For the FAIR project at GSI a beam intensity of 1012 ions/sec is planned to be extracted from the heavy ion synchrotron SIS18. Thus, a base pressure in the lower 10-12 mbar region has to be guaranteed during acceleration. Experiments in 2001 have shown that even under good vacuum conditions the loss of projectile ions (after charge exchange or on aperture limiting devices) can trigger vacuum instabilities, since desorbed particles are released from the chamber wall into the vacuum. The increased pressure reduces the beam life time and therefore the luminosity.
In the last years, experiments were carried out at GSI to study the desorption yield (released gas molecules per impinging ion) of several materials and target treatments. It was found that the desorption yield scales with the electronic energy loss of the ions inside the target material. However, it was unclear where the desorbed gas is coming from. To find correlations between target properties and desorption behaviour we built up an UHV-Elastic Recoil Detection Analysis (ERDA) experiment, where we can combine desorption yield measurement with an in-situ target characterization.
In the contribution we will give an overview about the GSI investigation on ion-induced desorption with a focus on recent ERDA and pressure rise measurements of differently treated copper surfaces and layered targets.
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