Measurement of H, He, C and O Cosmic Ray Primaries: Preliminary Results from the CREAM II Experiment

Open Access
Author:
Mognet, Samuel Adam Isaac
Graduate Program:
Physics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 10, 2009
Committee Members:
  • Stephane Coutu, Dissertation Advisor/Co-Advisor
  • Stephane Coutu, Committee Chair/Co-Chair
  • Paul Sommers, Committee Member
  • Richard Wallace Robinett, Committee Member
  • John Andrew Nousek, Committee Member
Keywords:
  • cosmic rays
  • geant4
  • scintillator
Abstract:
The direct measurement of the energy spectrum and composition of the incoming cosmic-ray flux at multi-TeV energies is of great interest. A feature located somewhere between 1000-10,000 TeV in the all-particle spectrum, referred to as the ‘knee’ characterized by a steepening of the power-law flux, has been observed by ground-based detectors for many years. It is believed to be related to an upper limit or change in efficiency of the Galactic accelerators of cosmic rays and/or properties of the propagation of cosmic rays in the Galaxy. Presented here is a preliminary analysis of the flux of primary H, He, C and O cosmic-ray species measured using the CREAM II instrument. This analysis is conducted using the Penn State-built Timing Charge Detector, distinct from other charge detectors used in alternative published CREAM II results. The second Antarctic flight of the CREAM instrument had a ∼ 28 day flight in the 2005-2006 Antarctic flight season. The instrument was launched on December 16th 2005 from Williams Field near McMurdo Station, Antarctica. The analysis presented here used events collected throughout the flight to calibrate the charge response of the Timing Charge Detector. High-energy events collected during the entire flight time (except for the first ∼ 3.5 days which were used for high-voltage tuning) are also analyzed here. Also presented in this thesis is a novel optical simulation of the Timing Charge Detector used in the various flights of the CREAM instrument. The model suggests fundamental limitations on the timing resolution of the detector arising purely from photon propagation physics in the scintillation and light-guide elements.