-
Dr Richaard Forbes (University of Surrey)16/09/2019, 17:30Field EmissionPoster
This Poster reports a small part of a multi-stage project to improve the interpretation of measured field electron emission (FE) current-voltage [I_m(V_m)] data. The first stage of the project involves five or so proposals that aim to improve data interpretation within the framework of the almost universally used (but not physically realistic) planar emitter approximation. This models...
Go to contribution page -
Dr Ashish Jindal (Sandia National Laboratories)16/09/2019, 17:35Modeling and SimulationsPoster
We are modeling the effects of a field enhancement factor (β) on the generated Fowler-Nordheim current using the Particle-in-Cell Direct Simulation Monte Carlo (PIC-DSMC) method for a vacuum environment. In the present work, we vary the DC voltage, and hence electric field, between two parallel Pt plates in which the modeled electrode surface elements are given a local work function and β by...
Go to contribution page -
Dr Richard Forbes (University of Surrey)16/09/2019, 17:40Field EmissionPoster
An ideal field electron emission (FE) device/system is one in which: (a) the measured current I_m equals the emission current I_e; (b) the characteristic local barrier field F_C is related to the measured voltage V_m by the formula F_C = V_m/ζ_C where the voltage conversion length ζ_C is effectively constant; and (c) the work-function is constant. An orthodox FE...
Go to contribution page -
Dr Wolfram Knapp (Otto-von-Guericke-Universitaet Magdeburg)16/09/2019, 17:45Field EmissionPoster
Highly-alloyed chrome-nickel stainless steel is the most important material in vacuum technology. Especially in high and ultra-high vacuum technology it is used for vacuum chambers and components. One of the main research focuses for 2005 [1] was the study of parasitic field emission of specially treated stainless-steel surfaces for applications in accelerator technology. The measured...
Go to contribution page -
Dr Min Park (Korea Atomic Energy Research Institute)16/09/2019, 17:50ApplicationsPoster
The development of a negative ion beam source has been in progress in KOREA as part of ITER technology R&D programme. The RF negative ion beam source is one of the key parts of ITER neutral beam injection (NBI) system. In particular, the use of Cs leads to a remarkable enhancement of negative ion production and thus enables the extraction of high current negative ion beams. The final...
Go to contribution page -
Mr Jan Paszkiewicz (University of Oxford (GB))16/09/2019, 17:55Field EmissionPoster
The dynamics of dislocation activity under intense electric fields has been proposed as a potential nucleation mechanism of breakdowns. Results of searches for high-frequency fluctuations in field-emitted current in the pulsed DC system at CERN, that could arise as a consequence of changes in the surface geometry as a result of dislocation motion.
Go to contribution page -
David Banon Caballero (CERN - IFIC - University of Valencia (ES))16/09/2019, 18:00ApplicationsPoster
The IFIC RF laboratory will perform the conditioning and high power tests of S-band accelerating structures designed for hadron-therapy with the purpose of investigate their high gradient behaviour. The facility is based on the scheme of the Xbox-3, a X-band test facility at CERN, adapted to operate in S-band. Two medium peak-power (7.5 MW) and high repetition rate (400 Hz) S-band klystrons...
Go to contribution page -
Mr David Banon Caballero (CERN - IFIC - University of Valencia (ES))16/09/2019, 18:05Modeling and SimulationsPoster
Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space...
Go to contribution page -
Dr Wolfram Knapp (Otto-von-Guericke-Universitaet Magdeburg)16/09/2019, 18:10Field EmissionPoster
An underestimated phenomenon in the operation of field electron emission is the smooth transition to glow discharge as a significant pre-stage of vacuum arcs, which usually occur more frequently at higher operation vacuum pressures and higher emission currents in the range of normal glow discharge (> 0.1 mA). This phenomenon can be understood by investigating the transition from field electron...
Go to contribution page -
Kyrre Ness Sjobaek (University of Oslo (NO))16/09/2019, 18:15Modeling and SimulationsPoster
ArcPIC is a 2D electrostatic particle-in-cell code for simulating vacuum arc discharge plasmas.
It is meant to be flexible, making it easy to modify with new surface boundary conditions, external circuits, and more.
ArcPIC was open-sourced 2014, and has since then gone through a technical development and started to be used by a larger community.Especially, the build system has been...
Go to contribution page -
Andrea Zamengo (Consorzio RFX)16/09/2019, 18:25ApplicationsPoster
SPIDER is the full-size prototype of ITER Neutral Beam Injector ion source, in operation since June 2018
Go to contribution page
as part of the ITER Neutral Beam Test Facility located in Padova, Italy. The ion source of SPIDER is
composed of eight Radio Frequency drivers operated in low hydrogen gas pressure, 0.3 Pa, driven at 1
MHz with a total power of 800 kW, an extraction and acceleration system is the used to... -
Yuliia Lebedynska16/09/2019, 18:30Field EmissionPoster
The work concerns relativistic effects and the influence of an external magnetic field on the
Go to contribution page
transmission coefficient. The Fowler-Nordheim equation has been relativistically generalized and effect of
the Lorentz contraction of a potential barrier at the metal-vacuum interface has been found. Influence of
the magnetic field parallel to a metal surface on the transmission coefficient is taken into... -
Dr Wolfram Knapp (Otto-von-Guericke-Universitaet Magdeburg)16/09/2019, 18:35Field EmissionOral
The commonest method of characterising a cold field electron emitter is to measure its current-voltage characteristics, and the commonest method of analysing these characteristics is by means of a Fowler-Nordheim (FN) plot [1]. For example, the field enhancement factor can be calculated. But for novel investigations of the transition from field emission to plasma discharges an extended use of...
