Tunnel junction sensors for HCI-surface measurements at low kinetic energies

In recent years, we have developed and deployed the capability to make and use tunnel junctions sensors (TJS) as extremely sensitive tools for the measurement of surface nanofeatures created by particle-surface interactions. The focus of our interest has been highly charged ion (HCI) produced nanofeatures, which we are able to produce in situ due to a direct vacuum connection to the NIST electron beam ion trap (EBIT). Using these sensors, we make systematic studies of the role of the charge state on the size of features created by HCIs and connect those measurements to the stopping power. Recently we have begun to study reduced velocities at a fixed charge state for which little previous theoretical or experimental work has been done. Due to many technical improvements that have been made to our methods, we offer a contemporary summary of the TJS fabrication and HCI irradiation method. Further, we present early experimental results showing increased surface damage when Xe41+ is extracted at ≈4.6 kV in comparison with ≈8.1 kV.