Performance of a Pumping System Combining Ion-Pump with Titanium Sublimation Pump

Abstract

The performance and pumping characteristics are described on an evaporator utilizing a getter-ion pump and a titanium sublimation pump. The titanium film which is discontinuously deposited from a stranded wire of titanium and tungsten onto the inner wall of the sump can evacuate the volume of about 401 from 10-4Torr to 10-8 Torr within 75 min. with the co-operation of an 8 l/sec ion pump. Mass spectrometric analyses during the evacuation show that the titanium sublimation pump can evacuate active gases exclusively and the appendage of small getter ion pump is very effective to eliminate methane and inert.gas such as argon.The major components of the residual gas at 8×10-8 Torr are M/e =2, 16, 18, 28, 29, 40, 44 and the heavy hydrocarbon peaks are negligiblly low.The temperature-dependency of the pumping characteristics is also investigated. The pump-down rate is promoted by use of a liquid nitrogen cryo-panel arranged around the sublimation pump cartridge. The variations of mass peaks with the panel temperature in the unbaked system are due to the desorption of loosely adsorbed gases, and the pumping speed by the evaporated film itself seems to be nearly constant in the temperature range of -50° to 100°C.The gas burst during evaporation of aluminum is depressed to 10-7 Torr order at room temperature and to 10-8 Torr order with the co-operation of cryopumping.