RadiationHelper
Beta, Alpha, Nuclides and Gamma analysis
Dan Fulea, Radiation Dept., National
SourceForge project
and download page
This software is intended to help physicists working in alpha and beta radiation detection field, internal and external dosimetry field as well as gamma spectroscopy. It is written entirely in Java and therefore is platform independent.
Its main features can be organized in two categories: experimental-based applications and theoretical-based applications. In some cases, a good detector calibration can not be achieved using experimental methods (such as measurement of a standard radiation source) and therefore a theoretical approach must be used to assess the calibration factor (i.e. detector efficiency). This is done using the Monte-Carlo simulation technique for radiation transport in the detector active volume.
1. Experimental based
applications
1.1 The alpha/beta
analysis
The same routine is used both for alpha and beta analysis, the sole difference being the usage of different databases.
First, one must enter the detector dead-time, which is the short amount of time the detector does not count any pulses. The detector dead time can be manually set if the value is known (for instance from the detector user manual or supplied by a metrology institute) or can be computed using some standard sources (see manual).
In order to compute the actual sample activity, the ambient background (counts per seconds for a blank measurement) as well as detector efficiency must be known.
1.2 The gamma analysis
1.2.1 Main features
Commercial acquisition software such as Assayer, Gamma2000, Maestro, etc. can save the gamma spectrum in various formats. The ASCII (text) format can be used as input file for this module with some modifications which have to be done by the user (see manual).
Features:
- peak unfolding by using the Gaussian fit operation
- powerful library of nuclides based on JAERI or ICRP database
- handling true coincidence effect
- good energy/FWHM calibration as well as efficiency calibration using modern data fit algorithms.
- automatic peak search and peak indentification are provided
2. Theoretical based applications
2.1 Alpha_MC
A typical standard source for alpha analysis has a disk shape (very thin thickness to avoid self-absorbtion). The efficiency is calculated based on distance from the source to the detector, source diameter and detector diameter (see manual). Due to the specifics of alpha interactions with matter, if the particle reaches the sensitive detector volume then it is considered to be recorded. Also the possible interaction with air is neglected and therefore, the results are accurate only for alpha systems equipped with a vacuum pump.
2.2 Beta_Gamma_MC
Features:
- it has an user-friendly graphical interface (GUI)
- several minor bugs fixed in original EGSnrc system codes
- an improved algorithm for solid angle evaluation and incident fluence of
radiation. Hence, an important change in starting the shower simulation
algorithm has been made.
- material creation for later use in simulation, providing useful
information such as computation of cross sections for electrons, positrons and
photon interactions as well as sugestive charts
- calculation of gamma activities based on computed efficiencies and the
comparision with experimental efficiencies
- the correction of net counts due to nuclide interferences (e.g. 238U,
232Th and 40K)
- the correction of net counts due to true concidence (photons emitted in
casacade)
- calculation for kerma parameter g
as well as mass energy transfer and mass energy absorbtion coefficients
- an application for computing the ideal surface detector efficiency for an
electron source with box or point source geometry
-a quick gamma global efficiency computation using a hybrid
analytical/MonteCarlo algorithm (crude estimate).
2.3 Nuclide exposure
This module is useful for calculation of external and internal exposure of individuals to a specific nuclide of a given activity or concentration. It is also used for computation of chain activities of series of nuclides, retrieving useful information regarding radiation energies and branching ratios and for dosimetry and shielding.
The parent and daughters activities are computed for every possible chain using the Bateman decay law. Final activities (overall activities) are computed using data for each possible chain using a simple search and summation routine. The activity derived from secular equilibrium is displayed as well as the activity after exposure time as computed by using Bateman, the time-integrated activity and the activity at 10 times parent half-life (see manual).
Final activities are used further for computation of organ doses (absorbed dose) of individuals which are subject to an external or internal exposure. External exposure conversion coefficients from activity to dose are taken from FGR12 database. Internal exposure conversion coefficients from activity to dose are taken from ICRP2001 database. The cancer risk coefficients are computed using BEIR VII recommendations.
The radiation type and dosimetry and shielding section provide information about radiation energies and yields for each nuclides according to user needs. If dosimetry is selected then it computes the total tissue dose rate as well as total tissue dose rate after shielding. If HVL and TVL option is checked then it provides information of required absorbent thickness in order to reduce the total tissue dose rate at 1/2 (HVL) or 1/10 (TVL).
SourceForge project
and download page