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Sergio Calatroni (CERN)05/10/2026, 09:00Oral
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Walter Wuensch (CERN)05/10/2026, 09:15
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Victoria Madeleine Bjelland05/10/2026, 10:00
Vacuum breakdowns remain the current limitation to achieving higher gradients in accelerating structures and also appear in accelerator components intended for the proposed CERN Future Circular Collider. To study vacuum breakdowns and other high-gradient phenomena such as field emission, CERN has developed a dedicated experimental test stand called the Large Electrode Systems. Past results...
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Mr Izan Valencia Ruiz (CERN)05/10/2026, 10:30
Vacuum arcs are a common problem for electrostatic septa equipment in particle accelerators. Observations during the Large Electron Positron (LEP) era showed an increase in the High-Voltage Breakdown Rate (HVBR) of electrostatic separators due to Synchrotron Radiation (SR) striking the equipment. As part of the studies for CERN's next accelerator, the Future Circular Collider (FCC-ee), an...
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Mircea-George Coman05/10/2026, 11:30
The maximum field that can be sustained in normal and superconducting cavities is limited by field emission and vacuum arcs and it can be improved after a conditioning process. The HV DC pulsing system located in FREIA has the capability of investigating the conditioning process for different materials at cryogenic and room temperatures. Because at the present, the conditioning process is not...
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Yinon Ashkenazy (The Hebrew University of Jerusalem (IL))05/10/2026, 12:00
Dislocation dynamics are a leading candidate mechanism for high-field conditioning. The mobile-dislocation-density fluctuation model predicts that conditioning changes the near-surface dislocation structure [1]. Cross-sectional microscopy of conditioned copper later revealed a dislocation-denuded zone within the top ~100–200 nm, but these measurements were limited to small, isolated regions...
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Nicola Pilan05/10/2026, 12:30
Content*
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The present contribute describes and analyzes recent experimental results obtained at the High Voltage Padova Test Facility (HVPTF), the laboratory aimed at supporting the development of the prototype for the ITER NBI.
A one-dimensional stationary model, which describes the development of a Townsend discharge including the effects due to bremsstrahlung radiation and photoelectric... -
Serhii Lebedynskyi (Institute of Applied Physics, National Academy of Sciences of Ukraine)05/10/2026, 14:30
Modern research treats vacuum electrical breakdown not as an instantaneous cathode-centric event, but as a complex, multistage process involving intense electro-thermal interactions between both poles of the electrode system. While the initial triggering stages are traditionally attributed to field electron emission from cathode micro-protrusions, the anode actively modulates the pre-breakdown...
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Dr Matej Klas (Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University)05/10/2026, 15:00
Vacuum microdischarges driven by repetitive voltage pulses exhibit non-random variations in breakdown voltage, indicating the presence of a memory effect between successive pulses. In previous experiments with palladium electrodes, the breakdown voltage was found to increase progressively over a series of discharges before undergoing a sudden reset after reaching a critical value [1]. This...
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Mr Jianyu Wang (Xi'an Jiaotong University)05/10/2026, 16:00
Electric-field-induced effects severely impact the long-term stability and reliability of nanoelectronic devices with nanogaps, such as field emission nanodiodes, field-effect nanotransistors and ultrafast switches. However, the damage mechanisms behind nanostructured electrode under high electric fields remain unclear. In this talk,we will introduce our collabrative work on the deformation...
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Prof. Veronika Zadin (University of Tartu (EE))05/10/2026, 16:30
High electric fields, in order of 100 MV/m and more, are common in particle accelerators, high electric field devices, electron sources, vacuum switches etc. These devices suffer from the presence of the vacuum breakdown. Vacuum breakdown is an electric discharge arc that forms spontaneously, is often hard to predict and is one of the limiting factors for such devices. One of the hypotheses...
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Victoria Madeleine Bjelland05/10/2026, 17:00Poster
Vacuum breakdowns remain the current limitation to achieving higher gradients in accelerating structures and also appear in accelerator components intended for the proposed CERN Future Circular Collider. To study vacuum breakdowns and other high-gradient phenomena such as field emission, CERN has developed a dedicated experimental test stand called the Large Electrode Systems. Past results...
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Dr Richard G. Forbes (University of Surrey)05/10/2026, 17:01Poster
The apex sharpness ratio sigma_a (=height/apex-radius) describes the sharpness of a "post-on-a-plane", here in parallel-planar-plate geometry. The apex field enhancement factor gamma_a = c_a(sigma_a)*sigma_a, where the apex sharpness coefficient c_a depends on the post shape. The two simplest post shapes are the "hemi-prolate-spheroid" (HPS) and the "hemisphere on a cylindrical post" (HCP)....
