Cold Test Results of the LARP HQ $\hbox{Nb}_{3} \hbox{Sn}$ Quadrupole Magnet at 1.9 K

Chlachidze

et al. 2017

Abstract-The U.S. LHC Accelerator Research Program, in close collaboration with CERN, has developed three generations of high-gradient quadrupole (HQ) Nb3Sn model magnets, to support the development of the 150 mm aperture Nb3Sn quadrupole magnets for the High-Luminosity LHC. The latest generation, HQ03, featured coils with better uniformity of coil dimensions and properties than the earlier generations. The HQ03 magnet was tested at FNAL, including the field quality study. The profiles of low-order harmonics along the magnet aperture observed at 15 kA, 1.9 K can be traced back to the assembled coil pack before the magnet assembly. Based on the measured harmonics in the magnet center region, the coil block positioning tolerance was analyzed and compared with earlier HQ01 and HQ02 magnets to correlate with coil and magnet fabrication. To study the capability of correcting the low-order non-allowed field errors, magnetic shims were installed in HQ03. The expected shim contribution agreed well with the calculation. For the persistent-current effect, the measured a4 can be related to 4% higher in the strand magnetization of one coil with respect to the other three coils. Finally, we compare the field errors due to the inter-strand coupling currents between HQ03 and HQ02.Index Terms-LARP, Nb3Sn quadrupole magnets, field quality.

Section: Introductionmentioning

confidence: 99%

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

Wang

Chlachidze

et al. 2017

“…The first phase of the HQ program included production of eight coils, and five assembly cycles (HQ01a-HQ01e) [3][4][5][6]. These models, while demonstrating operation well above the HQ target gradient of 170 T/m, were affected by stress degradation, electrical insulation failures, and large dynamic field errors [7][8][9][10]. Detailed analysis [11] led to critical revisions of the coil parameters and components which were validated through dedicated tests in a mirror structure [12][13] and gradually implemented in the HQ02 series [14].…”

Section: Introductionmentioning

confidence: 99%

Test Results of the LARP Nb3Sn Quadrupole HQ03a

DiMarco

Anerella

et al. 2016

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.

“…6, and it is compared to the HQ nominal inductance (measured at low dI/dt [13], a high current value is used for reference). It can be noted that the dynamic effects appreciably affect the curve at the beginning of the decay, when ≲ , where the dynamic inductance is ~30% lower than the nominal one.…”

Section: Dynamic Inductance Experimental Validationmentioning

confidence: 99%

“…In the design 2 the copper-plated bridges are made narrower with respect to the design 1, to allow further space for cooling the coils and also to allow more space for perforation, avoiding the formation of helium bubbles that have been observed in the HQ program. The distance between heating stations is in both cases of the order of 100 mm; having a longitudinal propagation speed of 20 m/s [13], the locations between heating stations get quenched 2.5 ms later, which is considered as an acceptable delay. Terminals of the heating stations are copper-plated to improve current flow uniformity.…”

Section: B Copper-plated Heater Designsmentioning

confidence: 99%

Study of Quench Protection for the Nb₃Sn Low-β Quadrupole for the LHC Luminosity Upgrade (HiLumi-LHC)

Marinozzi

Bellomo

et al. 2015

The HiLumi program is aiming to develop and build new Nb3Sn, high-field (12 T) and large aperture (150 mm) superconducting quadrupoles, which will be inserted in the LHC interaction regions and will provide the final focusing of the beam, in the program of the luminosity upgrade. The quench protection of these magnets is one of the most challenging aspects, mainly because of the large value of the magnet inductance (160 mH for the configuration with two 8 m long magnets in series), of the large value of the stored magnetic energy density in the coils (0.12 J/mm3, a factor 2 larger than in the conventional NbTi quadrupoles) and of the use of Nb3Sn as conductor, which has never been used for large accelerator magnets. Previous works have demonstrated that a "standard" conservative analysis, assuming quench heaters only on the coils outer layer, gives high hot spot temperature, close to the design limit (350 K). In this paper, a new study of quench protection is presented. The benefic effects of large dI/dt during the discharge and other dynamic effects are discussed together with options for having a partial coverage of the inner layer by quench heaters. The analysis is validated by experimental data from R&D Nb3Sn quadrupole magnets.