Ground state nuclei usually have compact geometries. However, there have been theoretical predictions that excited nuclei can take on more extended shapes such as toroids or bubbles. There have been many attempts to identify signatures of such shapes in experimental data. One signature, both predicted by theory and sought by experimental data, is narrow resonances at high excitation energy in peripheral intermediate-energy heavy-ion collisions. Potential evidence for toroidal states was reported in the alpha particle disassembly of 28Si after collision with a 12C target at 35 MeV/nucleon. The prior work was limited by angular resolution and statistical uncertainties. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duo-lateral (DADL) position-sensitive silicon detectors capable of sub-millimeter position resolution. The measured excitation energy distributions of 7-alpha disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment. A statistical likelihood analysis was performed to provide an upper limit to toroidal high-spin isomer cross section, as evidenced by this observable, as a function of the excitation energy and width of potential states.

Previous studies have quantified neutron-proton equilibration experimentally in dynamically deformed nuclei in heavy ion collisions (JEDELE A. et al., Phys. Rev. Lett., 118 (2017) 062501; RODRIGUEZ MANSO A. et al., Phys. Rev. C , 95 (2017) 044604). The results showed the composition of the two heaviest fragments from the excited projectile-like fragment evolve exponentially with respect to its angle of rotation. Simulations using constrained molecular dynamics and anti- symmetrized molecular dynamics were utilized for different slope parameterizations to compare the experimental results. The results indicate better agreement with a softer interaction.

Forward angle proton spectra from min-bias collisions in the reactions of various 47 MeV/u projectiles on Sn targets are analyzed. Energy Spectra transformed to momentum space in the projectile frame reveal a 1 /k 4 dependence indicating a possible signature that short range correlations are observed

Ground state nuclei usually have compact geometries. However, there have been theoretical predictions that excited nuclei can take on more extended shapes such as toroids or bubbles. There have been many attempts to identify signatures of such shapes in experimental data. One signature, both predicted by theory and reported in experimental data, is narrow resonances at high excitation energy in peripheral intermediate-energy heavy-ion collisions. This potential evidence for toroidal states was reported in the alpha particle disassembly of 28Si after collision with a 12C target at 35 MeV/nucleon. The prior work was limited by angular resolution and statistical uncertainties. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duo-lateral (DADL) position-sensitive silicon detectors capable of sub-millimeter position resolution. The measured excitation energy distributions of 7-α disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment.

The equation of state describes the emergent physical properties of matter. Experimental data is needed to help constrain the equation of state for nuclear matter. These constraints can help distinguish between an "asy-stiff" and an "asy-soft" equation of state, which has astrophysical implications. One path to help constrain the models is to analyze the nuclear caloric curve; some experiments have shown dependence on neutron excess, and may thus be sensitive to the asymmetry. A difference in the caloric curve based on the asymmetry of the reconstructed quasiprojectile (QP) had been observed using 70 Zn on 70 Zn at 35 MeV/nucleon taken with the NIMROD array. Antisymmetrized molecular dynamics calculations were performed for the same system and deexcited with GEMINI++. Both Gogny (asy-soft) and Gogny-as (asy-stiff) data sets were generated. The particles were then filtered based on detector geometric acceptance and thresholds. From the accepted particles, the excitation energy and temperature were calculated in the same way as for experimental data. Additionally, filter effects on the observed nuclear caloric curves were investigated. A tendency for the asy-stiff nuclear caloric curves to have higher temperatures than their asy-soft counterparts was observed for a number of probes. In addition, some probes may show sensitivity to the reconstructed composition of the QP, but this is inconclusive due to high statistical fluctuations and a large dependence on the exact method of event selection.

Ground state stable nuclei typically have near-spherical geometries but may exhibit exotic shapes and form alpha-particle clusters within their bulk if given excitation energy and/or angular momentum. It is predicted that such clustering can promote the production of angular-momentum stabilized toroidal nuclei. Previous experiment and theory suggest that such states may be evidenced by narrow resonances at high excitation energy in peripheral intermediate energy heavy-ion collisions. There has been recent focus on potential evidence for toroidal states in the alpha-particle disassembly of 28Si in collisions of 28Si + 12C at 35 MeV/nucleon; however, prior evidence is limited by the angular resolution and statistical uncertainties that exist in the measurement. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duolateral (DADL) position-sensitive silicon detectors capable of submillimeter position resolution. The performance and response of the array was previously characterized in detail to accurately predict the expected resolution of measuring narrow resonances. The measured excitation energy distributions for 7- and 8-alpha disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment. Further investigation of collision properties that lead to these exit channels revealed challenges in isolating clean projectile-mass decays, where many 7-alpha events do not originate from a single 28Si source. A statistical likelihood analysis was performed to determine the sensitivity of the present measurement for confidently determining resonant yield, providing an upper limit to toroidal high-spin isomer cross section as a function of the excitation energy and width of potential states.

