heetae kim - Academia.edu (original) (raw)

Papers by heetae kim

New Physics: Sae Mulli, 2015

Superconducting cavities, a HWR#2 cryomodule (type-2 cryomodule for a half-wave resonator cavity)... more Superconducting cavities, a HWR#2 cryomodule (type-2 cryomodule for a half-wave resonator cavity) and a local control system for remote control of HWR#2 cryomodule have been developed at the heavy ion accelerator RAON. PLC (programmable logic controller) and Labview software-based on a PC (Personal Computer) have been designed for the local control system of the cryomodule. This local control system operates devices and monitors and archives all signals from the devices. It includes an interlock and alarm system, as well. In this report, we describe the local control system of the HWR#2 cryomodule, which was developed in early 2015 and was tested at cryogenic temperatures.

Thesis (Ph. D.)--University of California, Los Angeles, 2002. Vita. Includes bibliographical refe... more Thesis (Ph. D.)--University of California, Los Angeles, 2002. Vita. Includes bibliographical references (leaves 66-67).

Journal of the Korean Physical Society, Jun 19, 2024

Journal of the Korean Physical Society, May 15, 2024

Nanomaterials, Feb 8, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of the Korean Physical Society, Nov 27, 2023

19th International Conference on RF Superconductivity (SRF'19), Dresden, Germany, 30 June-05 July 2019, Aug 1, 2019

Vertical tests of a prototype half-wave resonator (HWR) cavity have been carried out in SRF test ... more Vertical tests of a prototype half-wave resonator (HWR) cavity have been carried out in SRF test facility. Jacketed HWR (jHWR) cavity is tested both in the test pit and in the cryomodule, while bare HWR (bHWR) cavity is tested in the test pit. In a previous study, we reported that the heat treatment effect on the the cavity performance. Mainly, it was due to removing hydrogen gas which causes Q drop phenomenon during the heat treatment. To improve the cavity performance, we baked the jacketed HWR cavity (jHWR) with the same heat treatment conditions as those for bHWR. We baked a jacketed HWR cavity (jHWR) for 10 hrs at 650 • C under the partial pressure level of hydrogen as 10 −5 Torr (partial pressure peak of hydrogen was 10 −4 Torr) during the heat treatment. According to the results, the cavity performance improved as much as in the case of bHWR. In this study, we will report the heat treatment effect on the jHWR cavity performance with residual gas analysis (RGA) and the vertical test results.

대한기계학회 춘추학술대회, Nov 1, 2015

5th Int. Particle Accelerator Conf. (IPAC'14), Dresden, Germany, June 15-20, 2014, Sep 3, 2014

The superconducting linac of RAON consists of five types of cryomodules. The cryomodules host QWR... more The superconducting linac of RAON consists of five types of cryomodules. The cryomodules host QWR, HWR1, HWR2, SSR1, and SSR2 superconducting cavities, cryogenic pipe lines, magnetic shields and thermal shields. The cryomodules will be operated at 2K and 4.5K in order to test the performance of the superconducting cavities. The main components of the cryomodule are dressed superconducting cavities and two phase pipe, power couplers to supply RF power to the cavities, tuners to control the operation of the cavities, and support systems to fix the cavities along the beam line. The detailed fabrication design of the cryomodules will be presented in this paper.

대한기계학회 춘추학술대회, Apr 1, 2014

Journal of the Korean Physical Society, Apr 1, 2019

Thermionic emission for quasi-free electron metals is investigated in arbitrary dimension. The th... more Thermionic emission for quasi-free electron metals is investigated in arbitrary dimension. The thermionic emission for a constant temperature and work function is calculated for one, two and three dimensions. The generalized current density of the thermionic emission is calculated for arbitrary dimension. The current density is shown as a function of temperature for different work functions. The current density is also shown as a function of dimension for different temperatures and work functions.

