RF voltage breakdown facility for studying spacecraft antenna characteristics in space and planetary

RF breakdown is one of the major factors determining performance of high power rf components and rf sources. RF breakdown limits working power and produces irreversible surface damage. The breakdown limit depends on the rf circuit, ...

Increasing the power handling capabilities of rf components is an important issue for the design of rf accelerators and rf sources. RF breakdown is a phenomena that limit the high power performance. A major concern is the damage that can occur in rf components from ...

Comparison of Breakdown Characteristics in Copper and Stainless Steel under High RF Field with Narrow Waveguide

We outline a model of rf breakdown. Breakdown can be triggered by two mechanisms, one is fracture of the surface produced by tensile stress produced by the electric field, the second is Ohmic heating at grain boundaries and defects at very high current densities. We show how this model follows from measurements of local electronic ...

This paper presents a summary of rf breakdown-limited electric fields observed in experimental linac structures at SLAC and a discussion of how these experiments can be interpreted against the background of existing, yet incomplete, theories. The motivati...

This paper describes the dependency of the breakdowns measured at DESY on G4 with respect to the RF pulse length, forward power and repetition rate. A part of the work presented in this paper is also discussed in the reference [2

X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer damage due to Radio Frequency (RF) breakdown when processed to high gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing ...

RF breakdown is a critical issue in the conditioning of klystrons, accelerator sections, and rf components for the next linear collider (NLC), as well as other high gradient accelerators and high power microwave sources. SLAC is conducting a series of experiments using an X-band traveling wave ring to characterize the processes and ...

A number of recent papers describing a model of breakdown and high gradient limits should be directly applicable to all rf and DC applications. Although based on low frequency rf measurements, the model can explain and reproduce the effects of a wide range of variables, (B fields, gas pressure, materials, breakdown ...

A number of recent papers describing a model of breakdown and high gradient limits should be directly applicable to all rf and DC applications. Although based on low frequency rf measurements, the model can explain and reproduce the effects of a wide range of variables (B fields, gas pressure, materials, breakdown ...

... formation of a plasma layer at the aperture of an RF ... formation of such plasma layers will aid in the ... over some distance through the atmosphere. ...

... windows and on cathode surfaces as part of the MURI on Nano-physics of Electron Emission and Breakdown for High Power Microwaves. ...

The scaling laws for the initiation time of radio frequency (rf) window breakdown are constructed for three gases: Ar, Xe, and Ne. They apply to the vacuum, to the multipactor-triggered regime, and to the collisional rf plasma regime, and they are corroborated by computer simulations of these three gases over a wide range of pressures. ...

Protection of the accelerator RF system against break-downs is described. The protection operates in two modes: 1) locking the modulator till the end of the accelerating cycle immediately after the first break-down in the RF system to prevent avalanche br...

CVD diamond RF breakdown experiment at Yale is to apply strong tangential RF electric fields up to ~500 MV/m to surfaces of CVD diamond. To date, about 450 kW of power from Yale 34-GHz magnicon, corresponding to a surface field on diamond of 153 MV/m, has been applied to a hydrogenated sample, without evidence of ...

The authors are developing techniques for processing the high gradient (75MV/m) X-band accelerating structures for the NLC. Accelerometers attached to the structures detect surprisingly large acoustic signals believed to be due to RF heating. On a pulse that causes breakdown, these signals increase substantially, producing up to 50 G accelerations at ...

Interest in air breakdown phenomena has recently been re-kindled with the advent of advanced virtual prototyping of radio frequency (RF) sources for use in high power microwave (HPM) weapons technology. Air breakdown phenomena are of interest because the ...

RF breakdown is one of the major factors determining performance of high power rf components and rf sources. RF breakdown limits working power and produces irreversible surface damage. The breakdown limit depends on the rf circuit, ...

Studies of low frequency RF systems for muon cooling has led to a variety of new techniques for looking at dark currents, a new model of breakdown, and, ultimately, a model of RF cavity operation based on surface damage. We find that cavity behavior is st...

A multifaceted program to study high gradient structures and properties of RF breakdown is under way at SLAC. This program includes testing of simplified versions of traveling wave and standing wave structures at 11.4 GHz. RF power is fed into these struc...

Accelerator structures of a wide variety have been damaged by RF breakdowns. Very little is known about the mechanisms that cause the breakdown and the damage although there has been theoretical work [1,2]. Using an array of ultrasonic acoustic emission sensors we have been able to locate and classify breakdown ...

One of the crucial parameters in the design of TeV e/sup +-/ linear colliders is the maximum electric field gradient that can be attained and used safely in the accelerating structure. In the absence of definitive knowledge on the availability and cost of rf power sources, the optimum machine length for a given energy cannot be determined at this time. However, the designs ...

This paper presents a status report on rf field emission and high-gradient breakdown studies in linac structures at SLAC. The motivation behind these studies, begun in 1984, is to determine the maximum accelerating field gradients that could be used safely in future e/sup /plus minus// colliders, to contribute to the basic understanding of the ...

Any gauge theory is proved to arise from spontaneous breakdown of symmetry under certain infinite parameter group, the corresponding gauge field being the Goldstone field by which this breakdown is accompanied. (Atomindex citation 09:376918)

A study of breakdown mechanism has been initiated at the Argonne Wakefield Accelerator (AWA). Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated facility to test various models for ...

... similar to a conventional wing but is accompanied by ... flow separates, but flow separation is not the ... This vortex breakdown on stationary wings has ...

multipaction threshold � Voltage [2] � accuracy of model � field enhancement [3] � standing waves #12;13 Resonator [1] R. Woo, Final Report on RF Voltage Breakdown in Coaxial Transmission Lines, Jet Propulsion Lab-397, Sep. 1961. References #12;3 Outline � Ionization � Multipaction � Breakdown Thresholds � Resonator

Higher accelerating gradients are required by future demands for TeV electron linear colliders. With higher energy comes the challenge of handling stronger electromagnetic fields in the accelerator structures and in the microwave sources that supply the power. A limit on the maximum field gradient is imposed by rf electrical breakdown. Investigating ...

