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Tune Configuration

Tune Configuration

Owned by Michael Abbott
Last updated: Sept 25, 2019

Configuration of tune fitting algorithm.  All PVs are prefixed with $(device):$(axis).

Config

Most of the following control PVs should be left alone, as the involve adjusting hidden internal parameters of the fitting algorithm.

TitlePVDescription
Max peaks:TUNE:CONFIG:MAX_PEAKS_SThis determines how many peaks the fitter will attempt to find in the data before extracting the three largest and determining the tune.  For LMBF this should be set to 1, for horizontal TMBF this should be set to 3, and for vertical TMBF it may be helpful to set this to 4.
Smoothing:TUNE:CONFIG:SMOOTHING_SLeave this set to 32.
Min height:TUNE:CONFIG:MINIMUM_HEIGHT_SOnce a first peak has been found, all remaining peaks must be at least this high in relative units.  Leave set to 0.1.
Data:TUNE:CONFIG:WEIGHT_DATA_S

This selects the weighting of the model when fitting.  Normally "Weighted" should be selected.  The following options are available:

NameDescription
WeightedThe fit between the data and the model is weighted by the magnitude of the original data.  This forces the model to fit more tightly to peaks and less tightly to the troughs.  In practice this seems to produce a better result.
UnweightedAll data points are treated equally during the fit.
Min width:TUNE:CONFIG:MINIMUM_WIDTH_SThis is the minimum width of a peak which will be accepted.  The width is in tune frequency units.
Max width:TUNE:CONFIG:MAXIMUM_WIDTH_SMaximum acceptable peak width in tune frequency units.
Min spacing:TUNE:CONFIG:MINIMUM_SPACING_SThis parameter is used to reject fits where peaks have approached to close to one another.  Best to leave set to 1.
Max error:TUNE:CONFIG:MAXIMUM_FIT_ERROR_SThe main function of this parameter is to reject tune fitting when there is no valid data to fit.  Leave set to 0.2.
Window start:TUNE:CONFIG:WINDOW_START_SThis can be set to an offset into the detector sweep waveform to restrict the tune fitting to the part of the waveform starting at the specified offset.
Window len:TUNE:CONFIG:WINDOW_LENGTH_SThis can be set to the length of the window restricting tune fitting to part of the waveform.  As a special case, a value of 0 written here will select the entire window.

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