An apparatus for a transmission electron microscope includes a housing configured to be attached to the transmission electron microscope; a plunger received in the housing and movable relative to the housing; a first set of pieces coupled to the plunger, the first piece being configured to move relative to the housing in response to the plunger moving relative to the housing; and a second set of pieces positioned in a fixed spatial relationship relative to each other, the second set of pieces and the first set of pieces forming a perimeter of an opening, an extent of the opening being continuously variable by moving the first set of piece relative to the second set of pieces.

The invention comprises an alignment guide apparatus and a method of use thereof for aligning an imaging beam, longitudinally passing through an exit nozzle of an imaging system, to an imaging zone of a sample, includes the steps of: (1) providing an alignment guide, the alignment guide comprising: (a) a guide wall at least partially circumferentially enclosing an aperture, (b) a first laser element connected to the guide wall, and (c) a second laser element connected to the guide wall; (2) inserting the exit nozzle of the imaging system into the aperture; (3) projecting a first line from the first laser element onto the sample; (4) projecting a second line from the second laser element onto the sample; and (5) moving the sample relative to the exit nozzle of the imaging system to position an intersection of the first line and the second line at the imaging zone to align the imaging beam to the imaging zone.

The present disclosure relates to a collimator. The collimator may include a motor, a transmission unit having a first end and a second end, and a leaf unit having a leaf. The first end of the transmission unit may be connected to the motor and the second end of the transmission unit may be connected to the leaf. The present disclosure also relates to a collimator system. The collimator system may include a leaf module having a leaf, a driving module having a motor configured to drive the leaf, and a processing module to generate a movement profile of the leaf. The movement profile of the leaf may include a first speed during a first stage, a second speed of the leaf during a second stage, and a third speed of the leaf during a third stage.