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a gamma simulator

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Gamma_simulator

This is a gamma pulse simulator jointly developed by Shamoon College of Engineering(SCE) in Israel and Shanghai Advanced Research Institute,CAS in China.Here we will give a brief introduction to our software, including the what and why. For more specific implementation steps of the software, please refer to our paper. Of course,if you are a pure user, please jump directly to Use to see how to use it.

Contents

Introduction

What is Gamma Simulator?

Gamma simulator is a gamma pulse simulator with parameter customization function, you can specify the type of radioactive source and pulse count rate and other characteristics, generate pulse signals that meet the corresponding characteristics

Why do we creat it?

The original intention of the gamma simulator was to introduce deep learning into energy spectroscopy in the later stage. The use of deep learning to process pulse signals requires that the collected pulse signals have corresponding labels, which is impossible in commercial energy spectrometer. Therefore, we used the simulator to label the pulse signals while generating them, so as to facilitate the reference of deep learning methods. At the same time, simulators can greatly reduce the manpower, material and financial resources of the signal collection process, and can be used to preliminarily test signal processing methods

Software structure

Macrostructure

mainflow

Implementation structure

Flow_software

Parameter description

Setting Parameters: type Default value
verbose Whether to output detailed information bool False
verbose_plots Whether images need to be output dict None
source The simulated radioactive source str or dict 'Co-60'
signal_len Length of time to simulate sampling(s) int or float 1024
fs Analog sampling rate float 1
lambda_value Analog pulse count rate(cps) float 0.1
dict_type Shape type model of the simulated pulse str 'gamma'
dict_shape_params dict shape params dict Please see Notice
noise_unit Unit of noise str 'std'
noise The magnitude of noise in the given unit float 0.01
dict_size Shape dictionary size due to jitter int 100
seed The simulated random number seed int None

The above parameters can be set and customized by users. The chart shows the default values of parameters and draws discrete pulse signals. For specific parameter Settings in applications, please refer to the example section ,more specific parameter Settings and parameter tests are presented in the example folder

Shape parameters: type eg
t_rise rise time of the shape float 4.560e-07
t_fall fall time of the shape float 6.134e-05
shape_len length of the shape in samples int 61
shape_len_sec length of the shape in seconds float 6.180e-05
Events parameters:
hist_energy The energy contained in the spectrum (the transverse axis of the desired spectrum) array [0.02,0.04,0.06,... ,1667.20]
hist_counts The probability of generating energy corresponding to the simulated source(vertical axis of the desired energy spectrum) array [0.0002,0.001,0.0015,... ,0.0001]
n_events number of events in the signal int 16054
times arrival times of the events array [0.7e-05,1.8e-05,... ,0.92]
energies The energy sequence of the pulses produced in this simulation array [223.2,453.6,889.4,... ,635.4]
lambda_measured actual event rate float 13672.2
shape_param1, shape_param2 shape parameters for each event array two sequences of n_event values conforming to the Gaussian distribution of the given parameter
Signal parameters:
signal_len The number of samples at a given frequency in the simulated time int or float 1e6
signal_len_sec The length of time of the analog signal(s) int or float 1
duty_cycle The proportion of the time to detect the signal to the total analog time float 0.67
pile_up_stat number of the pile-ups in the generated signal int 4302
measured_snr measured SNR of the generated signal (dB) float 66.26

These values are intermediate values generated during the simulation, so there are no default values. Here are some examples of these values to give the reader an idea of what these values are

Main function

Function name input output Function action
load_weighted_spectrum source hist_energy hist_counts The energy spectrum of the simulated source (both elemental and mixture)
generate_energy_distribution seed, n_events, hist_energy, hist_counts energies Generate n_event pulses energy sequences conforming to the probability density distribution of the target energy spectrum
generate_arrival_times seed, lambda_value times Generates a Poisson process event arrival time series with a specified count rate(lambda_value)
generate_all_dict_shapes dict_type,dict_shape_params, dict_size shapes Produces a shape dictionary of the specified shapes generated by the specified parameters as a selection library of energy shapes
generate_signal_without_noise times, energies,shapes_len, shapes signal without noise The independent pulses and shapes that we have generated are pieced together to form an analog noiseless signal
generate_signal_with_noise signal without noise, noise_unit, noise signal The noiseless signal is superimposed on the specified unit and size of noise to obtain a real analog signal

