Catur Wibisono

We report on a highly selective experimental setup for particle-γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr 3 scintillators for γ-ray detection. Specifically, we report on the results of characterization tests for the first five CeBr 3 scintillation detectors of the CeBr 3 Array (CeBrA) with respect to energy resolution and timing characteristics. We also present results from the first particle-γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS. We show that with the new setup, γ-decay branching ratios and particle-γ angular correlations can be measured very selectively using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, we highlight that nuclear …

High-spin states in Co 59 (Z= 27), Ni 59 (Z= 28), and Co 61 have been populated by the fusion evaporation reactions, Ti 48 (C 14, p 2 n) Co 59, Ti 48 (C 14, 3 n) Ni 59, and Ti 50 (C 14, p 2 n) Co 61. The 9 MV tandem accelerator at the John D. Fox Laboratory, Florida State University (FSU) was used to accelerate the C 14 beam and the deexciting γ rays were detected by the FSU detector array consisting of six high-purity germanium (HPGe) clover detectors and three single crystals. Directional correlation of the γ rays deexciting oriented states (DCO ratios) and polarization asymmetry measurements helped to establish spin and parities of the excited states whenever possible. The level scheme of Co 59 has been expanded with the inclusion of positive-parity states up to 31/2+ at around 11 MeV. The Ni 59 positive-parity states known from previous study were verified with modifications to some of the spins and …

High spin states in Co (), Ni () and Co have been populated by the fusion evaporation reactions, Ti(C, p2n)Co, Ti(C, 3n)Ni, and Ti(C, p2n)Co. The 9 MV tandem accelerator at the John D Fox Laboratory, Florida State University (FSU) was used to accelerate the C beam and the de-exciting rays were detected by the FSU detector array consisting of six High Purity Germanium (HPGe) clover detectors, and three single crystals. Directional correlation of the rays de-exciting oriented states (DCO ratios) and polarization asymmetry measurements helped to establish spin and parities of the excited states whenever possible. The level scheme of Co has been expanded with the inclusion of positive parity states up to 31/2 at around 11 MeV. The Ni positive parity states known from previous study were verified with modifications to some of the spins and parities. On the other hand, the negative parity states were extended to 31/2 at an excitation energy of 12 MeV. No new transition was observed for Co, but one of the major bands has been reassigned as consisting of positive parity states by reason of this study which is a candidate for magnetic rotation band. Cross shell excitations were observed in the three nuclei studied and the prominent role of excitation to g orbital crossing the shell gap was established in relation to collective excitation in these nuclei by comparison with large-scale shell model calculations.

Detection of fission products (FPs) is at the basis of several applications, from reactor science, to non-proliferation and nuclear forensics. In most cases, an accurate quantification of FPs is only possible when the decay data of these isotopes-such as half-life, characteristic gamma-ray energies and intensities-are well known. This is not always the case, and-for many FPs-the current knowledge of decay data comes from measurements that were performed when gamma-ray spectroscopy was in its infancy. The National Nuclear Data Center at Brookhaven National Laboratory, is pursuing a campaign to precisely determine gamma-ray intensities of selected FPs. In this work, we present the results for La-140 and Ce-143, two fission products of particular interest for nuclear forensics. Both isotopes were produced via thermal neutron irradiation of natural samples of lanthanum and cerium at the University of …

Thermonuclear reactions drive stellar explosions including classical novae. Ashes from these reactions are found in presolar grains that are encapsulated in meteorites and then found on Earth. One reaction that affects the composition of these ashes from classical novae is the 34 Cl (p, γ) 35 Ar reaction. However, studying this reaction is very difficult because of the low cross section of 34 Cl (p, γ) 35 Ar and the lack of intense 34 Cl beams. Instead, we measured the 32 S (6 Li, t) 35 Ar*(p) 34 Cl reaction in order to mimic the 34 Cl (p, γ) 35 Ar reaction. In collaboration with Florida State University, we studied the 32 S (6 Li, t) 35 Ar reaction using the Super Enge Split-Pole Spectrograph (SE-SPS), which detects the reaction tritons with a focal plane detector. Proton-decays of excited states in 35 Ar populated via this transfer reaction were measured with the Silicon Array for Branching Ratio Experiments (SABRE). SABRE …

The design and performance of a new Compton-suppressed HPGe and charged-particle array, CLARION2-TRINITY, are described. The TRINITY charged-particle array is comprised of 64 Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG: Ce) crystals configured into five rings spanning 7–54 degrees, and two annular silicon detectors that can shadow or extend the angular coverage to backward angles with minimal γ-ray attenuation. GAGG: Ce is a non-hygroscopic, bright, and relatively fast scintillator with a light distribution well matched to SiPMs. Count rates up to 40 kHz per crystal are sustainable. Fundamental characteristics of GAGG: Ce are measured and presented, including light-and heavy-ion particle identification (PID) capability, pulse-height defects, radiation hardness, and emission spectra. The CLARION2 array consists of up to 16 Compton-suppressed HPGe Clover detectors (≈ 4 …

Fast gamma ray transitions often appear to be broad and hard to see accurately without correcting the emitted gamma rays for Doppler shifting. With the help of charged particle detector array Trinity, the energies of light charged particles emitted from fusion evaporation can be deduced; hence the energies and the angles of the recoil nuclei can be determined from simple kinematics. In this talk, techniques to do Doppler correction of the gamma rays from the data taken using Clarion2-Trinity at Florida State University from the reaction O16+ O18 at 30 MeV will be discussed. Furthermore, preliminary results from the proton and alpha decay channels will be reported.

