NUCLEAR EMULSIONS - TEXAS I

The objective of the flight was to expose a large area block of nuclear emulsions to investigate the existence of heavy nuclei belonging to the iron group and beyond (better known as trans-iron nuclei) in the primary cosmic radiation. The project was carried out by Dr. Peter Fowler from the H. H. Wills Physics Laboratory at the University of Bristol.

The "large area" detector designed for the flight was conditioned by the need to be sure that each individual heavy track was indeed caused by a particle with Z > 26, and not by a slow Fe nucleus. The exposure was therefore made over Texas where the Earth's geomagnetic field imposed a cutoff that practically removed all the slow primaries which arrive at higher geomagnetic latitudes. That's why the experiment would be known in the literature as "Texas I". It consisted of a 4 layer sandwich of photographic emulsions and lead measuring 4.5 square meters. The emulsion were Ilford G5 photographic plates composed by a suspension of AgBr crystals in gelatine which could be affected by the passage through them of any electrically charged atomic particle. The 3 Pb layers were incorporated in the detector to exclude from consideration a small proportion of the flux which was intercepted by the detector on the ascent or (to a lesser degree) on the descent.

Balloon launched on: 10/6/1966 at 18:26 cst
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Center for Atmospheric Research (NCAR)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven 5.000.000 cuft (0.75 mil. X-124)
Balloon serial number: 2323-545-8239 Serial Nº 132
Flight identification number: 256P
End of flight (L for landing time, W for last contact, otherwise termination time): 10/7/1966 at 8:26 cst
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 14 h 30 m
Landing site: 14 miles SW of Bracketville, Texas, US
Payload weight: 780 lbs.

After examining the plates, several examples of highly charged (Z > 40) cosmic ray primaries have been observed and reported for the first time in a balloon flight.

• Balloon Flight Record Facilities for Atmospheric Research Nº 2, Winter 1966/67
• Emulsion Detector Proceedings, 5th AFCRL Scientific Balloon Symposium, (1968) p. 89
• NCAR Scientific Balloon Facility Annual Report, 1966 National Center for Atmospheric Research, January 1967
• Production and Propagation of Particles with A>81 in the Galaxy Physical Review D, vol. 5, Issue 2, pp. 307
• Study of the Charge Spectrum of Extremely Heavy Cosmic Rays Using Combined Plastic Detectors and Nuclear Emulsions Physical Review D, vol. 3, Issue 4, pp. 815
• The Charge Spectrum of Very Heavy Cosmic Ray Nuclei roceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 301(1464), 39