Recent experiments in Alaska using the HAARP and HIPAS high power RF transmitters have succeeded in artificially generating oxygen neutral and molecular nitrogen ion emissions, or artificial airglow, in the ionosphere. An apparently different type of transient airglow generated by lightning, in the form of sprites and elves in the mesosphere and lower ionosphere, has been ...

The mechanisms that contribute to RF breakdown/arcing in an antenna environment are being studied. RF breakdown/arcing is a major power-limiting factor in antenna systems used for RF heating and current drive in fusion experiments. The factors that contribute to breakdown ...

The mechanisms that contribute to RF breakdown/arcing in an antenna environment are being studied. RF breakdown/arcing is a major power-limiting factor in antenna systems used for RF heating and current drive in fusion experiments. The factors that contribute to breakdown ...

Preliminary high-energy tests have been performed on the next linear collider test accelerator and the traveling wave structures have been examined with a scanning electron microscope. This has yielded the locations of radio frequency breakdowns, characte...

The purpose of this article is to serve as a tutorial review on the subject of field emission and rf breakdown in high-gradient room-temperature accelerator structures and associated devices. The need to understand and control these two phenomena has become increasingly important because of the prospect of using high-gradient structures in future linear ...

This paper presents a summary of rf breakdown-limited electric fields observed in experimental linac structures at SLAC and a discussion of how these experiments can be interpreted against the background of existing, yet incomplete, theories. The motivation of these studies, begun in 1984, is to determine the maximum accelerating field gradients that might ...

X-band accelerator structures, meeting the Next Linear Collider (NLC) design requirements, have been found to suffer damage due to radio frequency (RF) breakdown when processed to high gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and ...

Rf breakdown studies in an S-band standing-wave disk-loaded accelerator structure have been completed. An equivalent traveling-wave accelerating gradient as high as 147 MV/m and a peak field in excess of 300 MV/m have been obtained. At these high gradients, considerable amounts of field emission and x-ray radiation are observed. Some of the field-emitted ...

... all chamber data on low-pressure RF breakdown ... employed electron cyclotron resonance heating in ... values of Z for microwave plasmas were much ...

Historical Photo of the Month June 2010. Click on photo to see larger image. RF Voltage Breakdown Facility. Photograph Number 333-4315Ac ...

Nomograph for Prediction of RF-Breakdown Voltages ... It is emphasized that the nomograph is con- ... conductors, the nomograph can be used to determine ...

The electrical breakdown characteristics of the rf capacitive plasma source are investigated theoretically and experimentally. The plasma source is the electrode type consisting of the concentric cylinders for generating nonequilibrium plasma at atmospheric pressure. The theoretical model based on the diffusion-controlled breakdown ...

This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder (``symmetric parallel plate''), parallel plates surrounded by a grounded metallic cylinder (``asymmetric parallel plate''), and parallel ...

The rf R&D program for high gradient, low frequency cavities to be used in muon cooling systems is underway in the Fermilab MUCOOL Test Area. Cavities at 805 and 201 MHz are used for tests of conditioning techniques, surface modification and breakdown stu...

Recent experience with X-band accelerator structure development has shown the rf input coupler to be the region most prone to rf breakdown and degradation, effectively limiting the operating gradient. A major factor in this appears to be high magnetic fie...

The physics of pulsed microwave, or radio frequency (rf), transmission through a decaying plasma column, is studied experimentally. A plasma column is formed in Argon or Nitrogen gases, to represent the neutral gas breakdown due to an rf pulse. Initially ...

Experimental data on the behavior of superconductors under the application of rf fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting rf cavities should be expected has not been clearly established. Tests conducted with very ...

Experimental data on the behavior of superconductors under the application of RF fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting RF cavities should be expected has not been clearly established. Tests conducted with very ...

Preliminary high-energy tests have been performed on the next linear collider test accelerator and the traveling wave structures have been examined with a scanning electron microscope. This has yielded the locations of radio frequency breakdowns, characterized by surface craters, occurring on the oxygen-free electric copper traveling wave structure. It has been proposed that ...

Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the ...

This paper presents an investigation into radio frequency (rf) breakdown for electrodes with holes or protrusions, approximating the situation in real reactors and providing a benchmark for fluid simulations. rf breakdown curves (voltage versus pressure) generally show a steep left-hand branch at low pressures and ...

A detailed theoretical as well as experimental investigation has been made of the statistical properties of rf corona breakdown thresholds, relevant to situations where no artificial electron seeding is used and the electron breakdown avalanche is initiated from the weak naturally occurring electron seeding, primarily due to cosmic ...

We present the experimental results of a systematic study of rf breakdown phenomenon in high vacuum accelerator structures. In this study, the surface processing, geometry, and materials of the structures have been varied, one parameter at a time. The breakdown rate or alternatively, the probability of ...

The rf accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN in order ...

Rf breakdown studies in an S-band standing-wave disk-loaded accelerator structure have been completed. An equivalent traveling-wave accelerating gradient as high as 147 MV/m and a peak field in excess of 300 MV/m have been obtained. At these high gradient...

X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer damage due to Radio Frequency (RF) breakdown when processed to high gradients [F. Le Pimpec, et al., in: LINAC 2002, Korea, SLAC-PUB-9526, 2002 [1

In an effort to locate the cause(s) of high electric-field breakdown in x-band accelerating structures, we have cleanly-autopsied (no debris added by post-operation structure disassembly) an RF-processed structure. Macroscopic localization provided operationally by RF reflected wave analysis and acoustic sensor pickup was used to ...

In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events ...

Breakdowns occurring in rf accelerating structures will limit the ultimate performance of future linear colliders such as the Compact Linear Collider (CLIC). Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN to better understand the ...

The linacs of the Next Linear Collider / Global Linear Collider will contain several thousand traveling wave X-band accelerator structures operating at an input power of about 60 MW. At this input power, prototypes of NLC/GLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns ...

A computer program has been written to model thermal magnetic breakdown. It incorporates all the heat production and heat transport factors. The temperature of the defect and vicinity is calculated for increasing rf field levels until the defect grows unstably, determining the breakdown field level. Calculations are performed for a ...