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Dr Richard G. Forbes (Uni eersity of Surrey)05/10/2026, 17:02Poster
Theoretical aspects of the published literature of field electron emission (FE) can be confusing or misleading. In the last few years the author has detected over 200 published papers deserving of basic theoretical improvement. To help remedy this situation, this Poster: (a) outlines an overview of the present state of basic electrostatic FE theory, as used in technological contexts, at a...
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18. DC High Voltage Pulse test to Investigate new materials for High gradient accelerating structureShubham Tiwari (SOKENDAI-KEK)05/10/2026, 17:03Poster
This study presents the development of a DC high-voltage pulse test platform for investigating the breakdown characteristics of candidate materials for next-generation high-gradient accelerating structures operating at accelerating gradients of 100 MV/m or higher. Compared with RF-based test systems with cavities, the DC pulse approach offers a compact and versatile experimental scheme based...
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Mr Izan Valencia Ruiz (CERN)05/10/2026, 17:04Poster
Vacuum arcs are a common problem for electrostatic septa equipment in particle accelerators. Observations during the Large Electron Positron (LEP) era showed an increase in the High-Voltage Breakdown Rate (HVBR) of electrostatic separators due to Synchrotron Radiation (SR) striking the equipment. As part of the studies for CERN's next accelerator, the Future Circular Collider (FCC-ee), an...
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Momoko kato05/10/2026, 17:05Poster
The successful operation of Negative ion driven Neutral Beam Injectors (NBIs) for future fusion devices, such as ITER, relies strictly on multi-megavolt DC vacuum insulation. The Tokamak magnetic fields penetrating the beam source bushing—where individual intermediate gaps sustain up to 200 kV DC—are projected to significantly alter electron dynamics and degrade voltage holding due to the...
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Iaroslava Profatilova05/10/2026, 17:06Poster
Abstract
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The EU Horizon Europe project HIGHEST2 aims to explore the potential of high-temperature superconducting (HTS) tapes for future high-gradient RF and accelerator applications through a coordinated program of material development, RF characterization, and high-field testing. As part of the project, Uppsala University's FREIA Laboratory is responsible for investigating the... -
Mats Göhrmann (elenia Institute for High Voltage Technology and Power Systems - Braunschweig, Germany)05/10/2026, 17:07Poster
Vacuum arcs during AC‐current interruption constitute complex multiphysics phenomena whose behavior directly impacts the reliability and lifespan of electrical switching devices. Their dynamic development is governed by coupled electrical discharge dynamics, plasma‐radiative processes, and magnetic field interactions. A holistic measurement approach which is simultaneously capturing these...
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Chris Moore05/10/2026, 17:08Poster
Recent work on vacuum discharge with electrodes held at cryogenic temperatures [1] found interesting anode breakdown spot morphology that exhibited a “shielded” region at the center of the spot where melt did not occur. If the surface melt is due to electron energy flux, then the observed anode spot feature suggests a central region where the electron flux is excluded. This bears a striking...
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Prof. Veronika Zadin (University of Tartu (EE))05/10/2026, 17:09Poster
Surface diffusion may contribute to the formation and growth of field-enhancing protrusions preceding vacuum-arc breakdown in high-gradient metallic structures [1,2]. Electric-field gradients can bias atomic migration toward the edges and vertices of existing surface asperities [3,4]. As these features grow, their increasing aspect ratio enhances the local electric field and field gradient,...
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C. S. Cró (Universidade da Madeira / IPFN)05/10/2026, 17:10Poster
Vacuum breakdown is one of the main factors limiting the performance of high-power vacuum devices, including accelerator structures and vacuum interrupters. Although enhanced field emission is widely accepted as the initiating mechanism, the physical processes governing the transition from localised electron emission to a fully developed vacuum arc, and the associated surface damage, remain...
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Gerard Emile Lawler (Paul Scherrer Institute)05/10/2026, 17:11Poster
Terahertz (THz) electromagnetic structures have emerged as a promising platform for compact beam manipulation and acceleration, offering accelerating and deflecting fields comparable to those achievable in existing RF systems while operating with ultrashort pulses and high frequency. As these devices continue toward higher field amplitudes and practical implementation, many of the challenges...
