Minwoong Lee

This study experimentally compares the total ionizing dose (TID) responses of conventional and V-Gate regulated cascode transimpedance amplifier (RGC TIA)-based analog front ends (AFEs) fabricated in a 180 nm, 3.3 V CMOS process. Both AFEs were integrated on a single ASIC, and the V-Gate layout was applied to all NMOS devices in the hardened AFE. The powered circuits were driven with repetitive pulses and irradiated at 3.432 kGy/h to 13.73 kGy. At the final dose, pulse amplitude and slew rate decreased by 3.48% and 9.11% in the conventional AFE but by only 0.63% and 1.73% in the V-Gate AFE, corresponding to degradation reductions of approximately 82% and 81%, respectively. The IB_TP-derived bias current increased by 18.8% in the conventional AFE and 0.73% in the V-Gate AFE, while the input and output DC voltages remained stable. Leakage current sensitivity analysis identified the RGC TIA and bias generator as the main contributors to DC-level and pulse amplitude changes, whereas the Class-AB buffer and bias generator more strongly affected slew rate. A combined simulation reproduced the pulse amplitude reduction with a small DC shift. The results show that the V-Gate layout preserves the pulse response and bias stability of RGC TIA-based AFEs under TID irradiation.

Electromagnetic pulses (EMPs) generated by nuclear explosions can induce latch-up and burnout in semiconductor circuits through mechanisms similar to those caused by prompt gamma rays. Conventional nuclear event detectors (NEDs) mitigate radiation-induced latch-up by temporarily cutting power; however, they cannot respond to nanosecond-scale EMP transients. This paper presents a dual-sensor-based active protector (DAP) that extends the NED concept by adding an EMP detection channel while maintaining the same transient power-cutoff mechanism. The integrated DAP consists of an EMP sensor, a prompt gamma-ray sensor, and a shared high-speed signal-processing circuit that evaluates both sensor outputs in real time and generates a cutoff-control pulse when the predefined threshold is exceeded. The gamma-ray channel was verified to exhibit a dose-rate response consistent with that of the original NED design. In EMP detection experiments, the DAP generated stable cutoff-control signals within approximately 50 ns. System-level tests demonstrated that the DAP effectively protected an integrated circuit from EMP-induced malfunction by temporarily interrupting the power supply.

With advances in space, nuclear, and defense industries, the susceptibility of semiconductor integrated circuits (ICs) to radiation has increased. Radiation-induced degradation and malfunctioning of IC performance can lead to system failure, leading to significant damage. To address this limitation, this study employed mixed-stage modeling and simulation (M&S) techniques to evaluate the reliability of complementary metal-oxide semiconductor application-specific ICs (ASICs) in radiation environments. Radiation-hardened IC chips were designed and fabricated using layout modification techniques based on M&S. The ASIC, which includes the D-latch and Operational Amplifier (Op-Amp) circuits, was validated for resistance up to a total ionizing dose of 20 kGy(Si). The proposed radiation-hardened ICs demonstrated stable performance even in radiation-exposed environments, ensuring reliable operation under such conditions. The findings provide insights into overcoming radiation-induced degradation and malfunction in semiconductor integrated circuits, which is particularly relevant for advancing space, nuclear, and defense industries.

A high‐Z metal‐quercetin complex‐based material is developed by combining Hf, Ta, and Eu with quercetin (Qu) from a flavonoid series to apply to radiation protection materials. To demonstrate radiation energy absorbance, we utilize a polymer blend composed of carboxymethyl cellulose (CMC) and polyvinylpyrrolidone (PVP) as a matrix. This eco‐friendly film can be easily prepared by simply mixing it with the M‐Qu complex and the CMC‐PVP polymer blend. The possibility of radiation energy absorbance by the M‐Qu complex is confirmed through an analysis of the X‐ray energy absorption dose change rate. In addition, the radiation resistance characteristics of each film sample are measured using high‐energy electron‐beam irradiation. The results show that the Ta‐containing Qu complex has a high capability for UV energy downshift, X‐ray radiation absorption, and stability against electron‐beam radiation. This indicates that the material in question has the potential to serve as a superior radiation protection material for broad‐spectrum radiation energy. Also, it could effectively offer remarkable stability making it a compelling option for radiation‐resistant applications.

Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy is a powerful tool for identifying chemical bonding states at synchrotron radiation facilities. Advances in new materials require researchers in both academia and industry to measure tens to hundreds of samples during the available beam time on a synchrotron beamline, which is typically allocated to users. Automated measurement methods, along with analysis software, have been developed for beamlines. Automated measurements facilitate high-throughput experiments and accumulate vast amounts of measured spectral data. The analysis software supports various functions for analyzing the experimental data; however, these analysis methods are complicated, and learning them can be time-consuming. To process large amounts of spectral data, a new analysis software, dedicated to NEXAFS spectroscopy, that is easy to use and can provide results in a short time is desired. Herein, the development of Beagle is described, software calculating molecular orientation from NEXAFS spectroscopy data that can report results in a short time comparable with that required to measure one sample at the beamline. It was designed to progress in a single sequence from data loading to the printing of the results with a `click of a button'. The functions of the software include recognizing the dataset, correcting the background, normalizing the plot, calculating the electron yield and determining the molecular orientation. The analysis results can be saved as {\tt{.txt}} files (spectral data), {\tt{.pdf}} files (graphic images) and Origin files (spectral data and graphic images).

Silicon-based electronic components exposed to the radiation environment experience transient and cumulative damage, which causes performance degradation, malfunction, and burnout of the entire electronic system. In this study, the silicon-on-insulator (SOI) process technology was applied to enhance the single event effect (SEE) tolerance of bulk complementary metal–oxide–semiconductor (CMOS)-based logic circuits, which are vulnerable to space particle radiation. SOI CMOS processes are susceptible to total ionizing dose (TID) effects because of an additional oxide layer. A layout-modification technique (LMT) was proposed to overcome this problem. The SEE tolerance characteristics of the SOI process logic were verified in advance using radiation response modeling and simulation. The proposed radiation-hardened (RH) SOI CMOS logic was designed and implemented on a chip using a 0.5- $\mu $ m CMOS test process. Radiation tests were conducted on the proposed logic chip to validate its SEE resistance to 50-and 25-MeV proton particles and its tolerance to TID effects for a total dose of 15-kGy(Si) gamma rays. The proposed SOI CMOS logic with the LMT can mitigate the atypical effects caused by radiation particles in semiconductor devices in radiation environments, such as space and nuclear power plants, thereby ensuring sufficient survival time under cumulative effects.

This study designed a radiation-hardened (RH) complementary metal oxide semiconductor (CMOS) logic circuit based on an RH variable-gate (V-gate) n-MOSFET that was resistant to the total ionizing dose (TID) effect and evaluated its tolerance to radiation. Among the different CMOS logic circuits, NOT, NAND, and NOR gates were designed using V-gate n-MOSFETs by employing layout transformation techniques and standard p-MOSFETs. Before the process design, we predicted the radiation damage using modeling and simulation techniques and validated the tolerance by conducting actual radiation tests after the process design. Furthermore, we implemented the CMOS logic circuit process design in a 0.18 µm CMOS bulk process. The actual radiation test applied a total cumulative radiation dose of 25 kGy at 5 kGy per hour in a high-level gamma-ray irradiation facility. Consequently, the resistance of the RH CMOS logic circuit based on the RH V-gate n-MOSFET to the TID effect was validated through experiments.

High-energy radiation sources have provided a strong security inspection capability using a non-invasive imaging system. The use of multiple radiation sources in one imaging system can also lead to a more powerful system that can classify various materials compared to using a single radiation source. The Advanced Radiation Technology Institute of Korea Atomic Energy Research Institute has developed an air cargo inspection system using multiple radiation sources such as fast neutrons and gamma-rays to classify the plastics, metals, and organics among various sample materials. The fast neutron beam with an energy of 14.1 MeV, generated using the D-T neutron generator, and the gamma-ray beam with an energy of 6 MeV, generated by an electron linear accelerator, are projected onto the vertically aligned scintillator-based radiation detectors. The neutron and gamma-ray images of a cargo container moved by a motorized linear translation stage are acquired, and the image data processing shows good material classification results. In this paper, we describe a multi-radiation imaging system for air cargo inspection and investigate its material classification capability using various sample materials.

Electronic equipment in nuclear power plants and nuclear warfare is damaged by transient effects that cause high-energy pulsed radiation. There is a concern that this type of damage can even cause enormous economic losses and human casualties by paralyzing control systems. To solve this problem, this study proposes a complementary metal-oxide semiconductor (CMOS) logic-based, switching detection circuit that can detect pulsed radiations at a fast rate. This circuit improved response speed and power consumption by using the switching operation of digital logic compared with conventional circuits. Furthermore, radiation tolerance to total ionizing dose (TID) effects was achieved even in a cumulative radiation environment because of the use of the design using p-metal-oxide semiconductor field effect transistor (p-MOSFET). The proposed detection circuit was manufactured by a 0.18 µm CMOS bulk process for integration. Normal operation in the detection range of 2.0 × 10⁷ rad(si)/s was verified by pulsed radiation test evaluations, and the tolerance properties to a radiation of 2 Mrad was verified based on cumulative radiation test evaluations.

In the present study, the layout structure of an n-MOSFET, which is vulnerable to radiation, was designed in a different way to enhance its tolerance to radiation. Radiation damage assessment was conducted using modeling and simulation (M&S) techniques before actual semiconductor process fabrication and radiation tests to verify its tolerance properties. Based on the M&S techniques, the role of each layer was determined to improve the radiation tolerance of semiconductors, and the layout design of an n-MOSFET with enhanced radiation tolerance was optimized. The optimized radiation-tolerant n-MOSFET design was implemented in the 0.18-um CMOS bulk process, and radiation exposure tests were conducted on the device. A cumulative radiation dose up to 2 Mrad(Si) was applied to verify its radiation-tolerant performance. Developing new devices using M&S techniques for radiation damage assessment allows reliable estimates of their electrical and radiation-tolerant properties to be obtained in advance of the actual manufacturing process, thereby minimizing development costs and time.