CERN Accelerating science

Article
Report number	FERMILAB-PUB-22-860-TD
Title	Status of the MQXFB Nb$_3$Sn quadrupoles for the HL-LHC
Related title	Status of the MQXFB Nb3Sn quadrupoles for the HL-LHC
Author(s)	Izquierdo Bermudez, Susana (CERN) ; Ambrosio, Giorgio (Fermilab) ; Apollinari, Giorgio (Fermilab) ; Ballarino, Amalia (CERN) ; Barth, Christian (CERN) ; Crouvizier, Mickael Denis (CERN) ; Duarte Ramos, Delio (CERN) ; Devred, Arnaud (CERN) ; Feher, Sandor (Fermilab) ; Felice, Helene (CERN) ; Ferracin, Paolo (LBNL, Berkeley) ; Ferradas Troitino, Jose (CERN) ; Guinchard, Michael (CERN) ; Lusa, Nicholas (CERN) ; Mangiarotti, Franco (CERN) ; Milanese, Attilio (CERN) ; Moros, Alice (CERN) ; Prin, Herve (CERN) ; Russenschuck, Stephan (CERN) ; Sgobba, Stefano (CERN) ; Todesco, Ezio (CERN) ; Willering, Gerard (CERN)
Publication	2023
Imprint	2022
Number of pages	9
In:	IEEE Trans. Appl. Supercond. 33 (2023) 4001209
DOI	10.1109/TASC.2023.3237503
Subject category	Particle Physics - Theory
Accelerator/Facility, Experiment	CERN LHC
Project	CERN HL-LHC
Abstract	The cold powering test of the first two prototypes of the MQXFB quadrupoles (MQXFBP1, now disassembled, and MQXFBP2), the Nb3Sn inner triplet magnets to be installed in the HL-LHC, has validated many features of the design, such as field quality and quench protection, but has found performance limitations. In fact, both magnets showed a similar phenomenology, characterized by reproducible quenches in the straight part inner layer pole turn, with absence of training and limiting the performance at 93% (MQXFBP1) and 98% (MQXFBP2) of the nominal current at 1.9 K, required for HL-LHC operation at 7 TeV. Microstructural inspections of the quenching section of the limiting coil in MQXFBP1 have identified fractured Nb3Sn sub-elements in strands located at one specific position of the inner layer pole turn, allowing to determine the precise origin of the performance limitation. In this paper we outline the strategy that has been defined to address the possible sources of performance limitation, namely coil manufacturing, magnet assembly and integration in the cold mass.
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