My research group has been focusing on advanced radiation detector and nuclear instrumentation developments. Particularly, we developed the THick Gas Electron Multiplier (THGEM) detector, an advanced gaseous radiation detector, which showed an outstanding performance in contrast to the traditional gaseous detectors. We also developed new digital signal processing systems for radiation spectrometry and imaging. Selected current research projects are listed below.
THGEM neutron imaging detector development In 2013, we successfully developed a THGEM X-ray imaging detector.
The core work of this project was to devise a simple and efficient 2-D position readout board. For 2-D position encoding, we developed a digital signal processing system using time to digital converters and a field programmable gate array processor, which required an extensive amount of work in terms of circuit fabrication and processor programming. The detector was successfully tested for alpha and X-ray imaging. Founded on this work, we are currently designing an efficient neutron converter in order to develop a digital neutron imaging detector.
THGEM multi-element neutron dosemeter and 2-D neutron-gamma dosemeter developments
Tissue-equivalent gaseous proportional counters are made of tissue-equivalent plastics and filled with tissue-equivalent gases, which makes them the most accurate device for measuring neutron dose. However, their neutron detection efficiency is pretty low and therefore, they have not been employed for weak neutron field measurements typically encountered at nuclear power plants. To address this fundamental low efficiency problem, we have developed a “multi-element” detector consisting of a number of gaseous sensitive volumes using our THGEM technology. In order to optimize the multi-element design, we carried out extensive Monte Carlo simulations. With this Monte Carlo outcome, we accomplished a quantitative analysis for the neutron efficiency dependence on the multi-element geometry for the first time. We have built a prototype multi-element detector consisting of 7*3 gaseous volumes and its tests are currently underway.
Another advanced dosemeter we have been developing is a 2-D neutron-gamma dosemeter, which aims to measure a spatial distribution of the neutron and gamma-ray doses. The core work of this project was to build a multi-input digital signal processing system which can analyze signals from 25 detectors in parallel and real time. A preliminary result showed that the 2-D dosemeter shows the spatial neutron and gamma dose distributions quite accurately. Moreover, the digital processing system showed an excellent processing speed and energy resolution. Comprehensive tests for this 2-D detector are currently underway.
Low-level gamma-ray spectrometry
In ultra-low level gamma spectrometry, a common challenge is that owing to its weak activity, the counts from a sample are buried under background radiation counts. For the multi-photon emitters like 60Co and 26Al, important radionuclides of interests for meteorites and/or nuclear reactor samples, this challenge can be overcome by operating detectors in coincidence mode, in which case a large fraction of the background counts can be rejected while most cascade gamma-ray counts from a sample are saved. Although this principle has been well known, no systematic studies have been done in terms of optimizing the detector arrangement and segmentation to accomplish the best analytical performance.
This study will focus on measuring low level 26Al, 60Co and others radionuclides of interests. We will optimize the detector size and array pattern through an extensive Monte Carlo simulation study. The project scope also includes pulse processing development for multiple detectors in a digital architecture and investigation of optimizing time pickoff algorithm.