The vacuum system for the synchrotron radiation source ANKA

ANKA, a 2.5 GeV Synchrotron Radiation (SR) source with a circumference of 110.4 m, an emittance of 40-73 nmrad and a nominal current of 200 mA, is dedicated for micro-fabrication and analytics purposes. The vacuum chamber will be made of stainless steel. An in situ bake out is not foreseen. Most of the synchrotron radiation will be absorbed by discrete absorbers (two per bend) in ante chambers. Here 500 1/s and 300 1/s diode pumps will be installed. The pumping will be done by lumped ion pumps (diodes) with a total nominal pumping speed of 18800 Vs, respectively 13000 1/s at 10^-9 mbar. The installation of titanium sublimator or NEG pumps is foreseen as back up. Assuming a desorption coefficient of 10^-6 mel/ph the expected gas load is 1.5 10^-5 mbar 1/s. Pressure profile calculations show that the foreseen pumping speed should be sufficient to obtain a pressure of 3 10^-9 mbar, necessary to get a lifetime of more than 12 h