Master of Science (MS)


Physics and Astronomy

Document Type



The aim of this project is to build a prototype device that can select electrons of certain energy in order to have a monoenergetic beam suitable for the characterization of radiation detectors. Current options for sources of electrons are either from radioisotopes or accelerator facilities. Radioisotope sources are not tunable in energy since they depend on the nuclear and atomic structures of the daughter nucleus. On the other hand, even though accelerators offer the feature of a variable energy beam, they have limited availability and are not typically run at low intensities. Therefore, the motivation for this thesis is the development of a “table top” device that can be used in the laboratory. Theoretical calculations were performed for the design of the vacuum chamber and the magnet array. Magnetic field mapping was performed between magnets to check for uniformity. The vacuum chamber is made of aluminum with four connections on the sides for different measurements and allowing for pumping. The permanent magnets are positioned above and below the chamber using a holder made of High Density Polyethylene (HDPE) plastic with threaded rods on the corners for height variation. The electron source chosen was a 113Sn sample with an activity of 1.0 ± 0.1 Ci. A silicon detector with three sensitive elements of 3 x 0.5 cm² each on a wafer of 1-mm thickness was used as a diagnostic detector after the device. The whole assembly was kept under vacuum of around 80 mTorr. Energy spectra were taken with a source in line without magnets, and at an angle with magnets for comparison. The results show a selection of electrons in the lower range of the spectrum rejecting the higher energy electrons. Preliminary performance of the prototype device is presented.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Marley, Scott