Introduction

The Trans-Iron Galactic Element Recorder (TIGER) is a balloon borne instrument designed to measure the elemental abundances of Galactic Cosmic Rays. Galactic Cosmic Rays (GCRs) are energetic atomic nuclei that originate from outside our solar system and are believed to be accelerated by exploding stars (supernova) to extremely high energies. These nuclei have been detected and measured at earth by a variety of ground, balloon-borne and space experiments.

GCRs are of particular interest to the astrophysics community since they are one of only two types of matter that can be directly sampled from outside the solar system (the other is extra-solar dust grains found in certain meteorites). They serve as a probe of the galactic cosmic ray source and the interstellar medium within our galaxy.

The TIGER experiment is designed to measure GCRs with atomic number (Z) between 26 (Iron) and 40 (Zirconium). These elements are very rare in galactic cosmic rays and are difficult to measure, requiring large detectors with long duration of exposure and excellent resolution. The first successful TIGER balloon flight was in 1997 from Fort Sumner, NM and lasted about 24 hours. Although the duration of the flight was not long enough to gather many of the rare nuclei heavier than iron, it did prove that TIGER had ample resolution to do so effectively. TIGER was launched again from McMurdo Station, Antarctica in December 2001 and completed a 31.8 day balloon flight at an average altitude of 118,000 feet, thereby setting a record for the longest successful scientific balloon flight. Around 100 particles with Z = 31 and 32 were collected during this flight and some limited statistics were obtained for particles with Z > 32. With the second launch from McMurdo, in December 2003, TIGER added 18 more days of data.

Introduction

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