AstroBox: A novel detection system for very low-energy protons from β-delayed proton decay

摘要

An instrument, AstroBox, has been developed to perform low energy proton spectroscopy from β-delayed proton emitters of interest to astrophysics studies. Energetic precursor nuclei are identified and stopped in the gas volume of the detector. The subsequent β or β-proton decay traces ionized paths in the gas. The ionization electrons are drifted in an electric field and are amplified with a Micro Pattern Gas Amplifier Detector (MPGAD). The system was tested in-beam using the β-delayed proton-emitter ~(23)Al, which was produced with the p(~(24)Mg,~(23)Al)2n reaction and separated with the Momentum Achromat Recoil Spectrometer (MARS) at the Cyclotron Institute at Texas A&M University. Off-beam proton spectra have essentially no β background down to ～100 keV and have a resolution of～15 keV (fwhm) for proton-decay lines at E_p = 197 and 255 keV. Lines with βp-branching as low as 0.02% are observed. In addition, the device also gives good mass and charge resolution for energetic heavy ions measured in-beam.