Session R17: Science Opportunities with Stable and Long Lived Beams in Inverse Kinematics

Live

As new techniques and instrumentation have been developed for reaction studies with radioactive ions beams, it has become apparent that these new approaches can also be highly desirable for studies with stable and long-lived beams. This is particularly the case at linear-accelerator facilities such as ATLAS at Argonne National Laboratory and the reaccelerated (ReA) beam facility at the National Superconducting Cyclotron Laboratory (NSCL), which will operate in a standalone mode as NSCL transitions to the Facility for Rare Isotope Beams (FRIB). Access to a broad range of stable and long-lived beams at energies and intensities ideal for direct-reaction studies is available at these facilities. This presents researchers with a myriad of opportunities for studies related to nuclear structure, nuclear astrophysics, and fundamental symmetries. These include, among many others, the use of long-lived actinides for ($d$,$p$)-induced fission studies, reactions on long-lived $s$-process branching-point nuclei, and reactions on gaseous species involved in neutrinoless double-beta decay. A broad overview of near-future science programs at these facilities will be given, with a focus on opportunities using solenoidal-spectrometer based techniques.   

Live

The prospect of newly developed stable and long-lived radioactive beams at energies close to 10 MeV/u from the upgraded ReA6 re-accelerator at FRIB opens the door to many new opportunities. In this talk we will present a proposal to study several reactions simultaneously using a $^{\mathrm{10}}$Be beam at 10 MeV/u. Three reaction channels, $^{\mathrm{10}}$Be(d,p), $^{\mathrm{10}}$Be(d,d) and $^{\mathrm{10}}$Be(d,t) will be detected simultaneously in the AT-TPC placed in the large bore solenoid of the future SOLARIS project. This effort is the first attempt to use an active target detector to study transfer reactions. Due to its large acceptance and target thickness, the required beam intensity to achieve the scientific goals of this experiment is only 2 kHz. The $^{\mathrm{10}}$Be(d,p) reaction will populate bound and unbound states in $^{\mathrm{11}}$Be, with particular interest towards a 3.41 MeV state for which the parity is still unknown. The $^{\mathrm{10}}$Be(d,t) will populate unbound states in $^{\mathrm{9}}$Be that can decay via double $\alpha $ emission. The tracking capability of the AT-TPC will allow to observe the two $\alpha $ resulting from the $^{\mathrm{8}}$Be breakup as well as their angular correlation. The possibility to perform transfer reaction measurements at that intensity level will open many new exciting prospects with the soon-to-be available rare isotope re-accelerated beams of FRIB.   

Live

The Spin-orbital (SO) interaction plays a very important role in determining the magic numbers but is poorly constrained so far. We propose to study low-lying $l=1/l=3$ single-particle states to access the SO-splitting in $^{33}$Si and $^{34}$P using one neutron-adding transfer reactions. The SOLARIS magnet solenoid coupled with the HELIOS silicon array will be used to detect the protons. The goals of the experiment are to determine the $l=1$ and $l=3$ single-particle energies and SO-splitting in $^{33}$Si and $^{34}$P and compare with nuclei in the same isotonic chains. Special attention will be paid to determining the excitation energies of the $1/2^-$ and $5/2^-$ states in $^{33}$Si, which play an important role in determining the trend of the $p$-wave and $f$-wave SO-splitting. This information will determine if there is a sudden change of the SO-splitting in silicon isotopes, which links to the nucleus bubble effect, weak-binding effect, the SO interaction and the underlying mechanisms driving its evolution.   

Live

The St. George recoil separator at the Nuclear Science Laboratory of the University of Notre Dame was designed to study ($\alpha$,$\gamma$) reactions in inverse kinematics relevant to nuclear astrophysics. For the first time, the St. ANA Accelerator, St. George, a helium gas-jet target (HIPPO), and a particle identification system were coupled together to study the $\alpha$($^{14}$N,$\gamma$)$^{18}$F reaction. Preliminary results from the $\alpha$($^{14}$N,$\gamma$)$^{18}$F reaction will be presented. Additionally, ongoing and proposed improvements to St. George and the experimental setup will be presented.   

Live

Due to its importance as an astronomical observable in core-collapse supernovae (CCSNe), the reactions producing and destroying $^{44}$Ti must be well constrained. Generally, statistical model calculations such as Hauser-Feshbach are employed when experimental cross sections are not available, but the variation in such adopted rates can be large. In the case of the $^{44}$Ti($\alpha$,p)$^{47}$V reaction rate, data from the literature are compared with statistical model calculations of the cross section and used to constrain the possible reaction rate variation over the temperatures relevant to CCSNe. Suggestions for targeted future measurements using a beam of $^{44}$Ti and pure helium targets are given.   

Live

X-ray bursts (XRB) occur frequently on neutron stars in a binary system and offer unique opportunities to study nucleosynthesis and neutron star properties. The extreme conditions lead to capture reaction pathways on the proton-rich side of the chart of nuclei, where only few reaction rates are experimentally known. To reduce uncertainties in XRB, reactions with high impact on the XRB light curves and ash abundances must be measured experimentally. To study these reactions in the lab, radioactive ion beam accelerators such as the National Superconducting Cyclotron Laboratory (NSCL) or, in the near future the Facility for Rare Isotope Beams (FRIB) are used. To take advantage of these beams the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas target system at NSCL is used for direct measurements of alpha induced reactions. Sensitivity studies show that $^{\mathrm{59}}$Cu(p,$\alpha )^{\mathrm{56}}$Ni competes with the rp-process of $^{\mathrm{59}}$Cu in XRB and has a big impact on the light curve. The cross section of the reaction can be constrained by the time-inverse reaction $^{\mathrm{56}}$Ni($\alpha $,p)$^{\mathrm{59}}$Cu, because in that direction the ground state contribution dominates the astrophysical reaction rate. The talk presents preliminary results of a $^{\mathrm{56}}$Ni($\alpha $,p)$^{\mathrm{59}}$Cu experiment with JENSA and discusses status and future plans for JENSA.   

Towards a measurement of the $^{44}$Ti($\alpha $,p)$^{47}$V reaction

The detection of gamma-rays from the decay of the long lived radioisotope $^{44}$Ti (t$_{\mathrm{1/2}}=$ 60.0y) by satellite based observatories, has been associated with core collapse supernovae remnants. The detected amount of $^{44}$Ti in the interstellar medium might provide critical insight for understanding the explosion mechanism of core collapse supernovae. The rate of the $^{44}$Ti($\alpha $,p)$^{47}$V reaction is a key reaction which determines the final abundance of Ti produced in such explosive environment. We have successfully developed a $^{44}$Ti beam via the $^{42}$Ca(He,n) $^{44}$Ti reaction at the new in-flight Radioactive Ion Separator (RAISOR) at Argonne National Laboratory. Preliminary results on the development and characterization of a $^{44}$Ti beam will be presented as well as preparations on the use of this beam with the Multi-Sampling Ionization Chamber (MUSIC) detector to measure the $^{44}$Ti($\alpha $,p)$^{47}$V reaction in the astrophysically relevant energy region.