focusing strength, small footprint, very low fringe field, and embedded steering coils. To meet these requirements, a series of prototype lenses were built and tested. Performances of the lenses designed for low energy parts of the linac front end have been reported earlier. This report presents lens design and test data for the high energy part of a proton linac front end, up to an energy of ~ 100 MeV. For these lenses, reliable protection from high voltages or temperatures during a quench becomes important, and a new protection scheme was developed, which allows more flexibility and reliability. Details of the magnetic axis position have also been investigated.
[Show abstract][Hide abstract] ABSTRACT: Fabrication and preparation for test of the MuCool superconducting solenoid are now in progress. The solenoid's passive quench protection system is based on cold diodes and shunt resistors. The solenoid does not have heaters, and quench propagation relies on the superconductor quenching and the subsequent “quench back” effect caused by eddy currents in the coil's Al mandrel. The solenoid has a very large inductance of ~600 H and the stored energy is 100% dissipated into the cold mass during a quench. This makes the solenoid protection a challenging task. This paper presents the quench analysis of the solenoid based on a 3-D FEA solution of the coupled transient electromagnetic and thermal properties during the quench. The simulations used the Vector Fields QUENCH code. A new test facility, the solenoid test stand (STS), is being built at Fermilab to test these coils. One of the critical issues regarding the STS is the fringe field produced by the magnet under test, which interacts with the surrounding equipment. In this paper, we present the stray-field analysis and the corresponding magnetic forces. The STS includes a sophisticated DAQ system to carefully monitor quench events and temperatures.
[Show abstract][Hide abstract] ABSTRACT: Rotating coil probes are essential for measuring harmonic multipole fields of accelerator magnets. A fundamental requirement of these probes is their accuracy, which typically implies that the probes need to be very stiff and straight, have highly accurate knowledge of the placement of windings, and an ability to buck the fundamental fields well in order to suppress the effects of vibrations. Ideally, for an R&D test environment, probe fabrication should also be easy and low-cost, so that probe parameters (type, length, number of turns, radius, etc.) can be customized to the magnet requiring test. Such facility allows measurement optimization for magnets of various multipolarity, aperture size, cable twist pitch, etc. The accuracy and construction flexibility aspects of probe development, however, are often at odds with each other. This paper reports on application of printed-circuit board and fused-deposition modeling technologies, and what these offer to the fabrication of magnetic measurement probe systems.
[Show abstract][Hide abstract] ABSTRACT: A quench detection system for testing superconducting magnets with two concurrent data logging modes was developed at Fermilab. This system consists of two functional components: An active quench detection component, which is based on a reconfigurable input/output module with a field-programmable gate array, and a data logger component based on a set of simultaneous sampling data logger modules. The data logger component has two concurrent modes of operation: A fast logger mode that is triggered to capture a user specified window of data at rates up to 10 kHz, and a continuous data logger mode that can log data at rates between 0.1 and 100 Hz continuously using the same data loggers. The system was designed with a modular structure using commercially available hardware along with in-house developed programmable isolation amplifiers. This approach makes the new system easily scalable for multiple magnets or magnets with more complex coil and lead voltage tap configurations. The new system has been used for testing the MICE Spectrometer Solenoid. A detailed description of the system along with test results is presented in this paper.
[Show abstract][Hide abstract] ABSTRACT: The goal of the Muon Ionization Cooling Experiment (MICE) is to demonstrate muon cooling for a future muon collider. In order to quantify this cooling effect with high precision, scintillating fiber trackers in a uniform 4 Tesla field are required. The MICE spectrometer solenoids were designed to meet these requirements. Based on superconducting niobium-titanium (Nb-Ti), each of the two MICE spectrometer solenoids consists of five separate coils contained in a vacuum vessel of 2.7 m length and 1.4 m diameter. In this paper, we report on results from first measurements to verify initial magnet performance at the manufacturer site using a portable Hall-probe-based measurement system. A comparison with theoretical expectations based on OPERA simulations will be discussed and design aspects of the measurement system will be presented.
[Show abstract][Hide abstract] ABSTRACT: A program to develop model magnets for a helical cooling channel is under way at Fermilab. In the first steps of a planned sequence of magnets, two four-coil helical solenoid models with 300 mm aperture have been fabricated and tested. These two models, HSM01 and HSM02, used insulated NbTi Rutherford cable wound onto stainless steel rings with spliceless transitions between coils. Strip heaters were included for quench protection of each coil, and the coils were epoxy-impregnated after winding inside the support structures. Based on the results of the first model the second model was made using a cable with optimized cross-section, improved winding and epoxy-impregnation procedures, enhanced ground insulation, and included heat exchange tubing for a test of conduction cooling. We report on the results and lessons learned from fabrication and tests of these two models.
[Show abstract][Hide abstract] ABSTRACT: The first production focusing lens for the HINS beam line at Fermilab has been assembled into a cryostat and tested. A total of 5 devices will be tested before they are installed in the low energy section of the HINS beam line, which uses copper Crossbar-H (CH) style RF cavities. One of the tested CH-section lens assemblies includes a pair of weak orthogonal steering dipoles nested within a strong focusing solenoid, and has six vapor cooled power leads. The other device has only the strong focusing solenoid, and utilizes a single pair of HTS power leads. The production test program is designed to measure the thermal performance of the cryostat, minimum cooling requirements for the HTS leads, quench performance of all superconducting components, and precise determination of the magnetic axis and field angles. Results and future plans for the first production device tests are presented.
IEEE Transactions on Applied Superconductivity 07/2011; · 1.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In December 2009 during its first cold test, LQS01, the first Long Nb<sub>3</sub>Sn Quadrupole made by LARP (LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL and SLAC), reached its target field gradient of 200 T/m. This target was set in 2005 by the US Department of Energy, CERN and LARP, as a significant milestone toward the development of Nb<sub>3</sub>Sn quadrupoles for possible use in LHC luminosity upgrades. LQS01 is a 90 mm aperture, 3.7 m long quadrupole using Nb<sub>3</sub>Sn coils. The coil layout is equal to the layout used in the LARP Technological Quadrupoles (TQC and TQS models). Pre-stress and support are provided by a segmented aluminum shell pre-loaded using bladders and keys, similarly to the TQS models. After the first test the magnet was disassembled, reassembled with an optimized pre-stress, and reached 222 T/m at 4.5 K. In this paper we present the results of both tests and the next steps of the Long Quadrupole R&D.
IEEE Transactions on Applied Superconductivity 07/2011; · 1.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Several 90-mm quadrupole coils made of 0.7-mm Nb<sub>3</sub>Sn strand based on the “Restack Rod Process” (RRP) of 108/127 design, with cored and non-cored cables and different cable insulation, were fabricated and individually tested at Fermi National Accelerator Laboratory (Fermilab) using a test structure designed to provide a quadrupole magnetic field environment. The coils were instrumented with voltage taps and strain gauges to study quench performance and mechanical properties. The Nb<sub>3</sub>Sn strand and cable parameters, the coil fabrication details, the mirror model assembly procedure and test results at temperatures from 4.5 K to 1.9 K are reported and discussed.
IEEE Transactions on Applied Superconductivity 07/2011; · 1.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A compact R&D RF linac is being built at Fermilab to study several key technologies related to accelerating high intensity beams. One of the goals is reduction of beam losses through the use of solenoid lenses in the low energy front end of the linac. A total of 23 compact, high field, superconducting solenoids have been procured by Fermilab for the first (room-temperature RF) section of the linac. In this report we summarize the quench and magnetic performance of the lenses.
IEEE Transactions on Applied Superconductivity 07/2010; · 1.32 Impact Factor