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ITS is a powerful and user-friendly software package permitting state-of-the-art Monte Carlo solution of lineartime-independent coupled electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permitsthe more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 6, the latest version of ITS, contains (1) improvements to the ITS 5.0 codes, and (2) conversion to Fortran 90. The general user friendliness of the software has been enhancedthroughmemory allocationtoreducetheneedfor userstomodifyandrecompilethe code. 3 AcknowledgmentThere have been many people involved in the development of the ITS codes over the years. We have undoubtedly lost track of the contributions of some, and even if we had not, there would betoomanytolisthere.ITShasbeen assembledbyborrowingand linking algorithmsfrommany generous sources. We are grateful to those who have shared their methods and grateful also to the many users who have suggested improvements over the years. While recognizing that this is necessarily an abbreviated list, we would like to acknowledge some of the contributions that we deem to have been most significant or most recent.The ITS codes owe most of their development to John Halbleib. He wrote the TIGER code and was the primary developer of the ITS codes throughout most of their history. The original TIGER code was built on the ETRAN code developed by Steve Seltzer and Martin Berger, both of NIST (the National Institute of Standards andTechnology). Further collaborations with NIST, ledtoimprovementsofthe algorithmsandcross sections usedby ITS.Tom Mehlhorn playedan importantrolein the first integrationof the Integrated TIGER Series.This release of ITS includes the multigroup capability. The development of MITS (Multigroup ITS) owes much to the contributions of Jim Morel. MITS is also dependent on the CEPXS cross section generating code that was principally developedby Len Lorence.The parallel capabilityoftheITS codes was implementedbyGregValdez. Much testingand many improvements have been contributedbyWesley Fan. Recent improvementsin the physical modelsin the ITS codes were impleme...

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Elastic Rutherford scattering with subsequent momentum analysis has become a powerful tool for analyzing intense, pulsed light-ion beams for inertial confinement fusion studies. The ion spectrum is obtained by mathematical inversion of the data. This paper reports a product-integration solution to the inverse problem which is readily adapted to rapid data analysis and is simpler in form than reported previously. While this approach introduces some unphysical (negative) components into the solution, these are often negligible. Discussed here are the unfold method together with its accuracy and precision.