PAFF, a low-energy, low-flux proton accelerator for detector tests

We describe a proton accelerator with adjustable low energy and low flux (PAFF,Proton Accelerator for Femtoampere Flux), constructed for calibration and tests of proton detectors for neutron-decay experiments. The facility produces a stable proton beam with energies between 10 and 35 keV and currents between a few tens of protons per second and nA at the detector test area. It is employed to test counters for experiments on the neutron decay. In the set-up these detectors may be cooled down to temperatures around 10 K. An electron gun will be installed to produce parallel beams of protons and electrons for a future production of neutral hydrogen atoms of some tens of keV