This proposal seeks support for the continuation of a new suborbital program (helix the high-energy light isotope experiment), designed to make measurements of the isotopic composition of light…

The University of Chicago was awarded a $4.75M research grant on November 17, 2022, to support the continuation of the HELIX (High-Energy Light Isotope Experiment), a suborbital program designed to measure the isotopic composition of light cosmic-ray nuclei in the energy range of approximately 200 million to 10 billion electron volts per nucleon. The project extends beyond existing measurements from the ACE/CRIS mission by over an order of magnitude into energy ranges where fully resolved measurements do not currently exist. The program aims to advance understanding of cosmic-ray propagation in the galaxy and address recent anomalies in cosmic-ray measurements, including energy spectra variations and positron fraction increases at higher energies. Primary scientific objectives include high-statistics measurements of beryllium isotope ratios, helium isotope ratios, and neon isotope measurements, along with mass-resolved measurements of lithium and boron isotopes.

The research will be conducted by a team of U.S. scientists and engineers with extensive experience in cosmic-ray observations through balloon and space missions, particularly in magnet spectrometry. The award is structured as a research grant funded by a civilian federal agency and is not designated as a set-aside contract. The contract has an ultimate completion date of November 16, 2026, and will be performed at the University of Chicago's location in Chicago, Illinois. This project represents a continuation of the university's significant contributions to space science research and demonstrates its capability to manage complex, multidisciplinary scientific initiatives requiring specialized expertise in particle detection and cosmic-ray analysis.

This proposal seeks support for the continuation of a new suborbital program (helix the high-energy light isotope experiment), designed to make measurements of the isotopic composition of light cosmic-RAY nuclei from ~200 MEV/NUC to ~10 GEV/NUC. Past measurements of this kind have provided profound insights into the nature and origin of cosmic rays, revealing, for instance, information on acceleration and confinement time scales, and exposing some conspicuous discrepancies between solar and cosmicray abundances. The most detailed information currently available comes from the ACE/cris mission but is restricted to energies below a few 100 MEV/NUC. Helix aims at extending this energy range by over an order of magnitude, where, in many cases, no fully resolved measurements exist, and where relativistic time dilation affects the apparent lifetime of radioactive clock nuclei. The helix measurements will provide essential information for understanding the propagation history of cosmic rays in the galaxy. This is crucial for properly interpreting several intriguing anomalies reported in recent cosmic-RAY measurements, pertaining to the energy spectra of protons, helium, and heavier nuclei, and to the anomalous rise in the positron fraction at higher energy. The primary scientific goals of the full helix program are: - a high-statistics measurement of the 10BE/9BE 'clock ratio' to ~10 GEV/NUC - a high-statistics measurement of the 3HE/4HE ratio to ~12GEV/NUC - the first measurements of 22NE/20NE above 1 GEV/NUC - the first mass-resolved measurements of 7LI/6LI, and 10B/11B above 1 GEV//NUC a number of secondary goals will also be pursued including the measurement of several other isotopic and elemental abundance ratios and fluxes, the proposed work will be conducted by a team of US scientists and engineers with extensive experience in cosmic-RAY observations on balloons or in space, and, specifically in magnet spectroscopy, with the smili, p-bar, and heat programs. Significant participation from a crew of more than 10 graduate, post-graduate, and undergraduate students forms an important educational element of the program.