Irrad_Spectroscopy

Introduction

ìrrad_spectroscopy is a package which provides functions for gamma and X-ray spectroscopy, including isotope identification, activity determination and spectral dose calculations. Furthermore, it offers functions for calculating the gamma equivalent dose for given isotopes as a function of their initial activity.

The package was developed for spectroscopic analysis or proton-irradiated semiconductor devices but can be used to analyze various samples, from radioactive sources to activated machine parts. It consits of few independent methods which togehter allow for a complete spectroscopic analysis, including plotting, of radioactive gamma-spectra. A step-by-step full spectroscopy of an example spectrum can be found in the examples folder.

Installation

You have to have Python 3 with the following packages installed:

• numpy
• scipy
• pyyaml
• matplotlib
• jupyter (examples)
• pandas (creating gamma library from the web)
• pytest (run the tests)

It's recommended to use a Python environment like Miniconda. After installation you can use Minicondas package manager conda to install the required packages

conda install -y numpy scipy pyyaml matplotlib jupyter pandas pytest

To finally install irrad_spectroscopy run the setup file

python setup.py develop

Example usage

Full spectroscopy

Check the examples folder for several measured data sets of different sources for calibration and analysis. A Jupyter Notebook with a step-by-step analysis of an example spectrum of an irradiated chip is provided. Install jupyter and run

jupyter notebook

in order to open the web interface.

Equivalent dose calculation

The package implements dose rate calculations for individual gamma lines as well as full gamma spectra of isotopes for various materials (search materials in this table) Dose rate calculations are implemented, assuming a point-like source!

Calculating dose rate of an individual gamma line in air:

# Import
from irrad_spectroscopy.physics import gamma_dose_rate

# Get dose rate of single gamma line in uSv/h
# Zn65 line at 1115.564 keV, prob 50.60%, activity of 20 kBq at a distance of 100 cm in air
res = gamma_dose_rate(energy=1115.546,
                      probability=0.506,
                      activity=20e3,
                      distance=100,
                      material='air')

print(res)  # Prints 1.515e-3  # uSv/h

Calculating the (integrated) gamma dose rate of an isotope in air:

# Import
from irrad_spectroscopy.physics import isotope_dose_rate

# Zn65 with activity of 20 kBq at a distance of 100 cm in air
res = isotope_dose_rate(isotope='65_Zn',
                        activity=20e3,
                        distance=100,
                        material='air')

print(res)  # Prints {'65_Zn': 1.515e-3}  # uSv/h

# Zn65 with activity of 20 kBq at a distance of 100 cm in air
# integrated over 2000 hours
res = isotope_dose_rate(isotope='65_Zn',
                        activity=20e3,
                        distance=100,
                        material='air',
                        time=2000)

print(res)  # Prints {'65_Zn': 2.66}  # uSv

Calculating the gamma dose rate of multiple isotopes in air:

# Import
from irrad_spectroscopy.physics import isotope_dose_rate

# Multiple isotopes (Zn65 and Be7) with different activities
# (20 kBq, 100kBq) at a distance of 100 cm in air
res = isotope_dose_rate(isotope=('65_Zn', '7_Be'),
                        activity=(20e3, 100e3),
                        distance=100,
                        material='air')

print(res)  # Prints {'65_Zn': 1.515e-3, '7_Be': 0.73e-3}  # uSv/h

Particle fluence calculation from isotope activity

It is possible to calculate the number of particles per unit area, which penetrated a given sample material, by knowing their producion cross-section for activating an isotope in the material. Given the activity of the isotope, its molar mass as well as the mass of the sample , the irrad_spectroscopy.physics submodule provides a function for the calculation:

# Import
from irrad_spectroscopy.physics import fluence_from_activity

# Vanadium 48, generated with ~380 mb effective cross section from proton irradiation of Titanium foil, weighing 11 mg.
res = fluence_from_activity(isotope='48_V',  # needed for half-life determination
                            activity=28e3,  # Bq
                            cross_section=380,  # mb Ti -> 48 V, effective cross section
                            molar_mass=47.952, # g/mol
                            sample_mass=11)  # mg

print(res)  # Prints 1.062e15 protons/cm²

You can add a cooldown time to correct for the decay of isotope bewteen isotope activation and activity measurement. Furthermore, if the production cross-section is not "effective" but rather resolved specifically for the specific isotope, you can pass the abundance of the isotope's parent in the sample material to get the effective production:

# Import
from irrad_spectroscopy.physics import fluence_from_activity

# Vanadium 48, generated with ~380 mb effective cross section from proton irradiation of Titanium foil, weighing 11 mg.
res = fluence_from_activity(isotope='48_V',  # needed for half-life determination
                            activity=28e3,  # Bq
                            cross_section=550,  # mb for 48 Ti -> (p,n) -> 48 V, dedicated cross section
                            molar_mass=47.952, # g/mol
                            sample_mass=11,  # mg
                            abundance=0.7372,  # % of stable Titanium
                            cooldown_time=48)  # hours between activation and measurement of activity

print(res)  # Prints 9.1226e14 protons/cm²

Testing

The code in this package has unit-tests. These tests contain a benchmark with actual gamma-spectroscopy data of two calibrated, radioactive sources, namely 22-Na and 133-Ba. The activity reconstruction efficiencies for the tested data sets are tested to be above 90%. Furthermore, the irrad_spectroscopy.physics.isotope_dose_rate function is cross-checked with results from RadProCalculator for a handful of isotopes to be in agreement, with a maximum deviation of 20%.

Example spectrum

Generated spectrum, including background and identified peaks, of a radioactive sample after proton irradiation. Multiple isotopes can be assigned to one peak due to the uncertaiunty of the energy calibration.