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arrell_c c180a69891 Update Spectral data

2024-02-21 10:57:23 +01:00

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Channel list

All PSSS data channels are listed in the following sheet:

Sheet of PSSS data channels

Nomenclature

Style	Meaning
SARFE10-PSSS059:SPECTRUM*	Raw spectral data
SARFE10-PSSS059:FIT*	Results of Gaussian fit
SARFE10-PSSS059:SPECT*	Statistics from the raw (without fit) spectrum
SARFE10-PSSS059:AVG*	Data calculated from average (not single shot) spectra

Concepts

Width and center

Spectral width and central energy are calculated by both a Gaussian fit and directly from the spectra. Depending on the spectral intensity profile, the Gaussian may return a poor representation of the spectra, for example for a spectral with a long tail. Before both fitting and calculation the spiky single shot spectra are smoothed with a savgol filter:

# smooth the spectrum with savgol filter with 51 window size and 3rd order polynomial
smoothed_spectrum = scipy.signal.savgol_filter(spectrum, 51, 3)

The standard deviation and center of mass for the spectra are calculated as:

smoothed_spectrum_normed = smoothed_spectrum / np.sum(smoothed_spectrum)
spectrum_com = np.sum(axis * smoothed_spectrum_normed)
spectrum_std = np.sqrt(np.sum((axis - spectrum_com) ** 2 * smoothed_spectrum_normed))

Relative energy spread

Channels ending in RES are a measure of the relative energy spread in units of ‰. For FIT data the relative energy spread is calculated as:

\frac{2.355*\sigma}{\mu}

and for directly calculated values (SPECT):

\frac{2.355*RMS}{\text{Center of mass}}

where the factor or 2.355 is included to allow these values to be comparable.

Spectral brightness

To quantify an increase in the spectral intensity in a narrowing bandwidth the so called Spectral brightness is calculated:

\text{Spectral brightness} = \frac{\text{Single shot intensity [uJ]}}{\text{Single shot spectral FWHM [eV]}}

At Aramis the current channel used for the single shot pulse intensity is:
SARFE10-PBPG050:FAST-PULSE-ENERGY

and the spectral FWHM uses the single shot spectral width. The result channel name is:
<SPECTROMETER:DEVICE>:FIT-BRT
indicating the data uses a Gaussian fit. Beware this data is only meaningful if the spectral intensity distribution is near Gaussian.

Data flow schematic

CamServer setup

The PSSS has a dedicated server - sf-daqsync-11.psi.ch

Store pipeline

SARFE10-PSSS059_store
4 clients

This pipeline sends the camera image directly to the image buffer

Channels

SARFE10-PSSS059:FPICTURE

PSSS pipeline

SARFE10-PSSS059_psss
13 clients

This pipeline extracts the spectra, fits and produces the statistics