Felsenkeller 5 MV underground accelerator: Towards the Holy Grail of Nuclear Astrophysics ¹²C(α, γ)¹⁶O

Abstract

Abstract. Low-background experiments with stable ion beams are an important tool for putting the model of stellar hydrogen, helium, and carbon burning on a solid experimental foundation. The pioneering work in this regard has been done by the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. The present contribution reviews the status of the project for a higher-energy underground accelerator in Felsenkeller, Germany. Results from γ-ray, neutron, and muon background measurements in the Felsenkeller underground site in Dresden, Germany, show that the background conditions are satisfactory. Two tunnels of the Felsenkeller site have recently been refurbished for the installation of a 5 MV high-current Pelletron accelerator. Civil construction work has completed in March 2018. The accelerator will provide intense, 50 µA, beams of 1 H + , 4 He + , and 12 C + ions, enabling research on astrophysically relevant nuclear reactions with unprecedented sensitivity.

Constraints from Gravitational-wave Detections of Binary Black Hole Mergers on the 12C(α, γ)16O Rate

“…( ) reaction is one of the most important nuclear reaction rates (Burbidge et al 1957) in the evolution of stars yet also one of the most uncertain (Holt et al 2019). Reducing the uncertainty on this rate has been dubbed "the holy grail of nuclear astrophysics" (deBoer et al 2017;Bemmerer et al 2018). It plays a key role in governing the evolution and composition of stars beyond the main sequence, from the C/O ratio in white dwarfs (Salaris et al 1997;Straniero et al 2003;Fields et al 2016), to whether a star will form a neutron star or a black hole (Brown et al 2001;Woosley et al 2002;Tur et al 2007;West et al 2013;Sukhbold & Adams 2020), and the amount of C 12 and O 16 in the universe (Boothroyd & Sackmann 1988;Thielemann et al 1996).…”

Constraints from gravitational wave detections of binary black hole mergers on the $^{12}\rm{C}\left(α,γ\right)^{16}\!\rm{O}$ rate

“…The 12 C (α, γ) 16 O reaction is one of the most important nuclear reaction rates (Burbidge et al 1957) in the evolution of stars yet also one of the most uncertain (Holt et al 2019). Reducing the uncertainty on this rate has been dubbed "the holy grail of nuclear astrophysics" (deBoer et al 2017;Bemmerer et al 2018). It plays a key role in governing the evolution and composition of stars beyond the main sequence, from the C/O ratio in white dwarfs (Salaris et al 1997;Straniero et al 2003;Fields et al 2016), whether a star will form a neutron star or a black hole (Brown et al 2001;Woosley et al 2002;Tur et al 2007;West et al 2013;Sukhbold & Adams 2020), and the amount of 12 C r.j.farmer@uva.nl and 16 O in the Universe (Boothroyd & Sackmann 1988;Thielemann et al 1996) Thus improving our understanding of this key rate is of critical importance to stellar astrophysics.…”

The Study of Key Reactions Shaping the Post-Main Sequence Evolution of Massive Stars in Underground Facilities

“…On the side of the new underground accelerator facilities, new exciting opportunities for the study of this reaction will become available shortly. Measurements of 12 C(α,c) 16 O are among the scientific goals of the new MV facility at LNGS and the Felsenkeller shallow-underground accelerator laboratory for nuclear astrophysics, as in Bemmerer et al (2018). Both accelerators will provide beams not only of α particles but also of carbon ions, allowing for underground measurements of this reaction in inverse kinematics.…”