SUPPORTING ROUTINES TO THE SRIM-CODE
Márius Pavlovič and Ivan Strašík
Slovak University of Technology, Faculty of Electrical
Engineering and Information Technology, Ilkovičova 3, SK-812 19 Bratislava, Slovak Republic, marius.pavlovic@stuba.sk
Capabilities and application potential of the SRIM-code can be enriched by combining SRIM with additional modules:
A beam generation module – prepares SRIM input data
Statistical modules – process SRIM output data
A beam-transport module – performs matrix transformations of SRIM output data, calculates and displays some ion-optical parameters of the particle set and enables data-exchange between the SRIM-code and beam-transport codes
A file conversion module – converts SRIM output data to SRIM input data
Demonstrative examples are given for 50 MeV protons implanted to iron. Statistical analysis is performed at 3 mm depth. For more information, please, download the code with the manual, contact the authors and look at the: Scopus
Pavlovič, I. Strašík: Supporting Routines for the SRIM code, Nucl. Instr. and
Meth. B 257 (2007) 601-604 (SCIENCE DIRECT).
I. Strašík, M. Pavlovič: Improvements to the SRIM Simulations, Radiation Effects and Defects in Solids 164/7-8 (2009) 470-476.
A BEAM-GENERATION MODULE = RUNNING SRIM WITH A REAL BEAM
A standard SRIM Monte Carlo simulation uses a point-like mono-energetic input beam. In fact, it is a sequence of particles (histories) without taking into account real ion-optical parameters of the incoming beam. The beam-generation module generates the TRIM.DAT file according to ion-optical parameters of the incoming beam. These parameters are specified by the user in an interactive window. The following plots show a standard SRIM simulation in comparison with a real-beam simulation. The emittance diagram of the beam as generated by the module is included as well. The incoming beam-line may be chromatic, which may cause certain distribution of ranges across the beam-spot.
Standard SRIM simulation Emittance diagram of generated beam Real-size beam simulation Simulation of chromatic effects
A STATISTICAL MODULE = BEAM PARAMETERS INSIDE/BEHIND THE TARGET
This module processes the TRANSMIT.TXT file and enables the user to analyze various beam-parameters like energy-distribution, position-distribution (beam-profile), angular-distribution, momentum-distribution, etc. Based on the results of this statistical analysis, further manipulation with the particle set is possible, like filtering particles exceeding a certain threshold of a given parameter.
Energy distribution Position distribution (beam-profile) Emittance diagram Beam cross-section (real-space)
BEAM-TRANSPORT MODULE = TRANSFER-MATRIX TRANSFORMATION
This module applies a transfer-matrix transformation on particles’ co-ordinates (positions and angles), thus simulating an effect of an ion-optical element. In this way, beam-lines containing standard ion-optical elements in combination with passive matter element like stripping foils, beam-diagnostic elements, charge-exchange foils, vacuum windows, energy-degraders, scattering devices etc. can be simulated. This feature is especially relevant for beam-preparation lines of charged-particle medical beams. The beam-transport through matter is covered by SRIM Monte Carlo simulation. The TRANSMIT.TXT file is further transformed by action of ion-optical elements that is described by the transfer matrix. If the beam enters again a passive element, the TRANSMIT.TXT file can be converted to the TRIM.DAT input file and the Monte Carlo simulation is performed again. Any sequence of ion-optical elements and passive elements can be simulated in this way. At any position along the beam-line, the statistical module can be used to analyze and evaluate the current file containing the particles’ co-ordinates.
The next plot shows a beam passage down a simple beam line consisting of drifts and a quadrupole doublet. The ion-optical simulation is performed by WinAGILE. The upper set of plot shows the beam cross-section (in real-space) at the entrance-points to ion-optical elements for the beam without the scattering foil. The lower set of plot shows the same beam-line with an additional scattering foil at the beginning. This scattering foil could be a charge-exchange extraction foil from a cyclotron. The effect of scattering is clearly visible. The optical setting of the quadrupole doublet is the same in both cases.
Beam-transport module: focusing 5 mm beam to 5 mm beam.
Upper plots: no scattering foil; lower plots: a scattering-foil at the beginning of the beam-line.
The beam cross-sections in real-space as calculated and displayed by the S3M beam-transport module are given at the entrance-points to the ion-optical elements and at the end of the beam-line.