MEsskammer für FlugzeitInStrumente und Time-Of-Flight
Calibration Facility for Solar Wind Instrumentation
In our laboratory called MEFISTO we are operating an electron-cyclotron-resonance ion source (ECRIS) for producing highly charged ions. The main goal of the MEFISTO source is to reproduce all the elements in their different charge states found in the solar wind. The ions produced in the source are mainly used to calibrate instruments for solar wind applications. The instruments for calibration and other experiments are placed in a vacuum chamber mounted next to the ECR source.
For the calibration of a solar wind charged ions for all elements from hydrogen up to iron are needed. Although sources for these ions have been available for some time, the special demands of space instrumentation (beam current, purity, stability, available beam time, and instrument accommodation) made it necessary to build a dedicated facility in house, which also alleviates many logistic problems encountered during calibration campaigns.
In addition, post-launch calibrations of flight-spare instruments will allow to improve the knowledge of the transmission function of presently in-use instrumentation, and thus even improve the data quality of already launched instruments.
The heart of the new calibration facility we built is an electron-cyclotron resonance (ECR) ion source operating at 2.45 GHz using only permanent magnets. This type of ion sources allows the production of highly charged metallic and non-metallic ions within the given constraints in power consumption and physical space available on our high-voltage terminal. The ECR ion source is installed on this terminal to allow for post-acceleration potentials of up to 100kV to achieve solar wind-like energies.
Ion Source ECRIS
In the picture above the ECR ion source and the ion optical system following the source are shown. The ion source operates at a frequency of 2.45 GHz. The plasma is confined by a three dimensional magnetic well established by permanent magnets. Few permanent magnets have been removed from the drawing to see into the space where the ECR process happens.
Gaseous elements or metallic atoms introduced into the source are ionised by electron bombardment. The ions are extracted by the puller electrode with a potential of up to 10kV. With the first Einzel lens (lens 1) and deflection plates1 the beam can be focused onto the entrance aperture of the hemispherical E/q (Energy/charge) analyzer. On the way the ions pass the velocity filter where an m/q (mass/charge) filtering can take place.
After the E/q analyzer the beam is reshaped in the second Einzel lens (lens 2) and the second set of deflection plates. Before it can leave the source chamber into the experiment chamber (not shown on this drawing) the ions are post-accelerated in the high voltage insulator with a potential up to 100kV. After passing the high voltage insulator, the ions enter the vacuum recipient where the instrument to be tested is placed.
A beam scanning system equipped with a Faraday cup and a channeltron allows to measure the spatial intensity distribution of the ion beam. In combination with the Wien-Filter and the exit aperture, the beam scanning system allows the selection of the desired m/q in the ion beam.
Ion Beam caracteristics
- Energy range: 3 keV/e - 100 keV/e
- Pencil beam
- Ions from gas (H, He, O, Ne, Ar, …) and solid sources (Na, Mg, Al, Ca, Fe, Zn, …)
- Charge states: up to 8+ for gas sources, up 4+ for solid sources
Neutral Beam Chamber
- Energy range: 10eV.....3keV
- Species: H, He, O, C....
- Clean area (Class 100) in chamber door area
- Cryogenic shroud (liquid N2)
- Hexapod table (alpha, theta, x, y, z), temperature controlled (-80°C - +150°C)
- VUV source (126nm, 2 E-14 ph/cm2 s)
- DLD Delayline Detectors, Surface Concept GmbH
Mefisto Scada System
Plasma Sources Sci. Technol., Volume 14, pp. 692-699, 2005
Investigation of the density and temperature of electrons in a compact 2.45 GHz electron cyclotron ion source plasma by X-ray measurements
Hohl M., P. Wurz, and P. Bochsler
Physikalisches Institut, University of Bern, 3012 Bern, Switzerland