The test of LMQXFB04 (Q2 cold mass containing MQXFB04 and the corrector MCBXFB02b) has been completed, making it the fourth consecutive MQXFB magnet (CERN-produced Nb3Sn triple quadrupole magnet series), to reach the HL-LHC requirements for operation, after MQXFBP3, MQXFB02, and MQXFB03.
MQXFB04 reached target current at 1.9 K (nominal current plus 300 A), as required by the HL-LHC project, and showed good memory after a thermal cycle with only one training quench above nominal current to reach the target current.
The test started in April 2024, and MQXFB04 reached nominal current plus 300 A after three quenches. No measurable V-I was observed up to the tested current. 4.5 K tests and ramp rate tests up to 100 A/s showed that the magnet behaves like the short models and MQXFB03, with no performance limitation and a large temperature margin for operation. As with all MQXFB 7.15-metre-long magnets - six of which have been tested so far, there was no performance degradation after a thermal cycle. The final electrical tests were successfully completed, including the high voltage insulation test at 100 K and 1 bar. The corrector was powered in individual and combined mode without quench, and all the circuits were powered together (main magnet + corrector) at nominal current during an 8-hour plateau.
MQXFB04 was assembled using the same procedures as MQXFB03, demonstrating the reproducibility of the changes implemented in coil manufacturing to address the performance limitations observed in the previous magnets (MQXFBP1, MQXFBP2, MQXFBP3 and MQXFB02).
This result is significant, giving us confidence on the production of MQXFB magnets as series production continues, with the target of testing MQXFB05 later this year and MQXFB06 at the beginning of 2025. The Q2 cold mass containing MQXFB03 will be also tested in autumn 2024.
MQXFB04 is the first virgin MQXFB magnet assembled with a corrector in a Q2 cold mass since all previous magnets were tested first in a temporary cold mass. The first fully qualified cryo-assembly of WP3 is ready for its final preparation activities before the installation on HL-LHC.
Read more about HL-LHC magnet progress in the latest Collaboration Board Newsletter!
By Susana Izquierdo Bermudez