Luca Ghislotti

GAPS (General AntiParticle Spectrometer) is a stratospheric balloon experiment designed to detect low-energy cosmic ray antinuclei (<0.25 GeV) as an indirect signature of dark matter. The experiment exploits an innovative particle identification approach based on the formation of an excited atom and its consequent de-excitation and decay. GAPS will provide unprecedented sensitivity to cosmic antideuterons, an antiproton spectrum in a hitherto unexplored energy range and high sensitivity to cosmic antihelium. The first flight is foreseen to take place from the McMurdo Station in Antarctica during the austral summer of 2024. The instrument is currently undergoing integration and calibration in anticipation of launch. In this paper, the latest tracker electronics energy threshold calibration results will be presented.

This work describes a low-noise charge sensitive amplifier designed in a commercial 65nm CMOS technology for the second flight of the General AntiParticle Spectrometer balloon experiment, aimed at the indirect search of dark matter. The circuit has been developed as part of the upgrade of the chip employed in the readout of the lithium-drifted silicon detectors of the inner tracker and features dynamic signal compression to cope with the wide input dynamic range. A novel solution using dynamic threshold MOSFETs for the non-linear feedback capacitor implementation has been investigated. The paper will discuss the amplifier architecture, with a focus on the input and feedback device design and the relevant simulation results.

The General Antiparticle Spectrometer (GAPS) is a balloon-borne experiment designed to search for low-energy cosmic-ray antinuclei as a potential indirect signature of dark matter. Over the course of at least three long-duration flights over Antarctica, it will explore the sub-250 MeV/n energy range with sensitivity to antideuterons and antihelium, while also extending antiproton measurements below 100 MeV. The instrument features a tracker built from more than one thousand lithium-drifted silicon detectors, each read out by a dedicated custom integrated circuit. With the first flight scheduled for the austral summer of 2025, a new prototype chip, ANTARES4, has been developed using a commercial 65 nm complementary metal-oxide semiconductor process for use in the second flight. It integrates eight independent analog channels, each incorporating a low-noise charge-sensitive amplifier with dynamic signal compression, a CR–RC shaping stage with eight selectable peaking times, and on-chip calibration circuitry. The charge-sensitive amplifier uses metal-oxide semiconductor feedback elements with voltage-dependent capacitance to support the wide input energy range from 10 keV to 100 MeV. Four alternative feedback implementations are included to compare performance and design trade-offs. Leakage current compensation up to 200 nA per detector strip is provided by a Krummenacher current-feedback network. This paper presents the design and architecture of ANTARES4, highlighting the motivations, design drivers, and performance requirements that guided its development.