Speaker
Description
We report the preliminary results from a direct cross‐section measurement of the $^{59}$Cu(p, $\alpha$) $^{56}$Ni reaction, performed in inverse kinematics using the high-efficiency MUSIC active-target detector at the ReA6 facility at FRIB. This reaction is critical in explosive astrophysical environments. In type I X-ray bursts, where rapid proton capture and $\alpha$-induced processes drive the thermonuclear runaway, the competition between the $^{59}$Cu(p, $\alpha$) and $^{59}$Cu(p, $\gamma$) reactions governs the breakout from the NiCu cycle. This breakout is essential for synthesizing heavier nuclei and ultimately shapes the X-ray burst light curves and the composition of burst ashes. Similarly, in the $\nu$p-process—operating in the proton-rich ejecta of core-collapse supernovae—the $^{59}$Cu(p, $\alpha$) reaction rate strongly influences the formation of heavy, proton-rich isotopes that are observed in the aftermath of these stellar explosions.
Our measurement used a $^{59}$Cu beam delivered at 8.41 MeV/u with an intensity of ~1×10$^{4}$ pps, covering the center-of-mass energy range from 2.38 to 5.57 MeV. This energy window lies within the Gamow range for temperatures above 2 GK—a regime critically relevant for both X-ray bursts and the $\nu$p-process. The experiment employed methane gas in the MUSIC chamber to enable high-rate detection and event-by-event identification was achieved through characteristic energy-loss patterns, allowing a clear separation of (p, $\alpha$) events from potential contaminants.
