Differences of chamber pressure variations during stage separation between flight and detonation-shock-tube-based ground tests

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

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Studies of the scanning ion beam sputter-cleaned MgO crystal surface by scanning reflection electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125658 ◽

1987 ◽

Vol 45 ◽

pp. 144-145

Author(s):

H.-J. Ou ◽

J. M. Cowley ◽

A. A. Higgs

Keyword(s):

Crystal Surface ◽

Ion Beam ◽

Carbon Film ◽

Surface Region ◽

Bulk Sample ◽

Chamber Pressure ◽

Specimen Preparation ◽

Detailed Surface ◽

Gate Control ◽

Reflection Electron Microscopy

A scanning ion gun system has been installed on the specimen preparation chamber (pressure ∼5xl0-8 torr) of the VG-HB5 STEM microscope. By using the specimen current imaging technique, it is possible to use an ion beam to sputter-clean the preferred surface region on a bulk sample. As shown in figure 1, the X-Y raster-gate control of the scanning unit for the Krato Mini-Beam I is used to minimize the beam raster area down to a 800μm x800μm square region. With beam energy of 2.5KeV, the MgO cleavage surface has been ion sputter-cleaned for less than 1 minute. The carbon film or other contaminant, introduced during the cleavage process in air, is mostly removed from the MgO crystal surfaces.The immediate SREM inspection of this as-cleaned MgO surface, within the adjacent STEM microscope, has revealed the detailed surface structures of atomic steps, which were difficult to observe on the as-cleaved MgO surfaces in the previous studies.

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Electron behavior in the gaseous environment of the ESEM chamber

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166658 ◽

1996 ◽

Vol 54 ◽

pp. 838-839 ◽

Cited By ~ 2

Author(s):

S.A. Wight

Keyword(s):

Secondary Electron ◽

High Vacuum ◽

Beam Current ◽

Chamber Pressure ◽

Environmental Scanning ◽

Carbon Block ◽

Faraday Cup ◽

X Ray ◽

Gaseous Environment ◽

Working Distance

Measurements of electrons striking the sample in the Environmental Scanning Electron Microscope (ESEM) are needed to begin to understand the effect of the presence of the gas on analytical measurements. Accurate beam current is important to x-ray microanalysis and it is typically measured with a faraday cup. A faraday cup (Figure 1) was constructed from a carbon block embedded in non-conductive epoxy with a 45 micrometer bore platinum aperture over the hole. Currents were measured with an electrometer and recorded as instrument parameters were varied.Instrument parameters investigated included working distance, chamber pressure, condenser percentage, and accelerating voltage. The conditions studied were low vacuum with gaseous secondary electron detector (GSED) voltage on; low vacuum with GSED voltage off; and high vacuum (GSED off). The base conditions were 30 kV, 667 Pa (5 Torr) water vapor, 100,000x magnification with the beam centered inside aperture, GSED voltage at 370 VDC, condenser at 50%, and working distance at 19.5 mm. All modifications of instrument parameters were made from these conditions.

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Using a shock tube to predict the response of polymeric foam to a blast loading

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2006134121 ◽

2006 ◽

Vol 134 ◽

pp. 783-787 ◽

Cited By ~ 2

Author(s):

S. Ouellet ◽

D. Frost ◽

A. Bouamoul

Keyword(s):

Shock Tube ◽

Blast Loading ◽

Polymeric Foam

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Pyrolysis of methane in a single pulse shock tube

Journal of Applied Chemistry and Biotechnology ◽

10.1002/jctb.5020220303 ◽

1972 ◽

Vol 22 (3) ◽

pp. 303-317 ◽

Cited By ~ 11

Author(s):

D. H. Napier ◽

N. Subrahmanyam

Keyword(s):

Shock Tube ◽

Single Pulse

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Nanocrystalline silicon ( nc-Si ) from single ion beam sputtering

MRS Proceedings ◽

10.1557/proc-762-a7.3 ◽

2003 ◽

Vol 762 ◽

Cited By ~ 1

Author(s):

Z.B. Zhou ◽

G.M. Hadi ◽

R.Q. Cui ◽

Z.M. Ding ◽

G. Li

Keyword(s):

Solar Cell ◽

Ion Beam ◽

Nanocrystalline Silicon ◽

Silicon Films ◽

Chamber Pressure ◽

Ion Beam Sputtering ◽

High Hydrogen ◽

Beam Sputtering ◽

Si Films ◽

Nanocrystalline Silicon Films

AbstractBased on a small set of selected publications on the using of nanocrystalline silicon films (nc-Si) for solar cell from 1997 to 2001, this paper reviews the application of nc-Si films as intrinsic layers in p-i-n solar cells. The new structure of nc-Si films deposited at high chamber pressure and high hydrogen dilution have characters of nanocrystalline grains with dimension about several tens of nanometer embedded in matrix of amorphous tissue and a high volume fraction of crystallinity (60~80%). The new nc-Si material have optical gap of 1.89 eV. The efficiency of this single junction solar cell reaches 8.7%. This nc-Si layer can be used not only as an intrinsic layer and as a p-type layer. Also nanocrystalline layer may be used as a seed layer for the growth of polycrystalline Si films at a low temperature.We used single ion beam sputtering methods to synthesize nanocrystalline silicon films successfully. The films were characterized with the technique of X-ray diffraction, Atomic Force Micrographs. We found that the films had a character of nc-amorphous double phase structure. Conductivity test at different temperatures presented the transportation of electrons dominated by different mechanism within different temperature ranges. Photoconductivity gains of the material were obtained in our recent investigation.

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