The Elemental Composition of High-Energy Cosmic Rays: Measurements with TRACER

TL;DR

TRACER is a balloon-borne instrument that measures the composition and energy spectra of heavy cosmic ray elements up to 10^15 eV, revealing similar spectral indices across multiple elements.

Contribution

This paper presents the development and deployment of TRACER, a novel large-area detector for direct measurement of high-energy cosmic ray elemental spectra.

Findings

Measured energy spectra of multiple heavy elements up to 10^14 eV

Found nearly identical spectral indices (~2.65) for all elements

Demonstrated the capability of TRACER for high-energy cosmic ray studies

Abstract

TRACER ('Transition Radiation Array for Cosmic Energetic Radiation') is a balloon borne instrument that has been developed to directly measure the composition and energy spectra of individual heavy elements up to 10^15 eV per particle. TRACER achieves a large geometric factor (5 m^2 sr) through the use of a Transition Radiation Detector utilizing arrays of single wire proportional tubes. TRACER has measured the energy spectra of the elements O, Ne, Mg, Si, S, Ar, Ca, and Fe. The energy spectra reach energies in excess of 10^14 eV per particle and exhibit nearly the same spectral index (2.65 +/- 0.05) for all elements.