A 200 kV Proton Accelerator Dedicated to Low-Energy Beam-Plasma Interaction Experiments

In order to determine the Coulomb logarithm independently from the charge state, we need energy-loss measurement of protons (zeff = 1) with the same velocity as heavier projectiles. Such a measurement has already been performed using 350 keV protons delivered from the tandem accelerator by means of TOF method with a pulsed beam [4]. The terminal voltage of the accelerator was (350-20)/2 = 165 kV (20 kV = injection voltage). However the intensity of the pulsed beam was so small (< 1 nA) that the accuracy of the data was not sufficiently high for detailed discussion. This was due to the poor beam transmission efficiency in the accelerator at the extremely low terminal voltage.