A simple interfacer to MagBoltz, a program that solves the Boltzmann transport equations for electrons in gas mixtures given external electric and magnetic fields. It is one of the most fundamental programs in gaseous detector physics to simulate properties of gases used in gaseous detectors.

It requires magboltz as a binary somewhere in your PATH. See Installing Magboltz below if you’re unsure about how.

What this library allows you to do is to avoid having to manually write the extremely pedantic Magboltz input files. An example for a Magboltz input looks as follows:

2         1         1         1         0.00000   
2    11   80   80   80   80   
97.7000   2.3000    0.0000    0.0000    0.0000    0.0000    26.8500   787.5648  
60000.000 0.000     0.000     
0         0         0         0         0.00000   

Nice right?

Further, if you define multiple gas mixtures / settings this library will run multiple Magboltz processes for you in parallel, so you don’t have to manually start N processes each with their own input and output file names. The file names are created based on the used parameters.

Of interest is mainly the initMagboltz procedure:

proc initMagboltz*[F: SomeUnit, P: Pressure](
  gases: seq[Gas], pressure: P, temp: Kelvin, E: F,
  nMax: int,
  usePenning = true, gasMotionThermal = true,
  B: Tesla = 0.T,
  Bθ: Degree = 0.°,
  eFinal = 0.0,
  outpath = "resources"
                                          ): Magboltz

with which you construct a Magboltz object, which stores the gases and settings for a calculation. The gases come from either initGas or initGases:

proc initGas*(id: int, fraction: float): Gas =
  let gM = getGas(id)
  result = Gas(name: gM.name, id: gM.id, frac: fraction)

proc initGas*(name: string, fraction: float): Gas =
  let gM = getGas(name)
  result = Gas(name: gM.name, id: gM.id, frac: fraction)

proc initGases*[T: int | string](gases: varargs[(T, float)]): seq[Gas] =
  for arg in gases:
    result.add initGas(arg[0], arg[1])

where as you can see we either allow to take the Magboltz IDs for the gases as listed in #sec:available_gases below or their names. The names as strings are case insensitive.

Once a Magboltz object is defined all you need to do is run runMagboltz and it will call Magboltz for you. All files will be stored in the outpath directory as given to initMagboltz.

If you wish to run multiple processes in parallel, simply call runMagboltz with an array / seq input.

So for example:

import nimboltz
let gases = initGases([("argon", 97.7), ("isobutane", 2.3)])
let mb = initMagboltz(gases, 1050.mbar, 300.K, 60.kV•cm⁻¹, nMax = 10,
                      usePenning = true, gasMotionThermal = true)
# to run a single calculation:
# runMagboltz(mb)
# to run multiple in parallel:
var mb1 = mb # to keep modifying it simple, we just copy...
var mb2 = mb
var mb3 = mb
var mb4 = mb
mb1.temp = 300.K # ... and reassign what we want changed
mb2.temp = 330.K
mb3.temp = 360.K
mb4.temp = 390.K
let mbs = [mb1, mb2, mb3, mb4]
runMagboltz(mbs)

In the future this will likely also provide some basic parsing of the Magboltz output files, but not today.

Download the Magboltz source code from here:

https://magboltz.web.cern.ch/magboltz/

Assuming you are on a Unix system, you might want to do:

cd ~
mkdir -p src/Magboltz # for example for source code you compile
cd src/Magboltz
wget https://magboltz.web.cern.ch/magboltz/magboltz-11.17.f # for latest version as of writing
gfortran -O3 -o magboltz magboltz-11.17.f

which downloads and compiles Magboltz with optimizations enabled.

Then you should make sure to add ~/src/Magboltz to your PATH, by adding

export PATH=$PATH:$HOME/src/Magboltz

to your ~/.bashrc, ~/.zshrc or wherever you store your terminal configurations.

After starting a new terminal Magboltz should be available as magboltz from any directory.