Focusing glass capillary array molecular beam inlet for a high sensitivity mass spectrometer system

A molecular beam is formed using a focusing glass capillary array to serve as the gas inlet of a mass spectrometer beam system. The glass disk has a diameter of 13 mm. The number of pores in the capillary array is about a half‐million. The pore diameter is 10 μm and the pore length is 0.5 mm. The focal length of the glass capillary array is 9.5 cm. Results show that within the 0–30 mTorr input range, the molecular beam intensity is proportional to the inlet pressure. High sample transmission is obtained for low pressure gas input. Beyond this range, the beam intensity levels off rapidly. As opposed to the orifice beam formation, a relatively narrow operational window exists which limited the ability of the capillary array to obtain high sample transmission efficiency for high pressure gas input applications.