2,107 research outputs found
Revisiting the anomalous rf field penetration into a warm plasma
Radio frequency waves do not penetrate into a plasma and are damped within
it. The electric field of the wave and plasma current are concentrated near the
plasma boundary in a skin layer. Electrons can transport the plasma current
away from the skin layer due to their thermal motion. As a result, the width of
the skin layer increases when electron temperature effects are taken into
account. This phenomenon is called anomalous skin effect. The anomalous
penetration of the rf electric field occurs not only for transversely
propagating to the plasma boundary wave (inductively coupled plasmas) but also
for the wave propagating along the plasma boundary (capacitively coupled
plasmas). Such anomalous penetration of the rf field modifies the structure of
the capacitive sheath. Recent advances in the nonlinear, nonlocal theory of the
capacitive sheath are reported. It is shown that separating the electric field
profile into exponential and non-exponential parts yields an efficient
qualitative and quantitative description of the anomalous skin effect in both
inductively and capacitively coupled plasma.Comment: 44 pages, invited paper at "Nonlocal, Collisionless Phenomena in
Plasma" worksho
X-band microwave generation caused by plasma-sheath instability
It is well known that oscillations at the electron plasma frequency may
appear due to instability of the plasma sheath near a positively biased
electrode immersed in plasma. This instability is caused by transit-time
effects when electrons, collected by this electrode, pass through the sheath.
Such oscillations appear as low-power short spikes due to additional ionization
of a neutral gas in the electrode vicinity. Herein we present first results
obtained when the additional ionization was eliminated. We succeeded to prolong
the oscillations during the whole time a positive bias was applied to the
electrode. These oscillations could be obtained at much higher frequency than
previously reported (tens of GHz compared to few hundreds of MHz) and power of
tens of mW. These results in combination with presented theoretical estimations
may be useful, e.g., for plasma diagnostics.Comment: 12 pages, 7 figure
Beam Extraction and Transport
This chapter gives an introduction to low-energy beam transport systems, and
discusses the typically used magnetostatic elements (solenoid, dipoles and
quadrupoles) and electrostatic elements (einzel lens, dipoles and quadrupoles).
The ion beam emittance, beam space-charge effects and the physics of ion source
extraction are introduced. Typical computer codes for analysing and designing
ion optical systems are mentioned, and the trajectory tracking method most
often used for extraction simulations is described in more detail.Comment: presented at the CERN Accelerator School CAS 2012: Ion Sources,
Senec, 29 May - 8 June 201
Measurement of electric fields in the ionosphere, volume 2 Final report, Aug. 1966 - Sep. 1967
Electric field meter, using electron beam deflection techniques, for ionospheric measurement
New combined PIC-MCC approach for fast simulation of a radio frequency discharge at low gas pressure
A new combined PIC-MCC approach is developed for accurate and fast simulation
of a radio frequency discharge at low gas pressure and high density of plasma.
Test calculations of transition between different modes of electron heating in
a ccrf discharge in helium and argon show a good agreement with experimental
data.
We demonstrate high efficiency of the combined PIC-MCC algorithm, especially
for the collisionless regime of electron heating.Comment: 6 paged, 8 figure
Additional application of the NASCAP code. Volume 1: NASCAP extension
The NASCAP computer program comprehensively analyzes problems of spacecraft charging. Using a fully three dimensional approach, it can accurately predict spacecraft potentials under a variety of conditions. Several changes were made to NASCAP, and a new code, NASCAP/LEO, was developed. In addition, detailed studies of several spacecraft-environmental interactions and of the SCATHA spacecraft were performed. The NASCAP/LEO program handles situations of relatively short Debye length encountered by large space structures or by any satellite in low earth orbit (LEO)
Ionospheric effects to antenna impedance
The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations
A computer model of solar panel-plasma interactions
High power solar arrays for satellite power systems are presently being planned with dimensions of kilometers, and with tens of kilovolts distributed over their surface. Such systems face many plasma interaction problems, such as power leakage to the plasma, particle focusing, and anomalous arcing. These effects cannot be adequately modeled without detailed knowledge of the plasma sheath structure and space charge effects. Laboratory studies of 1 by 10 meter solar array in a simulated low Earth orbit plasma are discussed. The plasma screening process is discussed, program theory is outlined, and a series of calibration models is presented. These models are designed to demonstrate that PANEL is capable of accurate self consistant space charge calculations. Such models include PANEL predictions for the Child-Langmuir diode problem
Measurement of electric fields in the ionosphere. Volume 1 - Technical summary report Final report, Aug. 1966 - Sep. 1967
Design and performance of electron beam electric field meter for ionospheric measurements near spacecraf
- …