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Martin J. Guillon (Laboratoire de Physique des Plasmas (LPGP), Université Paris-Saclay, France.)05/10/2026, 17:12Poster
Among the scenarios for the initiation of an electrical arc in vacuum, the discharge along an insulating surface, called a "flashover" (FO), is the one under study. Primary electrons are assumed to be emitted by field emission from the triple point (local field > $10^9$ V/m). These electrons can then mutliply and propagate along the surface of the ceramic through secondary electron emission...
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Richard G. Forbes (University of Surrey)05/10/2026, 17:13Poster
A recent paper by Nongchan Tang et al. [Phys. Scripta 101 (2026) 01530] reports an experimental "Study on influence of temperature on field emission performance of pure titanium and oxygen-free copper". There are difficulties with the field electron emission (FE) theory presented in this paper. However, a theoretical re-examination by the present author shows that their experimental results...
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Shenli Jia05/10/2026, 17:14Poster
Alumina ceramics are widely used as insulating envelopes in vacuum interrupters, and their vacuum surface flashover voltage directly affects the insulation level. Conventional improvement by increasing ceramic length enlarges the equipment and raises manufacturing costs. In this study, periodic triangular microgrooves were fabricated on cylindrical alumina surfaces to improve the flashover...
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Dr Richard G. Forbes (University of Surrey)06/10/2026, 09:00
Recent modelling of electrical breakdown in vacuum [Koitermaa et al., arXiv:2606.05893] has explored the possibility that the emission of negatively charged nanoparticles contributes to vacuum arcing. With positively charged emitters, the emission of nanoparticles and droplets is a well-known and significantly studied phenomenon, in the contexts of liquid metal ion sources, focused ion beam...
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Dr Jonathan Ludwick (Air Force Research Laboratory/AeroVironment)06/10/2026, 09:30
Field emission calculations with atomic considerations using density functional theory (DFT) can yield vastly different results than standard field emission theory that neglects atomic level details. Historically, macroscopic properties such as bulk work function and conductivity have been used to characterize a promising emitter candidate, but DFT calculations can provide insight into why...
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Dr Salvador Barranco Cárceles (Université Claude Bernard Lyon 1)06/10/2026, 10:00
Increasing demands on electron sources necessitate an evolution of the simple models and canonical equations originally used to describe them. To support advanced beam optics simulations and complex emission scenarios, these foundational equations must be refined. Given the significant progress made over the last two decades, it is now appropriate to update these formulations into more...
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Dr Erik Taylor (S&C Electric Company)06/10/2026, 11:00
Field emission current measurements in vacuum are a function of the electric field stress within the device. The electric field stress is proportional to the applied voltage; it is also inversely proportional to the distance between the parts. Although some devices have fixed dimensions, vacuum interrupters (VI) have a moveable contact that allows for in-situ change of the contact gap. ...
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Dr Pascal Vincent (université Lyon 1)06/10/2026, 11:30
High-current field emission cathodes (HCC) are essential for the next generation of compact vacuum electronic devices, such as portable X-ray tubes and THz amplifiers. While vertically aligned carbon nanotubes (CNTs) are established emitters, they often suffer from mechanical instability and tearing under high electric fields. This study presents an original and robust alternative using...
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Brian Bentz (Sandia National Laboratories)06/10/2026, 12:00
Multi-species cathodic vacuum arcs can exhibit expansion dynamics that are not captured by single-ion or single-fluid descriptions. We report time-resolved two-dimensional measurements of electron density and temperature in the expansion region of a cathodic vacuum arc after electrode saturation with hydrogen. The measurements were obtained using laser-collision-induced fluorescence (LCIF)...
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Marzhan Toktaganova06/10/2026, 14:00
Vacuum breakdown can involve intense energy transfer to metallic surfaces, potentially leading to local melting of nanoscale asperities. In this work, we investigate whether such molten asperities can undergo Taylor-cone-like deformation under an applied electric field. Using FEMOCS coupled with molecular dynamics, we simulate molten copper surfaces containing pre-existing hemispherical...
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Juliette Plouin06/10/2026, 14:30
Muon colliders have a great potential for high-energy physics. They can offer collisions of point-like particles at very high energies, since muons can be accelerated in a ring without limitation from synchrotron radiation. However, a number of technical challenges must be overcome, one of them concerning the muon beam compression into a minimum phase-space volume before acceleration. Each of...
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ROLF KARL OTTO BEHLING (KTH Stockholm, Sweden)06/10/2026, 15:00
Microparticles have been known to play an important role in triggering vacuum discharges. However, the underlying mechanisms are still poorly understood. Large, slow-moving microparticles rebound elastically. Small, fast-moving microparticles may transfer their kinetic energy inelastically to the target electrodes, but the small amount of vapor produced appears insufficient for electrical...
