Work Function Measurement of Er-oxide/W(100) Surface by using of Photoemission Electron Microscope

A cathode material of a low work function is needed to achieve a high performance electron source. We measured the work function of W(100) surface modified with Er2O3 by using of photoemission electron microscope. The work function of Er-oxide/W(100) surface is measured to be 2.86eV. The work function of ZrO/W(100) thermal-field emission cathode has been reported to be 2.7~2.9eV. A work function of a cathode is generally estimated by Fowler-Nordheim plot (F-N plot). However, there are some ambiguities in this method. The work function measured by using of photoemission electron microscope (PEEM) is come from photo-electron emission phenomena. And the sample surface can be observed. These advantages on measurements make search of low work function materials easier. Therefore, we measure the work function of W(100) surface modified with Er2O3 by using of PEEM. The sample used in this experiment is a circular (100) oriented single crystal tungsten plate of 8mm in diameter and 0.1mm in thickness. A small amount of Er2O3 powder was dissolved in ethanol, and it is put on the sample surface. The sample was heated up to 2000K by electron bombardment in PEEM chamber of 10-8 Pa and the low work function surface was realized on the planar surface. The each PEEM images that the sample is irradiated with the light of wavelength from 300nm to 460 nm every 20nm are taken. In this study, the work function was estimated with the Fowler plot for the emission current density. However, the PEEM system cannot measure directly the emission current. Thus, we estimated the emission current density from the local brightness of the photoelectron image.The work function of Er-oxide/W(100) is measured in optical method by using PEEM. Fowler plot is used for estimating the work function of room temperature from PEEM data. The estimated work function of W(100) single crystalline surface modified with Er2O3 is 2.86eV

Superconducting Magnetic Sensors (SQUID, QFP) and Their Application

Superconducting magnetic sensors such as SQUID’s and QFP are extraordinary sensitive detectors of magnetic flux. Thin film and bulk devices are used at 4.2K in numerous high resolution magnetometer. High sensitivity of these sensors lead the applications of neuromagnetics and non-destructive evaluation. The present status of the device technology and the future subjects on these magnetic sensors are described in conjunction with recent high Tc superconductors

Work Function Measurement of Er-oxide/W(100) Surface by using of Photoemission Electron Microscope

A cathode material of a low work function is needed to achieve a high performance electron source. We measured the work function of W(100) surface modified with Er2O3 by using of photoemission electron microscope. The work function of Er-oxide/W(100) surface is measured to be 2.65eV.Location : Guangzhou, CHINADate : JUL 13-17, 201

The bulk high-Tc superconducting fluxgatemeter for nondestructiveevaluation

A high-Tc superconductive fluxgate magnetic sensor utilizing sintered YBa2Cu3O7-x core is constructed and applied to detect a flaw in an aluminum plate. The magnetic sensor successfully works in an unshielded environment. An electric current was supplied to an aluminum plate directly. A slit (0.2 mm width, 30 mm length), which is considered as a flaw, on an aluminum plate is successfully detected with this sensor, even though the slit is covered with another aluminum plate. The sensor can detect the flaw with its direction perpendicular to the electric current in the sample. It\u27s supposed that the sensor can determine the length of the flaw larger than the diameter of the detection coil. These results suggest that the sensor has a potential for nondestructive evaluation of non-magnetic metals such as aluminum alloys, and also for their multi-layered structures

Non-destructive testing using a HTS SQUID

We have used a high temperature superconductor (HTS) SQUID in an unshielded environment to perform eddy current nondestructive testing measurement of a multi-layer aluminum structure. The sensor consists of an YBCO dc superconducting quantum interference device (SQUID). As a demonstration of the system\u27s capabilities, subsurface defects in a multi-layer aluminum structure have been located and mapped using eddy current with no magnetic shielding around the specimen

Stratospheric aerosol increase after eruption of Pinatubo observed with lidar and aureolemeter

An increase in the amount of stratospheric aerosol due to the Pinatubo eruption (June 12-15, 1991, 15.14 deg N, 120.35 deg E) was observed from the end of June, 1991 by a lidar in NIES (National Institute for Environmental Studies), Tsukuba (36.0 deg N, 140.1 deg E). After large fluctuations in summer of 1991, the amount of the aerosols increased in mid-September as a result of enhanced transportation from the subtropical region. In autumn and winter of 1991, dense aerosol layers were continuously observed. Aureolemeter (scanning spectral radiometer) measurements were also carried out with lidar measurements and columnar size distribution of stratospheric aerosols was estimated for some cases. Collaborative measurements with the lidar and aureolemeter provided some information on height distribution of the surface area of aerosols in late 1991

Effects of atmospheric sphericity on stratospheric chemistry and dynamics over Antarctica

Atmospheric sphericity is an important factor that must be considered in order to evaluate an accurate ozone loss rate in the polar stratosphere. The built-in plane-parallel radiative transfer scheme of a nudging chemical transport model (CTM) and an atmospheric general circulation model (AGCM) with coupled chemistry is modified by a pseudospherical approximation. The plane-parallel atmosphere radiative transfer version (PPA version) is compared with the pseudospherical atmosphere radiative transfer version (SA version) for both the nudging CTM and AGCM. The nudging CTM can isolate the chemical effects for a given dynamical field, while the interaction among the chemical, radiative, and dynamical processes can be studied with the AGCM. The present analysis focuses on Antarctica during an ozone hole period. In the ozone loss period over Antarctica, ozone starts to decrease earlier and minimum value of total ozone becomes lower in the SA versions of both the nudging CTM and the AGCM than in the corresponding PPA versions. The ozone mixing ratio decreases earlier in the SA version because of an earlier increase of ClO concentration initiated by the upward actinic flux at solar zenith angles greater than 90°. Dynamics plays an important role as well as the chemical processes. During the ozone recovery period, the ozone distribution becomes almost the same in the SA and PPA versions of the nudging CTM, while in the AGCM the ozone amount in the SA version remains at lower values compared to those of the PPA version. In the AGCM, a decrease of ozone over Antarctica enhances the latitudinal gradient of temperature and thus strengthens the polar vortex in the SA version. A resultant delay of the polar vortex breakup causes the delay of the ozone recovery. For the AGCM, ensemble runs are performed. The ensemble experiment exhibits large ozone variances after the middle of December, when the ozone recovery is dynamically controlled. Most ensemble members of the AGCM show a delay of the polar vortex breakup in the SA version, while a few members show opposite results. In the latter members, the polar vortex breakup is strongly affected by the enhanced EP flux from the troposphere around 100 hPa, which causes the variances in the ozone recovery period. Most members, however, do not show large statistical variances; that justifies the conclusions from the ensemble means