Go to contribution page -
Sergio Calatroni (CERN)16/09/2019, 18:40Modeling and SimulationsPoster
Direct field ionisation of neutral atoms may happen when they are immersed in an external electric field of magnitude comparable to the atomic electric field seen by the outer electron shells. The resulting ionisation probability may have a magnitude comparable to the usual electron impact ionisation probability, and thus this process should not be neglected in plasma simulations codes. In...
Go to contribution page -
Xiaoli Guo16/09/2019, 18:45Field EmissionPoster
This research is on the COMSOL simulation of flashover occurring in a MEMS (Micro-Electro-Mechanical System) insulator and electrode unit, both of the electric field at triple point and of electron trajectories in several practical geometries. In some applications of MEMS technology, electrostatic field up to 5-20kV/mm is of interest. One of these applications is using MEMS components for...
Go to contribution page -
Mr David Banon Caballero (CERN - IFIC - University of Valencia (ES))19/09/2019, 17:35Experiments and DiagnosticsPoster
Dark current is particularly relevant during operation in high-gradient linear accelerators. Resulting from the capture of field emitted electrons, dark current produces additional radiation that needs to be accounted for in experiments. In this paper, an analysis of dark current is presented for four accelerating structures that were tested and conditioned in CERN's X-band test facility for...
Go to contribution page -
Dr Atsushi Kojima (QST)19/09/2019, 17:40Experiments and DiagnosticsPoster
A design technique with empirical scaling has been developed in order to design a robust vacuum insulation on the 5-stage electrostatic accelerator with large surface area and locally concentrated electric field, aiming for the acceleration of 1 MeV, 40 A deuterium beams for fusion application. So far, there was no practical design technique and no applicable database of the voltage holding...
Go to contribution page -
roberto cavazzana19/09/2019, 17:45Experiments and DiagnosticsPoster
In RFX-mod2, an experiment for the magnetic confinement of fusion relevant plasmas presently under construction, the in-vessel conductive plasma facing components are expected to be subjected during transient plasma current phases (start-up and termination) to significant electric fields, in the kV/mm range. While such electric fields are of no concern for components in vacuum, the presence of...
Go to contribution page -
Anton Saressalo (Helsinki Institute of Physics (FI))19/09/2019, 17:50Experiments and DiagnosticsPoster
Breakdowns generated with pulsed DC systems between large and fixed Cu electrodes are typically highly localized near the edge of the electrodes. The effect is especially strong on BDs which are generated after the electrode has been conditioned, i.e. when the electric field is near the maximum level. Understanding the reason for this phenomenon can be a key factor in hindering the breakdown...
Go to contribution page -
Brian Bentz (Sandia National Laboratories)19/09/2019, 18:00Experiments and DiagnosticsPoster
The laser-collision induced fluorescence (LCIF) diagnostic allows quantitative and multidimensional interrogation of electron densities and temperatures. We use this diagnostic to interrogate a cathodic arc expanding in 65 mTorr of Helium. Two-dimensional spatial and time resolved images of electron densities and temperatures within the plasma are shown. Optimization methods were implemented...
Go to contribution page -
Tommaso Patton (Consorzio RFX)19/09/2019, 18:05Modeling and SimulationsPoster
The high-Q operation of the ITER tokamak will require two Neutral Beam Injectors (NBIs) for plasma heating and current drive. Each beam will be generated by a 40A current of Deuterium negative ions, accelerated up to the specific energy of 1MeV and then neutralized. The power delivered to the plasma by each NBI shall reach 16 MW with duration up to 1h. The beam source will be constituted by an...
Go to contribution page -
Jan Borburgh (CERN)19/09/2019, 18:10Modeling and SimulationsPoster
In the framework of the Physics Beyond Colliders (PBC) study at CERN, the Electric Dipole Moment (EDM) working group is investigating the feasibility of building a storage ring to precisely measure the permanent electric dipole moment of the proton. As a preparation for this main ring, a prototype ring (PTR) is proposed to demonstrate the feasibility of technologies that are not yet...
Go to contribution page -
Gabriele Croci (Universita & INFN, Milano-Bicocca (IT))19/09/2019, 18:15Experiments and DiagnosticsPoster
The characterization of the X-ray energy spectrum during the high voltage conditioning of a multi electrode vacuum insulated system (such as the MITICA electrostatic accelerator) could be useful to understand which stage is causing the micro discharge onset. This technique seems particularly promising for measuring small dark currents (I< 10μA), which are generally difficult to be measured...
