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

Ghoshal

Fair

et al. 2020

Self Cite

The Super High Momentum Spectrometer (SHMS) of Hall C, part of the 12 GeV Upgrade at Jefferson Lab, was successfully commissioned in 2017. Early operation shows that fast dumps of the SHMS Q2/Q3 and Dipole superconducting magnets triggered quenches, causing some level of operational difficulty. Tests and detailed analyses indicate that a fast discharge produces a fast current decay, which results in substantial AC loss in the conductor and subsequently triggers a quench-back effect. The OPERA/ELECTRA software package was used to calculate the amount of heat deposited in the copper stabilizer from a fast current decay. The magnets' external protection dump resistor values were lowered to slow the fast dumping of the magnet's current, which therefore reduces or eliminates the quench-back effects. A worst-case adiabatic quench scenario was analyzed, assuming no external dump resistor and no liquid helium surrounding the coil, to ensure the safety of the magnets. The stress levels in the coil imposed by winding, collaring preload, Lorentz force, and temperature gradient during a quench, were also examined. The Tsai-Wu material failure criterion was used to determine the acceptable combined stress level. Linear orthotropic analysis of the coil indicates that the magnets can be operated safely with appropriately sized dump resistors. Fast dump tests with the modified dump resistors have been planned to verify the performance and suitability.  Index Terms-Magnet, fast discharge, superconducting, AC loss, quench-back, dump resistor, Tsai-Wu criterion I. INTRODUCTION Jefferson Lab's 11 GeV Super High Momentum Spectrometer (SHMS), consisting of Horizontal Bend (HB), Q1, Q2, Q3, and Dipole magnets has been commissioned successfully [1]-[5] with all magnets achieving the required 11 GeV specifications. Fig. 1 indicates the layout of all five superconducting magnets in experimental Hall C [5].Table 1 summarizes the key design parameters for the magnets. The magnet design employs 36-strand NbTi-Rutherford cable, originally manufactured for the dipoles of the now abandoned Superconducting Super Collider (SSC) [5]. The HB and Q1 used bare SSC cable while the Q2, Q3, and the Cos θ Dipole used copper stabilized SSC cable. During pre-commissioning, the HB experienced a series of training quenches, starting at 2640 A, before reaching 4000 A (3900 A is required for 11 The Manuscript received XXXXXX.

mentioning

confidence: 99%

Quench-Back Management for Fast Decaying Currents in SHMS Superconducting Magnets at Jefferson Lab

Ghoshal

Fair

et al. 2020

Self Cite

“…No quench-back perturbations or cryogenic effects were observed. Post-dump Q3 (1) 3,000 4.67 1.48 4.69 1.49 Q3 (1) 3,500 4.71 1.52 4.73 1.54 Q3 (2) 3,000 4.65 1.50 5.60 2.49 Q3 (2) 3,500 4.65 1.50 9.05 3.10 Dipole (3) 3,000 4.67 1.50 4.71 1.54 Dipole (3) 3,450 4.67 1.50 4.72 1.55 Dipole (2) 3,000 4.59 1.52 6.17 3.22 Dipole (2) 3,308 Rd = 0.0075 ; (2) Rd = 0.075  (design value); (3) Rd = 0.025  Table II compares the responses of the average coil temperature (from four temperature sensors, each placed on individual coil cold mass) and helium pressure with the reduced dump resistor and the original dump resistor. The average coil temperature would increase to a peak value after a fast dump, called the peak average coil temperature, before declining.…”

Section: A Test Results Of the Q3mentioning

confidence: 99%

“…Efferson Lab's 11 GeV Super High Momentum Spectrometer (SHMS)-comprising of the following dipole and quadrupole magnets: Horizontal Bend (HB) dipole, Q1, Q2, Q3, and main Dipole-has been successfully commissioned and in operation since 2017. The Q1 was commissioned in April 2015; HB in January 2016; Q2 in December 2016; and Q3 and Dipole in February 2017 [1][2][3][4][5]. All five superconducting magnets met their maximum current operational levels at the 11 GeV specifications for Hall C [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Test Results of Fast Decaying Current-Induced AC Losses in SHMS Superconducting Magnets at Jefferson Lab

Lassiter

Ghoshal

et al. 2020

Self Cite

The 11 GeV Super High Momentum Spectrometer (SHMS) of Hall C, part of the recent 12 GeV accelerator Upgrade at Jefferson Lab, was successfully commissioned in 2017. Fast current discharges of the SHMS Q2, Q3 quadrupoles and dipole superconducting magnets experienced some level of operational difficulty, during commissioning and normal operation. Measurements and analyses demonstrate that the fast current discharge leads to substantial AC losses in the conductor and subsequently triggers a quench-back effect. The details of the measurements and analyses have been reported previously. This paper focuses on the test results of the magnets using a reduced value of the protection dump resistor for each magnet to lower the current decay rate. The test results confirmed that the reduced dump resistances eliminated the quench-back effect for the SHMS Q2, Q3 and Dipole magnets, thus improving their cryogenic operability.

“…(fforest@sigmaphi.fr) Horizontal Bend (HB) Dipole and the Q1 quadrupole. Both have been tested and accepted [4][5][6.This paper is concerned with the final assembly and factory testing of the SHMS Q2 and Q3 [2] identical quadrupoles and the SHMS Dipole [3]. The Q2, Q3 and Dipole are under construction with SigmaPhi located in Vannes, Brittany, France as the result of a pair of design build contracts issued late in 2010.…”

Section: Introductionmentioning

confidence: 99%

Final Assembly and Factory Testing of the Jefferson Lab SHMS Spectrometer Quadrupole and Dipole Superconducting Magnets

Brindza

Lassiter

et al. 2017

Self Cite

Jefferson Lab is constructing an 11 Gev/c electron spectrometer called the Super High Momentum Spectrometer (SHMS) as part of the 12 GeV JLAB upgrade for experimental Hall C. Three of the five superconducting(SC) SHMS magnets are under construction at SigmaPhi in Vannes France as a result of an international competition for design and fabrication. The three magnets Q2 and Q3 60 cm bore quadrupoles and the 60 cm warm bore dipole are complete or near complete and have many design features in common. All three magnets share a common superconductor, collaring system, cryostat design, cold to warm support, cryogenic interface, burnout resistant current leads, DC power supply, quench protection, instrumentation and controls. The three magnets are collared, installed in cryostats and welded up and in various stages of final testing. The Q2 quadrupole is due to ship from France to America in August arriving during this ASC conference and has passed all final hipot, leak and pressure tests. The dipole is in leak and pressure testing as of July 2016 while the Q3 quadrupole requires some outer vacuum vessel assembly. Delivery of the Q3 and Dipole magnets will follow the Q2 at about 1 month intervals. Factory testing have included hipot and electrical tests, magnetic tests at low field, mechanical alignments to center the coils, leak tests and ASME Code required pressure tests. Upon installation in Hall C at JLAB cold testing will commence.