Low-energy studies of thermonuclear reactions in a laboratory at the earth's surface are hampered predominantly by background induced by cosmic rays in the detectors, leading typically to more than 10 events per hour in common detectors. Conventional passive or active shielding around the detectors can only partially reduce the problem. The best solution so far was to install an accelerator facility in a deep underground laboratory, in a similar way to solar neutrino detectors. In the case of

more »

... tional Laboratory of Gran Sasso the 1400 m of rock above the laboratory halls leads to a reduction of the muon flux, the most penetrating component of the cosmic-rays, by a factor 10 6 with respect to the Earth's surface. Several cross sections belonging to hydrogen burning have been studied in the framework of this unique project, called LUNA