28th Linear Accelerator Conf. (LINAC'16), East Lansing, MI, USA, 25-30 September 2016, May 1, 2017

Quality factor measurement method using multi decay time constants on superconducting cavity is s... more Quality factor measurement method using multi decay time constants on superconducting cavity is suggested. In most cases of vertical test, one decay time constant is measured around critical coupling and coupling constants are measured using forward and reflected rf power to get intrinsic quality factor. We use multi decay time constants method to measure the quality factor, which uses three decay time constants. Two more switches before and after the cavity are added to the measurement system. Decay time constants are measured by switching off the rf power switch in front of rf source, the forward power switch in front of input power coupler, and then the pickup power switch behind the pickup coupler, respectively, at the same power of steady state.

17th International Conference on RF Superconductivity (SRF2015), Whistler, BC, Canada, Sept. 13-18, 2015, Dec 1, 2015

β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently test... more β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently tested at TRIUMF. We briefly report the vertical test result: At 2K, the cavity achieved Q₀=2·10⁹ at E_{acc}=6.4 MV/m and the performance was limited at E_{acc}=7.8 MV/m by intense field emission. The surface processing was standard: 120 micron buffered chemical polishing followed by high pressure rinsing. After first cold test, 120C baking was done and the corresponding result was also obtained.

6th Int. Particle Accelerator Conf. (IPAC'15), Richmond, VA, USA, May 3-8, 2015, Jun 1, 2015

We report the current status of prototyping of the SSR1 cavity (= 0.3 and f = 325 MHz) for Korean... more We report the current status of prototyping of the SSR1 cavity (= 0.3 and f = 325 MHz) for Korean heavy ion accelerator RAON. Simulation results on target frequency for vertical test of the cavity prototype are presented. Clamp-up tests for the cavity assembly are in progress.

한국기계가공학회 춘추계학술대회 논문집, Nov 1, 2013

대한기계학회 춘추학술대회, Apr 1, 2014

29\textsuperscript{th} Linear Accelerator Conf. (LINAC'18), Beijing, China, 16-21 September 2018, Mar 9, 2019

Performance of a superconducting cavity, which is made of niobium, tends to be degraded easily de... more Performance of a superconducting cavity, which is made of niobium, tends to be degraded easily depending on the surface resistance. Surface residual resistance of the cavity can be increased during the cavity fabrication process such as pressing, cutting and welding, because these multiple steps can lower the crystallinity of the cavity surface not only by disordering the lattice atoms but also by supplying lattice atoms with impurity atoms. Among the impurity atoms, hydrogen is a well-known impurity that lowers the cavity performance in the form of Q-disease. High temperature heat treatment was performed to remove impurity gas (mainly hydrogen) from the surface of a cavity, and to anneal the cavity to increase the crystllinity. Optical images of the heat treated niobium sample were investigated. Crystallinity was improved after the heat treatment by investigating X-ray diffraction (XRD), thus it confirmed that the annealing was successfully carried out. The residual gas analysis (RGA) was investigated and it confirmed that hydrogen was removed successfully during the heat treatment.

대한기계학회 춘추학술대회, Dec 1, 2013

Optical Materials, Apr 1, 2016

Abstract Plasmonic tuning at mid-infrared wavelength by regulating the nanogap between the adjace... more Abstract Plasmonic tuning at mid-infrared wavelength by regulating the nanogap between the adjacent multilayer graphene nanoribbons (GNs) is investigated with Finite-Difference Time-Domain (FDTD) method. The 100-nm-wide multilayer GNs formed on a SiO 2 /p-Si show that plasmon resonance moves to longer wavelength by decreasing the nanogap from 100 nm to 5 nm, due to the inter-nanoribbon attractive interaction. Also, the resonance wavelength shifts are 7.0, 4.8 and 3.9–3.3 μm in this nanogap range for 1-, 2-, 3- and 4-layer GNs, respectively, at Fermi energy (E F ) of 0.2 eV, implying enhanced confinement in plasmonic oscillation as the number of graphene layer increases. Meanwhile, by shifting the E F from 0.2 eV to 0.4 eV, the resonance peaks for each multilayer GN move to shorter wavelengths, and the peak shifts in the same nanogap range are further decreased resulting from the increased charge carriers involved in the localized plasmonic oscillation. These observed results can provide an insight in designing mid-infrared plasmonic devices for advanced nano-photonic systems.

