Dennis Manos | College of William and Mary (original) (raw)

Papers by Dennis Manos

Vacuum, 1983

To increase the power throughput to a plasma of an e :isting lower hybrid waveguide, secondary el... more To increase the power throughput to a plasma of an e :isting lower hybrid waveguide, secondary electron production on tie walls and subsequent electron multiplication must be reduced. Si^ce carbon has a low secondary electron coefficient (6), measurements were per formed for several UHV compatible carbon coatings (Aquadag®, vacuum pyrolized Glyptal , and lamp black deposited by elactrophores.s) as a function of primary beam voltage (35 eV to 10 keV), surface oughness (60 through 600 grit mechanical polishing and electropolisning), coating thickness, and angle of incidence (9). Also measured were uncoated stainless steel,Mo,Cu,Ti, riC, C as soot and ATJ graphite. The yields were obtained by varying the sample bias and measuring the collected current while the samples were in the electron beam of a scanning Auger microprobe. This technique allows 5 measurements of Auger characterized surfaces with <.3 mm spatial resolution. Results show 6 to have a typical energy dependence, with a peak occurring at 200 to 300 eV for normal incidence, and at higher energy for larger 8. In general, S increases with 8 more for smooth surfaces than for rough ones. 90% of the secondary electrons have energies less than 2 5 eV. Some carbonized coating and surface treatment combinations qive 5 ' max = 0.88+0.01 for normal electron beam incidence-a reduction of almost 40% compared to untreated stainless steel. * Supported by the Fannie and John Hertz Foundation-.ind by the Dept. of Energy Contract #DE-AC0 2-76-CHO30 73.

D.L. Flamm and G.K. Herb, Plasma Etching Technology. An Overview. D.L. Flamm, Introduction to Pla... more D.L. Flamm and G.K. Herb, Plasma Etching Technology. An Overview. D.L. Flamm, Introduction to Plasma Chemistry. S.A. Cohen, An Introduction to Plasma Physics for Materials Processing. D.M. Manos and H.F. Dylla, Diagnostics of Plasmas for Materials Processing. A.R. Reinberg, Plasma Etch Equipment and Technology. J.M.E. Harper, Ion Beam Etching. G.K. Herb, Safety, Health, and Engineering Considerations for Plasma Processing.

Ultraviolet (UV) light induced or enhanced chemical reactions have many advanced applications. Th... more Ultraviolet (UV) light induced or enhanced chemical reactions have many advanced applications. This causes excimer lamps which deliver high power, large area UV radiations in demand. There have been extensive studies on rare gas or mixtures of rare gas halogen in different excimer lamps. But experimental data for high pressure KrI (iodine in krypton) spectra are scarce partially because the

Fusion Technology 1990, 1991

A diborane gas handling system has been constructed for the purposes of boronizing TFTR. Numerous... more A diborane gas handling system has been constructed for the purposes of boronizing TFTR. Numerous safety features have been incorporated to mitigate the toxic and inflammable nature of diborane, including many features adopted from the semiconductor industry. The carborane films deposited in TFTR have significantly improved the operational performance of the machine.

Journal of Vacuum Science and Technology

We describe the design for the vacuum vessel and vacuum pumping system for a 1.2 GeV electron sto... more We describe the design for the vacuum vessel and vacuum pumping system for a 1.2 GeV electron storage ring for light source applications. The hybrid vacuum vessel design consists of eight extruded aluminum (6063‐T4) dipole chambers curved to the ring radius of 2.93 m, with interconnecting stainless (304 L) steel straight vessel segments. The dipole chambers contain two 60 milliradian photon exit ports on the outer midplane, and an integral pumping chamber on the inner midplane which provides 500 1/s ⋅ m of active gas pumping with a circumferential array of a non‐evaporable getter (NEG) material. Ion pumping stations are distributed along the straight vacuum vessel segments to provide for pumping of CH4 and noble gases. The distributed pumping provided by the NEG offers a factor of five to ten times larger pumping speed in comparison to conventional designs based solely on the use of discrete or distributed ion pumps. Externally bonded cooling tubes on the dipole chambers offer a cos...

