Exploring Stars in Underground Laboratories: Challenges and Solutions

Abstract

For millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and are the furnaces where all chemical elements continue to be forged out of primordial hydrogen and helium. Studying these reactions in terrestrial laboratories presents serious challenges and often requires developing ingenious instrumentation and detection techniques. Here, we reveal how some of the major breakthroughs in our quest to unveil the inner workings of stars have come from the most unexpected of places: deep underground. As we celebrate 30 years of activity at the first underground laboratory for nuclear astrophysics, LUNA, we review some of the key milestones and anticipate future opportunities for further advances both at LUNA and at other underground laboratories worldwide. Expected final online publication date for the Annual Review of Nuclear and Particle Science, Volume 72 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Advances in radiative capture studies at LUNA with a segmented BGO detector

“…The observed data were iteratively fitted solving equation (1), and leaving Y as the only free parameter. In addition, the Poisson likelihood was calculated at each iteration.…”

“…Deep underground laboratories provide unique conditions for key experiments in nuclear astrophysics, thanks to their dramatic reduction of the background originating from cosmic radiation. Depending on the energy region of interest, the cosmic background can be reduced by many orders of magnitude, resulting in drastically enhanced sensitivities [1]. The combination of a deep underground location and a high-intensity accelerator has been the foundation of long successful campaigns at LUNA [2], and motivated the construction of several new deep-underground accelerator facilities-CASPAR [3], JUNA [4], LUNA-MV [5]-as well as a shallow-underground accelerator laboratory, the Felsenkeller [6].…”

The deep underground Bellotti Ion Beam Facility—status and perspectives

“…The machine can provide intense proton, 4 He + , 12,13 C + and 12,13 C 2+ with the specifications listed in Table 1. It features a terminal voltage stability of 10 ppm and a terminal voltage drift in the order of 10 -5 [6].…”

“…The first experiments, carried out by the LUNA collaboration, employed an accelerator constructed at University of Bochum (Germany). This machine was capable to produce Proton and 3,4 He beams with a beam energy of up to 50 keV. Most notably the machine was used to study the cross section of the fusion reaction 3 He+ 3 He at solar energies.…”

“…LUNA-400 has been put to service in the year 2000 [3] and allowed to study key hydrogen burning reactions relevant to big bang nucleosynthesis, the p-p chain, the CNO cycle, and the NeNa and MgAl cycles. These studies have led to an improved understanding of energy generation and nucleosynthesis in various astrophysical sites, including the Sun, red giant and asymptotic giant branch stars, and classical novae [4].…”