A large number of parameters mentioned above are used in the function introduction. In our real code, there is a high degree of integration and a large number of function reuse. Some inputs are not directly called in this function, but by calling other functions, and some output intermediate outputs are directly called by another function after the result is generated, so these temporary variables are not reflected in the description. So this function introduction is not particularly strict, but it is definitely the most suitable for readers to clarify the code logic of the introduction

Use

Install

Make sure you have the following libraries in your environment

  • numpy
  • scipy
  • matplotlib
  • urllib
    (It doesn't matter that you don't have these, because these dependencies will be installed when you install the gamma-simulator package)

Please use the following command to install our program

pip install gamma-simulator

Import

from gamma_simulator.gamma_simulator import gamma_simulator

Run

Step 1.Creat an instance

simulator = gamma_simulator()

Step 2.Define parameters

simulator = gamma_simulator(verbose=True,
                            verbose_plots={'shapes': True, 'signal': True},
                            source={'name': 'Co-60', 'weights': 1},
                            signal_len=1,  # "analog" signal of 1 second that are 1e7 samples
                            fs=10e5,
                            lambda_value=1e4,
                            dict_type='gamma',
                            dict_shape_params={'mean1':  0.1,
                                               'std1': 0.001,
                                               'mean2': 1e5,
                                               'std2': 1e3},
                            noise_unit='std',
                            noise=1e-3,
                            dict_size=10,
                            seed=42)

Step 3.Creat the signal

signal = simulator.generate_signal()

Notice

Shape parameter

If you are not familiar with shape parameters, use the following combination of parameters

{dict_type='gamma',
dict_shape_params={'mean1':  0.1,
'std1': 0.001,
'mean2': 1e5,
'std2': 1e3}

or

{dict_type='double_exponential',
dict_shape_params={'mean1': 1e-5, 
'std1': 1e-7,
'mean2': 1e-7,
'std2': 1e-9}

Plot setting

Our simulator supports drawing a variety of graphs, including energy, shape, signal and spectrum.

  • Energy:Ideal energy spectrum of the drawn signal source (simulator built-in database)
  • Shape:Draws a dictionary set of all possible signal shapes
  • Signal:When the length of the resulting signal is less than 2000, the generated signal is drawn, and when the length is greater than 2000, the first 2000 sampling points are drawn

The default option is not to draw, if you need to draw, you need to change the specified value in the parameter definition to True

verbose_plots={'energy':True, 'shapes': True, 'signal': True}

Examples

from gamma_simulator.gamma_simulator import gamma_simulator
simulator = gamma_simulator(verbose=True,
                            verbose_plots={'shapes': True, 'signal': True},
                            source={'name': 'Co-60', 'weights': 1},
                            signal_len=1,  # "analog" signal of 1 second that are 1e7 samples
                            fs=10e6,
                            lambda_value=1e4,
                            dict_type='double_exponential',
                            dict_shape_params={'mean1': 1e-5,  # continuous-time parameters measured in seconds
                                               'std1': 1e-7,
                                               'mean2': 1e-7,
                                               'std2': 1e-9},
                            noise_unit='std',
                            noise=1e-3,
                            dict_size=10,
                            seed=42)
signal = simulator.generate_signal()
from gamma_simulator.gamma_simulator import gamma_simulator
simulator = gamma_simulator(verbose=True,
                            verbose_plots={'energy': True, 'signal': True},
                            source={'name': ['Co-60', 'I-125'], 'weights': [1, 2]},
                            signal_len=1,  # "analog" signal of 1 second that are 1e7 samples
                            fs=10e6,
                            lambda_value=1e4,
                            dict_type='gamma',
                            dict_shape_params={'mean1':  0.1,  # continuous-time parameters measured in seconds
                                               'std1': 0.001,
                                               'mean2': 1e5,
                                               'std2': 1e3},
                            noise_unit='std',
                            noise=1e-3,
                            dict_size=10,
                            seed=42)
signal = simulator.generate_signal()

You can see the result in examples

Contributors

Dima Bykhovsky,Tom Trigano,Zikang Chen

Known issue

Todo

version

1.0.1 upload to pypi

1.0.2 add license and install_requires

1.0.3 can't import

1.0.4 successfully import and fix some bug about gamma.pdf and gamma.ppf parameters

1.0.5 change the bug about hist_energy

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