An apparatus for ablating a portion of a target using a beam of radiation pulses transmitted along a beam transmission path to produce an aerosol including material ablated from the target, the apparatus characterized by: an ablation beam source configured to produce a beam of radiation pulses; an ablation chamber defining an accommodation region within which the target can be accommodated; a first beam cropper having a first diaphragm defining a first aperture disposed in the beam transmission path, wherein the first beam cropper is configured such that a portion of a radiation pulse is selectively transmittable through the first aperture relative to the first diaphragm to pass a first cropped radiation pulse, wherein the first diaphragm includes a plurality of elements defining the first aperture, and wherein at least one of the plurality of elements is actuatable relative to another of the plurality of elements to adjust a size of the first aperture over a first range of sizes between a first intermediate size and a second intermediate size less than the first intermediate size; a second beam cropper having a second diaphragm defining a plurality of second apertures, wherein the second beam cropper is configured such that each of the plurality of second apertures is selectively disposable in the beam transmission path, wherein each of the plurality of second apertures is configured such that, when a second aperture is disposed in the beam transmission path, a portion of the first cropped radiation pulse is selectively transmittable there through relative to the second diaphragm to pass a second cropped radiation pulse, wherein at least one of the plurality of second apertures has a size that is less than the second intermediate size; an objective lens disposed in the beam transmission path and configured to focus the second cropped radiation pulse to produce a focused radiation pulse having a fluence sufficient to ablate a portion of a target and produce an aerosol including material ablated from the target; and an aerosol transmission conduit configured to transport the aerosol to an analysis system, wherein the first beam cropper and the second beam cropper are disposed outside the ablation chamber. an ablation beam source configured to produce a beam of radiation pulses; an ablation chamber defining an accommodation region within which the target can be accommodated; a first beam cropper having a first diaphragm defining a first aperture disposed in the beam transmission path, wherein the first beam cropper is configured such that a portion of a radiation pulse is selectively transmittable through the first aperture relative to the first diaphragm to pass a first cropped radiation pulse, wherein the first diaphragm includes a plurality of elements defining the first aperture, and wherein at least one of the plurality of elements is actuatable relative to another of the plurality of elements to adjust a size of the first aperture over a first range of sizes between a first intermediate size and a second intermediate size less than the first intermediate size; a second beam cropper having a second diaphragm defining a plurality of second apertures, wherein the second beam cropper is configured such that each of the plurality of second apertures is selectively disposable in the beam transmission path, wherein each of the plurality of second apertures is configured such that, when a second aperture is disposed in the beam transmission path, a portion of the first cropped radiation pulse is selectively transmittable there through relative to the second diaphragm to pass a second cropped radiation pulse, wherein at least one of the plurality of second apertures has a size that is less than the second intermediate size; an objective lens disposed in the beam transmission path and configured to focus the second cropped radiation pulse to produce a focused radiation pulse having a fluence sufficient to ablate a portion of a target and produce an aerosol including material ablated from the target; and an aerosol transmission conduit configured to transport the aerosol to an analysis system, wherein the first beam cropper and the second beam cropper are disposed outside the ablation chamber.