Commit 8c97e77c authored by ext-calvo_p's avatar ext-calvo_p
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Merge branch '67-update-documentation-for-beam-stripping' into 'master'

Resolve "Update documentation for beam stripping"

Closes #67

See merge request OPAL/documentation/manual!155
parents 73bf1b40 f339412d
......@@ -2685,39 +2685,46 @@ KHV:KICKER, HKICK=0.001, VKICK=0.0005;
The reference system for an orbit corrector is a Cartesian coordinate
system.
[[sec.elements.vacuum-opal-cycl]]
=== Vacuum (_OPAL-cycl_)
[[sec.elements.vacuum]]
=== Vacuum
Vacuum element represents the conditions and parameters to consider
interactions with the residual gas and the magnetic field
in a cyclotron. When the particle interacts,
it is recorded in the file, which contains the time,
interactions with the residual gas and the magnetic field. When the
particle interacts, it is recorded in the file, which contains the time,
coordinates and momentum of the particle at this moment.
The particle could produce a new particle, changing
the charge and mass.
There are 7 parameters to describe the vacuum space.
In _OPAL-cycl_ the vacuum region is defined according to the cyclotron
boundaries (`MINZ`, `MAXZ`, `MINR` and `MAXR`,
see link:elements#sec.elements.cyclotron[`CYCLOTRON` element]), whereas
in _OPAL-t_ is described by `L` and `ELEMEDGE` parameters
(see link:elements#sec.elements.common[Common Attributes]).
There are 7 specific parameters to describe the vacuum space.
PRESSURE::
The average pressure of the residual gas in the cyclotron. [mbar]
The average pressure of the residual gas. [mbar]
TEMPERATURE::
Temperature of residual gas. [K]
PMAPFN::
File name of the mid-plane pressure map.
The pressure data is stored in a sequence shown in 2D field map on the median
plane with primary direction corresponding to the azimuthal direction,
secondary direction to the radial direction
File name of the mid-plane pressure map. This feature is only available
for _OPAL-cycl_. The pressure data is stored in a sequence shown in 2D field
map on the median plane with primary direction corresponding to the azimuthal
direction, secondary direction to the radial direction
(same file structure as `Cyclotron` `TYPE=CARBONCYCL`).
If `PMAPFN` is specified, `PRESSURE` parameter is taken as default value
for regions in the accelerator out of the limits of the pressure map.
PSCALE::
Scale factor for the pressure field map (default: 1.0).
Only available for _OPAL-cycl_.
GAS::
Type of gas for residual vacuum: `H2` or `AIR`
STOP::
If STOP is true, the particle is stopped and deleted from the
simulation. Otherwise, the outcoming particle continues to be tracked
as `SECONDARY` particle (default: true).
simulation. Otherwise, the outcoming particle (according to the cross
section evaluation) continues to be tracked as `SECONDARY` particle
(default: true).
PARTICLEMATTERINTERACTION::
`PARTICLEMATTERINTERACTION` is an attribute of the element
(see Chapter link:partmatter#chp.partmatter[Particle Matter Interaction]).
......
......@@ -280,6 +280,12 @@ P(x) = 1 - e^{-x/\lambda}
where latexmath:[P(x)] is the statistic cumulative interaction
probability of the process.
<<fig_BstpPhysics>> summarizes the iterative steps evaluated by the algorithm.
.The diagram of BeamStrippingPhysics in _OPAL_.
[[fig_BstpPhysics,Figure {counter:fig-cnt}]]
image::figures/partmatter/OPALBSTP_flowchart.jpeg[{fig-width-default}]
[[sec.partmatter.residual-gas-interaction]]
==== Residual gas interaction
......@@ -307,13 +313,14 @@ each step latexmath:[\delta _s].
Gas stripping could be applied for four different types of incoming
particles: negative hydrogen ions (`HMINUS`), protons
(`PROTON`), neutral hydrogen atoms (`HYDROGEN`) and hydrogen
molecule ions (`H2P`). Single / Double - electron detachment
or capture reactions are considered for each of them.
(`PROTON`), neutral hydrogen atoms (`HYDROGEN`), hydrogen
molecule ions (`H2P`) and deuterons (`DEUTERON`). Single / Double - electron
detachment or capture reactions are considered for each of them.
Cross sections are calculated according to energy of the particle
employing analytic expressions fitted to cross section experimental data.
There are three different fitting expressions:
Cross sections are calculated according to energy of the particle employing
analytic expressions fitted to cross section experimental data. The suitable
function is selected in each case according to the type of incident particle
and the residual gas under consideration. There are different fitting expressions:
*** Nakai function <<bib.nakai>>
......@@ -343,7 +350,9 @@ incident projectile energy in keV, latexmath:[E_{th}] is the threshold energy
of reaction in keV, and the symbols latexmath:[a_i] denote adjustable parameters.
*** Tabata function <<bib.tabata>>: A linear combination of the Nakai function,
improved and fitted with a greater number of experimental data.
latexmath:[f(E)], improved and fitted with a greater number of experimental data
and considering more setting parameters. The enhancement of the function makes it
possible to extrapolate the cross section data to some extent.
