A 300 kA Pulsed Power Supply for LBNF

TL;DR

This paper presents the design and implementation of a robust 300 kA pulsed power supply for LBNF's magnetic horns, emphasizing reliability, fault tolerance, and quick reversal capabilities for neutrino and anti-neutrino production.

Contribution

It introduces a high-current, resonant pulser system with fault tolerance and rapid reversal features tailored for long-term neutrino beam focusing applications.

Findings

Designed a 300 kA pulsed power supply with 800μs pulse duration.

Implemented fault-tolerant circuit modifications for system reliability.

Ensured quick reversal capability for neutrino and anti-neutrino modes.

Abstract

The Long Baseline Neutrino Facility (LBNF) will produce the worlds most intense neutrino beam. Three series connected magnetic horns will require 5kV, 300kA, 800$\mu$s pulses at a rate of 0.7Hz to focus the beam. Fermilab has designed and built pulsed high current supplies for horns in the past. Pulsed currents of 205 kA for Neutrinos at Main Injector (NuMI - NOvA), focusing a 120 GeV beam, and 170 kA for Booster Neutrino Beam (BNB - MiniBooNE) for focusing an 8 GeV beam have been operational for about 18 years. While the magnetic horns are expected to be replaced, the LBNF horn power supply is expected to last the lifetime of the project, 30 years. A resonant, half sine wave pulser was used for NuMI and BNB and has many practical advantages. The system has impedance limited fault currents by design, albeit large ones. That along with the resonant behavior means that thyristor switches are well suited. Many fault modes of the system have also been calculated. Several circuit changes were incorporated so that a single fault can be tolerated. The supply must be reversable to enable both neutrinos and anti-neutrinos to be produced. These reversal requirements required a significant amount of mechanical design and consideration to allow for quick reversal of all the semiconductors.