Development of a ToF setup with an ion - guide for characterization of electrospray microthrusters

Electrospray microthrusters are a very promising micro-propulsion system which can potentially provide very high specific impulse (Isp ~ 3000s). In this paper, we report on the development of a time-of-flight (ToF) measurement setup for characterization of the spray composition of the electrospray sources. This setup consists of an electrostatic ion-guide built with 13 cascaded single-stage Einzel lenses along with a 65 cm long flight tube to focus the emitted charges on a Faraday cup detector. The distributed lens ensures a large fraction of the emitted beam can be collected, even when the beam divergence is high. Simulations of the focusing capabilities of the ion guide have been performed and are compared with a single stage Einzel lens, with excellent agreement. The efficiency of the lens has been characterized with microfabricated capillary electrospray devices and with electrochemically etched tungsten needles.