Steven Lassiter

The Cosine Two Theta Quadrupole Magnets for the Jefferson Lab Super High Momentum Spectrometer

The Jefferson Lab 12 GeV/c upgrade involves building a new 12 GeV/c spectrometer for JLABs Hall C called the super high momentum spectrometer (SHMS). This device achieves 4.5 mStr acceptance at bend angles for 5.5 to 40 by using five magnetic elements in a DQQQD configuration. The Q1 quadrupole is described elsewhere in this conference and is an evolution of a cold iron magnet used previously for the existing JLAB 7.5 GeV/c high momentum spectrometer (HMS). The pair of identical cosine two theta quads are an entirely new design with a large 60 cm warm bore and 13 T/m gradient. These 5 T Quads provide focusing for particles from 1 to 12 GeV/c and have an integral gradient strength of 23.5 (T/m)m. The magnetic design, including multipole strengths, will be presented. The quadrupole cold mass uses a stainless steel shrink fit force collar, titanium keys and a copper stabilized superconductor consisting of a 36 strand surplus SSC outer cable wave soldered to a copper extruded substrate. This combination provides for a very conservative magnet that can be assembled with little or no tooling and a high degree of stability. The force collar mechanical analysis will be presented as well as details of the magnet cryostat.

A Super Conducting 60 cm Warm Bore Cosine Theta Dipole Magnet for the Jefferson Lab Super High Momentum Spectrometer (SHMS)

The Jefferson Lab 12 GeV upgrade involves building a new 12 GeV/c spectrometer for JLAB Hall C called the Super High Momentum Spectrometer (SHMS). This device achieves 4.5 mSr acceptance at bend angles from 5.5 degrees to 40 degrees by using five magnetic elements. The other magnetic elements of the SHMS, including the small SC dipole used to achieve the small 5.5 degree scattering angle, are described elsewhere in this conference. The 4.5 T SC dipole provides momentum analysis for particles from 1 to 12 GeV/c and has bend strength of 13.5 Tm. The magnetic design, including multipole strengths, will be presented. The dipoles cold mass uses a stainless steel shrink fit force collar, titanium keys and a copper stabilized super conductor consisting of a 36 strand surplus SSC outer cable wave soldered to a copper extruded substrate. This combination provides for a very conservative magnet that can be assembled with little or no tooling and has a high degree of stability. The force collar mechanical analysis will be presented as well as details of the magnet cryostat.

Q1 for JLAB's 12 Gev/c Super High Momentum Spectrometer

The reference design for the first Quadrupole magnet of TJNAFs Super High Momentum Spectrometer (SHMS), Q1, is presented. The SHMS is a DQQQD design that will be capable of resolving particles up to 11 Gev/c in momentum. Q1 follows the successful design of the High Momentum Spectrometers (HMS) Q1, that of an elliptically shaped super ferric yoke, conformal mapped window frame coil, and helium bath cooled coil design. The primary differences between the two designs is in the choice of superconducting cable and an overall longer magnet length. A single stack of surplus SSC Rutherford NbTi cable replaces the original four stack copper stabilized conductor used in the HMSs Q1. The SHMS Q1 will have a warm bore diameter of 400 mm and produce field gradients up to 9.1 T/m with an effective length of 2.14 m. Test coil windings progress will be given as well as reports on forces, conductor stability and energy margins.

JLAB's Super High Momentum Spectrometer's Superconducting Q1 Magnet

The commissioning and test results of a superferric superconducting quadrupole magnet constructed by Scientific Magnetics, Inc., for Thomas Jefferson National Accelerator Facility (TJNAF also known as JLAB) will be presented. The quadrupole magnet, named Q1, is the first focusing element in the Super High Momentum Spectrometer (SHMS). The SHMS, which is located within JLABs experimental Hall C, consists of all superconducting magnets in a dQQQD configuration and is part of the JLABs 12-GeV upgrade. Here, “d” refers to the small horizontal bend dipole, “Q” stands for focusing quadrupole magnets, and “D” is the vertical-bending momentum-selecting dipole magnet. Characterization of the magnets cryogenic heat loads and magnetic field quality will be presented along with descriptions of the magnets control system, power supply, and quench detection system.

Structural Analysis of the SHMS Cosine Theta Superconducting Dipole Force Collar

Jefferson Laboratory is developing a set of innovative superconducting magnets for the 12 GeV upgrade in JLAB Hall C. We will report on the finite element analysis (FEA) of the force collar for the Super High Momentum Spectrometer Cosine Theta Dipole magnet. The force collar is designed with an interference fit and intended to provide enough pressure after cool down to operating temperature to counteract Lorentz forces acting on the dipole coil during operation. By counteracting the Lorentz forces and keeping the coil pack in overall compression, movement of the coils is expected to be minimized. The dimensional geometry of the cold mass is maintained in the commercial solid modeling code UG/I-DEAS while the magnetic field design is maintained in the commercial TOSCA code from Vector Fields. The three dimensional FEA was conducted in the commercial codes ANSYS and IDEAS. The method for converting the models and calculating the loads transferred to the structure is discussed. The results show the cold mass response to: force collar assembly preload, differential thermal contraction, and operational Lorentz loads. Evaluations are made for two candidate force collar materials and two candidate force collar designs.