Breakdown was produced in hydrogen and helium at pressures down to 10/ sup -6/ mm Hg in a toroidal chamber placed in a uniform r-f field and in a betatron focusing field. An explanation of the breakdown characteristics is attempted which relies on secondary electron emission from the walls to produce the initial rapid rise in ...

Microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments1 have been used to investigate the mechanism of RF breakdown.2 The images show evidence for melting and boiling in small regions of ~10 micron diameter on tungsten, molybdenum, and beryllium electrode surfaces. In ...

A self-consistent, diffusion-drift approximated fluid model including ion and electron continuity equations and an electron energy equation is presented for simulating the nonequilibrium characteristics during breakdown of argon rf glow discharge. The nonlinear partial differential equations of the model are solved numerically by using a so-called finite ...

Recent experiments on the breakdown of rf cavities revealed severe surface damage and a reduction of the maximum accelerating gradient after operation in an external magnetic field. This finding implies the possibility of serious problems for cooling lattices wherein rf cavities and external magnetic fields coexist, such as those of ...

We present a simple model of breakdown in rf cavities. For most events this involves tensile stress and tensile strength, however other effects can also contribute. We discuss the effects of different materials, fatigue, high pressure gas, primary and secondary emission sites, local field enhancements, dark currents, secondary emission, work functions, ...

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only ...

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only ...

The phenomenon of rf breakdown presents a technological limitation in the application of high-gradient particle acceleration in normal conducting rf structures. Attempts to understand the onset of this phenomenon and to study its limits with different materials, cell shapes, and pulse widths has been driven in recent years by linear ...

RF and induction linac approaches to phase rotation of the muon bunch have been studied. Shorter accelerator length, lower power consumption and shorter bunch length favor the RF linac approach. An important outstanding research issue is the operation of RF cavities within 2 - 3 meters of the production target and the ...

This paper was published with an incorrect entry in table 5. The full corrected table 5 is shown in the accompanying PDF file

RF breakdown studies are presently being carried out at SLAC with klystron cavities in a traveling wave resonator (TWR). Different kinds of fabrication methods and several kinds of semiconducting and insulating coatings have been applied to X-Band TM{sub 010} cavities. RF breakdown thresholds up to 250 MV/m have ...

Recent high-voltage breakdown experiments of periodic metallic-dielectric insulating structures have suggested several interesting high-gradient applications. One such area is the employment of high-gradient insulators in high-current, electron-beam, accelerating induction modules. For this application, the understanding of the rf characteristics of the ...

We are constructing a facility that combines an atom probe field ion microscope with a multi-element in-situ deposition and surface modification capability. This system is dedicated to rf studies and the initial goal will be to understand the properties of evaporative coatings: field emission, bonding, interdiffusion, etc., to suppress breakdown and dark ...

Research on the basic physics of high-gradient, high frequency accelerator structures and the associated RF/microwave technology are essential for the future of discovery science, medicine and biology, energy and environment, and national security. We will review the state-of-the-art for the development of high gradient linear accelerators. We will present the research ...

Translation termination in eukaryotes is governed by the concerted action of eRF1 and eRF3 factors. eRF1 recognizes the stop codon in the A site of the ribosome and promotes nascent peptide chain release, and the GTPase eRF3 facilitates this peptide release via its interaction with eRF1. In ...

Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating ...

The CLIC project is based on normal-conducting high-gradient accelerating structures with an average accelerating gradient of 100 MV/m. The maximum achievable gradient in these structures is limited by the breakdown phenomenon. The physics of breakdowns is not yet fully understood quantitatively. A full knowledge could have strong impact on the design, ...

A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW peak RF power to 3 GHz cavities, for pulse ...

Ion solid interactions have been shown to be an important new mechanism of unipolar arc formation in high-gradient rf linear accelerators through surface self-sputtering by plasma ions, in addition to an intense surface field evaporation. We believe a non-Debye plasma is formed in close vicinity to the surface and strongly affects surface atomic migration via intense ...

Time-resolved helium ion production and bremsstrahlung emission from JYFL 14 GHz ECRIS is presented with different radio frequency pulse lengths. rf on times are varied from 5 to 50 ms and rf off times from 10 to 1000 ms between different measurement sets. It is observed that the plasma breakdown occurs a few milliseconds after ...

Time-resolved helium ion production and bremsstrahlung emission from JYFL 14 GHz ECRIS is presented with different radio frequency pulse lengths. rf on times are varied from 5 to 50 ms and rf off times from 10 to 1000 ms between different measurement sets. It is observed that the plasma breakdown occurs a few milliseconds after ...

The next linear collider will require 200 MW of rf power per meter of linac structure at relatively high frequency to produce an accelerating gradient of about 100 MV/m. The higher frequencies result in a higher breakdown threshold in the accelerating structure hence permit higher accelerating gradients per meter of linac. The lower frequencies have the ...

In the Next Linear Collider (NLC), the high power rf components must be capable of handling peak rf power levels in excess of 600 MW. In the current view of the NLC, even the rectangular waveguide components must transmit at least 300 MW rf power. At this power level, peak rf fields can greatly exceed 100 MV/m. The ...

Transport of high-power rf fields and the subsequent deposition of rf power into plasma is an important component of developing tokamak fusion energy. Two limitations on rf heating are: (i) breakdown of the metallic structures used to deliver rf power to the plasma, and (ii) a detailed ...

We have examined the spontaneous breakdown of fermion-number-conserving supersymmetry. In the tree approximation the vacuum expectation values of the difermion fields play a passive role, the values of the potential at the minima being entirely determined by the vacuum expectation values of the usual boson fields. One-loop calculations for three different models show that the ...

This is a slightly revised version of the paper that will be published in the AAC06 proceedings. A number of minor changes have been made in the interest of clarity. A significant revision, however, has been made in the treatment of backscattering of inci...

The basic scaling relations for important linear collider design parameters are introduced. Some of the basic concepts concerning the design of accelerating structures are presented, and breakdown limitations are discussed. Rf power sources are considered...

. Insepov, J. Norem, A. Moretti, Z. Qian, A. Bross, Y. Torun, R. Rimmer, D. Li, M. Zisman, D. N. Seidman

A fundamentally new technique for the measurement of the number of subexcitation electrons produced by the passage of ionizing radiation through a gas has ben developed by us during the past few years. The new detector is based on the digital characteriza...

