Dresden 2003 – wissenschaftliches Programm
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VA: Vakuumphysik und Vakuumtechnik
VA 2: Vakuumverfahrenstechnik
VA 2.3: Vortrag
Montag, 24. März 2003, 15:30–15:50, HSZ105
Ion Beam Induced Desorption Measurements at GSI — •Krämer Andreas, Weinrich Udo, Spiller Peter, Mustafin Edil, Reich-Sprenger Hartmut, Boine-Frankenheim Oliver, Franczak Bernhard, Kaufmann Wolfgang, Reeg Hansjörg, and Schütt Petra — GSI Darmstadt, Planckstr. 1, 64291 Darmstadt
In 2001 for the first time a vacuum pressure increase during a high intensity U28+ run in SIS-18 was observed [1]. It was noticed that the lifetime of the ions was no longer independent of the injected ion current. During injection ions are lost at the chamber wall or other aperture limiting devices and desorb there gas molecules. This leads to a pressure increase and therefore to a higher charge exchange rate. Similar observations where reported in Ref. [2]. Here the reported desorption coefficient is about 104 molecules/ion. Out of the data measured at SIS-18 it was possible to calculate the ion induced desorption yield to 4200−103.
To confirm this observation a dedicated experiment was done. Therefore the U28+ ion beam was steered onto the chamber wall. Approximately 5m behind this point the pressure increase was measured. With continuous injection every 1.8 sec after about 80 sec a pressure increase of 3.5×10−11 mbar was observed. This increase corresponds to a desorption yield of 5200 and is in good agreement with previous observations.
[1] A. Krämer et al., Proc. EPAC2002, Paris, 2547 (2002)
[2] J. Hansen et al., LHC/VAC Note 2001-007, PS/AE Note 2001-009 (2001)