Character of the Radiation Field and Shielding at the 184-Inch Cyclotron.
Abstract
The beam of 200 Mev deuterons in the 184-inch cyclotron gives rise to a conical spray of fast neutrons. (Refer to papers A 10 and A 11 of this meeting) with an upper limit of neutron energy somewhat above 100 Mev. The angle of the cone from axis to half-height is about 5.5 for a target of high atomic number, as measured by Helmholz, MacMillan, and Sewell with carbon detectors. In planning for final shielding of the cyclotron It was necessary to study the attenuation of the neutron beam in concrete. Due to the nature of the information desired the experimental arrangement employed was that shown in Figure 1. The monitor and detector employed were aluminum-walled ionization chambers, with DC Amplification, indicating on microammeters placed outside the magnetic field of the cyclotron. With this same arrangement data were also obtained with water as an absorber, contained in steel tanks made to fit Into the cavity and in front of it. Results of these measurements are given in Figure 2(a). The data for water have been corrected for the absorbing contribution of the tank walls. The displacements of the linear portions of the absorption plots are evidence of transition effects to be discussed later in this paper. In Figure 2(b) are shown concrete absorption data obtained with carbon disc detectors using the C 12 (n,2n) C 11 reaction whose threshold is about 20 Mev.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 19, 1947
- Accession Number
- ADA319220
Entities
People
- B. J. Moyer
- H. York
- N. Knable
- Robert Hildebrand
- T. J. Parmley
Organizations
- Oak Ridge National Laboratory