Neutron-proton equilibration has previously been studied experimentally in dynamically deformed nuclei in heavy ion collisions [Phys. Rev. Lett. 118, 062501 (2017); Phys. Rev. C 95, 044604 (2017)] using the NIMROD detector array at the Cyclotron Institute at Texas A&M University. Results indicated the composition of the two heaviest fragments originating from the excited projectile-like fragment evolved exponential with respect to their orientation angle to be more similar. Constrained Molecular Dynamics and Antisymmetrized Molecular Dynamics simulations were performed for different formulations of the density dependence of the asymmetry energy term of the nuclear equation of state. The simulations are compared to experimental results, which indicate a better agreement with a softer interaction in the nuclear equation of state.

The dual-axis duo-lateral (DADL) position-sensitive silicon detector was developed to obtain precise position and energy information for detected charged particles. The Forward Array Using Silicon Technology (FAUST) is currently equipped with 68 DADL detectors backed by CsI(Tl) scintillators for the study of charged particle correlations in heavy-ion collisions where precise position and energy information is essential. When conventional signal processing electronics were used for the DADL detectors, a position dependence of the measured energy as well as distortions in the calculated particle positions were observed. In previous work, waveforms from the detector after preamplification were studied to better understand the features that give rise to these distortions; therein, a waveform analysis technique was developed to improve the energy resolution and linearity in position reconstruction. However, the reading and writing of waveforms for an entire detector array limits data collection rates and adds significant burden in data storage and analysis speed. In this work, the integrators of a Struck SIS3316 ADC were utilized to process 228Th source data to develop and optimize a new analysis method that captures the benefits of the waveform analysis technique while circumventing the waveform writing requirement. This integrator method – capable of 59 keV (FWHM) energy resolution – was used in the collection of 35 MeV/nucleon 28Si + 12C collision data using FAUST to investigate exotic decays of highly excited highly deformed nuclei. In this data, a position resolution of 0.4 mm (FWHM) was obtained for 25 MeV α-particles; for α-particles near this energy that originate from 8Be ground state decays, a 8Be ground state width of 30 keV (FWHM) was obtained. The impact of the energy-dependent DADL position resolution emergent from electronic noise on the quality of excited state measurement was modeled and compared to the experimental data.

The possibility of the dependence of the nuclear caloric curve on neutron excess sets a limit on the accuracy of our knowledge of the nuclear equation of state, and thus impacts predictive capabilities of nuclear reaction and nuclear astrophysics models. To date, theoretical models have not reached consensus on the magnitude or sign on the asymmetry dependence. To provide constraints, we have measured evaporated particles and heavy residues for complete and incomplete fusion-evaporation reactions in inverse kinematics. The temperatures extracted from the observed light charged particles tend to favor higher temperatures for the neutron-rich fused systems, though they are near the limits of the systematic uncertainty. The present measurement may be used as an upper limit to constrain the asymmetry dependence of the nuclear caloric curve.

The role of neutron excess in the nuclear equation of state is impor-tant in many systems from the microscopic to the astronomical, and yet the asym-metry energy remains the largest source of uncertainty in the equation of state. Wecontinue our study of the asymmetry dependence of nuclear caloric curve, measur-ing evaporation of light charged particles from compound nuclei produced Kr+ Cfusion reactions. The composition and excitation of the compound nuclei are variedby varying the isotope and kinetic energy of the krypton projectile. Temperaturesare extracted with kinetic and chemical probes. The more neutron-rich compoundnuclei exhibit higher temperatures than the less neutron-rich compound nuclei. Wediscuss this in light of previous experimental efforts theoretical predictions.

The performance characteristics of single-crystalline diamond detectors at varying rates of heavy-ions below 50 MeV/u have been investigated. When tested with a Th-228 source, the energy resolution of these detectors is better than 1.0% FWHM for 8.8 MeV alpha-particles. With a slight reduction in the energy resolution, simultaneous timing resolution of 314 ps has been achieved. Isotopic resolution has been achieved up to magnesium using a diamond telescope at low rates with a 20 MeV/u Ne-20 + C-12 reaction. At moderate rates of direct 7.5 MeV/u Kr-78, polarization effects are observed, though this effect can be diminished by increasing the applied voltage on the detector up to a limit. After an accumulated dose of 6.9 x 10(8) direct Kr-78 particles transmitting through the detector, a degradation in the energy resolution of the 8.8 MeV peak from 1.6% to 5.3% is observed, indicating that permanent damage has been done to the detector.