*** Barnett function <<bib.barnett>>:
......@@ -359,14 +368,31 @@ X=\frac{(\ln{E}-\ln{E_{min}})-(\ln{E_{max}}-\ln{E})}{\ln{E_{max}}-\ln{E_{min}}}
where latexmath:[T_i] are the Chebyshev orthogonal polynomials.
*** Bohr function <<bib.betz>>:
[latexmath]
++++
\sigma =
\left\{\begin{array}{l}
4\pi a_0^2 \displaystyle\frac{z_t+z_t^2}{z_i}\left(\frac{v_0}{v}\right)^2 \hspace{8mm} z_t < 15\\
\\
\pi a_0^2 \displaystyle\frac{z_t^{2/3}}{z_i}\left(\frac{v_0}{v}\right) \hspace{14mm} z_t > 15
\end{array}\right.
++++
where latexmath:[z_i] and latexmath:[z_t] are the charge of the incident
particle and the charge of the target nuclei, latexmath:[a_0] is the Bohr
radius, latexmath:[v_0=e^2/4\pi\varepsilon_0\hslash] is the characteristic
Bohr velocity and latexmath:[v] is the incident particle velocity.
[[sec.partmatter.electromagnetic-stripping]]
==== Electromagnetic stripping
In case of latexmath:[H^-], the second electron is slightly bounded, so
In case of `HMINUS` particles, the second electron is slightly bounded, so
it is relevant to consider the detachement by the magnetic field. The
orthogonal component of the magnetic field to the median plane (read
from `Cyclotron` element), produces an electric field according to
from `CYCLOTRON` element), produces an electric field according to
Lorentz transformation, latexmath:[E\!=\!\gamma\beta cB]. The fraction
of particles dissociated by the electromagnetic field during a time
step latexmath:[\delta _t] is:
......@@ -390,20 +416,11 @@ latexmath:[S_{\!0}] is a spectroscopy coefficient, and the normalization constan
is latexmath:[N=(2k_0(k_0+\alpha)(2k_0+\alpha))^{1/2} / \alpha], where
latexmath:[\alpha] is a parameter for the ionic potential function.
The electromagnetic stripping calculation is restricted to _OPAL-cycl_.
[[sec.partmatter.the-flow-diagram-of-scatteringphysics-class-in-opal]]
=== The Flow Diagram of _ScatteringPhysics_ Class in OPAL
.The diagram of ScatteringPhysics in _OPAL_.
[[fig_CollPhysics,Figure {counter:fig-cnt}]]
image::figures/partmatter/diagram.png[scaledwidth=16cm,width=70%]
.The diagram of ScatteringPhysics in _OPAL_ (continued).
[[fig_CollPhysics2,Figure {counter:fig-cnt}]]
image::figures/partmatter/Diagram2.png[scaledwidth=8cm,width=30%]
[[sec.partmatter.the-substeps]]
==== The Substeps
=== The _ScatteringPhysics_ Substeps
Small step is needed in the routine of ScatteringPhysics.
......@@ -411,15 +428,27 @@ If a large step is given in the main input file, in the file
_ScatteringPhysics.cpp_, it is divided by a integer number
latexmath:[n] to make the step size using for the calculation of
scattering physics less than 1.01e-12 s. As shown by
<<fig_CollPhysics>> and <<fig_CollPhysics2>> in the previous section, first we track one
step for the particles already in the element and the newcomers, then
another (n-1) steps to make sure the particles in the element
<<fig_CollPhysics>> and <<fig_CollPhysics2>> in the following subsection,
first we track one step for the particles already in the element and the
newcomers, then another (n-1) steps to make sure the particles in the element
experience the same time as the ones in the main bunch.
Now, if the particle leave the element during the (n-1) steps, we
track it as in a drift and put it back to the main bunch when finishing
(n-1) steps.
[[sec.partmatter.the-flow-diagram-of-scatteringphysics-class-in-opal]]
==== The Flow Diagram of _ScatteringPhysics_ Class in OPAL
.The diagram of ScatteringPhysics in _OPAL_.
[[fig_CollPhysics,Figure {counter:fig-cnt}]]
image::figures/partmatter/diagram.png[scaledwidth=16cm,width=70%]
.The diagram of ScatteringPhysics in _OPAL_ (continued).
[[fig_CollPhysics2,Figure {counter:fig-cnt}]]
image::figures/partmatter/Diagram2.png[scaledwidth=8cm,width=30%]
[[sec.partmatter.available-materials-in-opal]]
=== Available Materials in _OPAL_
......@@ -549,8 +578,11 @@ anchor:bib.tabata[[{counter:bib-cnt}\]]
anchor:bib.barnett[[{counter:bib-cnt}\]]
<<bib.barnett>> C. F. Barnett, https://inis.iaea.org/collection/NCLCollectionStore/\_Public/22/011/22011031.pdf[__Atomic Data for Fusion Vol. I: Collisions of H, H2, He and Li atoms and ions atoms and molecules__], Tech. Rep. ORNL-6086/V1, Oak Ridge National Laboratory (1990).
anchor:bib.betz[[{counter:bib-cnt}\]]
<<bib.betz>> H.-D. Betz, https://journals.aps.org/rmp/pdf/10.1103/RevModPhys.44.465[__Charge States and Charge-Changing Cross Sections of Fast Heavy Ions Penetrating Through Gaseous and Solid Media__], Rev. Mod. Phys. 44, 465 (1972).
anchor:bib.scherk[[{counter:bib-cnt}\]]
<<bib.scherk>> L. R. Scherk, _An improved value for the electron affinity of the negative hydrogen ion_, Can. J. Phys., 57, 558 (1979).
<<bib.scherk>> L. R. Scherk, https://cdnsciencepub.com/doi/10.1139/p79-077[__An improved value for the electron affinity of the negative hydrogen ion__], Can. J. Phys., 57, 558 (1979).
anchor:bib.atomic[[{counter:bib-cnt}\]]
<<bib.atomic>> https://www.qmul.ac.uk/sbcs/iupac/AtWt/[_Atomic Weights of the Elements 2019_], International Union of Pure and Applied Chemistry (IUPAC).
......
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