Users Manual

This manual has instructions that cover basic beamline operation, some troubleshooting tips, XAS data acquisition software and sample loading procedure.   Any VLSPGM users can benefit from a read-through of this document.

BL Process Variables

Although this document is of particular importance for the XAS Users, the listed PVs cover every optical component of the whole BL.   In particular, for every XAS saved file the recorded process variables (Energy, TE yield, FL yield etc.) are listed using the following Process Variables format.

Most frequent problems and troubleshutting instructions

Section of the manual that covers the most frequent problems the Users encounter.   The assistence of the Floor Coordinator (x3639) will be required.

Sample preparation

 It offers step-by-step instructions on how to prepare samples using the provided sample holders.

XAS Sample transfer procedure

It offers step-by-step instructions on how to load and unload a sample in the XAS chamber.

• How to write a proposal for beamtime at CLS

• Critical points to be addressed in a VLSPGM proposal

• VLSPGM example proposal

-- Section from the Users Manual --

Data Acquisition at the VLSPGM

For the standard XAS measurements, where Total Electron Yield (TEY) and Total Fluorescence Yield (FLY) are recorded, the VLSPGM provide two alternative forms of data acquisition configurations: Step Scan and Fast Scan. Users can choose the configuration best suited to their study.

In case Users experiments required data collected with the XEOL detector for Total Luminescence yield, only Step Scan is available.

The differences between Step and Fast scans are briefly outlined:

Step scan characteristics

• Users decide the energy range (e.g. 158eV to 130eV), the dwell time (e.g. 1 second) and the step size (e.g. 0.1eV) for each scan.
• The measurement at each energy point (e.g. 158; 157.9; 157.8 etc.) occurs after the motors have stopped.
• The total duration of a typical 1sec-dwell-time scan is largely caused by the dead time required for starting and stopping the motors at each energy point.
• The points are equally energy spaced by the value input as step size (Delta Value).
• Typically, the duration of a 25eV scan is ~20 minutes

Fast (on-the-Fly) scan characteristics

• Energy range, dwell time and step size for each scan are pre-set and not changeable.
• At the start of the scan the motors go to the final point and the instrumentation recording the signals (e.g. I0, TEY and FLY) are sampled along the motion at consistent measurement times (1 second).
• The provided “mean Energy fbk” value should be used when analyzing the data and as x-axis when plotting the resulting spectrum.
• The points within a scan are not equally energy spaced.
• Typically the duration of a 25eV scan is ~5 minutes