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We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target., submitted to Nuclear Instruments and Methods A

The operation of Thick Gas Electron Multipliers (THGEMs) in Time Projection Chambers (TPCs) using various gas mixtures has applications in various nuclear and particle physics experiments. Of particular interest in low-energy nuclear physics is study of nuclear reactions involving Ne isotopes. These reactions can be studied using Ne-based gas mixtures at low pressures in TPCs used as active targets for radioactive beams. We report on the low-pressure operation of THGEMs in Ne + H2 gas mixtures. We show that, since the Ne+H2 forms a Penning pair, higher gains with THGEMs are achievable compared to pure neon gas. Moreover, H2 acts as a quench gas allowing for higher THGEMs voltages while producing minimal background in reactions such as fusion compared to carbon-based neon gas mixtures. Detailed electron transport and amplification simulations have been performed and they qualitatively agree with the increased gain H2 provides in the Ne:H2 mixture. The higher THGEM gains that are achieved with a Ne:H2 mixture will enhance the study of Ne-based reactions in active-target detectors that have high-granularity pad planes, leading to higher spatial resolution heavy-ion track data.

Active-target detectors have the potential to address the difficulties associated with the low intensities of radioactive beams. We have developed an active-target detector, the Notre Dame Cube (ND-Cube), to perform experiments with radioactive beams produced at $\mathit{TwinSol}$ and to aid in the development of active-target techniques. Various aspects of the ND-Cube and its design were characterized. The ND-Cube was commissioned with a $^{7}$Li beam for measuring $^{40}$Ar + $^{7}$Li fusion reaction cross sections and investigating $^{7}$Li($\alpha$,$\alpha$)$^{7}$Li scattering events. The ND-Cube will be used to study a range of reactions using light radioactive ions produced at low energy., Comment: 13 pages, 12 figures

A solenoid spectrometer for nuclear astrophysics (SSNAP) has been developed to study heavy-ion fusion reactions of astrophysical importance near stellar energies. Charged particles follow helical trajectories within the strong magnetic field of a superconducting solenoid. The 12 C ( 12 C , p ) 23 Na reaction was studied as the first measurement using the solenoid spectrometer at the University of Notre Dame within the energy range of E c.m. = 4 . 0 to 6.0 MeV. This experiment demonstrated that the solenoid spectrometer is able to provide outstanding capability for detection of light charged particles produced by nuclear fusion reactions having a relatively wide energy range.

We report on some of the recent developments and experimental work done at the twin-solenoid low-energy radioactive-ion-beam (RIB) facility TwinSol installed at the U Notre Dame 10 MV FN tandem accelerator. The TwinSol facility is a joint project of the University of Michigan (UM) and the University of Notre Dame (UND), and includes several U.S. and foreign collaborators. A number of significant experiments including RIB-induced transfer reactions, elastic scattering, resonant scattering, and fusion at energies near and well below the Coulomb barrier have been performed with this facility. Several of these as well as future work and upgrades planned will be described.

An increase in scintillation of up to 17% has been observed in liquid argon with the application of low electric fields (

We have performed the first search for 3{gamma} decays of the hypothesized {ital X}{sup 0} particle, related to GSI {ital e}{sup +}{ital e{minus}} peaks, using positrons from {sup 68}Ga decay striking a Be target and Ge detectors to search for 3{gamma} events. The geometry of the experiment was optimized for detection of decays of the {ital X}{sup 0} nearly at rest in the Be. No evidence is found for a stopped, unbound {ital X}{sup 0} in the mass range 1.1--1.7 MeV.

"Evaporation residues (ERs) and fission products were measured following bombardment of 64 Ni with radioactive Sn and Te neutron rich isotopes. The experimental setup was tailored to measurements with low intensity radioactive beams and the data obtained show the obvious enhancement of ER production (survival) with the addition of neutrons to the fused system. A calculation of nucleus-nucleus capture within a WKB formalism incorporating neutron transfer in a two step approach was performed. Using global potentials in our calculations we attempted to predict trends as well as account for measured capture cross sections of collisions between heavy nuclei with large neutron excess."

The quadrupole transfer strength associated with the deformed pairing field has been studied by measuring ground-state rotational band angular distributions for the ( 12 C, 14 C) reaction on 154 Sm, 182 W and 186 W. It is shown that, through competition between direct and multistep transitions involving intermediate inelastic excitation, reactions of this type may provide a useful means of studying an underlying structure description of deformed nuclei.

The total fusion cross section σ f for 16 O + 12 c.m. has been measured in 250 keV steps between 17 and 28 MeV c.m. energy via γ -ray techniques. Individual yields for 10 nuclides in the evaporation chain were determined. The oscillations in σ f , which agree in gross structure but not in detail with previous work, appear to be most closely associated with reactions leading to 20 Ne. It is observed that the reaction yield is >80% dominated by nuclides having at least one α particle in the evaporation chain.

The almost pure two-step population of the 2 + ground-state rotational band member of 184 W in the two-neutron transfer reaction 186 W( 12 C, 14 C) 184 W, resulting in an angular distribution characterized by a dramatic nuclear-Coulomb interference minimum in the vicinity of the grazing angle, is compared with the corresponding angular distribution for the two-proton transfer reaction 186 W( 12 C, 10 Be) 188 Os, where the interference minimum is shown to arise primarily from direct-two-step (nuclear-dominated) interference.

Tables are presented for observed properties of the nuclear gamma rays emitted following the bombardment of 24,26 Mg, 27 Al, and 28 Si targets with 14 N, 16,18 O, and 19 F beams. Energy, emitting nucleus, intensity, and angular-distribution coefficients are listed for each gamma where known. The beam energies were between 20 and 60 MeV. The gamma rays are from various final nuclei produced by the fusion of projectile and target nuclei into a compound nucleus and the subsequent evaporation of a few light particles.

A coupled-channels Born-approximation analysis of the reaction $^{192}\mathrm{Os}$($^{12}\mathrm{C}$, $^{14}\mathrm{C}$)$^{190}\mathrm{Os}$ at ${E}_{\mathrm{lab}}=70$ MeV demonstrates that the direct quadrupole transfer strength is very weak, in continuation of the trend found previously in a study of the tungsten nuclei. Elastic and inelastic scattering data for the $^{12}\mathrm{C}$ channel were also taken and analyzed in a conventional coupled-channels model to determine the relative motion.NUCLEAR REACTIONS $^{192}\mathrm{OS}$($^{12}\mathrm{C}$, $^{12}\mathrm{C}$), $^{192}\mathrm{OS}$($^{12}\mathrm{C}$, $^{14}\mathrm{C}$), ${E}_{\mathrm{lab}}=\mathrm{MeV}$, measured $\ensuremath{\sigma}(\ensuremath{\Theta})$. CCBA analysis. Demonstrated effect of shape transitions on quadrupole transfer strength.

An emittance-measuring device which can operate at the rate of two measurements per second has been developed. It consists of a rotating wire scanner interfaced to a small on-line computer.

The level structure of 156 Dy has been investigated with the (p, t) reaction at E p = 29.9 MeV. A strong (7.7% of ground-state strength) transition is observed to a state at 1520 keV, assigned J π = 2 + . It is suggested that this state is the two-phonon βγ-vibration predicted by the theory of Davydov. Possible connections to the “super-band” in 156 Dy are discussed.

The mean life of the J/sup ..pi../ = 5/sup -/, T = 0 state at 4848 keV in /sup 18/F has been measured to be 5.2 +- 0.9 ps via the recoil-distance method. The corresponding E2 transition strength of 14.8 +- 2.6 Weisskopf unit for decay to the 3/sup -/ level at 3791 keV establishes a strongly collective transition.

The measured angular distribution for excitation of 184W to its 4+ state by 12C projectiles at 70 MeV exhibits a deep interference minimum near the grazing angle. This characteristic feature is well reproduced by a rotor model coupled-channels calculation with a negative nuclear hexadecapole deformation length determined to within 20% by the data and is in agreement with the value reported from studies of α-particle excitation functions.

Elastic scattering of 8B and 7Be on a 58Ni target has been measured at energies near the Coulomb barrier. The total reaction cross sections were deduced from Optical-model fits to the experimental angular distributions. Comparison with other systems shows evidence for protonhalo effects on 8B, as well as for neutron-halo on 6He reactions. While the enhancement in the cross section observed for 8B is explained in terms of projectile breakup, in the case of 6He reactions, the particle transfer proces explains the observed enhancement.