Reacting both to the preliminary results of the neutron analysis student experiment and to the crew's request for additional things to do, Gerald Fishman of Teledyne Brown Engineering, Inc., Huntsville, Ala., proposed a complementary analysis of the neutron flux aboard Skylab. Like Terry Quist's experiment, the measurement technique was passive while in orbit, but it made use of a different detection device. Rather than using the solid-state track detector, it utilized the fact that nuclear particles such as protons and neutrons are capable of transforming stable nuclei into radioactive nuclei, which emit gamma rays with a known energy of decay.
Four "activation packets" containing samples of tantalum, nickel, titanium, hafnium, and cadmium-covered tantalum were launched with the third crew. During the fifth day of its mission, these packets were deployed in the workshop, one in a film-vault drawer, one on the outside of a water-storage tank, one on the dome of the forward compartment in the workshop, and one on the outside wall of the sleep compartment. These packets remained in place for 76 days, after which they were returned to Earth by the crew. In addition to these specially designed activation packets, a large sample of stainless steel from an experiment container and samples of tantalum and indium antimonide from other Skylab experiments were returned for analysis.
A low-level gamma-ray spectrometer system measured the gamma-ray decay rates of all samples over an extended period of time after their return to Earth. All induced radioactivities were found to be very weak. However, the neutron fluxes derived from the demonstration compared well with those derived from analysis of Quist's experiment. In particular, Fishman's results confirmed that the Skylab neutron environment was dominated by high-energy or fast neutrons and that their flux was higher than previously predicted.
The data provided by this demonstration, together with that from Quist's experiment, should provide assistance in the planning and analysis of future particle-physics experiments and astronomy experiments that utilize X-ray, gamma-ray, and other high-energy phenomena to explore the universe.