Test Results of the LARP HQ02b Magnet at 1.9 K

Abstract

The HQ magnet is a 120 mm aperture, 1-meter-long Nb3Sn quadrupole developed by the LARP collaboration in the framework of the High-Luminosity LHC project. A first series of coils was assembled and tested in 5 assemblies of the HQ01 series. The HQ01e model achieved a maximum gradient of 170 T/m at 4.5 K at LBNL in 2010-2011 and reached 184 T/m at 1.9 K at CERN in 2012. A new series of coils incorporating major design changes was fabricated for the HQ02 series. The first model, HQ02a, was tested at Fermilab where it reached 98% of the short sample limit at 4.5 K with a gradient of 182 T/m in 2013. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased pre-load, quench origin and propagation, and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the Coupling-Loss Induced Quench (CLIQ) system. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased preload, quench origin and propagation, and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the Coupling-Loss Induced Quench (CLIQ) system.

Test Results of the LARP Nb3Sn Quadrupole HQ03a

“…The HQ02a model confirmed that the previous performance issues had been resolved, but its gradient was limited to 182 T/m due to the choice of a conservative pre-load level [15][16][17]. The next assembly, HQ02b, featured an increased pre-load and achieved a maximum gradient of 194 T/m at 1.9K, corresponding to 94% of the short sample limit [18][19]. In parallel, a third series of coils was fabricated to consistently apply the optimized design solutions, and improve the coil-tocoil uniformity [20].…”

Analysis of Field Errors for LARP Nb$_3$ Sn HQ03 Quadrupole Magnet

“…In LARP HQ02 magnet, a dummy shim consisting of bronze and carbon steel was successfully fabricated and installed. The mechanical stability of the shim was demonstrated during the magnet cold test and no obvious impact on the magnet quench performance was observed [11].…”

“…Improved insulation schemes and electrical quality assurance procedures were also implemented [9]. As a result, HQ02 magnets had no electrical failures as observed in HQ01 and achieved higher performance, i.e., 98% SSL at 4.5 K and 90% of SSL at 1.9 K [10], [11]. In addition, Rutherford cables with a stainless steel core were used in HQ02 magnets to suppress the strong inter-strand coupling current effects observed in HQ01 magnets [10]- [13].…”

Fabrication of First 4-m Coils for the LARP MQXFA Quadrupole and Assembly in Mirror Structure

“…The bore size was then increased to 120 mm in the High-Field Quads (HQ) and became the testing ground for the final 150- mm-aperture MQXF IR quad design. The key features include spliceless two-layer coil design [6], shell based support structure with bladder and key assembly [7][8][9], provisions to accommodate cable dimensional changes during reaction [10], alignment and field quality [11]. The first long coils were designed to provide 4.0 meters in magnetic length.…”