Balloon-borne particle astrophysics with HELIX
Keith McBride
University of Chicago

Highly energetic astrophysical processes are studied through measurements of cosmic radiation. The mechanisms that accelerate particles to these energies (>1 GeV) have yet to be confirmed, with many candidate sources existing inside the Milky Way. Galactic cosmic rays consist of high-energy nuclei produced within sources and as byproducts of cosmic ray propagation through the Interstellar Medium. To date, many nuclear species have high-precision measurements over large energy ranges. To deepen our understanding of these sources and the propagation of galactic cosmic rays, new isotope measurements of long-lived unstable nuclei such as beryllium-10 provide a unique lifetime constraint on the cosmic-ray halo of the Milky Way. The High Energy Light Isotope eXperiment (HELIX), a balloon-borne magnet spectrometer, directly measures a cosmic ray?s charge, magnetic rigidity, and velocity to identify the isotopes of beryllium and other light nuclei. The HELIX program will resolve the beryllium-10 nuclei from 0.2 GeV/n to beyond 10 GeV/n, extending the resolved spectra measurements by a factor of 10 in energy from previous missions. A high-precision drift chamber tracker in a 1 Tesla magnetic field is used for rigidity measurements and time-of-flight scintillator paddles are used for charge measurements, as well as velocity at lower energies. At higher energies, velocity is measured with an aerogel-based ring-imaging Cherenkov detector. For the sought-after beryllium isotope measurements, HELIX expects to have detected hundreds of events in the energy range of 0.2 GeV/n to 3 GeV/n in its first Arctic flight from Esrange, Sweden during the summer of 2024. I will present an update and overview of the HELIX program, including science goals, highlighting the recent first launch of the payload.

Date:	Mardi, le 25 février 2025
Heure:	15:30
Lieu:	Université McGill
	Bell Room (Rutherford 103)