Abstract
Outgassing rates from a turbomolecular pump (TMP) were measured for two different roughing pump systems, a rotary pump (RP) and a combination of another TMP and the rotary pump (tandem operation). The TMP tested was a TPU 170 (Balzers) with a nominal pumping speed of 0.17 m3s-1 for N2. Before baking, no difference was found in the outgassing rates from the TMP for the two roughing pump systems. In an ultimate pressure region after baking, the out-gassing rate was 2.1 × 10-9 Pa·m3s-1 with the RP and 8.2 × 10-10 Pa·m3s-1 in tandem operation. The outgassing rate originating from the TMP parts and the amount of gas passing through the TMP from an outlet to an inlet were evaluat-ed to be 8.2 × 10-10 Pa·m3s-1 and 1.3 × 10-9 Pa·m3s-1, respectively. On comparing these results with those of another type of TMP, it was found that the outgassing rate from a TMP is useful for the analytical evaluation of the effects of materials, surface treatments and configurations of a TMP on its performance.
