A low input power consumption, compact thermal field emitter is suitable for use in electron beam systems, particularly those systems that use an array of electron beams or a miniature electron beam system. It is proposed that the guard device has an actuator system, which is provided for monitoring an opening which is formed at least by the guard element and is adaptable to at least one geometric feature of a workpiece. Using this information, the server computer generates a specialized learning curriculum based upon each user’s selected interests and other information.