Disclosed herein is a substrate stack comprising a plurality of substrates, wherein: each substrate in the substrate stack comprises at least one alignment opening set; the at least one alignment opening set in each substrate is aligned for a light beam to pass through corresponding alignment openings in each substrate; and each substrate comprises at least one alignment opening that has a smaller diameter than the corresponding alignment openings in the other substrates.

A charged particle buncher includes a series of spaced apart electrodes arranged to generate a shaped electric field. The series includes a first electrode, a last electrode and one or more intermediate electrodes. The charged particle buncher includes a waveform device attached to the electrodes and configured to apply a periodic potential waveform to each electrode independently in a manner so as to form a quasi-electrostatic time varying potential gradient between adjacent electrodes and to cause spatial distribution of charged particles that form a plurality of nodes and antinodes. The nodes have a charged particle density and the antinodes have substantially no charged particle density, and the nodes and the antinodes are formed from a charged particle beam with an energy less than or equal to 500 keV.

A charged particle buncher includes a series of spaced apart electrodes arranged to generate a shaped electric field. The series includes a first electrode, a last electrode and one or more intermediate electrodes. The charged particle buncher includes a waveform device attached to the electrodes and configured to apply a periodic potential waveform to each electrode independently in a manner so as to form a quasi-electrostatic time varying potential gradient between adjacent electrodes and to cause spatial distribution of charged particles that form a plurality of nodes and antinodes. The nodes have a charged particle density and the antinodes have substantially no charged particle density, and the nodes and the antinodes are formed from a charged particle beam with an energy less than or equal to 500 keV.

A charged particle buncher includes a series of spaced apart electrodes arranged to generate a shaped electric field. The series includes a first electrode, a last electrode and one or more intermediate electrodes. The charged particle buncher includes a waveform device attached to the electrodes and configured to apply a periodic potential waveform to each electrode independently in a manner so as to form a quasi-electrostatic time varying potential gradient between adjacent electrodes and to cause spatial distribution of charged particles that form a plurality of nodes and antinodes. The nodes have a charged particle density and the antinodes have substantially no charged particle density, and the nodes and the antinodes are formed from a charged particle beam with an energy less than or equal to 500 keV.

A charged particle buncher includes a series of spaced apart electrodes arranged to generate a shaped electric field. The series includes a first electrode, a last electrode and one or more intermediate electrodes. The charged particle buncher includes a waveform device attached to the electrodes and configured to apply a periodic potential waveform to each electrode independently in a manner so as to form a quasi-electrostatic time varying potential gradient between adjacent electrodes and to cause spatial distribution of charged particles that form a plurality of nodes and antinodes. The nodes have a charged particle density and the antinodes have substantially no charged particle density, and the nodes and the antinodes are formed from a charged particle beam with an energy less than or equal to 500 keV.

Disclosed herein is a substrate stack comprising a plurality of substrates, wherein: each substrate in the substrate stack comprises at least one alignment opening set; the at least one alignment opening set in each substrate is aligned for a light beam to pass through corresponding alignment openings in each substrate; and each substrate comprises at least one alignment opening that has a smaller diameter than the corresponding alignment openings in the other substrates.