Second test of HQ02: even better

Margarita Synanidi — Wed, 17 Sep 2014 13:36:23 +0000

Second test of HQ02: even better
by Gian Luca Sabbi (LBNL), Ezio Todesco (CERN)

Fig1: First training of HQ02 (red diamonds), slow training at 2.2 K (blue squares), and second test with fast training towards 17 kA (black circles)
Image credit: CERN and US LARP

HQ is a 120 mm aperture Nb₃Sn quadrupole developed by the US LHC Accelerator Research Program (US LARP). It presents all features and technological choices that will be used in the 150 mm quadrupole triplet (QXF in the CERN jargon) for the HL-LHC era.

During the first test, the magnet proved to be able to operate at the nominal current of 15 kA. It has then been pushed towards larger currents (in the LHC we require the magnet to reach 110% of nominal current), showing a pretty long training in the region 15-16 kA [see Fig1]. The analysts suggested to have a second assembly increasing the compression of the coil to guarantee a faster training. In the second test at CERN, the magnet reached nominal current without any quench, and trained to 110% of nominal current in a few quenches. This confirmed once more the validity of mechanical structure, allowing fine tuning of the stress in the coil. HQ outperformed the Nb-Ti twin of the same aperture, which showed a slower training.

The magnet was also used as a test bed for studying quench protection. HL LHC magnets will have a ratio between the stored energy and the coil volume (which absorbs that energy) which is twice of what we have today in the LHC. During the HQ test, special test were done to understand when coil degradation takes place, resulting in broader limits than expected. Moreover, a novel technique (CLIQ) (CLIQ) based on the discharge of a capacitor in the magnet provoking fast quench of the coils, has also been also successfully tested. Results have been presented at the ASC conference in August, where the CLIQ paper got a special award.

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Second test of HQ02: even better