Abstract
Cryogenic bypass diodes are part of the baseline powering layout for the circuits of the new ${\mathrm{Nb}}_{3}\mathrm{Sn}$ based final focus magnets of the high luminosity Large Hadron Collider. They will protect the magnets against excessive transient voltages during a nonuniform quenching process. The diodes are located inside an extension to the magnet cryostat, operated in superfluid helium and exposed to ionizing radiation. Therefore, the radiation tolerance of different types of diodes has been tested at cryogenic temperatures in CERN's CHARM irradiation test facility during its 2018 run. The forward bias characteristics, the turn-on voltage and the reverse blocking voltage of each diode were measured weekly at 4.2 K and 77 K, as a function of the accumulated radiation dose. The diodes were submitted to a total dose close to 12 kGy and a 1 MeV neutron equivalent fluence of $2.2\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$. After the end of the irradiation program the annealing behavior of the diodes was tested by increasing the temperature slowly to 293 K. This paper describes the experimental setup, the measurement procedure and the analysis of the measurements performed during the irradiation program as well as the results of the annealing study.
Highlights
CERN’s Large Hadron Collider (LHC) and its upgrade high-luminosity LHC (HL-LHC) rely on superconducting magnets to achieve high magnetic fields and large field gradients, which are necessary to guide high energy hadrons on a circular trajectory and to focus the charged particle beams in four interaction points where two counterrotating beams collide
The new HL-LHC final focus quadrupole magnets, called the inner triplets, will be installed in the high luminosity interaction regions located at IR1 (ATLAS) and IR5 (CMS) [1]
This paper describes the experimental setup of the irradiation program and its results
Summary
CERN’s Large Hadron Collider (LHC) and its upgrade high-luminosity LHC (HL-LHC) rely on superconducting magnets to achieve high magnetic fields and large field gradients, which are necessary to guide high energy hadrons on a circular trajectory and to focus the charged particle beams in four interaction points where two counterrotating beams collide. The diodes in the LHC main dipole and quadrupole magnets are mounted in proximity to the magnets allowing short, local routing of the current bus bars Due to their proximity to the beam axis, the diodes are impacted by secondary particle debris from interaction of the beams with residual gas molecules or by collision debris from the interaction region. The new HL-LHC final focus quadrupole magnets, called the inner triplets, will be installed in the high luminosity interaction regions located at IR1 (ATLAS) and IR5 (CMS) [1]. They will be based on Nb3Sn superconducting coils [1,2,3,4]. This paper describes the experimental setup of the irradiation program and its results
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