The large capacity and streamlined design of cryo-pumped chambers help drive down overall costs and allow for long-term stability testing.
Ion thrusters must be tested for long periods in a vacuum chamber under space conditions, including the presence of the xenon gas the satellite will emit. To achieve gas flow at pressures of 10 x 10-5 mbar or below, the chamber must support pumping speeds of between 10,000 l/s to several 100,000 l/s.
Xenon is not easy to pump — its poor heat conductance can overheat turbomolecular pumps (TMPs) during compression. Also, its substantial molecular weight causes poor baffle and valve conductance, which can reduce the pumping speed of cryopumps and diffusion pumps by more than 50 percent. Thankfully, Leybold's TURBOVAC 1 was designed to overcome these challenges. Learn more about these best-in-class high vacuum pumps in our introductory video.
To achieve the tremendous pumping speed needed for space simulation in the presence of xenon, cold panels are added to the chamber. The panels are cooled to temperatures below 50K by single stage cryocoolers. Xenon gas is condensed directly on the panels inside the vacuum chamber.
The potential for extended, comprehensive stability testing is clear. A small cryo panel of 600mm in diameter has a pumping speed of 16,000 l/s inside the chamber with zero conductance losses as it is directly exposed in the chamber. This figure increases exponentially with each additional pump panel.