Description of the payload
Is a high-pressure gas ionization detector which provides measurements of total energy and trajectory for heavy nuclei which stop in its active volume.
The main portion of the instrument consists of a gas volume which has an entrance aperture of 1 m x 0.8 m and a sensitive depth of 1.95 m. A thin foil cathode located along the mid-plane of the gas volume is held at a negative high voltage, while the outside of the volume is surrounded by field-shaping electrodes designed to produce a uniform electric field parallel
to the "y" direction. This field causes the ionization electrons produced by the passage of an energetic heavy nucleus to drift to one of two outside surfaces which are divided into a number of anodes which provide measurements of the ionization along well defined segments of the particle's track, the individual anode signals provide multiple measurements of the particle energy loss rate, while their sum gives the total energy.
The particle's trajectory through the gas volume is measured using a set of position-sensitive single-wire proportional counters which sample a small segment of the ionization signs between adjacent chamber anodes. The coordinate parallel to the particle track is obtained from a drift time measurement based on a start signal from a scintillator located above
the ionization chamber and a stop signal from the proportional counter wire. The orthogonal coordinate is obtained using the division of the charge induced on a set of interleaved wedge-shaped electrodes by the proportional counter avalanche.
The ionization chamber is operated in a pressure vessel (which also serves as the balloon gondola) filled with a mixture of 95% Argon plus 5% of Methane at an absolute pressure of ~1 atm. Signals from all of the sensors are processed by
electronics housed in a separate vessel mounted below the ionization chamber.
Details of the balloon flight and scientific outcome
Launch site: Lynn Lake Airport, Manitoba, Canada
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon N41I-8/8/8/8T-39.95
Balloon serial number: R39.95-3-102
Flight identification number: 364N
External references and bibliographical sources
- An Ionization Chamber Based Instrument for Isotopic Composition Studies 20th International Cosmic Ray Conference Moscow, Volume 2, p.386
- Balloon Flight Tests of a Gas-Ionization Chamber-Based Isotope Spectrometer 24th International Cosmic Ray Conference, Vol. 3, held August 28-September 8, 1995 in Rome, Italy
- Identification of energetic heavy isotopes using a gas ionization detector AIP Conference Proceedings 183, 402 (1989)
- NASA Balloon Flights (1989-1998) in NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998