Radiation and magnetic field effects on commercial DC-DC converters for HL-LHC experiments

THE High Luminosity upgrade of the Large Hadron Collider will pose new challenges to the installed detectors. Higher beam background, combined with new requirements in terms of power supply for the upgraded detectors, and the presence of magnetic fields up to 1 T, make the choice of power supply electronic components a crucial point for the successful operation of the detectors for the new physics run. We took the case of the ATLAS New Small Wheel muon detector installation [1], foreseen for the Phase I upgrade, which will integrate over its lifetime a Total Ionizing Dose (TID) of 1.7 kGy, up to 3×1014 1 MeV-equivalent n/cm2, and will operate in a magnetic field ranging between 0.3 and 0.6 T [2], [3], [4]. We carried out a test campaign on different DC-DC power converters and voltage regulators, by exposing test modules to gamma-rays up to 4 kGy TID, neutrons up to 5×1014 n/cm2, protons up to 5×1012 p/cm2, with a wide range of integrated doses and fluences, and magnetic field up to 1 T. A list of candidate devices was identified by a combination of market survey and recommendation. The devices fall into two categories: single-inductor buck converters are intended for one-step reduction of a 12 V-24 V supply voltage to the delivery voltage; low-dropout voltage regulators (LDOs) may optionally follow the buck converters for noise reduction or to provide additional voltages. The selected candidate parts include a variety of desirable features, such as multiple outputs (LTM4619, LTM4628, ADP5052), low radiated noise (LTM8033), or integrated magnetics (LTM8033, LTM4619, LTM4628).