Thermal Design of Refridgerated Hexapole 18 GHZ ECRIS HIISI

A project is underway for constructing a new 18 GHz ECR ion source HIISI at University of Jyväskylä. An innovative plasma chamber structure with grooves at magnetic poles for larger chamber radius at poles. The hexapole will be refridgerated to sub-zero temperatures to boost the coercivity and the remanence of the permanent magnet material and to allow the use of high remanence, low intrinsic coersivity permanent magnet materials. The hexapole structure is insulated from high temperature solenoid coils and plasma chamber by vacuum. The thermal design of the structure has been made using a thermal diffusion code taking in account radiative, conductive and convective heat transfer processes. …

The extraction of negative carbon ions from a volume cusp ion source

Acetylene and carbon dioxide gases are used in a filament-powered volume-cusp ion source to produce negative carbon ions for the purpose of carbon implantation for gettering applications. The beam was extracted to an energy of 25 keV and the composition was analyzed with a spectrometer system consisting of a 90° dipole magnet and a pair of slits. It is found that acetylene produces mostly C−2 ions (up to 92 µA), while carbon dioxide produces mostly O− with only trace amounts of C−. Maximum C−2 current was achieved with 400 W of arc power and, the beam current and composition were found to be highly dependent on the pressure in the source. The beam properties as a function of source settings…

Microwave emission from ECR plasmas under conditions of two-frequency heating induced by kinetic instabilities

Multiple frequency heating is one of the most effective techniques to improve the performances of ECR ion sources. It has been demonstrated that the appearance of the periodic ion beam current oscillations in ECRIS at high heating power and low magnetic field gradient is associated with kinetic plasma instabilities. Recently it was proven that one of the main features of multiple frequency heating is connected with stabilizing effect, namely the suppression of electron cyclotron instability in ECRIS plasmas. Due to this kind of stabilization it is possible to run the ion source in stable mode using higher total microwave power and thus to obtain better ion beam parameters. Unfortunately, ev…

Development and use of computational tools for modelling negative hydrogen ion source extraction systems

The effect of plasma instabilities on the background impurities in charge breeder ECRIS

International audience; Experimental observations of plasma instabilities in the 14.5 GHz PHOENIX charge breeder ECRIS are summarized. It has been found that the injection of 133Cs+ or 85Rb+ into oxygen discharge of the CB-ECRIS can trigger electron cyclotron instabilities, which results to sputtering of the surfaces exposed to the plasma, followed by up to an order of magnitude increase of impurity currents in the extracted n+ charge state distribution. The transition from stable to unstable plasma regime is caused by gradual accumulation and ionization of Cs/Rb altering the discharge parameters in 10 - 100 ms time scale, not by a prompt interaction between the incident ion beam and the EC…

ESTCube-1 in-orbit experience and lessons learned

ESTCube-1 is a student satellite project lead by the University of Tartu, Estonia, and supported by the European Space Agency (ESA) via Plan for European Cooperating States (PECS). Development of ESTCube-1 has been a collaborative effort with many international partners. The satellite is shown on Figure 1 [1].

Investigation into the gas mixing effect in ECRIS plasma using Kα and optical diagnostics

Mixing a lighter gas species into the plasma of an ECRIS is known to enhance high charge state production of the heavier gas species. With this investigation, Kα diagnostics, optical emission spectroscopy and the measured charge state distribution of the extracted beam were combined to shed more light on the physics governing this phenomenon. Kα diagnostics data from two ion sources, the JYFL 14 GHz ECRIS and the GTS at iThemba LABS, are presented to gain confidence on the observed trends. The results seem to favor ion cooling as the most likely mechanism responsible for the favorable influence of the gas mixing.Mixing a lighter gas species into the plasma of an ECRIS is known to enhance hi…

Photo-assisted O− and Al− production with a cesium sputter ion source

It has been recently proposed that the production of negative ions with cesium sputter ion sources could be enhanced by laser-assisted resonant ion pair production. We have tested this hypothesis by measuring the effect of pulsed diode lasers at various wavelengths on the O− and Al− beam current produced from Al2O3 cathode of a cesium sputter ion source. The experimental results provide evidence for the existence of a wavelength-dependent photo-assisted enhancement of negative ion currents but cast doubt on its alleged resonant nature as the effect is observed for both O− and Al− ions at laser energies above a certain threshold. The beam current transients observed during the laser pulses s…

A study of the optical effect of plasma sheath in a negative ion source using IBSIMU code

A plasma sheath inside an ion source has a strong focusing effect on the formation of an ion beam from the plasma. Properties of the beam depend on the shape and location of the plasma sheath inside the source. The most accessible experimental data dependent on the plasma sheath are the beam phase space distribution. Variation of beam emittance is a reflection of the properties of the plasma sheath, with minimum emittance for the optimal shape of the plasma sheath. The location and shape of the plasma sheath are governed by complex physics and can be understood by simulations using plasma models in particle tracking codes like IBSimu. In the current study, a model of the D-Pace’s TRIUMF lic…