measurement-of-outgassing-rates-of-steels

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Korea Research Institute of Standards and Science

An extremely high vacuum cold-field electron emission (CFE) gun operating at pressures ranging from ~10(-8) Pa to ~10(-10) Pa was constructed. Only the CFE current emitting from W(310) surfaces revealed the existence of a "stable region" with high current angular density just after tip flash heating. In the "stable region," the CFE current was damped very slowly. The presence of non-hydrogen gas eliminated this region from the plot. Improvement of the vacuum prolonged the 90% damping time of the CFE current from ~10 min to 800 min. The current angular density I' of CFE current was 60 and 250 μA/sr in the "stable region" for total CFE currents of 10 and 50 μA, respectively. These results were about three times larger than I' when measured after the complete damping of the CFE current. The CFE gun generated bright scanning transmission electron microscopy images of a carbon nanotube at 30 kV.

W(310) cold-field emission characteristics reflecting the vacuum states of an extreme high vacuum electron gun.

We present a reliable method for aligning an electron gun which consists of an electron source and lenses by controlling a stack of rubber O-rings in a vacuum condition. The beam direction angle is precisely tilted along two axes by adjusting the height difference of a stack of O-rings. In addition, the source position is shifted in each of three orthogonal directions. We show that the tilting angle and linear shift along the x and y axes as obtained from ten stacked O-rings are ±2.55° and ±2 mm, respectively. This study can easily be adapted to charged particle gun alignment and adjustments of the flange position in a vacuum, ensuring that its results can be useful with regard to electrical insulation between flanges with slight modifications.

Note: O-ring stack system for electron gun alignment.

The electromechanical properties of ternary InAsP nanowires (NWs) were investigated by applying a uniaxial tensile strain in a transmission electron microscope (TEM). The electromechanical properties in our examined InAsP NWs were governed by the piezoresistive effect. We found that the electronic transport of the InAsP NWs is dominated by space-charge-limited transport, with a I ∞ V(2) relation. Upon increasing the tensile strain, the electrical current in the NWs increase linearly and the piezoresistance gradually decreases nonlinearly. By analyzing the space-charge-limited I-V curves, we show that the electromechanical response is due to a mobility that increases with strain. Finally, we use dynamical measurements to establish an upper limit on the time scale for the electromechanical response.

Article	Year
W(310) cold-field emission characteristics reflecting the vacuum states of an extreme high vacuum electron gun. The Review of scientific instruments\| PubMed ID: 23387640	2013
Note: O-ring stack system for electron gun alignment. The Review of scientific instruments\| PubMed ID: 25638137	2015
Electromechanical Properties and Spontaneous Response of the Current in InAsP Nanowires. Nano letters\| PubMed ID: 27704850	2016

Boklae Cho

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