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C. S. Cró (Universidade da Madeira / IPFN)06/10/2026, 16:00
Space charge strongly influences electron transport in high-field vacuum gaps, as electrons emitted from a cathode modify the electrostatic field governing their subsequent motion. The space-charge-limited current density was originally derived by Child and Langmuir for a one-dimensional planar diode [1,2], and analytical expressions have subsequently been obtained for selected non-planar...
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Wei Yang (Institute of Applied Physics and Computational Mathematics)06/10/2026, 16:30
An electrostatic particle-in-cell simulation code with Monte Carlo collision (PIC-MCC) and direct simulation Monte Carlo (DSMC) frameworks has been developed in this work. The code integrates particle pushers and collision modules to track macro-particles including electrons, neutral atoms, ions and photons. Its collision modules cover Coulomb collisions, elastic collisions, excitation and...
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Ansar Aryngazin06/10/2026, 17:00
Although widely used, the physics of arcs seems to be advancing slowly, partially due to the wide variety of variables, measurement difficulties, and experimental priorities. In a rf system, the maximum gradient is determined by the behavior of arcs that short the system. We describe details of our arc model based on results of experiments done at 805 MHz, over a decade in the Muon Collider...
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Dr Flyura Djurabekova (Helsinki Institute of Physics (FI)), Flyura Djurabekova06/10/2026, 17:30
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Sergey Gortschakow07/10/2026, 09:00
One of the most widespread applications of high-current vacuum arcs are the vacuum switching devices. Their lifetime and reliability depend on many factors, such as number of operations at standard and short-circuit conditions, cumulative thermal and electric load of the contact system, electrode material. The arc plasma has a direct impact on those factors. Analysis of arc plasma properties...
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XU Huikai07/10/2026, 09:30
Cathode spots are the most fundamental plasma sources in vacuum arcs. The metal vapor, ions, and electrons ejected from cathode spots into the interelectrode gap determine the characteristics of vacuum arcs. Although conventional slit spectroscopy can resolve the spatial distribution of different components along a one-dimensional path, the limited one-dimensional spatial information restricts...
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Xiaoxi Le (Sichuan University)07/10/2026, 10:00
During vacuum interruption, contact surface melting and metal particles motion critically impair post-arc dielectric recovery and elevate reignition risks. Experimental observations reveal that when the current density exceeds a specific threshold, the cathode exhibits macroscopic molten pool activity, characterized by localized luminescence, fluctuations in the molten region, and rapid...
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Xiyuan Liao07/10/2026, 11:00
Active current injection DC circuit breakers (ACI DCCBs) offer low conduction losses and economic advantages, while their interruption performance is strongly influenced by the post-arc dielectric recovery of the vacuum interrupter (VI) following an artificial current zero (CZ). Short arcing durations, high and nonuniform electrode temperatures, high di/dt at forced CZ, and a rapidly rising...
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Mr Andreas Lawall (Siemens AG)07/10/2026, 11:30
Vacuum interrupters are widely used in medium-voltage switching devices due to their reliability and environmental advantages. This study evaluates CuCr40 disk-shaped contacts produced through sintering and arc-melting process. To investigate their behavior during arc interruption, experiments were conducted at four different current levels and different polarities. We used near-infrared (NIR)...
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Jianyu Wang07/10/2026, 12:00
Vacuum breakdown in CuCr contacts severely affects the operational reliability of vacuum circuit breakers. Although previous studies have mainly focused on the macroscopic breakdown characteristics and microstructure regulation of CuCr contacts, the intrinsic vacuum breakdown behavior associated with individual constituent phase (e.g., Cu phase and Cr phase) remains unclear. In this work, an...
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Sergio Calatroni (CERN)07/10/2026, 12:30
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Deniz Libert (Institut de Recherche Dupuy de Lôme, Laboratoire Plasma et Conversion d'Energie, Schneider Electric)08/10/2026, 09:00
Vacuum circuit-breakers are increasingly adopted as the electrical industry transitions away from SF₆-based technologies, yet the thermal behavior of CuCr electrodes during arc interruption remains insufficiently characterized. Prior studies using Short-Wave Infrared (SWIR) imaging, 2D pyrometry, or intensified CCD systems have reported contact-surface temperatures ranging from ~1400 K to...
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Yongjia Luo (Sichuan University)08/10/2026, 09:30
High-voltage vacuum interrupters impose increasingly stringent requirements on the dielectric strength of the main contact gap. AC spark conditioning is an effective method for improving the dielectric strength of vacuum gaps. This study investigated the dependence of AC spark-conditioning effectiveness on the breakdown current action integral under a quasi-uniform electric field. CuCr50...