... Abstract : Dielectric thin films of the stacked Ta2O5/SiO2 type were deposited on indium tin oxide coated glass substrates by the rf magnetron ...

A new high-voltage scaling based on Kilpatrick's criterion is presented that suggests that voltages more than twice the Kilpatrick limit can be obtained with identical initial conditions of vacuum and surface cleanliness. The calculations are based on the...

DC and rf measurements have shown that beam-evaporated aluminum oxide constitutes a highly promising material for passivation of electron-beam-semiconductor targets. Aluminum-oxide-passivated targets are characterized by reverse breakdown voltages that ra...

... 30 KV/cm to about 6 KV/crv, can affect the voltage ... attach to the gas molecules. ... The effect of the presence of impurities such as water drops, salt ...

We outline a model of breakdown in RF cavities. In this model, the breakdown trigger is the injection of ions, atoms and clusters into cavities by either of two mechanisms. One mechanism is some combination of fracture and field evaporation of ions from solid surfaces caused by locally high electric fields. The second mechanism, driven ...

This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder ('symmetric parallel plate'), parallel plates surrounded by a grounded metallic cylinder ('asymmetric parallel ...

At SLAC, a 5-cell, normal-conducting, L-band (1.3 GHz), standing-wave (SW) cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the decay rate of the stored energy in the ...

The rf R&D program for high gradient, low frequency cavities to be used in muon cooling systems is underway in the Fermilab MUCOOL Test Area. Cavities at 805 and 201 MHz are used for tests of conditioning techniques, surface modification and breakdown studies. This work has the Muon Ionization Cooling Experiment (MICE) as its immediate goal and ...

The rf R&D program for high-gradient, low frequency cavities to be used in muon cooling systems is underway in the Fermilab MUCOOL Test Area. Cavities at 805 and 201 MHz are used for tests of conditioning techniques, surface modification and breakdown studies. This work has the Muon Ionization Cooling Experiment (MICE) as its immediate goal and ...

The rf R&D program for high gradient, low frequency cavities to be used in muon cooling systems is underway in the Fermilab MUCOOL Test Area. Cavities at 805 and 201 MHz are used for tests of conditioning techniques, surface modification and breakdown studies. This work has the Muon Ionization Cooling Experiment (MICE) as its immediate goal and ...

We consider an axisymmetric microwave cavity for an accelerator structure whose eigenfrequency for its second lowest TM-like axisymmetric mode is twice that of the lowest such mode, and for which the fields are asymmetric along its axis. In this cavity, the peak amplitude of the rf electric field that points into either longitudinal face can be smaller than the peak field ...

A comprehensive theoretical study has been performed on the reduction of the electrical breakdown potential of liquid and gaseous helium under neutron and gamma radiation. Extension of the conventional Townsend breakdown theory indicates that radiation fields at the superconducting magnets of a typical fusion reactor are potentially capable of ...

Gas breakdown represents the first step in generation of plasma and therefore is one of the most fundamental processes. In large scale systems, the experimentally observed Paschen law has been successfully explained by the Townsend theory. This paper contains the results of the detailed simulation studies of low-pressure gas breakdown in dual-frequency ...

This paper is an overall review of studies carried out by the authors and some of their colleagues on RF breakdown, Field Emission and RF processing in room temperature electron linac structure. The motivation behind this work is twofold: in a fundamental way, to contribute to the understanding of the RF ...

A CLIC designed 18 cells, low group velocity (2.4% to 1.0% c), X-band (11.4 GHz) accelerator structure (denoted T18) was designed at CERN, its cells were built at KEK, and it was assembled and tested at SLAC. An interesting feature of this structure is that the gradient in the last cell is about 50% higher than that in the first cell. This structure has been RF conditioned at ...

In this study, we have performed both the channel modification of the conventional MHEMT (Metamorphic High Electron Mobility Transistor) and the variation of gate recess width to improve the breakdown and RF characteristics. The modified channel consists of the InxGa1-xAs and the InP layers. Since InP has lower impact ionization coefficient than ...

This investigation examines temperature effects on avalanche breakdown in GaAs MESFETs to determine if this failure mechanism is accelerated by high temperature life tests. The specific objective is to assess whether the accelerated life test evaluations ...

Conditions leading to initiation of corona streamers and breakdown in gases are reviewed. The effect of electric field strength at electrode surfaces and the pressure of the gas in the electrode gap on the acceleration of free electrons with the ions and molecules in the gas are identified. The presence of water drops or contaminants can reduce corona onset field from about 30 ...

Voltage breakdown is one of the major limiting factors in the design of a high accelerating gradient linear accelerator structure. A multiple-use cavity test system was developed to establish the criteria for voltage breakdown in S-band pulsed electron linear accelerator cavities, in terms of cavity geometry, accelerating gradient, RF ...

The discussion is confined to high gradient, room-temperature accelerators which have clean well-finished cavity surfaces and good vacuum conditions. Breakdown-initiating mechanisms due to ''cold'' field electron emission occurring at isolated sites on broad-area cavity surfaces, where the field is enhanced, are described. The influences of ...

In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a renewed interest in breakdown phenomena for nanosecond pulse, multi-megavolt per centimeter fields has been sparked by recent R and D work in the area of ...

The following topics are covered in this report: (1) toroidal field system, (2) induction and poloidal field coil systems, (3) neutral beam heating system, (4) rf heating, (5) mm wave rf plasma breakdown, (6) divertors/limiters, (7) fuel injection, (8) tr...

Multi-mode accelerating structures aimed at increasing accelerating gradient are described. Such structures operating in several resonant, equidistantly-spaced, axisymmetric, TM-like eigenmodes allow reduction of exposure time to surface fields, reduction of high-field areas and reduction of those fields which are responsible for electron emission. These effects are planned for use in studying the ...

Pulsed, high-power RF ion sources are needed to produce copious amounts of negative H- ions for high-power accelerators with charge-changing injection schemes. When increasing the RF power, the plasma inductance changes the RF resonance, which drifts away from the low-power resonance. When the RF circuit is tuned ...

