[Show abstract][Hide abstract] ABSTRACT: The Muon-to-Electron conversion experiment, under development at Fermilab, utilizes a complex superconducting solenoid magnet system. Usage of high temperature superconductor (HTS) power leads and reliable superconducting bus system and splice joints are essential to the assuring safe, continuous and cost effective operation of the magnets. Left over HTS power leads from the Tevatron era combined with superconducting bus (made from aluminum-clad NbTi Rutherford cable) and three different types of splices were successfully tested in a single dewar test configuration up to 10150 A. In this paper we summarize the test results.
[Show abstract][Hide abstract] ABSTRACT: A superconducting solenoid-based focusing lens was designed and built for use in the SSR1 cryomodule of PXIE test facility at FNAL. As the cryomodule contains superconducting spoke-type cavities, one of main goals during design stage was minimization of magnetic field on walls of the cavities. The design also attempted minimization of the uncertainty of the magnetic axis position in the lens. This report describes main features of the design and summarizes results of performance tests and magnetic axis position measurements.
[Show abstract][Hide abstract] ABSTRACT: FNAL and CERN are developing a twin-aperture 11-T Nb3Sn dipole suitable for installation in the LHC. This paper describes the design and parameters of the 11-T dipole developed at FNAL for the LHC upgrades in both single-aperture and twin-aperture configurations, and presents details of the constructed dipole models. Results of studies of magnet quench performance, quench protection, and magnetic measurements performed using short 1-m-long coils in the dipole mirror and single-aperture configurations are reported and discussed.
[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: The muon-to-electron conversion experiment at Fermilab is designed to explore charged lepton flavor violation. It is composed of three large superconducting solenoids, namely, the production solenoid, the transport solenoid, and the detector solenoid. Each subsystem has a set of field requirements. Tolerance sensitivity studies of the magnet system were performed with the objective of demonstrating that the present magnet design meets all the field requirements. Systematic and random errors were considered on the position and alignment of the coils. The study helps to identify the critical sources of errors and which are translated to coil manufacturing and mechanical support tolerances.
[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 definition of the magnetic center in the Mu2e solenoid system is not trivial given the S-shaped nature of the transport solenoid. Moreover, due to the fringe field of the larger bore adjacent magnets-production solenoid and the detector solenoid-the magnetic center does not coincide with the geometric center of the system. The reference magnetic center can be obtained by tracking a low-momentum charged particle through the whole system. This paper will discuss this method and will evaluate the deviations from the nominal magnetic center given the tolerances in the manufacturing and the alignment of the coils. Methods for the correction of the magnetic center will also be presented.
[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 ionization beam profile monitor system for the Main Injector ring is under construction at Fermilab. The beam profile detector unit is installed inside the main magnet gap. The magnet has a novel configuration previously used for this type of application in the Main Injector. However, this magnet is far more compact with a higher quality field. Most flux from the main gap returns symmetrically along the beam pipe through two side gaps. It provides nearly full compensation to yield integrated magnetic field close to zero, and helps eliminate distortions of the circulating proton beam. The permanent magnet poles are assembled from SmCo5 bricks (0.5"×1"×2"), which have good thermal stability and reasonable cost. Further integrated field reduction is obtained by the use of a ferromagnetic plate that shunts the main gap. The plate position and flux shunting are adjusted in conjunction with magnetic measurements. Three permanent magnets were successfully fabricated and measured. Results of the magnet design, 3-D FEA analysis, and magnetic measurements by the rotational coil and the 3-D Hall probe will be presented.
[Show abstract][Hide abstract] ABSTRACT: The Mu2e experiment at Fermilab is designed to explore charged lepton flavor violation by searching for muon-to-electron conversion. The magnetic field generated by a system of solenoids is a crucial component of Mu2e and requires accurate characterization to detect any potential flaws and to produce a detailed field map. In order to design and build a precise field mapping system consisting of Hall and NMR probes, tolerances and precision for such a system need to be evaluated. To generate a final magnetic field map of the Mu2e solenoids, a continuous field has to be extracted from a discrete set of measurement points. A design for the Mu2e field mapping hardware, and results from simulations to specify parameters for Hall and NMR probes are presented. A fitting procedure for the analytical treatment of our expected magnetic measurements is introduced.
[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: With the first test of LQS03, the long quadrupole (LQ) R&D by LARP (the US LHC Accelerator Research Program, a collaboration of BNL, FNAL, LBNL, and SLAC) is approaching conclusion. LQS03 is the third 3.7-m-long quadrupole, with 90mm aperture, using a full new set of Nb3Sn coils. The LQS03 coils were made using 108/127 RRP strand (with 108 Nb3Sn subelements) produced by Oxford Superconducting Technology, whereas both previous models used 54/61 RRP strand (with 54 larger Nb3Sn subelements). In this paper, LQS03 test results are presented and discussed. The test results are also compared with the performances of the previous models. Observations are made for the future use of Nb3Sn in accelerator magnets.