Review of Scientific Instruments, 1986

ABSTRACT

Review of Scientific Instruments, 1995

Reduction of indigenous metal impurities in tokamak plasmas and impurity requirements for the x-r... more Reduction of indigenous metal impurities in tokamak plasmas and impurity requirements for the x-ray diagnosis of central plasma parameters necessitates artificial introduction of metal atoms. A new inexpensive method is described using ferrocene, Fe(C5H5)2, a substance which sublimes. A prototype device was tested at the Atomic-Beam Facility at PPPL. Ferrocene was injected into a pulsed helium plasma with an electron

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1991

Measurements by moveable Langmuir probes and edge spectroscopy diagnostics have documented the co... more Measurements by moveable Langmuir probes and edge spectroscopy diagnostics have documented the conditioning effect of low density helium-initiated discharge sequences on the Tokamak Fusion Test Reactor (TFTR) edge plasma. Langmuir probe measurements show in general that the edge electron density n e decreases by less than a factor of 2 while the edge electron temperature T e doubles. Radial profiles to the plasma boundary show that the density scrape-off length increases somewhat while the temperature scrape-off length decreases substantially. The particle flux density is unaffected. The spectral emission of C II decreases by a factor of 2, a much smaller change than that exhibited by the D a signal. These results complement previous accounts of the conditioning technique. Comparisons of these He conditioning measurements are made to edge measurements during a deuterium density scan experiment, showing many similarities, and to an existing edge model of the conditioning process, showing qualitative agreement.

Journal of Nuclear Materials, 1982

Journal of Nuclear Materials, 1992

This report was prepared as an account of work sponsored by an agency of the United , States Gove... more This report was prepared as an account of work sponsored by an agency of the United , States Government.

Journal of Vacuum Science & Technology A - J VAC SCI TECHNOL A, 1984

The approaching use of tritium in tokamaks necessitates precursory studies to assess safety and h... more The approaching use of tritium in tokamaks necessitates precursory studies to assess safety and handling, to ready diagnostics of T in plasmas, and to study T--H exchange, loss of T from solids, and T transport. To aid these efforts, eight carbon foils 12.7 x 1.25 cm were implanted in a linear plasma device with ions from hydrogen plasma containing 10â»Â³ fraction of T. These foils will be used in future PLT plasma experiments. Experimental guidelines are: low activity, high safety, and sufficient T for detection. Incident ion energies and total fluxes yielded deposits of approx.100 ..mu..Ci cmâ»Â² (2 x 10Â¹âµ cmâ»Â²) of tritium. Using autoradiography, we find that variations of < or approx. =20% of an average concentration of 100 ..mu..Ci cmâ»Â² of T can be detected. Areas of <1 mmÂ² can be examined by the use of densitometry, thus providing a nondestructive method of analyzing surface distribution. Absolute calibrations were made by the measurement of tritium in one of ...

Journal of Vacuum Science & Technology A, 1982

The flux of deuterium in the plasma edge several centimeters outside the limiter were measured us... more The flux of deuterium in the plasma edge several centimeters outside the limiter were measured using collector probes during neutral beam heating experiments on the PDX Tokamak and RF heating experiments on the PLT Tokamak. The dependence of the flux on the distance from the plasma was determined, and the time dependence of the flux was measured with a time resolution of 90 ms. In PDX the deuterium flux decreased rapidly with increasing distance from the plasma. The deuterium flux increased strongly when the beams came on and decreased when they turned off. The depth distribution of the deuterium in the samples, measured using SIMS, shows that when the beams are on about 30% of the deuterium incident on the probe is superthermal deuterium from the beams. In the deuterium flux decreased only slightly with increasing distance from the plasma. The ICRH heating in PLT caused an increase of about 30% in the flux of deuterium to the samples and in the plasma density. In both machines the the deuterium fluxes were fairly low at the positions sampled.

Journal of Vacuum Science & Technology A, 1989

A rotatable collector probe was used to expose several graphite samples to a deuterium-to-hydroge... more A rotatable collector probe was used to expose several graphite samples to a deuterium-to-hydrogen-to-deuterium exchange experiment in the Tokamak Fusion Test Reactor (TFTR) at the start of the 1988 operations period. This experiment proved the utility of helium conditioning discharges in accelerating the changeover process. Samples included portions of a tile taken from the inner bumper limiter (POCO AXF-5Q graphite)

Circular limiter H-modes are obtained on TFTR during high power neutral beam heating. The transit... more Circular limiter H-modes are obtained on TFTR during high power neutral beam heating. The transition is usually from the supershot to the H-mode rather than the usual L-to H-transition, and thus is obtained in a low recycling environment with core fueling mainly ...

Physical Review Letters, 1982

Plasma heating by near-perpendicular injection of up to 7.2 MW of neutral-beam power has been stu... more Plasma heating by near-perpendicular injection of up to 7.2 MW of neutral-beam power has been studied in the PDX tokamak. Collisionless plasmas with centrla ion temperatures up to 6 keV have been obtained. The total plasma energy, which is dominated by contributions from ...

Physical Review Letters, 1983

Strong magnetohydrodynamic activity has been observed in PDX neutral-beam-heated discharges. It o... more Strong magnetohydrodynamic activity has been observed in PDX neutral-beam-heated discharges. It occurs for β T q>~0.045 and is associated with a significant loss of fast ions and a drop in neutron emission. As much as 20%-40% of the beam heating power may be ...