An on-chip Charged Device Model (CDM) ESD protection method for RF ICs is proposed in a 0.13�m RF process and evaluated by using very fast Transmission Line Pulse (vf-TLP) system. Key design parameters such as triggering voltage (Vt1) and the oxide breakdown voltage from the vf-TLP measurement are used to design input ESD protection ...

Damage to thin gate oxides from etchings of polysilicon gates was studied using gate oxide breakdown histograms and time-dependent dielectric breakdown measurements. The effect of various polysilicon etch parameters was investigated in a radio frequency (rf) triode etcher. Increasing rf power a substantial increase ...

To avoid surface erosion damage and to assist in studying RF breakdown thresholds in 17 GHz TW linac structures, a gradient hardened structure has been fabricated with high temperature brazed and machined stainless steel surfaces located in the peak E-field region of the beam apertures and the peak H-field regions of the input coupler cavity. The microwave ...

To avoid surface erosion damage and to assist in studying RF breakdown thresholds in 17 GHz TW linac structures, a gradient hardened structure has been fabricated with high temperature brazed and machined stainless steel surfaces located in the peak E-field region of the beam apertures and the peak H-field regions of the input coupler cavity. The microwave ...

A high pressure hydrogen gas filled RF cavity has been proposed for use in the muon collection system for a muon collider. It allows for high electric field gradients in RF cavities located in strong magnetic fields, a condition frequently encountered in a muon cooling channel. In addition, an intense muon beam will generate an electron swarm via the ...

The desire to construct electron linacs of higher and higher energies, coupled with the realities of available funding and real estate, has forced machine designers to reassess the limitations in both accelerator gradient (MeV/m) and energy. The gradients achieved in current radio-frequency (RF) linacs are sometimes set by electrical breakdown in the ...

We analyzed and cold tested a 17 GHz 1-1/2-cell RF gun cavity excited through two coupling holes in the broad wall of a rectangular waveguide. An equivalent circuit theory and an advanced field theory were developed to describe the excitation of an 1-1/2-cell RF gun cavity. SUPERFISH was used to calculate the majority of the equivalent circuit elements as ...

Several comprehensive studies of radio frequency (rf) breakdown and rf heating are reported. They are of general interest to magnetic confinement fusion, rf linac, and high power microwave source development. The major results include: (1) a ground-breaking theory of multipactor discharge on dielectric, including a ...

We discuss a possible implementation of high-pressure gas-filled RF (HPRF) cavities in a linear cooling channel for muons and some of the technical issues that must be dealt with. The approach we describe is a hybrid approach that uses high-pressure hydrogen gas to avoid cavity breakdown, along with discrete LiH absorbers to provide the majority of the ...

We discuss a possible implementation of high-pressure gas-filled RF (HPRF) cavities in a linear cooling channel for muons and some of the technical issues that must be dealt with. The approach we describe is a hybrid approach that uses high-pressure hydrogen gas to avoid cavity breakdown, along with discrete LiH absorbers to provide the majority of the ...

The RFOFO ring and its derivative Guggenheim helix are the two efficient lattices for the initial stage of cooling in the Muon Collider. However, they have a certain disadvantage, namely, the RF cavities operate in a strong magnetic field. R&D results to date suggest that this may cause breakdown of cavities before reaching desired ...

Multipacting current can cause breakdowns in high power rf components such as input couplers, waveguide windows, and higher-order mode (HOM) dampers. To understand and prevent the loss of a ceramic window or an input coupler in the Advanced Photon Source (APS) storage ring rf cavity, the multipacting phenomenon is being investigated ...

Experiments in which the powers of two SLAC klystrons were combined and fed into a resonant cavity pulse-compression system (SLED) are described. Pulse powers up to 65 MW into SLED were reached. The corresponding instantaneous peak power out of SLED was 390 MW. After normal initial aging, no persistent RF breakdown problems were encountered. X-radiation at ...

The choice of superconducting materials for accelerator rf cavities has been determined in the past only in part by basic properties of the superconductors, such as the critical field, and to a larger extent by criteria which include fabrication processes, surface conditions, heat transfer capabilities and so on. For cw operated cavities the trend has been toward choosing ...

A study is made of the breakdown of a fine wire during its electric explosion in vacuum. The problem of how the wire diameter, the rate of energy deposition in the wire, and the insulation of the electrode surface near the electrode-wire contact influence the wire explosion and the accompanying breakdown is investigated experimentally. ...

This paper gives a progress report on RF breakdown studies carried out at SLAC on an S-band standing-wave disk-loaded accelerator structure. The structure is the same as described at two earlier conferences but it has been equipped with eight new radial probes and one output port to observe the emission of light, which has not yet been used. The earlier ...

Hisorically, Radio Frequency (RF) windows have been a common point of failure in input power couplers; therefore, reliable RF windows are critical to the success of the Spallation Neutron Source (SNS) project. The normal conducting part of the SNS accelerator requires six RF windows at 402.5 MHz and eight RF ...

By destructive breakdown we mean a breakdown event that results in surface melting over a macroscopic area in a high E-field region of an accelerator structure. A plasma forms over the molten area, bombarding the surface with an intense ion current ({approx}108 A/cm2), equivalent to a pressure of about a thousand Atmospheres. This pressure in turn causes ...

By destructive breakdown we mean a breakdown event that results in surface melting over a macroscopic area in a high E-field region of an accelerator structure. A plasma forms over the molten area, bombarding the surface with an intense ion current ({approx} 10{sup 8} A/cm{sup 2}), equivalent to a pressure of about a thousand Atmospheres. This pressure in ...

By destructive breakdown we mean a breakdown event that results in surface melting over a macroscopic area in a high E-field region of an accelerator structure. A plasma forms over the molten area, bombarding the surface with an intense ion current (~108 A/cm2), equivalent to a pressure of about a thousand Atmospheres. This pressure in turn causes molten ...

Muscle atrophy prevails in numerous diseases (cancer cachexia, renal failure, infections, etc.), mainly results from elevated proteolysis, and is accelerated by bed rest. This largely contributes to increased health costs. Devising new strategies to prevent muscle wasting is a major clinical challenge. The ubiquitin proteasome system (UPS) degrades myofibrillar proteins, but the precise mechanisms ...

