Here, the door of the main chamber of the CAlibration SYstem for space ion Mass Spectrometers (CASYMS) is open. The heavy structure inside the chamber is the turntable; it is not used for the calibration of the GENESIS targets. The beam enters the chamber horizontally from the left.

The beam scanner (not visible) consists of a Faraday cup and an electron multiplier for measuring the beam current. It can be moved in horizontal or vertical direction to scan the beam profile.

The targets ( two large gold foil pieces) are mounted on a backplate which is fixed to the beam scanner. For exposure, the target holder is rolled horizontally into the chamber and into the ion beam. It is then moved up and down at a steady speed to ensure that the ion fluence is constant in the vertical direction.

This schematic (see enlarged image with details) shows the CASYMS calibration facility in Bern with all its components. Targets of the same materials as they were used on GENESIS were irradiated here with noble-gas ions of solar-wind energy in known amounts. The fraction of the incident ions that got stuck in the targets (between 80 and 100 percent, depending on target material, incident isotope, and energy) was later determined by extracting them from the targets for analysis in a mass spectrometer. This fraction, the so-called trapping probability, serves to correct for the solar-wind atoms which are lost during exposure by backscattering from the target surfaces. + See detailed schematic