EXPERT, afforded an opportunity to solve the complete general case by employing codes to perform direct analysis. This direct approach unfolds the produced spectrum with no assumptions made about the sample. Instead it calculates through separated spectrum signals and solves a set of linear equations for each layer. Problems still arise, though, and adjustments made to reduce noise in the measurements and room for uncertainty. Class-C In a trip back to square one, this third class of programs, created in the 1990s, take a few principles from Class A in accounting for the general case, however, now through the use of indirect methods. RUMP and SENRAS, for example, use an assumed model of the sample and simulate a comparative theoretical spectra, which afforded such properties as fine structure retention and uncertainty calculations. In addition to the improvement in software analysis tools came the ability to analyze other techniques aside from back-scattering; i.e. ERDA and NRA. Class-D Exiting the Class C era and into the early 2000s, software and simulation programs for ion beam analysis were tackling a variety of data collecting techniques and data analysis problems. Following along with the world's technological advancements, adjustments were made to enhance the programs into a state more generalized codes, spectrum evaluation, and structural determination. Programs produced like SIMNRA now account for the more complex interactions with the beam and sample; also providing a known database of scattering data. Class-E This most recently developed class, having similar characteristics to the previous, makes use of primary principles in the Monte Carlo computational techniques. This class applies molecular dynamic calculations that are able to analyze both low and high energy physical interactions taking place in the ion beam analysis. A key and popular feature that accompanies such techniques is the possibility for the computations to be incorporated in real time with the ion beam analysis experiment itself. Footnotes References External links International Conference on Ion Beam Analysis (Biennial scientific conference devoted to IBA): 2007, 2009, 2011, 2013, 2015, 2017). European Conference on Accelerators in Applied Research and Technology ECAART (Triennial European scientific conference): 2007, 2010, 2013, 2016. International Conference on Particle Induced X-ray Emission (Trienniel scientific conference devoted to PIXE): 2007, 2010, 2013, 2015. "Nuclear Instruments and Methods": The international peer reviewed scientific journal largely devoted to IBA developments and applications SIMNRA program for the simulation and analysis of RBS, EBS, ERD, NRA and MEIS spectra