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Measuring $^{19,20}$O(p,n)$^{20,21}$F reactions using an active target detector

Rohit Kumar, H. Desilets, R. T. deSouza

TL;DR

This study demonstrates a method to measure proton fusion cross sections in inverse kinematics using the active-target MuSIC detector with CH$_4$ gas, targeting $^{19,20}$O + p reactions in the $E_{cm}$ range of $1$–$2$ MeV. A detailed, stage-wise trace-based analysis isolates proton fusion events from unreacted beam and competing channels, enabling the cross section to be computed as $\sigma_F = N_{ER}/(N_{Beam}\Delta x)$ with angle-integrated results and quantified uncertainties. Excitation functions for $^{20}$O(p,n) and $^{19}$O(p,n) reveal oscillatory, non-smooth structures consistent with resonant and quasi-bound-state effects, illustrating the viability of studying proton fusion with neutron-rich beams and providing a framework to test reaction theories via microscopic reversibility and Hauser–Feshbach-type considerations.

Abstract

Proton capture on $^{19,20}$O nuclei is measured in inverse kinematics with the active target detector MuSIC@Indiana using CH$_4$ as the target gas. Rejection of unreacted and inelastically scattered beam, along with transfer and fusion on the $^{12}$C allows extraction of the (p,n) cross section. As the cross-section for direct (p,n) processes at these energies is small, the measurement provides access to the proton fusion cross-section. An analysis approach that allows extraction of the proton fusion cross-section is detailed.

Measuring $^{19,20}$O(p,n)$^{20,21}$F reactions using an active target detector

TL;DR

This study demonstrates a method to measure proton fusion cross sections in inverse kinematics using the active-target MuSIC detector with CH gas, targeting O + p reactions in the range of – MeV. A detailed, stage-wise trace-based analysis isolates proton fusion events from unreacted beam and competing channels, enabling the cross section to be computed as with angle-integrated results and quantified uncertainties. Excitation functions for O(p,n) and O(p,n) reveal oscillatory, non-smooth structures consistent with resonant and quasi-bound-state effects, illustrating the viability of studying proton fusion with neutron-rich beams and providing a framework to test reaction theories via microscopic reversibility and Hauser–Feshbach-type considerations.

Abstract

Proton capture on O nuclei is measured in inverse kinematics with the active target detector MuSIC@Indiana using CH as the target gas. Rejection of unreacted and inelastically scattered beam, along with transfer and fusion on the C allows extraction of the (p,n) cross section. As the cross-section for direct (p,n) processes at these energies is small, the measurement provides access to the proton fusion cross-section. An analysis approach that allows extraction of the proton fusion cross-section is detailed.

Paper Structure

This paper contains 12 sections, 1 equation, 9 figures, 1 table.

Table of Contents

  1. Introduction
  2. Experimental details
  3. Analysis framework
  4. Stage 1: Identify incoming beam and reject outgoing beam
  5. Stage 2: Reject residual beam and fusion on carbon
  6. Stage 3: Distinguish F-like from O-like events based on the deviation from reference lines
  7. Stage 4: Determine the location (energy) of proton fusion
  8. Stage 5: Select events based on $<$E$>$$_{after}$
  9. Stage 6: Reject residual two-body scattering for anode $\ge$ 12
  10. Calculation of the proton fusion cross section
  11. Conclusions
  12. Acknowledgments

Figures (9)

  • Figure 1: Schematic illustration of the different reaction channels.
  • Figure 2: Typical traces for fusion on carbon (black, dotted), two-body scattering on carbon (red, dash-dot), and proton fusion (blue, solid) events are superimposed on the anode structure of MuSIC@Indiana. Multiple beam traces (light gray) are shown for reference.
  • Figure 3: Flowchart depicting the analysis logic utilized.
  • Figure 4: Identification of the incident beam based upon the energy deposit of the first four anodes of MuSIC@Indiana. Panel a) For incident $^{20}$O beam, no evidence of beam contamination is observed. Panel b) Three peaks are observed corresponding to the presence of $^{19}$F ($\sim$37%) and $^{19}$Ne ($\sim$4%) along with $^{19}$O beam. However, when averaging over all the measured dataset $^{19}$F is $\sim$55% and $^{19}$Ne remains unchanged.
  • Figure 5: Putative proton fusion trace (solid, magenta) is compared to a few beam traces (solid, gray). The average of the beam traces used as the dotted (black) line indicates the reference beam trace. Indicated by the solid (red) line, based upon a Z$^2$ scaling is the reference line for F ions.
  • ...and 4 more figures