Create Aramis Intensity Diagnostics/PBPS data

Aramis-Intensity-Diagnostics/PBPS-data.md

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+## Channel list
+All PSSS data channels are listed in the following sheet:
+
+[Sheet of PSSS data channels](https://docs.google.com/spreadsheets/d/16Hz7MZR3E7-OmLHfakkT2K6yPMFUzp4eIFZxrzXWjFk/edit?usp=sharing)
+
+## 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.
+
+## Data flow schematic
+<img src="https://docs.google.com/drawings/d/e/2PACX-1vRShOtDRMpQTAY1p5oZKvRcuyLToMvmgzTQHOS_JrdQArvqcul-RoMcIobmKFc8RPgJVjGzULKczS5-/pub?w=1440&amp;h=1080">