Design and Fabrication of the Superconducting Horizontal Bend Magnet for the Super High Momentum Spectrometer at Jefferson Lab

A collaboration exists between NSCL and JLab to design and build JLabs Super High Momentum Spectrometer (SHMS) horizontal bend magnet that allows the bending of the 12 GeV/c particles horizontally by 3° to allow SHMS to reach angles as low as 5.5°. Two full size coils have been wound and are cold tested for both magnetic and structural properties. Each coil is built from 90 layers of single-turn SSC outer conductor cable. An initial test coil with one third the turns was fabricated to demonstrate that the unique saddle shape with fully contoured ends could be wound with Rutherford superconducting cable. Learned lessons during the trial winding were integrated into the two complete full-scale coils that are now installed in the helium vessel. The fabrication of the iron yoke, cold mass, and thermal shield is complete, and assembly of the vacuum vessel is in progress. This paper presents the process and progress along with the modified magnet design to reduce the fringe field in the primary beam region and also includes the impact of the changes on coil forces and coil restraint system.

Coupled Transient Finite Element Simulation of Quench in Jefferson Lab's 11 GeV Super High Momentum Spectrometer Superconducting Magnets

This paper presents coupled transient thermal and electromagnetic finite element analysis of quench in the Q2, Q3, and dipole superconducting magnets using Vector Fields Quench code. Detailed temperature distribution within coils and aluminum force collars were computed at each time step. Both normal (quench with dump resistor) and worst-case (quench without dump resistor) scenarios were simulated to investigate the maximum temperatures. Two simulation methods were utilized, and their algorithms, implementation, advantages, and disadvantages are discussed. The first method simulated the coil using nonlinear transient thermal analysis directly linked with the transient circuit analysis. It was faster because only the coil was meshed and no eddy current was modeled. The second method simulated the whole magnet including the coil, the force collar, and the iron yoke. It coupled thermal analysis with transient electromagnetic field analysis which modeled electromagnetic fields including eddy currents within the force collar. Since eddy currents and temperature in the force collars were calculated in various configurations, segmentation of the force collars was optimized under the condition of fast discharge.

Magnetic measurements of large aperture superconducting quadrupole magnets for TJNAF's High Momentum Spectrometer

The results of the field mapping measurements of Thomas Jefferson National Accelerator Facilitys three large aperture, cold iron, laminated yoke superconducting quadrupole magnets for the High Momentum Spectrometer will be presented. These magnets were mapped using a rotating coil assembly housed within a G-10 drum. A description of the apparatus and technique used to map the magnets over an excitation range of 0 to 2 Tesla will be described. This method of mapping provides for an almost real time measurement of field strength, effective field length, field gradient, transfer function and the determination of symmetry planes. The hysteresis loop and affects of eddy currents will be shown. A comparison of the measured field values with calculated values will also be given.

Commissioning of Horizontal-Bend Superconducting Magnet for Jefferson Lab's 11-GeV Super High Momentum Spectrometer

Commissioning of the characteristics of the superconducting high momentum spectrometer horizontal-bend (HB) magnet was presented. The precommissioning peer review of the magnet uncovered issues with eddy currents in the thermal shield, resulting in additional testing and modeling of the magnet. A three-stage test plan was discussed. A solution of using a small dump resistor and a warm thermal shield was presented. Analyses illustrated that it was safe to run the magnet to full test current. The HB magnet was successfully cooled at 4 K and reached its maximum test current of 4000 A.

CRYOSTAT DESIGN AND ANALYSIS OF THE SUPERCONDUCTING MAGNETS FOR JEFFERSON LAB’S 11 GEV/C SUPER HIGH MOMENTUM SPECTROMETER

This paper describes the mechanical design and analysis of the cryostats for the two cos(2θ) quadrupoles and the cos(θ) dipole. All the magnets are currently being bid for commercial fabrication. The results of finite element analysis for the magnet cryostat helium vessels and outer vacuum chambers which investigate the mechanical integrity under maximum allowable internal working pressure, maximum allowable external working pressure, and cryogenic temperature are discussed. The allowable stress criterion is determined based on the allowable stress philosophy of the ASME codes. The computed cryogenic heat load of the magnets is compared with the allowable cryogenic consumption budget. The presented cool‐down time of the magnets was studied under the conditions of a limited supply rate and a controlled temperature differential of 50 K in the magnets.