Effect of the residual atmosphere pressure on collective acceleration of ions in the Luce diode

Abstract

Number and energy of protons and 12C ions collectively accelerated in the Luce diode were determined by radioactivation techniques for residual atmosphere pressure controlled from 5.5 Pa down to 12 mPa. We demonstrate for the first time that the reduction of pressure dramatically reduces average number of 12C ions with energy of up to 2.64eU/amu (U = 250 kV) but in turn increases number of protons accelerated to the same specific energies as well as it enables observation of protons with energies higher than 12eU. We suggest that the 2.64eU/amu protons and 12C ions are accelerated by the same relativistic electron bunches to equal velocities but 12C ions are directly captured in acceleration on the whole way of the bunches from the cathode to the target, while the protons are mostly extracted from the anode plasma.