System and Method for Photocathode Illumination Inspection

An inspection system comprising:

• a high-brightness electron beam source comprising:
• a broadband illumination source configured to generate broadband illumination;
• a tunable spectral filter configured to filter the broadband illumination to provide filtered illumination having an excitation spectrum;
• and
• a photocathode configured to emit one or more electron beams in response to the filtered illumination, wherein emission from the photocathode is adjustable based on the excitation spectrum of the filtered illumination from the tunable spectral filter;
• and
• one or more electron focusing elements configured to direct the one or more electron beams from the high-brightness electron beam source to a sample;
• and
• one or more detectors to detect radiation from the sample generated in response to the one or more electron beams.

A method for generating high-brightness electron beams comprising:

• generating broadband illumination with a broadband illumination source;
• filtering, with a tunable spectral filter, the broadband illumination to provide filtered illumination having an excitation spectrum;
• and
• emitting, with a photocathode, one or more electron beams in response to the filtered illumination, wherein emission from the photocathode is adjustable based on the excitation spectrum of the filtered illumination from the tunable spectral filter.