The silicon telescopes of the Forward Array Using Silicon Technology (FAUST) have been recently upgraded with silicon detectors which use resistive charge-splitting to measure the position of charged particles. This is in addition to the measurement of the total energy that these charged particles deposit in the detector. The upgrade results in increased angular resolution with a much smaller number of signals than silicon strip detectors with similar resolution. A novel method of calibration has been used to demonstrate the efficacy of these position-sensitive detectors, and the detectors have been used in a commissioning experiment.

Albergo thermometers with double isotope, isotone, and isobar yield ratio pairs with one proton and/or neutron difference are investigated. Without any extra sequential decay correction, a real temperature value of $4.9\ifmmode\pm\else\textpm\fi{}0.5$ MeV is deduced from the yields of the experimentally reconstructed primary hot intermediate mass fragments (IMFs) from $^{64}\mathrm{Zn}+^{112}\mathrm{Sn}$ collisions at 40 MeV/nucleon using the Albergo thermometer for the first time. An experimental sequential decay correction from the apparent temperatures to the real ones for 12 other reaction systems with different neutron-proton ($N/Z$) asymmetries in the same experiment, $^{70}\mathrm{Zn}$, $^{64}\mathrm{Ni}$ on $^{112,124}\mathrm{Sn}$, $^{58,64}\mathrm{Ni}$, $^{197}\mathrm{Au}$, and $^{232}\mathrm{Th}$ at 40 MeV/nucleon, is performed using an empirical correction factor approach of Tsang et al. [Phys. Rev. Lett. 78, 3836 (1997)] with the deduced 4.9-MeV temperature value. The dependence of nuclear temperature on the source $N/Z$ asymmetry is further investigated using these deduced real source temperature values from the present 13 systems. It is found that the deduced real source temperatures at the present source $N/Z$ range show a rather weak dependence on the source $N/Z$ asymmetry. By comparison between our previous results and those from other independent experiments, a consistent description for the $N/Z$ asymmetry dependence of nuclear temperature is addressed.

The dual-axis duo-lateral position-sensitive silicon detector was developed to detect charged particles with high quality position and energy resolution. When these detectors were used with conventional signal processing electronics, an empirically determined correction was used to improve energy resolution. In this work, the waveforms from the detector after preamplification are studied in detail to investigate position information contained in the waveforms. A 7.22 MeV/nucleon alpha particle beam was impinged directly on a masked dual-axis duo-lateral detector. Data obtained using a 228Th alpha particle source was also used. By studying the waveform characteristics that give rise to the position-dependent distortions, a new summed trigger analysis method has been developed to significantly improve linearity in position reconstruction without sacrificing energy resolution.

Alpha emitting radionuclides with medically relevant half-lives are interesting for treatment of tumors and other diseases because they deposit large amounts of energy close to the location of the radioisotope. Researchers at the Cyclotron Institute at Texas A&M University are developing a program to produce 211At, an alpha emitter with a medically relevant half-life. The properties of 211At make it a great candidate for targeted alpha therapy for cancer due to its short half-life (7.2 h). Astatine-211 has now been produced multiple times and reliability of this process is being improved.

The mass dependence of the transverse flow for Z = 1-5 fragments from the collisions of Ar-40 + Al-27, Ar-40 + Ti-48, and Ar-40 + Ni-58 at 47 MeV/nucleon is investigated experimentally in this article. The transverse flow values are determined using the in-plane components of the fragment transverse momenta, where three conventional methods, i.e., the kinetic flow tensor method, the transverse momentum analysis method, and the azimuthal correlation method, are applied to reconstruct the reaction plane in an event-by-event basis. It is demonstrated from the comparison of the present experimental mass dependent flow measurements and the model simulations using an improved antisymmetrized molecular dynamics model that the experimentally observed abnormal alpha transverse flow enhancement is closely related to the reaction plane reconstruction procedure in the flow extraction. We further investigate the physical existence of the abnormal alpha flow behavior using a two-particle azimuthal correlation method, which allows us to provide the relative flow magnitude information with an identification of fragment charge number without the knowledge of the reaction plane differing from the three conventional methods. It is found that the relative flow magnitudes deduced from the two-particle azimuthal correlation functions with an identification of Z, with the correction for the recoil effect imposed by the momentum conservation, show a monotonically increasing trend as a function of fragment charge number, with no exception of the alpha flow enhancement. These results, in addition to those from the improved antisymmetrized molecular dynamics model simulations, definitely provide experimental evidences for the inexistence of the abnormal alpha flow behavior in the heavy-ion collisions at the present incident energy region in nature.