Basic Beamline Knowledge

This is really just a brain-dump of the parts of a beamline, rather than an organized lesson plan. I just wanted to write down all the parts of a beamline that a user might ever want/need to know about.

There are several links to wikipedia pages here. We might consider editing wikipedia pages as part of our mission.

Sources

1. bend magnets and 3-pole wigglers (aka wavelength shifters)

1. wigglers
2. undulators work
3. explain how the spectral qualities of the three sources differ.
4. Polarization properties of the different sources, including different sorts of undulators, use of quarter-wave plates

Mirrors

1. Explain the concept of total external reflection

1. Vertical collimating mirror
2. Toroidal focusing mirror
3. Harmonic rejection mirror

4. Kirkpatrick-Baez mirror

Monochromator

1. Explain wavelength selection by Bragg diffraction

1. Harmonic content of the beam

2. Crystal types, Si(111), Si(220), Si(311), InSb, Beryl, YB₆₆: advantages and disadvantages of each

3. Gratings for low energy monochromators: spherical grating, plane grating, variable spacing
4. Saggital focusing, advantages (XRD beamlines often use it -- unlike a toroidal mirror, it does not mix veritcal and horizontal divergence) and difficulties of operation for a scanning mono
5. Cooling the mono: He bath, water cooling, cryo cooling
6. Calibration and encoding, reproducibility of the mono
7. Distance of the mono from the source, to the sample

White beam slits

1. Define the beam on the first mirror/mono

1. Heat load management

Other beamline infrastructure

1. shutters

1. valves, vacuum pumps, vacuum guages
2. transport pipe, vacuum chambers
3. hutches: optical and experimental

4. shielding, scatter and Bremsstrahlung

5. diagnostics
6. beam stops
7. bellows
8. PPS and EPS systems

Hutch slits

1. Define the beam size entering the experiment

1. Match sample dimensions
2. Match dimensions of apparatus, e.g. a high pressure cell
3. Match acceptance of KB mirrors

Sample stage

1. XYZ motion

1. rotational degrees of freedom
2. multi=-sample holders: ladders and wheels
3. Sample robotics
4. Microscopy set up with YZ motion of stage and camera

Considerations for adapting instrumentation for use with XAS

1. electrochemistry, high/low temperature, high pressure, fluid flow (peristaltic or stop-flow), magnets, and so on...

1. x-rays have to get in, x-rays have to get out

Detectors

1. Detection -

1. How does an ion chamber work? (Grant Bunker's explanation)

2. How does an energy dispersive detector work? Ge, SiLi, Si drift.

3. Stern-Heald (aka Lylte) detector
   • it's an ion chamber, but short so use thick gas

   • Z-1 filter (from Grant) (Hephaestus)

   • Soller slits

4. How does Total Electron Yield detection work?

5. How does Partial Electron Yield detection work?

6. How does an analyzer work? Bragg analyzer, bent Laue analyzer
7. Signal processing chain -
   • amplifier -- what is a proper level of amplification -- high enough to be linear without oversaturating
   • V2F converter
   • signal crate
   • sources of noise in the signal chain
8. MED signal chain
   • analog output, into a single channel analyzer, need to set ROIs with a screwdriver
   • digital output, into a digital pulse processor, need to set ROIs with software

Focusing optics

1. horizontally focusing with a bending mirror

1. saggital focusing crystal or mirror
2. KB mirrors
3. zone plates
4. refractive optics
5. kineform plates