ptychoscopy

Table of Contents

Electron beam settings
Scanning parameters
Detection
CL guide - build in checks for proper camera length selections for iterative reconstruction

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List of controls consists of all parameters needed for proper dataset acquisition design. These are taken from calibration file calibrations.xlsx and may differ from microscope to microscope. They are classified by their dominant impact, with potential overlaps (some of them may affect several features).

Electron beam settings

Energy energy of primary electron beam in keV
Probe probe setting together with chosen probe forming aperture giving the probe current (in two condenser lens system)
Defocus moves focus out of the sample plane - enlarges beam diameter
Aperture probe forming aperture gives probe semi-angle (α)

Scanning parameters

Magnification controls image field of view
Matrix gives beam position to position distance + beam defocus = beam overlap
Dwell time a time for an electron beam to stay per pixel

Detection

Nominal CL sample to detector distance (usually ADF) gives maximal detected angle as well as angular sampling
Detector detector used for data collection
Use PAAR Pumping Aperture Angular Restriction, in some microscopes, differential pumping aperture which can limit maximal scattering angles for shortest camera lengths
Binning reduction in pixel array size usually increases maximum frame rate (when available)

CL guide - build in checks for proper camera length selections for iterative reconstruction

Low angle approximation - scattering angle < 10deg (unequally sampled pixel around optical axis versus around detector edge)
Ptycho pixel < step size - set step size is smaller than final pixel in reconstructed image - loose of resolution
Beam fits inside the probe window - probe window is capable to accommodate for defocused probe
Detector cover < 1α - no reconstruction method for such a dataset
Detector cover > 6α - usually no scattering beyond 5α

Always carefully check maximal detector frame rate, needed binning and set dwell time!!