Silicon controlled switch for detection of ionizing radiation

Abstract

The purpose of this thesis is to utilize the developed knowledge of key semiconductor components at the Naval Postgraduate School (NPS) and build a circuit design toward the specific goal of detecting CS- 137 sources. A Silicon-Controlled Switch (SCS), under the presence of a direct current (DC) voltage bias (VBIAS), was connected in series to a resistor and capacitor (RC) load. Additionally, a photodiode (PD) was connected to the anode gate (AG) of the SCS. The PD produced a triggering current that allowed the SCS-based circuit to create self-terminating pulses by operating in the SCS intermediate state. VBIAS and PD produced current on the AG of the SCS where the methods for triggering self-terminating pulses. Various circuit elements such as a Zener (Zn) diode connected to the AG, feedback resistor (RF), and RC load were varied to achieve diverse pulsation results. The final circuit design produced a circuit that had ten times the resolution and five times the sensitivity of previous NPS silicon controlled rectifier (SCR) based circuits. Additionally, the circuit in this thesis was able to detect AM-241 and CS-137 sources for the first time at NPS. Future NPS thesis research is proposed to further understand and fine-tune semi-conductor– based radiation detectors. It is proposed that future naval feasibility assessments be centered on the signal amplification and processing techniques from SCS-based circuits.