First operation of LArTPC in the stratosphere as an engineering GRAMS balloon flight (eGRAMS)

TL;DR

This paper reports the first successful operation of a Liquid Argon Time Projection Chamber (LArTPC) at balloon altitudes during a 3-hour scientific flight, demonstrating its potential for astrophysics and dark matter research.

Contribution

It is the first to operate a LArTPC in the stratosphere, validating its use in high-altitude environments for cosmic-ray detection and future astrophysical missions.

Findings

Successfully operated LArTPC at 28.9 km altitude

Collected 0.5 million cosmic-ray events

Demonstrated feasibility for future high-altitude experiments

Abstract

GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite experiment utilizing a LArTPC (Liquid Argon Time Projection Chamber), to simultaneously target astrophysical observations of cosmic MeV gamma-rays and conduct an indirect dark matter search using antimatter. While LArTPCs are widely used in particle physics experiments, they have never been operated at balloon altitudes. An engineering balloon flight with a small-scale LArTPC (eGRAMS) was conducted on July 27th, 2023, to establish a system for safely operating a LArTPC at balloon altitudes and to obtain cosmic-ray data from the LArTPC. The flight was launched from the Japan Aerospace Exploration Agency's (JAXA) Taiki Aerospace Research Field in Hokkaido, Japan. The total flight duration was 3 hours and 12 minutes, including a level flight of 44 minutes at a maximum altitude of 28.9 km. The flight system was landed on the sea and successfully recovered. The LArTPC was successfully operated throughout the flight, and about 0.5 million events of the cosmic-ray data including muons, protons, and Compton scattering gamma-ray candidates, were collected. This pioneering flight demonstrates the feasibility of operating a LArTPC in high-altitude environments, paving the way for future GRAMS missions and advancing our capabilities in MeV gamma-ray astronomy and dark matter research.