Skip to content

README.md

Latest commit

 

History

History
53 lines (43 loc) · 2.39 KB

README.md

File metadata and controls

53 lines (43 loc) · 2.39 KB
Raw

Loading scripts

A loading script corrects a measurement as it is read: the viewer's load with list (Files panel, above the file list) applies the one you choose to every file you open. Because it happens at loading, the map, the 1D plots, every export, the notebook and the analysis modules all see the corrected data.

Drop a .py file into this folder and it is listed (press the list's ↻). Reload reads the open file again through the chosen script, e.g. after you edit the script. Files whose name starts with _ are not listed, so they can hold helpers that scripts share. More folders can be added with the AALTOVIEW_LOADING_SCRIPTS environment variable (separated by ;).

The contract

"""One line: what it does (shown as the tooltip)."""
NAME = "My correction"                  # optional; else the file name

def load(ds, path):                     # xarray.Dataset, pathlib.Path (or None)
    ...                                 # correct ds
    return ds

ds arrives as AaltoFlow wrote it: a complex detector is still its <name>_real / <name>_imag pair. Return a Dataset with the same layout. Helpers are in aaltoview.loading: frequency_dim(ds), alias(f, f_rep) and tr_moke_unfold(ds, f_rep_mhz, invert=False).

The scripts here

script what it does
trmoke_unfold_80MHz.py TR-MOKE, 80 MHz laser: conjugates the complex lock-in signal back on the frequencies whose alias f − n·80 MHz is negative
trmoke_unfold_100MHz.py the same for a 100 MHz laser

Why unfold? The laser samples the precession f_rep times a second, so the lock-in sees it at the alias f − n·f_rep. It cannot tell a negative alias from a positive one, and on those frequencies it records the complex conjugate: a wave running the other way. In a spatial FFT (the Spin-wave FFT module) the branch then jumps between +k and −k every f_rep/2.

Some details:

  • Frequencies exactly on a harmonic or half-way between two carry no direction and are left alone.
  • Real detectors (e.g. rf power) are not touched.
  • Unfold only once. The Spin-wave FFT module has the same switch for data loaded without a script. Leave it off for data loaded with one of these, because unfolding twice undoes the correction.
  • If the branch comes out at −k instead of +k, your lock-in uses the other sign convention. Copy a script and call tr_moke_unfold(ds, 80.0, invert=True).