Potku – A New Analysis Software for Heavy Ion Elastic Recoil Detection Analysis K. Arstila 1, J. Julin 1, M.I. Laitinen 1, J. Aalto 2, T. Konu 2, S. Ka ̈ rkka ̈ inen 2, S. Rahkonen 2, M. Raunio 2, J. Itkonen 2, J.-P. Santanen 2, T. Tuovinen 2, T. Sajavaara 1 1 Department of Physics, P.O. Box 35, University of Jyva ̈ skyla ̈, Finland 2 Department of Mathematical Information Technology, P.O. Box 35, University of Jyva ̈ skyla ̈, Finland

Time-of-flight – ERD measurements Typically 1–20 MeV Cl, Br, I or Au ions from 1–3 MV tandem accelerator Time-of-flight–energy spectrometers for isotopic identification and energy spectrum measurement Time of flight (velocity) and energy are measured for the same particle E=½mv 2 ⇔ m=2E/v 2 Different masses can be identified and depth profiles quantitatively determined 35 Cl Time-of-flight Energy H 6 Li 7 Li C 16 O 18 O 19 F Na Si 35 Cl – scattered beam (8.5 MeV) V N T1T1 T2T2

Design principles Open source software developed together with the community –All source code to be licenced under GPLv2 –Physicist-friendly programming language for GUI: Python –Subroutines with other programming languages (C etc.) –Development using Git source code management in GitHub Truly multi-platform –Developed simultaneously in Linux, OS X (Mac) and Windows Generic stopping force library –User defined stopping model –Easy to add specific experimental stopping values High performance –Critical subroutines programmed with C High throughput –Automated analysis for large number of similar measurements

Creating a project and reading data

Measurement settings Beam settings –Ion –Isotope –Energy Detector settings –Detector angle –Target angle –ToF lenght –Carbon foil thickness Depth profile settings –Step for stopping –Bin width –Density –Conc. scaling

Event selection Basic viewing –Zoom and Pan –Undo and Redo –Reset view –Change compression Selections –Points can be cancelled –Zoom and pan also during selections Selection completed –Recoiled or scattered ion –Element –Isotope –Weight factor according to abundance –Display color Several selections can be made for the same isotope –Surface/film/interface

Composition changes Beam induced composition changes inspected by splitting the list mode data –relative to the reference cut selected from deep substrate –typically 10 splits Splits can be shown in –linear scale –logarithmic scale –relative scale (first split normalized) Splits can be saved and analysis can be limited to specific splits –reduced amount of events compensated by higher weight

Time-of-flight calibration Fit ToF edge –error function Calculation of flight time Display of fitting points and linear fit Points can be removed before accepting the calibration

Energy spectra Selectable bin width Intensity scale –linear –logarithmic Can be saved for further analysis –comparisons with simulations (SimNRA, MCERD)

Depth profiles Iterative calculation –event-by-event calculation of recoiling depths –no assumptions on sample composition –concentrations scaled to 100% within the given region Heavy elements –recoiling atom or scattered beam ion Relative concentrations –user-selected region –user-selected elements Absolute concentrations –10 15 at./cm2 –allows to quantify surface and interface contributions

Master – Slave

Future developments Response to user feedback –all (ToF)-ERD users are welcome to test the software Performance improvements –Remaining performance critical routines to be programmed in C –Multi-threading to apply multi-core processors Display ToF−M and E−M histograms Graphical interface for ToF efficiency calibration

Conclusions Open software for TOF-ERD data analysis has been developed –Graphical interface created with Python –Numerical routines with C –Generic stopping power libraries –Quick and easy ToF calibration –Calculation of composition changes –Calculation of energy spectra –Calculation of depth profiles by an iterative procedure –Master – slave procedure to analyse several measurements simultaneously Available from Will be developed further by us, but everyone is welcome to join – For suggestions, questions, complaints, contact Demonstration by request after the session!

Generic stopping force calculation Stopping force library gsto –Stopping values are interpolated from a tabulated Z 1,Z 2,E values –Table size is still reasonable for modern computers (11 MB for SRIM data) Designed for any software requiring stopping force data –Simple and generic library interface for programmers Easy to add experimental stopping forces without programming –Analysis in the previous example required 64 Z 1,Z 2 stopping values => ERD analysis requires always large number of stopping values –Often analyst wants to see effect of changing stopping for single Z 1,Z 2 pair –=> drop a stopping file to gsto folder, edit single text file –=> SRIM (or other pre-defined model) is used as a fallback for all other Z 1,Z 2 pairs