Abstract: The invention relates to Transmission Charged Particle Beam (TCPB) apparatus comprising a sample holder, for holding a sample, a source for producing a beam of charged particles and an illuminator for directing said beam so as to irradiate the sample; The TCPB apparatus comprises an imaging system, for receiving a flux of charged particles transmitted through the sample and directing it onto a sensing device. Further, a controller is provided for controlling at least some operational aspects of the TCPB apparatus. As defined herein, the controller is arranged for receiving calibration data of said TCPB apparatus and using said calibration data for optically aligning said TCPB apparatus. Said calibration data may be obtained in a calibration session, wherein different settings for eucentric focus can be used as a measure of eucentric height, so that the TCPB apparatus can be optically aligned in absence of a sample on the sample holder.

Abstract: Disclosed herein are radio frequency (RF) cavities and systems including such RF cavities. The RF cavities are characterized as having an insert with at least one sidewall coated with a material to prevent charge build up without affecting RF input power and that is heat and vacuum compatible. One example RF cavity includes a dielectric insert, the dielectric insert having an opening extending from one side of the dielectric insert to another to form a via, and a coating layer disposed on an inner surface of the dielectric insert, the inner surface facing the via, wherein the coating layer has a thickness and a resistivity, the thickness less than a thickness threshold, and the resistivity greater than a resistivity threshold, wherein the thickness and resistivity thresholds are based partly on operating parameters of the RF cavity.