An ion generation device is provided, which includes: a heater; a counter electrode arranged on one side of the heater; at least one electric member arranged between the heater and the counter electrode, the electric member being made of a pyroelectric element or a piezoelectric element; an electrode arranged between the heater and the electric member to be in contact with the electric member; and a temperature control circuit to control a temperature of the heater. An ion detection device is provided, which includes the above-described ion generation device, an ion filter to sort ions generated at the ion generation device, and a detector to detect the ions sorted in the ion filter.

The present invention relates to an electron gun cathode mount adapted at one end to secure a thermionic cathode and at the other end to be connected to an attachment member, wherein the electron gun cathode mount is structured so as to be capable of, when in use, reducing heat transfer from the thermionic cathode to the attachment member, and the material forming the electron gun cathode mount has a thermal conductivity of less than 10 Wm.sup.1K.sup.1 at the operating temperature of the thermionic cathode in a direction from the thermionic cathode to the attachment member. The present invention also relates to an electron gun assembly having the electron gun cathode mount installed therein.

Provided is an electron beam source for generating an electron beam comprising a cathode, an anode and a grid for regulating an electron beam current. The cathode has a base and a protrusion with sidewalls and a top surface. The base surface and the top surface are essentially flat. The base surface and the top surface are arranged at a predetermined distance from each other. The base is larger than the protrusion. The electron beam source further comprising a control unit adapted for changing an applied voltage to the grid for switching a spot size of the electron beam on a target surface between at least a first a first spot size corresponding to emission from the top surface of the cathode only and to a second spot size corresponding to emission from the top surface and the base surface of the cathode.