Experiments were performed to determine if small particles are capable of passing through a turbo-molecular vacuum pump. A test aerosol was generated at atmospheric pressure and injected into the vacuum system upstream of the turbo pump. Particles were measured immediately upstream and downstream of the turbo pump using two laser-based vacuum particle detectors. Tests were performed with solid and liquid particles. Solid particles were found to pass through the pump, although the efficiency of transmission is not known. Liquid particles did not pass through the pump. These results indicate that vacuum particle counters employed downstream of turbo pumps may be sensitive to upstream particle levels.

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