11th International Workshop on the Mechanisms of Vacuum Arcs (MeVArc 2024)

Session

Experiments and Diagnostics

5 Mar 2024, 10:30

9. The influence of arcing on radio-frequency capacitively coupled plasma

chul hee cho (Chungnam national university)

05/03/2024, 10:30

Experiments and Diagnostics

Oral

While arcing formation mechanism has been widely studied, the influence of arcing on background plasma has remained underexplored. In this study, we investigated the effect of arcing on capacitively coupled plasma by employing arcing induced probe (AIP), which plays a role in localizing arcing on probe tip edge. We analyzed behavior of capacitively coupled plasma by analyzing various...

43. Emission Characteristics of a Broad-Area Molybdenum Cathode under an Inhomogeneous Electric Field

Moein Borghei (Avalanche Energy)

05/03/2024, 11:00

Experiments and Diagnostics

Oral

In electrostatic fusion reactors like the Orbitron, maintaining reliable high-voltage levels is crucial for the confinement of charged particles. Avalanche Energy's ultra-compact bushing, MAKO, plays the key role of transferring voltage from ambient pressure to an ultra-high vacuum environment with pressures below 1e-8 Torr. It features a coaxial configuration with a 1.8-5 cm gap distance and...

24. A 500 kV SF6 insulated feedthrough for inverted insulator photoguns

Gabriel Palacios Serrano (Thomas Jefferson National Accelerator Facility)

05/03/2024, 11:30

Experiments and Diagnostics

Poster

Nuclear physics experiments at Jefferson Lab (JLab) require spin-polarized electron beams generated from delicate semiconductor photocathodes in a photoemission electron gun (photogun). The JLab photogun operates at 130 kV using an inverted geometry alumina insulator (feedthrough) as a holding structure to the highly polished stainless steel cathode electrode inside an ultra-high vacuum...

4. Analysis of the micro-scale dynamics of X-Ray emission profiles collected with a GEM detector in needle-plane experiments at HVPTF

Federico Caruggi (Universita & INFN, Milano-Bicocca (IT))

06/03/2024, 08:00

Experiments and Diagnostics

Oral

The High Voltage Padova Test Facility (HVPTF) is an experiment set in Padova, Italy, operating in the framework of the Neutral Beam Test Facility project of the ITER tokamak. The purpose of HVPTF is to study the phenomenology of discharge events occurring between electrodes at high voltage differences over long vacuum gaps, which is crucial in the development of the Neutral Beam Injector (NBI)...

16. X-ray Micro-Discharges Fine Dynamics in a Vacuum High Voltage Experiment

Silvia Spagnolo (Consorzio RFX)

06/03/2024, 08:30

Experiments and Diagnostics

Oral

The High Voltage Padova Test Facility (HVPTF) is an experimental device for investigating High Voltage Direct Current insulation in vacuum, in support of the realization of MITICA, the prototype of a neutral beam injector for ITER. Inside a high vacuum chamber, two stainless steel electrodes, separated by a few centimeters gap, can achieve a voltage difference up to 800 kV. During the...

49. Aspect of High Field Testing

Victoria Madeleine Bjelland

06/03/2024, 09:00

Experiments and Diagnostics

Oral

The Large Electrode System (LES) is a pulsed high-voltage DC test stand located at CERN where its main objective is investigating the origin behind breakdowns. Breakdowns are an important limiting factor in high electric field applications and ongoing studies are performed to better understand the origin behind this phenomenon. Our experimental setup requires two electrodes, having a gap...

17. Study of different materials exposed to low energy H- irradiation and its effects on high voltage breakdown resistance

Catarina Serafim (CERN)

06/03/2024, 09:30

Experiments and Diagnostics

Oral

During the operation of LINAC4, up to 25% of the source beam current is routinely lost in the Radio Frequency Quadrupole (RFQ) at an energy between 0.045 and 3 MeV. These losses can cause surface modifications which in turn may lead, in areas of high electric field, to an increased vacuum breakdown rate. An experimental study has been made to identify materials with high electric field...

12. Field Dependence of Conditioning Part 1: Electrode Simulation and Design

Mr Lee Millar (CERN)

06/03/2024, 13:00

Experiments and Diagnostics

Oral

A model has been developed at CERN to simulate the procession of conditioning in high-field systems [1]. Any arbitrary geometry may be meshed and simulated in spatially resolved fashion, and the effects associated with a variation in the surface electric field, and different algorithmic approaches to conditioning, have been investigated. To test and validate these hypotheses, the model was...

14. Field Dependence of Conditioning-Experimental Measurements

Victoria Madeleine Bjelland

06/03/2024, 13:30

Experiments and Diagnostics

Oral

Two chamfered electrodes were tested in the Large Electrode System (LES) at CERN. Having a flat-shaped cathode and a frustum shaped anode gives a higher electric field in the centre of the electrodes, while it linearly decays towards the edge.
Normal breakdown rates are observed in the centre of the electrodes. However, lower breakdown rates with regards to the electric field was found for...

37. Signs of plastic response in surfaces exposed to high electric fields.

Yinon Ashkenazy (The Hebrew University of Jerusalem (IL))

06/03/2024, 14:00

Experiments and Diagnostics

Oral

Various theoretical efforts explored the link between breakdown nucleation and pre-breakdown plastic activity in surfaces exposed to high electric fields. However, identifying such a mechanism is challenging as there are no clear indications of what structural evolution evidence should be identifiable in ex-situ post-mortem samples. The current state of research efforts to identify and measure...

48. In-situ observation of field-induced nano-protrusion growth on a carbon-coated tungsten nanotip

Andreas Kyritsakis

06/03/2024, 14:30

Field Emission

Oral

Nano-protrusion (NP) on metal surface and its inevitable contamination layer under high electric field is often considered as the primary precursor that leads to vacuum breakdown, which plays an extremely detrimental effect for high energy physics equipment and many other devices. Yet, the NP growth has never been experimentally observed. Here, we conduct field emission (FE) measurements along...

15. Aspect of High Field Testing

Victoria Madeleine Bjelland

Experiments and Diagnostics

Oral

The Large Electrode System (LES) is a high voltage pulsed DC test stand to investigate breakdowns. Many materials have undergone testing by conditioning, as well as field emission measurements and light spectroscopy investigation.

35. Study on Transition from Field Emission to Delay Breakdown

Xinguo Zhang

Experiments and Diagnostics

Oral

The application of an electric field to a metal surface induces field emission (FE), serving as the initial electron source for vacuum breakdown. Delay breakdown, occurring randomly under a relatively low electric field, poses a critical challenge in engineering applications compared to immediate breakdown. However, the physical mechanisms that lead from FE to delay breakdown are still...