Conveners
Experiments & Diagnostics: Effects of H- irradiation
- Walter Wuensch (CERN)
Experiments & Diagnostics: DC systems
- Sergio Calatroni (CERN)
Experiments & Diagnostics
- Marek Jacewicz (Uppsala University (SE))
Experiments & Diagnostics: Breakdown in RF structures
- Antonio De Lorenzi (Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, Padova, Italy)
The LINAC 4 is a negative hydrogen linear ion injector, scheduled to become the next proton bream source for the Large Hadron Collider (LHC) at CERN. A Radio Frequency Quadrupole (RFQ) is the first stage of acceleration in LINAC 4, capturing a 70mA, 45keV beam from the ion source and accelerating it to 3MeV. After one year of test operation the RFQ was inspected with an endoscope and surface...
The Advanced Electron Microscopy team at CERN uses advanced material characterization techniques, such as Scanning Electron Microscope – Focused Ion Beam (SEM-FIB), Electron Backscattered Diffraction (EBSD), or 3D FIB tomography in order to evaluate production techniques, help to optimize fabrication processes, and to analyse materials used in accelerator facility (e.g. as collimators,...
In order to determine if beam loss damage can induce breakdown, tests have been done in the pulsed DC system at CERN. This system consists of 2 large surface area high precision machined electrodes that are placed in parallel to each other with a gap between 40um and 100um, under high vacuum. The systems are dedicated to studying electrical breakdown phenomena and conditioning processes. A...
Recent tests have been carried out in a cryogenic pulsed high-voltage system in the FREIA Laboratory to investigate the aptness of heat-treated (soft) copper and non-treated (hard) copper as a candidate for CLIC accelerating structures. The surface of the soft copper electrodes was exposed to high electric fields in the range from room temperature to cryogenic temperatures. We calculate the...
One of the major topics in the vacuum arcing community during the recent years has been the balance between the bulk and surface effects on the breakdown generation.
In our recent study, argon and oxygen plasma were used to clean the surfaces of copper electrodes prior exposing them to high-voltace DC pulses and breakdowns. This was done without the need to open the vacuum and expose the...
Cu electrodes are widely used in accelerators, for example in CLIC [1]. One of the problems arising in the accelerator is the breakdown phenomenon [2] causing damage to the accelerating structures and disturbances in the accelerated beam. The cause of the vacuum breakdowns is still under investigation and the electrodes regularly investigated for clues.
In this study a Cu cathode with its...
The possibility that the flow of electrons emitted by a cathode at high dc voltage is essentially due to local emission of a covering dielectric layer is at the basis of the BIRD (Breakdown Induced by Rupture of Dielectric) model. This model assumes that, in presence of sufficient electric field, the electrons trapped in polarization structures of the dielectric layer are extracted by quantum...
This work compares three different procedures for the application of the Lightning Impulse Voltage Waveform (LIVW) with 1.2/50 μs front/half value times: Up & Down (UD), Always Breakdown (AwBD) and Multilevel (ML) to obtain the voltage breakdown distribution for Vacuum Interrupters (VIs).
The voltage pulses were applied to several VIs for medium voltage application with both fixed and...
Feasibility of the production with ionized sputtering of Mo/Cu multilayers with nanometer periodicity inside compact X-band radio-frequency cavities is studied. High gradients require high electromagnetic fields and power flows, which pose serious issues with the materials. Pulsed stress at surface could be responsible of the surface breakup by cyclic fatigue. Nanometer periodicity metallic...
As breakdowns are a major concern in the use of vacuum electronics systems and DC/RF accelerators, there is a need then to be able to characterize these breakdowns and measure the probability rate during conditioning of these devices in real time [1,2]. This results in the need for a software that can automate the conditioning process. Such automation could allow for high accuracy calculations...
