Date of Award

Summer 1962

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Barkow, Arthur G.

Second Advisor

Karioris, Frank

Third Advisor

Berners, Edgar


This paper is a final report on the energy spectrum of neutrons from a stopped π interactions. A stack of 50 (2x2) in. 600u G-5 emulsions was exposed to the π beam of the cyclotron at the University of Chicago. The pion flux was 150 π's per cm2 per sec, the contamination was less than 1%, and the neutron background was less than 5% by isotropy measurement of the knock-on protons. A lino spectrum of neutrons is detected after scattering by a continuous spectrum of protons extending from zero to the full neutron energy, with all intermediate energies equally probable. The neutrons after scattering have an energy spectrum similar to that of the protons. By differentiating the knock-on spectrum, one can obtain the spectrum of neutrons produced in π interactions. The data has been programmed for the IBM 650. The results of some 10,000 knock-on proton events indicate that in spite of the 5% isotropy conclusion, there existed an external neutron source. This source, in all probability, originated in the copper degraders used to slow down the pion beam. The presence of this external source is believed to be responsible for the appearance of the peak in the neutron spectrum around an energy of 27 Mev. The results of this experiment indicate that the neutrons produced in π interactions have a Maxwellian distribution with a most probable energy near 5 Mev. It was assumed that the neutron spectrum follows statistical theory and that the peak of the distribution appears at E=T. By integrating the equation for the neutron spectrum as a function of the knock-on proton spectrum, one obtains a theoretical curve for the knock-on proton spectrum. The results show that there is excellent agreement between the experimental and theoretical curves. It can be concluded that from the interactions studied in this experiment, the neutrons follow statistical theory and can be said to have a nuclear temperature of T=5 Mev.