The LUNA II 400 kV accelerator

A second high current accelerator of 400 kV has been installed at the underground laboratory of Gran Sasso, called LUNA II. We describe this new facility as well as measurements of the proton beam characteristics: absolute energy, energy spread, and long-term energy stability. The absolute energy was determined to a precision of +/-300 eV at E-p = 130-400 keV using the energy of the capture gamma-ray transition of C-12(p,gamma)N-13 as well as resonance energies at E-p = 309-389 keV of Na-23(p, gamma)Mg-24, Mg-26(p, gamma)Al-27, and Mg-25(p, gamma)Al-26. The resonance studies led to a proton energy spread of better than 100 eV and a long-term energy stability of 5 eV per hour. (C) 2003 Elsevier Science B.V. All rights reserved.