A Google Scholar search for "Kratos AXIS" shows that there have been over 15,300 for the 20 year period of 1996 - 2016 or 760 publications per year. This period spans publications using the AXIS Ultra, which was launched in 1997, the AXIS Nova (2004) and the AXIS Supra (2016). If the search is widened to 'any time' there are about 16,200 publications from the "Kratos AXIS" search term which will also include the AXIS 165, AXIS HSi and AXIS HS photoelectron spectrometers. Whilst this is a simplistic review of the published work using Kratos photoelectron spectrometers it gives a great insight into the volume and breadth of research undertaken using these instruments.
One of the highest sited papers using a Kratos AXIS Ultra was published in Nature Materials 6, 497 - 500 (2007) with the title Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols.