Development of Kraków External Microbeam - Single Ion Hit Facility

Abstract

The main purpose of building the microbeam setup for the external (i.e out-of-vacuum) measurements is single cell with single ions irradiation. The single-ion hit facility is based on the existing Kraków microbeam setup characterized by the spatial resolutions of about 3 μm. Present work introduces the setup and the measurement chamber that was developed, constructed and assembled in IFJ PAN. The passage of single ions from vacuum to atmosphere (where the cell dish is located) is registered using the channeltron detector installed inside the chamber. Channeltron registers secondary electrons emitted from CsI layer covering the Si3N4 exit window. The system of very precise diaphragms reduces the beam intensity down to a fluence of about 103 protons/sec. The beam blanking, correlated with single proton passage is provided by the fast, electrostatic deflecting system. The precise 3D table, installed outside the chamber, allows positioning the cell dish at a 200 μm distance from the exit window and change the targeted cell with a sub-micrometer precision within the dish. The paper shows results of the preliminary investigations aimed towards optimization of the most important issues: resolution of external microbeam, proton registration efficiency, efficiency of deflecting system and accuracy of single-proton-hit system.