The investigation of nuclear structure in the mass 16-60 region has provided rich experimental data to test microscopic theory. Previously our group has used the tools and techniques of multi-gamma spectroscopy to chart out the high-spin yrast states in this mass region. It has been shown that (α, d) reactions also have a preference for high spin states since the proton and neutron from the deuteron can both occupy the same state of maximal J. I will present work using the FSU Super Engie Split Pole Spectrograph (SE-SPS). Angular distributions for states produced via 27 Al (α, d) 29 Si will be shown for high spin states for the first time. Comparison of these states will be made with the FSU shell model interaction.

KG. 00008: First results from CLARION2-TRINITY: Coulomb Excitation of 49 Ti and Emerging Collectivity*

To further test the FSU shell model interaction we have observed gamma rays from high spin states in 32 P using the 18 O (16 O, pn) reaction at Ela b= 30 MeV at the FSU Fox Laboratory. From the preliminary analysis, most gamma ray transitions from the previous work proposed by Chakrabarti et al. can be confirmed. Polarizations of some observed transitions have been deduced from the use of Compton scattering in the Clover spectrometers. Also for the first time, results from the new Clarion 2 gamma array will be reported to further investigate this nucleus. The level scheme agrees very well with calculations of the FSU interaction which illustrate the hierarchy of multiparticle-hole excitations in generating higher spin.

GG. 00001: High spin states of 29 Si populated by two particle trasfer reactions*

Certain nuclei of astrophysical interest can be difficult to study experimentally. In such cases, mirror nuclei are sometimes used to estimate quantities such as spectroscopic factors. A study to examine the accuracy of mirror symmetry in attaining these quantities was completed at Florida State University using the Super-Enge Split Pole Spectrograph and associated focal plane detector. Accelerated beams of 3He and deuterons impinged targets of 28Si and 24Mg to study mirror pairs via the 28Si (3He, d) 29P, 28Si (d, p) 29Si, 24Mg (3He, d) 25Al and 24Mg (d, p) 25Mg reactions. The resulting light reaction particles were measured in the focal plane detector. Data were taken at laboratory angles of 10-45 in 5 increments. The excitation energy range was up to and beyond the proton and neutron separation energies for each reaction: 0 mev to 8 MeV in all cases. The resultant proton and deuteron spectra were analyzed …

PE. 00002: Measurement of 19 Ne Excited States Relevant to the 18 F (p, α) 15 O Reaction in Classical Novae*

EG. 00009: Measuring cross-sections of unbound mirror states: a systematic study of one-proton and one-neutron reactions adding on N= Z targets*

LE. 00001: Using transfer reaction Si ( Li, t) S (p) P to study resonances near proton-threshold in S*

The investigation of nuclear structure in the mass A= 16-60 region has provided rich experimental data to test microscopic theory. Previously our group has used the tools and techniques of multi-gamma spectroscopy to chart out the high-spin yrast states in this mass region. Yrast states tend to be more unique for comparison with theory, hence our interest is focused on high spin states. To provide complementary data to gamma spectroscopy, we have explored using the (α, d) direct reaction to produce two nucleon excitations. It has been shown 1 that (α, d) reactions have a preference for high spin states since the proton and neutron from the deuteron can both occupy the same state of maximal J. Surprisingly no results for 27 Al (α, d) 29 Si have been published above 5 MeV of excitation in 29 Si. Results from such a study conducted at FSU with the Super Enge Split-Pole Spectrograph (SE-SPS) will be reported and …

G04. 00004: Reaction for High Spin Spectroscopy with the SE-SPS and the Fox Lab Superconducting Linear Accelerator*

The P nucleus was populated through two separate experiments at the FSU Fox Laboratory using Mg ( B, ) and O ( O, ) reactions both at E = 30 MeV. Subsequent decays were observed with 3 or 4 Clover spectrometers. - coincidences were sorted into symmetric matrices and analyzed by projections. From the preliminary analysis using both data sets, several gamma ray transitions from the previous work as proposed by Chakrabarti\textit {et. al}\footnote {R. Chakrabarti\textit {et al.}, PRC\textbf {84}, 054325 (2011).} can be confirmed, however some of gamma ray transitions proposed to populate the yrast J = 5 state cannot be confirmed, as will be discussed. Furthermore, the observed states were then compared with the FSU\textit {psdpf} shell model calculations\footnote {RS Lubna\textit {et al.}, PRR\textbf {2}, 043342 (2020).}. The two highest level states from the previous work which were …