New Physics: Sae Mulli, 2015

Superconducting cavities, a HWR#2 cryomodule (type-2 cryomodule for a half-wave resonator cavity)... more Superconducting cavities, a HWR#2 cryomodule (type-2 cryomodule for a half-wave resonator cavity) and a local control system for remote control of HWR#2 cryomodule have been developed at the heavy ion accelerator RAON. PLC (programmable logic controller) and Labview software-based on a PC (Personal Computer) have been designed for the local control system of the cryomodule. This local control system operates devices and monitors and archives all signals from the devices. It includes an interlock and alarm system, as well. In this report, we describe the local control system of the HWR#2 cryomodule, which was developed in early 2015 and was tested at cryogenic temperatures.

Thesis (Ph. D.)--University of California, Los Angeles, 2002. Vita. Includes bibliographical refe... more Thesis (Ph. D.)--University of California, Los Angeles, 2002. Vita. Includes bibliographical references (leaves 66-67).

Journal of the Korean Physical Society, Jun 19, 2024

Journal of the Korean Physical Society, May 15, 2024

Nanomaterials, Feb 8, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of the Korean Physical Society, Nov 27, 2023

19th International Conference on RF Superconductivity (SRF'19), Dresden, Germany, 30 June-05 July 2019, Aug 1, 2019

Vertical tests of a prototype half-wave resonator (HWR) cavity have been carried out in SRF test ... more Vertical tests of a prototype half-wave resonator (HWR) cavity have been carried out in SRF test facility. Jacketed HWR (jHWR) cavity is tested both in the test pit and in the cryomodule, while bare HWR (bHWR) cavity is tested in the test pit. In a previous study, we reported that the heat treatment effect on the the cavity performance. Mainly, it was due to removing hydrogen gas which causes Q drop phenomenon during the heat treatment. To improve the cavity performance, we baked the jacketed HWR cavity (jHWR) with the same heat treatment conditions as those for bHWR. We baked a jacketed HWR cavity (jHWR) for 10 hrs at 650 • C under the partial pressure level of hydrogen as 10 −5 Torr (partial pressure peak of hydrogen was 10 −4 Torr) during the heat treatment. According to the results, the cavity performance improved as much as in the case of bHWR. In this study, we will report the heat treatment effect on the jHWR cavity performance with residual gas analysis (RGA) and the vertical test results.

대한기계학회 춘추학술대회, Nov 1, 2015

5th Int. Particle Accelerator Conf. (IPAC'14), Dresden, Germany, June 15-20, 2014, Sep 3, 2014

The superconducting linac of RAON consists of five types of cryomodules. The cryomodules host QWR... more The superconducting linac of RAON consists of five types of cryomodules. The cryomodules host QWR, HWR1, HWR2, SSR1, and SSR2 superconducting cavities, cryogenic pipe lines, magnetic shields and thermal shields. The cryomodules will be operated at 2K and 4.5K in order to test the performance of the superconducting cavities. The main components of the cryomodule are dressed superconducting cavities and two phase pipe, power couplers to supply RF power to the cavities, tuners to control the operation of the cavities, and support systems to fix the cavities along the beam line. The detailed fabrication design of the cryomodules will be presented in this paper.

대한기계학회 춘추학술대회, Apr 1, 2014

Journal of the Korean Physical Society, Apr 1, 2019

Thermionic emission for quasi-free electron metals is investigated in arbitrary dimension. The th... more Thermionic emission for quasi-free electron metals is investigated in arbitrary dimension. The thermionic emission for a constant temperature and work function is calculated for one, two and three dimensions. The generalized current density of the thermionic emission is calculated for arbitrary dimension. The current density is shown as a function of temperature for different work functions. The current density is also shown as a function of dimension for different temperatures and work functions.

