0000000000851618
AUTHOR
R. Kronholm
Experimental evidence on photo-assisted O$^-$ ion production from Al$_2$O$_3$ cathode in cesium sputter negative ion source
The production of negative ions in cesium sputter ion sources is generally considered to be a pure surface process. It has been recently proposed that ion pair production could explain the higher-than-expected beam currents extracted from these ion sources, therefore opening the door for laser-assisted enhancement of the negative ion yield. We have tested this hypothesis by measuring the effect of various pulsed diode lasers on the O$^-$ beam current produced from Al$_2$O$_3$ cathode of a cesium sputter ion source. It is expected that the ion pair production of O$^-$ requires populating the 5d electronic states of neutral cesium, thus implying that the process should be provoked only with s…
Method for estimating charge breeder ECR ion source plasma parameters with short pulse 1+ injection
A new method for determining plasma parameters from beam current transients resulting from short pulse 1+ injection into a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS) has been developed. The proposed method relies on few assumptions, and yields the ionisation times $1/n_e\left\langle\sigma v\right\rangle^{\text{inz}}_{q\to q+1}$, charge exchange times $1/n_0\left\langle\sigma v\right\rangle^{\text{cx}}_{q\to q-1}$, the ion confinement times $\tau^q$, as well as the plasma energy contents $n_e\left\langle E_e\right\rangle$ and the plasma triple products $n_e \left\langle E_e\right\rangle \tau^q$. The method is based on fitting the current balance equation on the extract…
The role of rf-scattering in high-energy electron losses from minimum-B ECR ion source
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 origin of the …