Astrobox - a novel detector for nuclear astrophysics studies with low-energy protons

In many radiative proton capture reactions on sd-shell nuclei or heavier, resonances dominate. One way these resonances can be studied is by measuring very-low energy protons from $\beta$-delayed proton decays. In the past, we produced and separated chosen exotic nuclei with MARS, implanted them in thin silicon strip detectors and observed the $\beta$-delayed protons while pulsing the beam. With this technique, we measured protons with low background for E$_{p}$ = 400-1500 keV. However, to measure lower-energy protons, careful subtraction of a substantial background from the positrons was needed. To reduce this background, we have developed Astrobox, a gas detector using micromegas electron amplifiers. In the first in-beam test of this gas detector at Texas A\&M University, it was found to be more transparent to positrons than the thin silicon detectors, and we were able to measure low-energy protons down to 200 keV with no positron background. The design of Astrobox and the results of the first test measurement of the device, which observed low-energy protons from the $\beta$-delayed proton decay of $^{23}$Al with very-low positron background for the first time, will be presented.