Test Results of the LARP Nb3Sn Quadrupole HQ03a

Abstract

Abstract-The US LHC Accelerator Research Program (LARP) has been developing Nb3Sn quadrupoles of increasing performance for the high luminosity upgrade of the Large Hadron Collider. The 120 mm aperture High-field Quadrupole (HQ) models are the last step in the R&D phase supporting the development of the new IR Quadrupoles (MQXF). Three series of HQ coils were fabricated and assembled in a shell-based support structure, progressively optimizing the design and fabrication process. The final set of coils consistently applied the optimized design solutions, and was assembled in the HQ03a model. This paper reports a summary of the HQ03a test results, including training, mechanical performance, field quality and quench studies.

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

“…This proof-of-principle test showed that the capability of the shims installed in the bladder slots can effectively correct the selected low-order geometric harmonics. However, limitations on the correction capability based on the magnetic shims were also observed [15]. For example, the correction on the sextupoles is up to ±2.5 units and up to ±0.3 units for the octupoles at 15000 A, which were lower than the actual amplitudes of the field errors measured in HQ03.…”

“…To verify the computational model of the magnetic shims and their impact on the field errors, magnetic shims made of carbon steel were installed after the first cold test of HQ03 and was tested in the second thermal cycle [15]. Because of the relatively large amplitudes of the field errors, magnetic shims occupied the whole available bladder slots to achieve the maximum correction capability.…”

“…To prove the principle, the shims were installed in the four bladder slots in quadrants 1 and 4 ( Fig. 1), breaking the left-right symmetry, to provide a partial correction of about +2.5 units on b 3 at 15 kA [15]. Longitudinally, the shims covered the whole length of the magnet.…”

“…The core was 25 µm thick and 8 mm wide and biased towards the thick edge of the Rutherford cable, covering about 60% of the available space. While HQ02 and HQ03 used the same nominal core configuration, HQ03 had a smaller dependency of field errors on ramp rates [12], [15]. As an example, Fig.…”

“…The HQ03 magnet used the third generation of coils that were fabricated with the optimized design and improved coil-to-coil uniformity [14]. The magnet reached 90% of SSL at 1.9 K. Detailed test results, including the field quality of HQ03, were presented in [15]. Here, we analyze the measured field errors of HQ03 and compare them with earlier generations of HQ magnets.…”