28th Linear Accelerator Conf. (LINAC'16), East Lansing, MI, USA, 25-30 September 2016, May 1, 2017

Quality factor measurement method using multi decay time constants on superconducting cavity is s... more Quality factor measurement method using multi decay time constants on superconducting cavity is suggested. In most cases of vertical test, one decay time constant is measured around critical coupling and coupling constants are measured using forward and reflected rf power to get intrinsic quality factor. We use multi decay time constants method to measure the quality factor, which uses three decay time constants. Two more switches before and after the cavity are added to the measurement system. Decay time constants are measured by switching off the rf power switch in front of rf source, the forward power switch in front of input power coupler, and then the pickup power switch behind the pickup coupler, respectively, at the same power of steady state.

17th International Conference on RF Superconductivity (SRF2015), Whistler, BC, Canada, Sept. 13-18, 2015, Dec 1, 2015

β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently test... more β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently tested at TRIUMF. We briefly report the vertical test result: At 2K, the cavity achieved Q₀=2·10⁹ at E_{acc}=6.4 MV/m and the performance was limited at E_{acc}=7.8 MV/m by intense field emission. The surface processing was standard: 120 micron buffered chemical polishing followed by high pressure rinsing. After first cold test, 120C baking was done and the corresponding result was also obtained.

6th Int. Particle Accelerator Conf. (IPAC'15), Richmond, VA, USA, May 3-8, 2015, Jun 1, 2015

We report the current status of prototyping of the SSR1 cavity (= 0.3 and f = 325 MHz) for Korean... more We report the current status of prototyping of the SSR1 cavity (= 0.3 and f = 325 MHz) for Korean heavy ion accelerator RAON. Simulation results on target frequency for vertical test of the cavity prototype are presented. Clamp-up tests for the cavity assembly are in progress.

한국기계가공학회 춘추계학술대회 논문집, Nov 1, 2013

대한기계학회 춘추학술대회, Apr 1, 2014

29\textsuperscript{th} Linear Accelerator Conf. (LINAC'18), Beijing, China, 16-21 September 2018, Mar 9, 2019

Performance of a superconducting cavity, which is made of niobium, tends to be degraded easily de... more Performance of a superconducting cavity, which is made of niobium, tends to be degraded easily depending on the surface resistance. Surface residual resistance of the cavity can be increased during the cavity fabrication process such as pressing, cutting and welding, because these multiple steps can lower the crystallinity of the cavity surface not only by disordering the lattice atoms but also by supplying lattice atoms with impurity atoms. Among the impurity atoms, hydrogen is a well-known impurity that lowers the cavity performance in the form of Q-disease. High temperature heat treatment was performed to remove impurity gas (mainly hydrogen) from the surface of a cavity, and to anneal the cavity to increase the crystllinity. Optical images of the heat treated niobium sample were investigated. Crystallinity was improved after the heat treatment by investigating X-ray diffraction (XRD), thus it confirmed that the annealing was successfully carried out. The residual gas analysis (RGA) was investigated and it confirmed that hydrogen was removed successfully during the heat treatment.

대한기계학회 춘추학술대회, Dec 1, 2013

Optical Materials, Apr 1, 2016

Abstract Plasmonic tuning at mid-infrared wavelength by regulating the nanogap between the adjace... more Abstract Plasmonic tuning at mid-infrared wavelength by regulating the nanogap between the adjacent multilayer graphene nanoribbons (GNs) is investigated with Finite-Difference Time-Domain (FDTD) method. The 100-nm-wide multilayer GNs formed on a SiO 2 /p-Si show that plasmon resonance moves to longer wavelength by decreasing the nanogap from 100 nm to 5 nm, due to the inter-nanoribbon attractive interaction. Also, the resonance wavelength shifts are 7.0, 4.8 and 3.9–3.3 μm in this nanogap range for 1-, 2-, 3- and 4-layer GNs, respectively, at Fermi energy (E F ) of 0.2 eV, implying enhanced confinement in plasmonic oscillation as the number of graphene layer increases. Meanwhile, by shifting the E F from 0.2 eV to 0.4 eV, the resonance peaks for each multilayer GN move to shorter wavelengths, and the peak shifts in the same nanogap range are further decreased resulting from the increased charge carriers involved in the localized plasmonic oscillation. These observed results can provide an insight in designing mid-infrared plasmonic devices for advanced nano-photonic systems.