[Show abstract][Hide abstract] ABSTRACT: The planned upgrade of the Large Hadron Collider (LHC) collimation system will include installation of additional collimators in the dispersion suppressor areas. The longitudinal space for the collimators could be provided by replacing 15-m-long 8.33 T NbTi LHC main dipoles with shorter 11 T Nb3Sn dipoles compatible with the LHC lattice and main systems. FNAL and CERN have started a joint program with the goal of building a 5.5-m-long twin-aperture Nb3Sn dipole prototype suitable for installation in the LHC. The first step of this program is the development of a 2-m-long single-aperture demonstrator dipole with a nominal field of 11 T at the LHC nominal current of 11.85 kA. This paper summarizes the results of quench protection studies of 11 T dipoles performed using the single-aperture Nb3Sn demonstrator.
[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: The Mu2e experiment at Fermilab is being designed to measure the rare process of direct muon-to-electron conversion in the field of a nucleus. The experiment comprises a system of three superconducting solenoids, which focus secondary muons from the production target and transport them to the stopping target, while minimizing the associated background. The detector solenoid is the last magnet in the transport line and it consists of an axially graded-field section at the upstream end, where the stopping target is located, and a spectrometer section with uniform field at the downstream end for accurate momentum measurement of the conversion elections. The detector solenoid has a warm bore of 1.9 m and is 10.75 m long. The stored energy of the magnet is 30 MJ. The conceptual design of the magnet is presented, in particular the challenge of achieving tight magnetic field specification in a cost-effective design.
[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: After the successful test of the first long NbSn quadrupole magnet (LQS01), the US LHC Accelerator Research Program (LARP) has assembled and tested a new 3.7 m-long NbSn quadrupole (LQS02). This magnet has four new coils made of the same conductor as LQS01 coils, and it is using the same support structure. LQS02 was tested at the Fermilab Vertical Magnet Test Facility with the main goal to confirm that the long models can achieve field gradient above 200 T/m, LARP target for 90-mm aperture, as well as to measure the field quality. These long models lack some alignment features and it is important to study the field harmonics. Previous field quality measurements of LQS01 showed higher than expected differences between measured and calculated harmonics compared to the short models (TQS) assembled in a similar structure. These differences could be explained by the use of two different impregnation fixtures during coil fabrication. In this paper, we present a comparison of the field quality measurements between LQS01 and LQS02 as well as a comparison with the short TQS models. If the result supports the coil fabrication hypothesis, another LQS assembly with all coils fabricated in the same fixture will be produced for understanding the cause of the discrepancy between short and long models.
[Show abstract][Hide abstract] ABSTRACT: A new superconducting quadrupole magnet for linear accelerators was fabricated at Fermilab. The magnet is designed to work inside a cryomodule in the space between SCRF cavities. SCRF cavities must be installed inside a very clean room adding issues to the magnet design, and fabrication. The designed magnet has a splittable along the vertical plane configuration and could be installed outside of the clean room around the beam pipe previously connected to neighboring cavities. For more convenient assembly and replacement a “superferric” magnet configuration with four racetrack type coils was chosen. The magnet does not have a helium vessel and is conductively cooled from the cryomodule LHe supply pipe and a helium gas return pipe. The quadrupole generates 36 T integrated magnetic field gradient, has 600 mm effective length, and the peak gradient is 54 T/m. In this paper the quadrupole magnetic, mechanical, and thermal designs are presented, along with the magnet fabrication overview and first test results.
[Show abstract][Hide abstract] ABSTRACT: A new generation of precision muon conversion experiments is planned at both Fermilab and KEK. These experiments will depend upon a complex set of solenoid magnets for the production, momentum selection and transport of a muon beam to a stopping target, and for tracking detector momentum analysis of candidate conversion electrons from the target. Baseline designs for the production and detector solenoids use NbTi cable that is heavily stabilized by an extruded high RRR aluminum jacket. A U.S.-Japan research collaboration has begun whose goal is to advance the development of optimized Al-NbTi conductors, gain experience with the technology of winding coils from this material, and test the conductor performance as modest length samples become available. For this purpose, a “conductor test” solenoid with three coils was designed and built at Fermilab. A sample of the RIKEN Al-NbTi conductor from KEK was wound into a “test” coil; this was sandwiched between two “field” coils wound from doubled SSC cable, to increase the peak field on the RIKEN test coil. All three solenoid coils were epoxy impregnated, and utilized aluminum outer bandage rings to apply preload to the coils when cold. The design and fabrication details, and results of the magnet quench performance tests are presented and discussed.