A guide to operation principles of PSSS and how to align

# Introduction

The PSSS can be used either in full beam or with a grating where the 1st order from the grating is incident in the bent crystal.  It is recommend only to use the full beam for alignment purposes and not for machine optimization.  Use of full beam for optimization is likely to give artificial bandwidths due to saturation of the detection system.

There are different bent crystals suitable for different energy ranges and spectral resolutions.  Theses are:
- 4 - 5.5 keV  -  Si(111) bending radius 155 mm
- 5.5-8 keV - Si(220) bending radius 75 mm
- 8-10.25 keV -Si(220) bending radius 145 mm
- 10.25-13 keV - Si(220) bending radius 200 mm

# Alignment tweaks
First, is the PSSS spectrum updating?  If not the processing may need restarting see [contacts](Aramis Contacts)

## Photon energy outside window
**Description**  
There can be an offset between reported machine photon energy and actual photon energy

**Solution** 
- Run Energy scan on PSSS panel, Alignment tab.  PSSS energy will be scanned and for each scan step the average single shot signal for each step recorded.  After the scan the optimum position will be automatically set
<img src="https://docs.google.com/drawings/d/e/2PACX-1vTgqGH0cfCZdF1tNIWeELWJVUKil_bn7xwOEAkgdKG7Xrmh7vytoVzlCsZW_yI8Hz5-zrCOiNboFzL3/pub?w=1307&amp;h=864">


## Weak signal
**Description**  
Spectrum seen, but very weak signal  

**Solution**  
The most common reason for a weak signal is the height of the spectrometer crystal.
- Run Crystal height scan on PSSS panel, Alignment tab.  Crystal will be scanned in height, after the scan the optimum position will be automatically set
<img src="https://docs.google.com/drawings/d/e/2PACX-1vTQudIV1-lfgKAqzmeoKBRklZWa1ANKxQ8LNHqpcs5_6VnuN6CY_6pKUIcNU98lZBA51OV3FxSvGk6E/pub?w=1307&amp;h=864">