http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Characteristics of a PDP-Based Radiation Detector Dependent on Different Electrode Structures
Sangheum Eom,Jongseok Kim,Jungwon Kang IEEE 2015 IEEE transactions on plasma science Vol.43 No.9
<P>In this study, a flat-panel detector based on plasma display technology was investigated as a candidate for a flat-panel radiation detector. We studied the dependence of multiplication factors on various electrode structures using the 3-D Garfield code that calculates the passage of particles through the gas-filled gap. Prototype detectors having three different electrode structures were designed and fabricated based on the simulation results. The performances of these detectors were examined by measuring the collected charge density, dark current density, and sensitivity. The collected charge density had the highest value at the condition when the ridged electrode structure was 1.57 μC/cm<SUP>2</SUP> at -1500 V. The dark current of the same detector was varied between 4.8 and 6.17 nA/cm<SUP>2</SUP> at the bias range of -500 to -1500 V. The sensitivity of the ridged electrode detector was 0.363 nC/mR · cm<SUP>2</SUP> at 0.54 V/μm, and it is approaching to 18% of the sensitivity reported for the commercially available amorphous selenium (a-Se) detector at 10 V/μm.</P>
Simulation Study of Plasma Display Panel-Based Flat Panel X-Ray Detector
Hakjae Lee,Kisung Lee,Sangheum Eom,Hanho Park,Jungwon Kang IEEE 2013 IEEE transactions on nuclear science Vol.60 No.2
<P>Screen-film-based radiography is being rapidly replaced by digital radiography (DR). Thin-film-transistors (TFT) with amorphous silicon (a-Si) or amorphous selenium (a-Se) are usually used in DR X-ray imaging systems. Another flat panel display, plasma display panel (PDP), has a structure that is similar to that of the conventional gas type radiation detectors, and can be manufactured with lower costs than the TFT-based detector panels. The motivation of this study was to develop a cost-effective DR detector using the PDP. In order to apply the PDP technologies in gaseous detectors for X-ray imaging, we modified the pixel's structure and optimized the materials inside the PDP panel. To maximize the signal's intensity, we re-designed the panel's structure based on the gas microstrip detector (GMD), and estimated the performance of the proposed detector using the Monte Carlo simulation method. Signal intensity of gaseous detector is determined by the amount of ionization as well as by the avalanche effect. The ionization and avalanche processes were simulated using the Geant4 and Garfield, respectively. Four types of gas mixtures and various values of electric fields have been explored. The results show that a higher proportion of Xe helps to generate more ionization electrons. The results also suggest that the electric field, which is applied between anode and cathode strips, is a dominant factor for the avalanche effect to occur. In this study, the GMD structure was adopted for the plasma-display-panel-based X-ray detector. A quantitative verification of the effectiveness of the proposed structure was performed as well.</P>
Development of a DAQ system for a plasma display panel-based X-ray detector (PXD)
Lee, Hakjae,Jung, Young-Jun,Eom, Sangheum,Kang, Jungwon,Lee, Kisung Elsevier 2015 Nuclear Instruments & Methods in Physics Research. Vol.784 No.-
<P><B>Abstract</B></P> <P>Recently, a novel plasma display panel (PDP)-based X-ray detector (PXD) was developed. The goal of this study is to develop a data acquisition system for use with the PXD as an imaging detector. Since the prototype detector does not have any barrier ribs or a switching device in a detector pixel, a novel pixelation scheme—the line-scan method—is developed for this new detector. To implement line scanning, a multichannel high-voltage switching circuit and a multichannel charge-acquisition circuit are developed. These two circuits are controlled by an FPGA-based digital signal processing board, from which the information about the charge and position of each pixel can be sent to a PC. FPGA-based baseline compensation and switching noise rejection algorithms are used to improve the signal-to-noise ratio (SNR). The characteristic curve of the entire PXD system is acquired, and the correlation coefficients between the X-ray dose, and the signal intensity and the SNR were determined to be approximately 0.99 and 52.9, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We developed a data acquisition circuit for a novel X-ray imaging detector. </LI> <LI> Line scan, noise rejection, and data transmission methods have been implemented by the FPGA. </LI> <LI> The linearity and SNR of the proposed detector system have been measured quantitatively. </LI> </UL> </P>