Ion sources

The Solarwind-Laboratory

A calibration-lab for future missions inside the heliosphere

A new laboratory is currently under development at the extraterrestrial department of the institute for experimental and applied physics (IEAP), with the ambitious goal to create a laboratory, where satellite-based particle detectors can be preflight calibrated. For that purpose, we will be able to simulate the particle radiation of the sun, known as the solar wind, under controlled conditions.

The main objective of the department of extraterrestrics is the development and design of particle detectors, often in collaboration with NASA and ESA. An internal calibration facility will increase the efficiency of the department significantly. Such a facility must be able to produce all the particle species found inside the solar wind and to accelerate them up to solar wind energies. Besides that, the assembling of sensitive particle detectors demands special requirements regarding the cleanliness of the laboratory, therefore the new laboratory will also be a clean-room.

Figure 1: CAD-drawing of the complete Solarwind Laboratory

The heart of the facility will be an electron-cyclotron-resonance ion source, or ECRIS in short terms. This ECRIS will be able to generate all kinds of positive charged ions from gases and metal vapors, which are then extracted and accelerated.

Figure 2 shows a typical ion spectrum, which our ECRIS can create by default from residual gas (air). ECRIS like the Kiel ECRIS are in use worldwide due to their high performance. Since we have special requirements for our ECRIS, we decided to custom build it here at the department. As a result we have some unique possibilities, for example we can variate the extraction point of the ions inside the ECR plasma in three dimensions. To achieve a wide energy range for our calibrations, we can level the acceleration-voltage to accelerate the ions from a few kV up to 450 kV. Therefore we can cover almost all particle energies found in the solar wind. Additionally, we cannot only generate ions, but also electrons and accelerated-neutral atoms. The instruments and particle detectors will be placed inside a large vacuum chamber, where they are mounted on a movable table. This table can be rotated and traversed in six dimensions, in order to simulate different income angles of solar particles.

Figure 2: Ion spectrum created by the ECRIS. The measured currents are plotted against the mass per charge value.

While the solar-wind laboratory is still under construction, the ECRIS itself is already operating for testing purposes. Besides its function as centerpiece for the new laboratory, it gives our students and scientist an excellent opportunity to study ECRIS physics. Although commonly in use, the physics behind an ECRIS are still an active field of research. Especially the generation and distribution of ions inside the ECRIS plasma are not sufficiently understood. Several publications could be made by our group regarding these questions. Our unique extraction system and specially designed ion-beam detectors helped us to achieve our scientific goals.

Figure 3: Custom made ion-beam profile detector, designed by on of our PhD students.

Figure 3 shows one of our self-made detectors. It is capable of measuring a spatially resolved two-dimensional ion-beam profile. Formerly only so called scintillation screens were used for that purpose, which could only produce a qualitative measurement. Our detector is now able to produce quantitative measurements, as shown in Figure 4.

Figure 4: Quantitative measurement of the ion beam. The color code represents real measured electrical currents.

Another detector designed by us was able to measure the ion and electron distribution inside the plasma chamber of our ECRIS. The detector is shown in Figure 5.

Figure 5: Self-made detector for the measurement of ion and electron distributions inside the plasma chamber.

The respective publication earned international appreciation due to its novelty. Other ECRIS physicists, who focused on the creation of theoretic models describing the ECRIS plasma, could use our measurements in order to compare the predictions of their models with real measured data.