Nexa: Material Descriptions for Nuclear Analysis

Nexa is a Python-based tool for specifying isotopic compositions of material.

Pre-release components only are implemented. Currently just material handling.

Install

Basic Idea

• Configure git and python
• Create a virtual environment
• Clone the nexa repo
• Install nexa as editable. Editable install allows edit of src files without reinstall.

Windows

• Download/install/configure latest python 3.13 from https://www.python.org/downloads/
• Download/install/configure git
• Working in your repos folder (e.g., C:\Tools\Repos)
• Create a python virtual environment and activate it
• Clone the repo. E.g.,
  • git clone git@github.com:RokShox/nexa.git
• Install the repo as editable
  • cd nexa
  • pip install -e .

Linux

• Configure git
• Configure python 3.13
• Work in repos directory (e.g., ~/repos)
• Create and activate venv
  • $ python -m venv venv313
  • $ source ./venv313/bin/activate
• Clone the repo
  • $ git clone git@github.com:RokShox/nexa.git
• Pip install as editable
  • $ cd nexa
  • $ pip install -e .

Uninstall

To uninstall use pip or just delete the venv.

$ pip uninstall nexa

Usage

Invoke

The pip installation creates two executables automatically available on your path:

Run main() in nexa/src/main.py

$ nexa

Run main_cli() which just drops you into a repl loop

$ nexa-cli

Basic Usage

See main.py function main() for examples.

The primary class is Constituent(name, CompositionMode). A composition is a tree of Constituents. A composition knows the mass/atom fractions of its children but does not know its total mass or atom density.

Three dicts are created and are available for defining compositions:

• isos = Isotopes(): Isotope instances keyed by symbol
• elms = Elements(): Element instances keyed by symbol. Not used directly to build compositions.
• abund = Abundances(): Each value is a Constitutent containing isotopes at their natural abundances.

Only sealed Constituents may be added to a parent. Once sealed, a Constituent may not be modified. Constituents maintain copies of their child Constituents, not references.

To output to a file, create a filehandle and pass it as argument to display() method. See main().

Example

cl = abund["cl"]
na = abund["na"]
salt = Constituent("salt", CompositionMode.Atom)
salt.add(na, 1).add(cl, 1).seal()
salt.display()

sn = abund["sn"]
cu = abund["cu"]
bronze = Constituent("bronze", CompositionMode.Mass)
bronze.add(cu, 0.88).add(sn, 0.12).seal()
bronze.display()
bronze.flatten().display()

salty_bronze = Constituent("salty_bronze", CompositionMode.Mass)
salty_bronze.add(salt, 0.1).add(bronze, 0.9).seal()
salty_bronze.display()
salty_bronze.demote().display()

Contact

• Charles Henkel (csh@henktech.com)