To study the beam's energy repartition after reflection on the channel cut the older instrument file described in the [older readme](old_README.md) did not use a Monitor_nD component, it used two energy monitors one on top of the other. It's still worth glancing at the older readme for other considerations (e.g. the beam geometrically cut by the channel-cut).
# Main result and status
# Main result and status
## Result
## Result
The ROCK beamline has been simulated.
The ROCK beamline has been simulated.
Two results are of interest, the XANES/EXAFS graphs generated by the simulated beamline and the energy repartition of the beam after reflection on the channel cut.
Two results are of interest, the XANES/EXAFS graphs generated by the simulated beamline and the energy repartition of the beam after reflection on the channel cut.
Give the commands to create those results:
Here are the commands used to generate the examples displayed in the following text.
The simple case with the CC and monitors placed after it is simulated.
Here the centre of the energy monitor is placed relative to the centre of the CC's second crystal.
Let's take as an example three energies of the CC Si 220, E_min = 11752 eV, E_max = 34055 eV and an intermediate energy of 23keV.
### Energy monitors
The bell shaped curve of the energy is cut for the energies 11.752 and 34.055 keV. For 11.752 keV, the lowest energies of the bell are cut. For the second, the highest energies of the bell are cut.
And for 23 keV, the bell stays symmetrical, there is no longer any cut from one side or the other.
The signal's spot moves vertically as explained before. For a small energy (big attack angle) the spot is towards the bottom because `H1-H2 < 0`. To be exact, in the case of the long CC, `H1-H2>0` from 4 to 8 degrees approximately (exact values to be done), and `H1-H2<0` from 8 to 35 degrees.
The signal's spot is smaller vertically for a bigger energy.
This is explained by the fact that the divergence cone is smaller for a smaller attack angle, and inversely, bigger for a bigger attack angle of the beam (explain in more detail, show a diagram).
### Top and bottom energy monitors
An energy monitor is cut in half horizontally at mid-height. This is done to observe the energy repartition of the signal.
The energy is again cut in half, the part with the highest energies is on the top monitor, and the part with the lower energies is on the bottom monitor.
The centre of the optic following the CC is positionned relative to the centre of the CC's second crystal modulo `h`. The ray is followed.
(maybe insert images here if it's not clear)
A special monitor (made with the the Monitor_nD component) is placed after the M2b mirror but before the sample. It indicates the energy repartition of the beam.
The rays that hit the top monitor are of higher energies than those hitting the bottom monitor.
The rays forming the beam hit the crystal at different angles, it's the angular divergence, but there is also a divergence in energy with `dE = 1% *E`.
As explained in page 152 of the book "An Introduction to Synchrotron Radiation" by Willmott, Philip, John Wiley & Sons, 2019:
As explained in page 152 of the book "An Introduction to Synchrotron Radiation" by Willmott, Philip, John Wiley & Sons, 2019:
...
@@ -178,49 +141,31 @@ than that part of the beam that strikes the cristal at a shallower angle.
...
@@ -178,49 +141,31 @@ than that part of the beam that strikes the cristal at a shallower angle.
where the equation 5.25 is Bragg's law: `2*d*sin(β)=n*λ`
where the equation 5.25 is Bragg's law: `2*d*sin(β)=n*λ`
## Simulation of the ROCK beamline
(share the pic of the book here?)
The whole beamline is simulated (without the sample).
Here the centre of the energy monitor is positionned relative to the centre of the CC's second crystal modulo `h`. The ray is followed.
Let's take as an example three energies of the CC Si 220, E_min = 11752 eV, E_max = 34055 eV and an intermediate energy of 23keV.
### Energy monitors
The energy monitors show the same results as previously.
The rays forming the beam hit the crystal at different angles, it's the angular divergence, but there is also a divergence in energy with `dE = 1% *E`. As a consequence the rays are of higher energy from top to bottom.
The presence of the M2b mirror has for main purpose to focus the beam towards the detector's entrance, a ionisation chamber of aperture 10mm. Furthermore, it attenuates the vertical movement of the beam caused by the channel-cut's rotation. Another effect of this mirror is to inverse the beam's spot due to it's concavity.
The presence of the M2b mirror attenuates the beam's vertical movement although it is a minimal movement.
This inversion is also seen in the following part.
To get the above, simply execute:
`mxrun SOLEIL_ROCK.instr Etohit=17000 cc=2 -n1e8`
### Top and bottom energy monitors
`--mpi=4` can be added after mxrun to run it on 4 cpu cores like so: `mxrun --mpi=4 SOLEIL_ROCK.instr Etohit=17000 cc=2 -n1e8`
The energy is once more cut in half but this time the part with the higher energies is on the bottom monitor, and the part with the lower energies is on the top monitor.
The M2b mirror is the cause of the inversion.
The presence of the M2b mirror has for main purpose to focus the beam towards the detector's entrance, a ionisation chamber of aperture 10mm. Furthermore, it attenuates the vertical movement of the beam caused by the channel-cut's rotation(although the vertical movement is minimal).
(...)
## Simulation of the ROCK beamline with a sample
## Simulation of the ROCK beamline with a sample
The sample is positioned at the end of the beamline.
The sample is positioned at the end of the beamline.
### Energy scan copper
### XANES/EXAFS
#### Energy scan copper
Here is the XANES/EXAFS graph for an energy scan from 8.5 to 9.5 keV with the copper sample.
Here is the XANES/EXAFS graph for an energy scan from 8.5 to 9.5 keV with the copper sample.
The oscillations due to backscattering in the EXAFS part can't be seen because McXtrace does not simulate that effect.
The oscillations due to backscattering in the EXAFS part can't be seen because McXtrace does not simulate that effect.
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@@ -229,19 +174,9 @@ The oscillations due to backscattering in the EXAFS part can't be seen because M
...
@@ -229,19 +174,9 @@ The oscillations due to backscattering in the EXAFS part can't be seen because M
### Energy scan Mn and Cr
#### Energy scan Mn and Cr
Here is the XANES/EXAFS for an energy scan of 5.7 to 7.2 keV with a sample composed of Manganese and Chrome.
Here is the XANES/EXAFS for an energy scan of 5.7 to 7.2 keV with a sample composed of Manganese and Chrome.
# Energy repartition monitor
`mxrun SOLEIL_ROCK.instr Etohit=17000 cc=2 -n1e8`
You can add `--mpi=4` after mxrun to run it on 4 cpu cores like so: `mxrun --mpi=4 SOLEIL_ROCK.instr Etohit=17000 cc=2 -n1e8`
