Search results for " plasma"
showing 10 items of 2522 documents
Hydrogen plasma induced photoelectron emission from low work function cesium covered metal surfaces
2017
Experimental results of hydrogen plasma induced photoelectron emission from cesium covered metal surfaces under ion source relevant conditions are reported. The transient photoelectron current during the Cs deposition process is measured from Mo, Al, Cu, Ta, Y, Ni, and stainless steel (SAE 304) surfaces. The photoelectron emission is 2–3.5 times higher at optimal Cs layer thickness in comparison to the clean substrate material. Emission from the thick layer of Cs is found to be 60%–80% lower than the emission from clean substrates. peerReviewed
Cyclotron instability in the afterglow mode of minimum-B ECRIS.
2016
It was shown recently that cyclotron instability in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source (ECRIS) causes perturbation of the extracted ion current and generation of strong bursts of bremsstrahlung emission, which limit the performance of the ion source. The present work is devoted to the dynamic regimes of plasma instability in ECRIS operated in pulsed mode. Instability develops in decaying plasma shortly after heating microwaves are switched off and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high energy electrons. Time-resolved measurements of microwave emission bursts are presented. I…
THE GYROTRON STARTUP SCENARIO IN THE SINGLE MODE TIME DEPENDENT APPROACH
2019
The paper explains how to solve the Gyrotron equation system in the Single Mode Time Dependent Approach. In particular, we point out problems encountered when solving these well-known equations. The starting current estimation approach a using time model is suggested. The solution has been implemented in the Matlab code, which is attached to the article.
Lead evaporation instabilities and failure mechanisms of the micro oven at the GTS-LHC ECR ion source at CERN
2020
The GTS-LHC ECR ion source (named after the Grenoble Test Source and the Large Hadron Collider) at CERN provides heavy ion beams for the chain of accelerators from Linac3 up to the LHC for high energy collision experiments and to the Super Proton Synchrotron for fixed target experiments. During the standard operation, the oven technique is used to evaporate lead into the source plasma to produce multiple charged lead ion beams. Intensity and stability are key parameters for the beam, and the operational experience is that some of the source instabilities can be linked to the oven performance. Over long operation periods of several weeks, the evaporation is not stable which makes the tuning …
An Experimental Study of Waveguide Coupled Microwave Heating with Conventional Multicusp Negative Ion Source
2015
Negative ion production with conventional multicusp plasma chambers utilizing 2.45 GHz microwave heating is demonstrated. The experimental results were obtained with the multicusp plasma chambers and extraction systems of the RFdriven RADIS ion source and the filament driven arc discharge ion source LIISA. A waveguide microwave coupling system, which is almost similar to the one used with the SILHI ion source, was used. The results demonstrate that at least one third of negative ion beam obtained with inductive RF-coupling (RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHz microwave power in CW mode without any modification of the plasma chamber. The co-extracted electro…
Ultrasonic nebulization inductively coupled plasma optical emission spectrometry method for wine analysis
2020
Abstract A methodology was developed to determine mineral elements in wines using Inductively Coupled Plasma Optical Emission Spectrometry combined with ultrasonic nebulization. The concentration of 36 elements (Al, B, Ba, Bi, Ca, Cd, Ce, Co, Cr, Dy, Er, Eu, Fe, Gd, K, La, Lu, Mg, Mn, Mo, Na, Nd, Ni, Pb, Pr, Sb, Sc, Sm, Sr, Tb, Ti, Tm, V, Y, Yb, and Zn) was determined in 59 wine samples and used to distinguish between Brazilian and Spanish wines. The best conditions for the plasma were selected using a two-level factorial design: radiofrequency power 1500 W; plasma gas flow rate 15 L min−1; auxiliary 0.70 L min−1; and nebulizer 0.40 L min−1. An exploratory multivariate analysis by Principal…
Spark Plasma Sintering of Metallic Glasses
2019
Spark plasma sintering (SPS) of metallic glasses (MG) can be quite different from sintering crystalline metallic alloys. Indeed, MG behave differently with increasing temperature, as they encounter a glass transition and devitrification. Their shaping can thus be compared to what can be performed on thermoplastic polymers. SPS is a promising way to prepare bulk parts from amorphous powders, since it allows very fast heating and cooling rates. It gives an advantage to avoid or limit devitrification of the amorphous phase upon the thermal cycle. However, diffusion mechanisms, which generally control densification, are activated at temperatures that are not compatible with MG structural integr…
Production of dense nanostructured materials using FAPAS and SPS techniques
2011
International audience
The role of radio frequency scattering in high-energy electron losses from minimum-B ECR ion source
2021
Abstract The measurement of the axially lost electron energy distribution escaping from a minimum-B electron cyclotron resonance ion source in the range of 4–800 keV is reported. The experiments have revealed the existence of a hump at 150–300 keV energy, containing up to 15% of the lost electrons and carrying up to 30% of the measured energy losses. The mean energy of the hump is independent of the microwave power, frequency and neutral gas pressure but increases with the magnetic field strength, most importantly with the value of the minimum-B field. Experiments in pulsed operation mode have indicated the presence of the hump only when microwave power is applied, confirming that the origi…
The biased disc of an electron cyclotron resonance ion source as a probe of instability-induced electron and ion losses
2019
International audience; Electron Cyclotron Resonance Ion Source (ECRIS) plasmas are prone to kinetic instabilities resulting in loss of electron and ion confinement. It is demonstrated that the biased disk of an ECRIS can be used as a probe to quantify such instability-induced electron and ion losses occurring in less than 10 µs. The qualitative interpretation of the data is supported by the measurement of the energy spread of the extracted ion beams implying a transient plasma potential >1.5 kV during the instability. A parametric study of the electron losses combined with electron tracking simulations allows for estimating the fraction of electrons expelled in each instability event to be…