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Lijun Wang (Xi'an Jiaotong University)08/10/2026, 10:00
Numerical simulation is very useful to understand the internal mechanism of vacuum arcs and vacuum interruptions. In this paper, a three-dimensional MHD model of Transverse Magnetic Field (TMF) Vacuum Arcs has been established, and the arc behavior in AC and DC interruption processes has been simulated. Firstly, the characteristics of fully constricted vacuum arc under TMF for AC interruption...
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Prof. Michael Kurrat (Institute for High Voltage Technology and Power Systems. Technische Universitaet Braunschweig)08/10/2026, 10:30
Publishing research data is essential to harness collective expertise, foster new insights, and drive cross-disciplinary innovation. Open datasets let researchers build on prior work, avoid duplication, and reveal otherwise hidden patterns. Yet simply sharing raw files is not enough: poorly organized repositories become chaotic and hinder discovery. Every publication must rest on three...
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Michael Keidar08/10/2026, 11:30
We will present recent results related to control of vacuum arc ignition and erosion in pulsed vacu-um arc devices. As a particular example, we will consider vacuum arc microthruster device. To this end, we will discuss breakdown process in the case of a micro-vacuum arc thruster. In these de-vices ignition analysis includes effects of insulator material, cathode material deposition and cyclic...
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Dr Tetsuo Abe (KEK)08/10/2026, 12:00
Multiple-sector X-band accelerating structures were designed and fabricated with four quadrants [Nucl.Instrum.Meth.A 1063 (2024), 169272]. We carried out high-power tests at Nextef2, an X-band high-power test stand in KEK, for two such test cavities fabricated using hard pure-copper and copper-silver with the same electrical design. We report the results of the tests and postmortem...
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WONNYOUNG JEONG (Chungnam National University)08/10/2026, 12:30
Radio-frequency (RF) plasmas are widely used in industry, especially in semiconductor manufacturing, which makes arcing in RF plasmas an important problem. Research on this arcing has so far focused mostly on mitigating or avoiding it, while the intrinsic physics of the arcing itself remains far less studied than in vacuum arcs and related fields.
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In this work we built an arcing-induction... -
shilong gao (Institute of Modern Physics, Chinese Academy of Sciences)08/10/2026, 14:30
Conventional RFQ accelerators are built for engineering needs, not for breakdown studies. Their electrode geometry is fixed, and the breakdown data they produce during conditioning and operation are too sparse and uncontrolled to support systematic mechanism research. As a result, despite decades of progress in threshold criteria, from the Kilpatrick limit to the modified Poynting vector Sc,...
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Connor Gunter (SLAC National Accelerator Laboratory)08/10/2026, 15:00
Maximizing accelerator operating gradients can reduce system cost and footprint while enabling higher beam energies. However, radiofrequency (RF) breakdown remains a primary limit on achievable accelerating gradient. In this study, we observe breakdown dynamics in a distributed coupling accelerating structure by measuring the low-power RF response of a coupled-cavity system in various...
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21. Basic studies of titanium and molybdenum high-field electrodes for high-brightness electron gunsDr Kazuaki Togawa (RIKEN SPring-8 Center)08/10/2026, 15:30
To increase the electron-beam brightness at the X-ray free-electron laser facility SACLA, we are developing a next-generation high-field thermionic electron gun. In 2024, we achieved accelerating fields exceeding 40 MV/m in a few-microsecond pulses using electrodes made of ultra-pure titanium [1, 2]. We consider a molybdenum anode, which is robust against beam irradiation, preferable for...
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Nicolas Fil08/10/2026, 16:30
CNES, the French Space Agency, has been studying high power radio frequency (RF) effects – Multipactor, Corona and Passive Intermodulation – on space systems for many decades, starting from J. Sombrin Multipactor theory and models [1] to ongoing activities spanning TRL◊ from 1 to 7 with our collaborators from academia, agencies, and industries. Our main objective is to better understand and...
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Dr Moein Borghei (Avalanche Energy)08/10/2026, 17:00
Crossed-field devices use a magnetic field ($B$) perpendicular to the electric field ($E$) to modify the motion of charged particles. Such devices find applications in magnetrons, space propulsion, pulsed power systems, plasma sources, and fusion energy. In a crossed-field gap, a transverse magnetic field restricts the mobility of electrons moving toward the anode, forcing them into curved...
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Sergio Calatroni (CERN)08/10/2026, 17:30Oral
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