Go to contribution page -
Ruth Peacock (Lancaster University (GB))19/09/2019, 18:20Experiments and DiagnosticsOral
LES (Large Electrode System) is the DC system at CERN, used for observations of the gap between electrodes. This system has view ports that allow for different imaging devices to be set up in parallel to observe the breakdown process. Vacuum arcs can often be seen by eye due to relatively high light intensity, but there are other possible sources of light that may exist before a breakdown....
Go to contribution page -
Iaroslava Profatilova (CERN)19/09/2019, 18:25Experiments and DiagnosticsOral
Pulsed DC systems dedicated to the study of electrical breakdown phenomenon and the conditioning process are part of the CLIC (Compact Linear Collider) project. There are two pulsed DC systems operational at CERN, as well as similar systems at Helsinki and Uppsala Universities. In the systems, two plane electrodes with large surface areas are placed parallel to each other with a separation of...
Go to contribution page -
Jim Norem (Argonne (Retired))19/09/2019, 18:30Experiments and DiagnosticsOral
Useful models of arcing capable of predicting operating gradients in limited environments are beginning to be produced, but generalizing these models to many applications is coming very slowly. We will show how each stage of the arcing process can be explained by many possible mechanisms, each with its own parameter space and peculiarities, and outline how a general model, applicable to many...
Go to contribution page -
Ekaterina Baibuz (University of Helsinki)19/09/2019, 18:35Experiments and DiagnosticsOral
Combining classical electrodynamics and density functional theory (DFT) calculations, we develop a general and rigorous theoretical framework that describes the energetics of metal surfaces under high electric fields. We show that the behavior of a surface atom in the presence of an electric field can be described by the polarization characteristics of the permanent and field-induced charges...
Go to contribution page -
Jyri Kimari19/09/2019, 18:40Modeling and SimulationsOral
Kinetic Monte Carlo (KMC) is among the most efficient methods for modelling diffusion. In the context of CLIC, we're interested in the diffusion processes on the Cu surface - especially under high electric fields that are present prior to electric breakdown events.
The accuracy of a KMC model relies on the comprehensiveness of the catalogue of different migration events that are available...
Go to contribution page -
151. STATISTICAL ANALYSIS OF CURRENT AND X-RAYS SIGNALS FOR A VACUUM HIGH VOLTAGE HOLDING EXPERIMENTsilvia spagnolo19/09/2019, 18:45Experiments and DiagnosticsOral
The High Voltage Padova Test Facility (HVPTF) is an experimental device for investigating HV insulation in vacuum, in support of the realization of MITICA, the prototype of a neutral beam injector for ITER. The facility investigates the physical phenomena underlying voltage holding in vacuum, such as the mechanisms causing breakdowns and the electrode conditioning process, along with testing...
Go to contribution page -
Lee Millar (Lancaster University (GB))19/09/2019, 18:50Experiments and DiagnosticsOral
The CLIC project aims to establish an accelerating gradient of 100MV/m within novel high gradient X-band accelerating structures, this leads to surface electric fields on the order of 220MV/m. In this context, CERN have developed high power X-band RF test stands (Xboxes) to test the prototype structures for CLIC at high power. A summary and analysis of recent RF results from the test stands...
Go to contribution page -
Marco Cavenago (INFN-LNL)19/09/2019, 18:55ApplicationsOral
High voltage platform are of widespread use in nuclear physics accelerator in order to provide the initial acceleration of ion. The ion source environment is particular challeging for high voltage holding, since discharge can be energized from source radiation or secondary particle generated by the ion beam.
Go to contribution page
Moreover spectrometers for charge to mass ratio of exotic nuclei requires a well... -
Sagy Itschak Lachmann (Hebrew University of Jerusalem)19/09/2019, 19:00Experiments and DiagnosticsOral
The prevaling way of analyzing dark currents is by looking only at the mean current. While there have been some work to extract usefull information from that, there's a lot of data being ignored by neglecting the inherently statistical nature of the current.
Go to contribution page
In this talk, I will present a novel method for field estimation and its advantages as opposed to the current method of beta estimation... -
Dr Clark Snow (Sandia National Labs)Experiments and DiagnosticsPoster
Vacuum arc initiation is sensitive to the initial state of the metal electrodes. Surface roughness, oxide thickness, and other surface contaminants impact the arc initiation. In this poster we present results on the impact on arc initiation of dosing metal electrodes with a variety of common gases, such as CO, H2O, O2, Ar, methane, and others. We show results of how the current and voltage...
Go to contribution page -
Dr Byungkeun Na (National Fusion Research Institute)Experiments and DiagnosticsPoster
The neutral beam injection (NBI) system in KSTAR (Korea Superconductor Tokamak Advanced Research) provide heating and current drive to KSTAR tokamak plasma. It is composed of a plasma generator, an accelerator, and neutralizers. The plasma generator and the neutralizer decide the plasma chemistry and finally the beam fraction while the accelerator decides the beam optics. In general, the...
Go to contribution page
Choose timezone
Your profile timezone: