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kwangsunryu,박미영,jangsoochae,이인,yukiouchihori,hisashikitamura,takeshitakashima 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.3
We developed a mass-memory chip by staking 1 Gbit double data rate 2 (DDR2) synchronous dynamic random access memory (SDRAM) memory core up to 4 Gbit storage for future satellite missions which require large storage for data collected during the mission execution. To investigate the resistance of the chip to the space radiation environment, we have performed heavy-ion-driven single event experiments using Heavy Ion Medical Accelerator in Chiba medium energy beam line. The radiation characteristics are presented for the DDR2 SDRAM (K4T1G164QE) fabricated in 56 nm technology. The statistical analyses and comparisons of the characteristics of chips fabricated with previous technologies are presented. The cross-section values for various single event categories were derived up to ~80 MeVcm2/mg. Our comparison of the DDR2 SDRAM, which was fabricated in 56 nm technology node, with previous technologies, implies that the increased degree of integration causes the memory chip to become vulnerable to single-event functional interrupt, but resistant to single-event latch-up.
Simulation and Ground Test for the Total Ionizing Dose Effects of STSAT-2
Kwangsun Ryu,Dai Ho Ko,Goo hwan Shin,Heejun Kim,김형명,민경욱,sungJoon Kim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I
STSAT-2, the fifth small satellite developed by the Satellite Technology Research Center, will pass through the lower edge of the inner radiation belts. While passing through these belts, the spacecraft is expected to encounter a large number of energetic particles, which have the potential to cause failures of the satellite's microelectronics systems. The space radiation environment of STSAT-2 is estimated through computer-aided simulations. Ground radiation environment tests for the subsystems and major electrical parts of STSAT-2 were performed by using a Co-60 $\gamma$-ray irradiation facility. Of the major electrical parts, two types of MOSFETs were tested in situ. The causes of changes in the electrical performance are discussed, as are the annealing effects.
SEU Measurements of Memory Chips for the Langmuir Probe on STSAT-2
Kwangsun Ryu,Goo-Hwan Shin,Heejoon Kim,hyung-Myung Kim,민경욱 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
We have measured the single event effect (SEE) of candidate memory chips for a Langmuir probe, one of the secondary payloads of STSAT-2 (Science and Technology Satellite-2). The measurements were performed using the cyclotron proton accelerator at Korea Institute of Radiological and Medical Sciences. An ion chamber detector was used for the calibration of the flux of the proton beam. SEU (single event upset) cross-sections for 3 different kinds of memory chips were derived according to the incident proton energy. The SEU rate at the STSAT-2 orbit environment was estimated from the SEU cross-section and the modeled particle flux. The program memory chip for the flight model was selected from the candidates.
New Iron-Containing Electrode Materials for Lithium Secondary Batteries
홍영식,장순호,KwangSunRyu 한국전자통신연구원 2003 ETRI Journal Vol.25 No.5
Using a galvanostatic charge/discharge cycler and cyclic voltammetry, we investigated for the first time the electrochemical properties of iron-containing minerals, such as chalcophanite, diadochite, schwertmannite, laihuite, and tinticite, as electrode materials for lithium secondary batteries. Lithium insertion into the mineral diadochite showed a first discharge capacity of about 126 mAh/g at an average voltage of 3.0 V vs. Li/Li+, accompanied by a reversible capacity of 110 mAh/g at the 60th cycle. When the cutoff potential was down to 1.25 V, the iron was further reduced, giving rise to a new plateau at 1.3 V. Although the others showed discharge plateaus at low potentials of less than 1.6 V, these results give an important clue for the development of new electrode materials.