FORTE and GPS satellite studies have shown that satellite-based VHF lightning sensors are particularly sensitive to a ubiquitous and unique type of strong in-cloud RF lightning pulse that is sometimes accompanied by a Narrow Bipolar Event (NBE). The physical relationship between NBEs and their impulsive VHF counterparts is not clear. Presumably, the ...

This paper presents measurements of the electron drift velocity Vdr in SF6 gas for high reduced electric fields (E/N = 330-5655 Td (1 Td = 10?17 V cm2)). The drift velocities were obtained using the method of Lisovskiy and Yegorenkov (1998 J. Phys. D: Appl. Phys. 31 3349) based on the determination of the pressure and voltage of the turning points of rf capacitive discharge ...

Abstract The major organic components of smoke particles from biomass burning are monosaccharide derivatives from the breakdown of cellulose, accompanied by generally lesser amounts of straight-chain, aliphatic and oxygenated compounds and terpenoids from vegetation wa...

The mechanisms of high-power microwave breakdown for single and repetitive short pulses are analyzed. By calculation, multipactor saturation with electron density much higher than the critical plasma density is found not to result in microwave cutoff. It is local high pressure about Torr class that rapid plasma avalanche and final breakdown are realized in ...

Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating ...

We have measured the effects of high (0 4.5 T) magnetic fields on the operating conditions of 805 MHz accelerating cavities, and discovered that the maximum accelerating gradient drops as a function of the axial magnetic field. While the maximum gradient of any cavity is governed by a number of factors including conditioning, surface topology and materials, we argue that J x B forces within the ...

The Plasma Material Interaction Group at the University of Illinois and the Fusion Energy Division of ORNL have been conducting breakdown studies to improve voltage hold-off to ultimately improve the performance of ICRF antennas used in fusion applications. The current understanding of the breakdown initiation on RF systems points to ...

Optical breakdown by predetermined laser pulses in transparent dielectrics produces an ionized region of dense plasma confined within the bulk of the material. Such an ionized region is responsible for broadband radiation that accompanies a desired breakdown process. Spectroscopic monitoring of the accompanying ...

This paper reports which gypsum dehydration step is responsible, and to what degree, for developing the morphology of the reaction product and whether it is possible to affect it by changing the reaction conditions. The authors show that the thermal breakdown (200 D) of gypsum single crystals in a 1.33 Pa vacuum changed the original monoclinic structure to a hexagonal and then ...

The exposure of metal targets in N2 and Ar gases at a pressure of 1-50 atm to laser radiation of moderate intensity is studied. This exposure is accompanied by the formation of an optical breakdown in aerosol particles. The sounding ruby laser radiation loses its coherence in the vicinity of these particles.

The condition of the gas breakdown is investigated. Two distinct types were found. One is accompanied with a full production and subsequent contraction of plasma; in the other are glow discharges without the full plasma production. The former was observed by photomultiplier measurement of the light intensity, high-speed camera observation of the ...

Significant performance degradation of superconducting RF (radio frequency) niobium cavities in high RF field is strongly associated with the breakdown of superconductivity on localized multi-scale surface defects lying within the 40 nm penetration depth. These defects may be on the nanometer scale, like grain boundaries and ...

A compact resonant loop antenna is installed on the ORNL Radio Frequency Test Facility (RFTF). Facility characteristics include a steady-state magnetic field of approx. =0.5 T at the antenna, microwave-generated plasmas with n/sub e/approx. =10/sup 12/ cm/sup -3/ and T/sub e/approx. =8 eV, and 100 kW of 25-MHz rf power. The antenna is tunable from approx.22--75 MHz, is ...

A compact resonant loop antenna is installed on the ORNL Radio Frequency Test Facility (RFTF). Facility characteristics include a steady-state magnetic field of {approx} 0.5 T at the antenna, microwave-generated plasmas with n{sub e} {approx} 10{sup 12} cm{sup {minus}3} and T{sub e} {approx} 8 eV, and 100 kW of 25-MHz rf power. The antenna is tunable from {approximately}22--75 ...

In this paper, we present a comparison of the direct-current (DC) and radio-frequency (RF) breakdown behaviours of representative wurtzite- and zinc-blende-phase GaN MESFET structures based on a theoretical analysis. The calculations are made using a full-band ensemble Monte Carlo simulation that includes a numerical formulation of the impact ionization ...

An RF pre-preionizer (applied prior to the main preionization discharge) has been implemented for the FRCHX experiment to increase plasma lifetime. The present 46 MHz system is based on one used on previous experiments such as LSX and TRAP at the University of Washington. RF from a 2.5 KW power supply charges conductors on either side of the quartz vacuum ...

SLAC is committed to developing an X-band source capable of producing 100 Megawatt, 1 microsecond pulses to power the next linear collider. The first experience encountered at SLAC in the X-Band Regime above a few Megawatts was in the relativistic klystron program in cooperation with LLNL and LBL. About 280 MW had been transmitted through a variety of waveguide components but at very short pulse ...

Experiments to investigate copper surface fatigue caused by pulsed rf radiation were carried out using the 30 GHz free electron maser. The copper surface of a special test cavity was exposed to 15�20MW/150�200ns rf pulses with a repetition rate of 1 Hz, providing a temperature rise of up to 250�C in each pulse. An electron microscope was used to ...

Nitric oxide (NO) is one of the universal regulators of cell and tissue metabolism. Besides, it plays the role of one of the main cytotoxic effectors in cell immunity system. High reactivity of NO determines its short lifetime (several seconds) in organism. Low-molecular-weight S-nitrosothiols, S-nitrosocompounds of proteins, dinitrosyl compounds, along with nitrosohemoglobin, nitrosomyoglobin are ...

A study of dark currents has been initiated at the Argonne Wakefield Accelerator Facility (AWA). Emission of dark current is closely related to a breakdown. Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated ...

An experiment to measure the exchange heat capacity of solid /sup 3/He is described. The exchange heat capacity was measured in terms of the Zeeman heat capacity by r-f heating of the exchange bath and measuring the accompanying temperature rise. (L.B.S.)

The electromagnetic radiation emitted in the rf domain by small HE explosions (order of one kg) was previously studied. In particular, the slower structure of the time-domain EMP (1 to 20 milliseconds was studied. The ''hash'' that commonly accompanies th...

