04/06/2026
By Marian Jandel
The Kennedy College of Sciences, Department of Physics and Applied Physics, invites you to attend a Master’s Thesis defense by Daniel Fernandez on “Development of Preamplifier for High Resolution Measurements of Neutron-Capture Gamma Rays.”
Candidate Name: Daniel Fernandez
Degree: Master’s
Defense Date: Friday, April 10, 2026
Time: 2 to 4 p.m.
Location: 104 Olsen Hall, North Campus
Thesis/Dissertation Title: Development of Preamplifier for High Resolution Measurements of Neutron-Capture Gamma Rays
Committee:
- Advisor: Marian Jandel, Ph.D., Department of Physics and applied Physics, University of Massachusetts Lowell
- Mark Tries, Ph.D., Department of Physics and applied Physics, University of Massachusetts Lowell
- Andrew Rogers, Ph.D., Department of Physics and applied Physics, University of Massachusetts Lowell
Brief Abstract:
Transistor-reset preamplifiers (TRP) are often used in cooled semiconductor-based radiation detectors for high count rate applications to mitigate saturation effects found in more common RC-based charge sensitive preamplifier (CSP) configurations. This architecture additionally improves energy resolution by replacing the feedback resistor responsible for discharging the parallel capacitor with a transistor switch, thereby reducing the thermal noise introduced by the former. The following work details the development of an active high-pass filter to couple and shape the fast AC component of the resulting voltage steps to a 14 bit waveform digitizer. We present two circuit designs and validate performance by measuring the energy resolution of 1.4 MeV gamma rays from Eu-152. Measurement of capture gamma rays from the (nat}Gd(n,g) and {nat}Fe(n,g) reactions are also presented for both designs to determine stability and uniformity at high count rates with energies up to 9 MeV.