On the threshold of ion track formation in CaF2
  There is ongoing debate regarding the mechanism of swift heavy ion track formation in CaF2. The objective of this study is to shed light on this important topic using a range of complimentary experimental techniques. Evidence of the threshold for ion track formation being below 3 keV/nm is provided by both transmission electron microscopy and Rutherford backscattering spectroscopy in the channeling mode which has direct consequences for the validity of models describing the response of CaF2 to swift heavy ion irradiation. Advances in the TEM and RBS/c analyses presented here pave the way for better understanding of the ion track formation. 
Marko Karlusic, Corneliu Ghica, Raluca Florentina Negrea, Zdravko   Siketic, Milko Jaksic, Marika Schleberger, Stjepko Fazinic
cond-mat.mtrl-sci