• Title/Summary/Keyword: beamline

Search Result 80, Processing Time 0.024 seconds

Angle-resolved Photoemission Study of Epitaxial Graphene on Cu(111)

  • Lee, Wang-Geun;Jeon, Cheol-Ho;Hwang, Han-Na;Kim, Kwang-S.;Park, Chong-Yun;Hwang, Chan-Cuk
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2012.02a
    • /
    • pp.126-126
    • /
    • 2012

  • Copper is considered to be the most promising substrate, especially Cu(111), for the growth of high quality monolayer graphene. Since interactions between graphene and Cu substrates will influence on the orientation, quality, and electrical properties of synthesized graphene, we experimentally determine a weak interfacial interaction between Cu(111) substrate and graphene using angle-resolved photoemission spectroscopy (ARPES). The measurement was conducted from the initial stage to the formation of a graphene monolayer. Graphene growth was initiated along the Cu(111) lattice, and two rotated graphene domains were grown, where no significant differences were observed in the band structure depending on different orientations. The interaction, including electron transfer from the Cu(111) to graphene, was limited between the Shockley state of the Cu(111) surface and the ${\pi}$ bands of graphene. These results provide direct information on the growth behavior and interactions between the Cu(111) and graphene.

  • PDF

Characterization of a Neutron Beam Following Reconfiguration of the Neutron Radiography Reactor (NRAD) Core and Addition of New Fuel Elements

  • Craft, Aaron E.;Hilton, Bruce A.;Papaioannou, Glen C.
    • Nuclear Engineering and Technology
    • /
    • v.48 no.1
    • /
    • pp.200-210
    • /
    • 2016

  • The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes, General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. The East Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutron radiography, which sits beneath a large hot cell and is primarily used for neutron radiography of highly radioactive objects. Additional fuel elements were added to the NRAD core in 2013 to increase the excess reactivity of the reactor, and may have changed some characteristics of the neutron beamline. This report discusses characterization of the neutron beamline following the addition of fuel to the NRAD. This work includes determination of the facility category according to the American Society for Testing and Materials (ASTM) standards, and also uses an array of gold foils to determine the neutron beam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. Gold foil activation experiments show that the average neutron flux with length-to-diameter ratio (L/D) = 125 is $5.96{\times}10^6n/cm^2/s$ with a $2{\sigma}$ standard error of $2.90{\times}10^5n/cm^2/s$. The neutron beam profile can be considered flat for qualitative neutron radiographic evaluation purposes. However, the neutron beam profile should be taken into account for quantitative evaluation.

  • https://doi.org/10.1016/j.net.2015.10.006 인용 PDF KSCI

Stereoselective attachment of S-Proline on Ge(100)

  • Youn, Young-Sang;Kim, Ki-Jeong;Kim, Bong-Soo;Lee, Hang-Il;Kim, Se-Hun
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2010.02a
    • /
    • pp.367-367
    • /
    • 2010

  • The adsorption configurations of S-proline on Ge(100) were studied using scanning tunneling microscopy (STM), density functional theory (DFT) calculations, and high-resolution core-level photoemission spectroscopy (HRCLPES). We identified three adsorption structures of S-proline on Ge(100) through analysis of the STM images, DFT calculations, and HRCLPES results: (i) an 'intrarow O - H dissociated and N dative bonded structure', (ii) an 'O - H dissociation structure', and (iii) an 'N dative bonded structure'. Moreover, because adsorption through the N atom of S-proline produces a new chiral center due to symmetry reduction by N dative bonding, the adsorption configurations have either (R,S) or (S,S) chirality, yielding an (R,S)-'intrarow O - H dissociated and N dative bonded structure' and an (R,S)-'N dative bonded structure', with a preference for reaction at the Re face. This work presents a novel method for generating stereoselective attachment using S-proline molecules adsorbed onto a Ge(100) surface.

  • PDF

Catalytic Breakdown of Graphene by Gold

  • Lee, Gyeong-Jae;Yang, Mi-Hyeon;Im, Gyu-Uk;Gang, Tae-Hui;Jeong, Seok-Min
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2012.08a
    • /
    • pp.214-214
    • /
    • 2012

  • It was reported that oxidative etching of graphene occurs at about $450-550^{\circ}C$ under oxygen atmosphere. We found catalytic breakdown of graphene by Au on the SiOx surface. This catalytic process was investigated using x-ray photoelectron spectroscopy and absorption spectroscopy at 4D PES beamline in PAL. Spectrosopic results suggest that the destruction of graphene is initiated by catalytic interaction between the oxidized gold and carbons in vacancy defects of graphene.

  • PDF

$H^-$ Stripping Simulation with a Magnet and $H^{\circ}$ Beam Extractor Design

  • Ahn, Hyo-Eun
    • Proceedings of the Korean Nuclear Society Conference
    • /
    • 1998.05b
    • /
    • pp.951-956
    • /
    • 1998

  • The beam extraction system for the KOMAC[1] (Korea Multi-purpose Accelerator Complex) project is to be designed to partially extract H￣ beam at both 100 and 260 MeV This paper describes a simulation study of charge changing extraction with a stripper magnet and a possible design of a H$^{0}$ extractor by utilizing the simulation study The method consists of converting the negative hydrogen (H￣) ion beam from the linac to a chosen intensity (0-100%) of neutral hydrogen (H$^{0}$ ) beam having an acceptable omittance and drifting it directly onto a stripper foil followed by a downstream beamline.

  • PDF