Experimental work performed by the Bureau of Mines in a laboratory environment has shown that the formation of failure zones within certain rock types is accompanied by the emission of significant amounts of radiofrequency (RF) electromagnetic (EM) energy...

Studies of low frequency RF systems for muon cooling has led to a variety of new techniques for looking at dark currents, a new model of breakdown, and, ultimately, a model of RF cavity operation based on surface damage. We find that cavity behavior is strongly influenced by the spectrum of enhancement factors on field emission sites. ...

Studies of low frequency RF systems for muon cooling has led to a variety of new techniques for looking at dark currents, a new model of breakdown, and, ultimately, a model of RF cavity operation based on surface damage. We find that cavity behavior is strongly influenced by the spectrum of enhancement factors on field emission sites. ...

It is shown experimentally that a laser-induced breakdown of a liquid is accompanied by chemical reactions initiated by radicals and excited species formed in the spark. It is found that, in water, the laser-induced breakdown is accompanied by the dissociation of water and dissolved nitrogen molecules with the ...

Radio-frequency (rf) atmospheric pressure glow discharges (APGD) are a capacitive nonthermal plasma with distinct advantage of low gas temperature and long-term stability. In practice their ignition is challenging particularly when they are generated at large electrode gaps. To this end, this contribution reports a one-dimensional fluid simulation of gas ...

Because of turnover, protein synthesis and breakdown can each be involved in the regulation of the growth of tissue protein. To investigate the regulation of skeletal-muscle-protein growth we measured rates of protein synthesis and breakdown in growing rats during development on a good diet, during development on a marginally low-protein diet and during ...

The transport of rf-generated plasma through gaps, slots, or tubes is both of physical interest and has important technological applications. We consider a capacitive discharge with the main discharge connected to a peripheral (pumping) region through an insulating annular slot within the discharge gap. We determine the conditions for which ignition occurs, in order to prevent ...

We describe breakdown in rf accelerator cavities in terms of a number of mechanisms. We divide the breakdown process into three stages: 1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, 2) the ionization and plasma growth is modeled using a particle in cell code, 3) we model ...

We describe breakdown in rf accelerator cavities in terms of a number of mechanisms. We divide the breakdown process into three stages: 1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, 2) the ionization and plasma growth is modeled using a particle in cell code, 3) we model ...

The RF breakdown is a phenomenon critical for operation of high-gradient accelerating structures. One of possible reasons for the breakdown is the ohmic heating of microprotrusions on structure surfaces due to the field emitted electron current. In long enough pulses this heating may result in the protrusion melting. In this work we ...

An effort is underway to improve the voltage standoff capabilities of ion cyclotron range of frequencies (ICRF) heating and current drive systems. One approach is to develop techniques for determining the location of an electrical breakdown (arc) when it occurs. A technique is described which uses a measurement of the reflection coefficient of a swept frequency signal to ...

The additional heating of the klystron window is due to the intense x-ray level, produced inside the klystron, illuminating the entrance of the output wave guide. Photo-electric effect, although of low efficiency, produces enough electrons at the right location and right phase to start multipactor, which progresses with increasing intensity towards the window. The intercepted charge and the ...

A new high-voltage scaling based on Kilpatrick's criterion is presented that suggests that voltages more than twice the Kilpatrick limit can be obtained with identical initial conditions of vacuum and surface cleanliness. The calculations are based on the experimentally observed decrease in secondary electron emission with increasing ion-impact energy above 100 keV. A generalized ...

A new high-voltage scaling based on Kilpatrick's criterion is presented that suggests that voltages more than twice the Kilpatrick limit can be obtained with identical initial conditions of vacuum and surface cleanliness. The calculations are based on the experimentally observed decrease in secondary electron emission with increasing ion impact energy above 100 keV. A generalized ...

We describe a model of damage in rf cavities and show how this damage can limit cavity operation. We first present a review of mechanisms that may or may not affect the ultimate fields that can be obtained in rf cavities, assuming that mechanical stress explains the triggers of rf breakdown events. We present a ...

A magnetic field has been applied to the 800 MHz four-waveguide lower-hybrid heating grill on the Versator II tokamak to suppress plasma formation and RF breakdown in the evacuated waveguides during tokamak operation. Without an auxiliary magnetic field, the incident power density is limited typically to 0.13 kW/cm/sup 2/. When the imposed magnetic field ...

The propagation of an rf asymmetric surface barrier discharge in atmospheric pressure air has been investigated. Measurements of the pulse-modulated 13.56 MHz voltage and current together with ICCD images of the plasma were recorded to study the visible plasma structure with respect to the rf pulses, time within the pulses and the rf ...

Two basic designs have been developed for waveguide hybrids, or 3-dB couplers, capable of handling hundreds of megawatts at X-band. Coupling is provided by one or two connecting waveguides with h-plane junctions and matching elements. In the former case, the connecting waveguide supports two modes. Small apertures and field-enhancing e-bends are avoided to reduce the risk of ...

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF ...

A waveguide valve with a peak rf power handling capability of 70 MW and a reliable vacuum seal was needed for changing the new SLC klystrons. The original SLAC indium seal valve experienced rf breakdown above 35 MW and did not make a reliable vacuum seal. A new design was developed which incorporates the old valve housing but employs a ...

The Radiation Sources Working Group addressed advanced concepts for the generation of RF energy to power advanced accelerators. The focus of the working group included advanced sources and technologies above 17 GHz. The topics discussed included RF sources above 17 GHz, pulse compression techniques to achieve extreme peak power levels, components ...

The Radiation Sources Working Group addressed advanced concepts for the generation of RF energy to power advanced accelerators. The focus of the working group included advanced sources and technologies above 17 GHz. The topics discussed included RF sources above 17 GHz, pulse compression techniques to achieve extreme peak power levels, component ...

The Radiation Sources Working Group addressed advanced concepts for the generation of RF energy to power advanced accelerators. The focus of the working group included advanced sources and technologies above 17 GHz. The topics discussed included RF sources above 17 GHz, pulse compression techniques to achieve extreme peak power levels, component ...

Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 260 mJ, 10 MW high power laser radiation inside a 6 cm diameter helical RF coil. We observe quantum resonant multi-photon (REMPI)2 and collisional cascade laser ionization processes that produce high density (ne�7 x 1016/cm^3) cylindrical seed plasmas at 760 ...

The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing, is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds because, in general, a quiet environment is required for the auditory response. The sound is similar to other common sounds such as a click, ...

It is shown that magnicons can be scaled up to high frequency ({ital X}-band and above) at high power and efficiency. Magnicons have an advantage over other slow wave devices in that the structure sizes are comparable to or larger than a wavelength, so RF breakdown should be less of a problem. However, they require higher voltage. The magnicon has the ...

Dual-waveguide lasers transversely excited in parallel from a common source of radio frequency are provided with one or more channels or bores connecting the laser cavities. The dimensions and configuration of the connecting channels are chosen so that the electric field from the applied RF excitation source will be higher in the connecting channels than in either of the ...

The NLC main linac contains 1,116 RF power units, of which 5% are considered ''spares'' for replacement of failed power units, make-up of the energy gain during an RF breakdown, and energy feedback. A more careful accounting for the effects of beam loading indicates that the NLC can operate with less ...

In this letter, the authors present experimental evidence of electron trapping in radio-frequency (rf) atmospheric-pressure glow discharges. By linking electron density to nanosecond plasma images and optical emission spectroscopy, they show that electron trapping occurs under most discharge conditions. The level of electron trapping increases with increasing discharge current ...

The following topics are covered in this report: (1) toroidal field system, (2) induction and poloidal field coil systems, (3) neutral beam heating system, (4) rf heating, (5) mm wave rf plasma breakdown, (6) divertors/limiters, (7) fuel injection, (8) tritium system, (9) materials, (10) vacuum, (11) instrumentation and control, (12) ...

Using a welded beam hole cavity in the range 2 to 4 GHz, the effect of surface treatments of Nb superconducting cavities on Q/sub 0/ and peak rf fields were studied. Values of peak rf fields of 400 and 800 G were obtained respectively for modes with and without electron loading. The latter corresponds to a Q/sub 0/ of 10/sup 11/ and was obtained for ...

A systematic study of structure-mechanical properties relation is reported for MoSi{sub 2}-SiC nanolayer composites. Alternating layers of MoSi{sub 2} and SiC were synthesized by DC magnetron and rf-diode sputtering, respectively. Cross-sectional transmission electron microscopy was used to examine three distinct reactions in the specimens when exposed to different annealing ...

In an effort to locate the cause(s) of high electric-field breakdown in X-band accelerating structures, a systematic study was begun on characterizing the effect of etching time on surface roughness, using OFE copper witness coupons made of the same material that was used for structures and machined in identical fashion to those structures. It was found that the minimum ...

Recently, high-power microwave (HPM) dielectric multipactor is theoretically discovered to be suppressed by utilizing external resonant magnetic field. This paper gives the related experimental demonstration of increasing the vacuum window breakdown thresholds. In the S-band HPM experiment with 0.5 ?s width, the magnetic field with gyrofrequency ? close to ...

Immediately after focal retinal lesions, receptive fields (RFs) in primary visual cortex expand considerably, even when the retinal damage is limited to the photoreceptor layer. The time course of these changes suggests that mere lack of stimulation in the vicinity of the RF accompanied by stimulation in the surrounding region causes the ...

Immediately after focal retinal lesions, receptive fields (RFs) in primary visual cortex expand considerably, even when the retinal damage is limited to the photoreceptor layer. The time course of these changes suggests that mere lack of stimulation in the vicinity of the RF accompanied by stimulation in the surrounding region causes the ...

This investigation examines temperature effects on avalanche breakdown in GaAs MESFETs to determine if this failure mechanism is accelerated by high-temperature life tests. The specific objective is to assess whether the accelerated life-test evaluations performed on a GaAs MESFET planned for use in future Defense Satellite Communications System (DSCS) spacecraft have ...

Session Topics include: Electron-atom collisions; Charged particle distributions and electric fields; Thermal and high pressure plasma processes; Electron and photon interactions; Workshop on the design, calibration, and modeling of research RF plasma processing systems; Posters -- Gaseous electronics; Models and diagnostics of lighting discharges; Electron collisions, ...

This paper is a progress report on studies carried out at SLAC to assess the high-gradient behavior of 11.4 GHz copper accelerator structures for future linear colliders. the structures which have been examined in the last year are a 7-cavity standing-wave (SW) section and a 30-cavity traveling-wave (TW)section. Both structures are of the constant-impedance uniform-aperture type with a 2{mu}/3 ...

This paper is a progress report on studies carried out at SLAC to assess the high-gradient behavior of 11.4 GHz copper accelerator structures for future linear colliders. the structures which have been examined in the last year are a 7-cavity standing-wave (SW) section and a 30-cavity traveling-wave (TW)section. Both structures are of the constant-impedance uniform-aperture type with a 2{mu}/3 ...

This paper describes the current SLAC R&D program to develop room temperature accelerator structures for the Next Linear Collider (NLC). The structures are designed to operate at 11.4 GHz at an accelerating gradient in the range of 50 to 100 MV/m. In the past year a 26 cm constant-impedance traveling-wave section, a 75 cm constant-impedance traveling-wave section, and a 1.8 m traveling-wave ...

A new design for X band dielectric accelerator using a TE-TM mode converter has been proposed and studied. It first converts RF from TE to TM mode in a pure metal section, then a tapered transition section is used for high efficiency transmission to the dielectric accelerator section. Because there is no dielectrics near the RF coupler, this scheme has ...

Ionization cooling is a critical building block for the realization of a muon collider. To suppress breakdown in the presence of the external magnetic field, an idea of using an RF cavity filled with high pressure hydrogen gas is being considered for the cooling channel design. One possible problem expected in the high pressure RF ...

A plasma model is presented for the formation of cathode spots and subsequent crater development near field emission sites on a copper surface in the presence of a strong dc electric field. Adding to previously published models, we propose that the two-stream plasma instability relates the plasma density to its dimensions. Arguments are presented that suggest that the formation and dynamics of ...