We present experimental results for the density of states (DOS) of a superconducting microwave Dirac billiard which serves as an idealized model for the electronic properties of graphene. The DOS ...exhibits two sharp peaks which evolve into van Hove singularities with increasing system size. They divide the band structure into regions governed by the relativistic Dirac equation and by the nonrelativistic Schrodinger equation, respectively. We demonstrate that in the thermodynamic limit, a topological transition appears as a neck-disrupting Lifshitz transition in the number susceptibility and as an excited-state transition in the electronic excitations. Furthermore, we recover the finite-size scaling typical for excited-state quantum phase transitions involving logarithmic divergences and identify a quasiorder parameter.
Abstract
The electron accelerator S-DALINAC at TU Darmstadt was successfully operated in single- and double-turn energy-recovery mode. The latter was realized using a shared beam-transport where two ...beams are superimposed in the first recirculation beamline. Due to its current design, the S-DALINAC can be upgraded with reasonable effort to be operated in triple-turn energy-recovery mode with shared beam-transport. Here, two beams are superimposed in both the first and the second recirculation beamline. This mode is particularly challenging since it does not allow for on-the-fly beam tuning compared to a triple-turn energy-recovery mode with individual beam-transport. Therefore, the triple-turn energy-recovery mode requires precise determination of the accelerator setup obtained from beam-dynamics simulations prior to beam-tuning. First results of the necessary beam-dynamics simulations for this mode are presented.
.
The perspectives for photonuclear experiments at the new Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility are discussed in view of the need to accumulate novel and more precise ...nuclear data. The parameters of the ELI-NP gamma beam system are presented. The emerging experimental program, which will be realized at ELI-NP, is presented. Examples of day-one experiments with the nuclear resonance fluorescence technique, photonuclear reaction measurements, photofission experiments and studies of nuclear collective excitation modes and competition between various decay channels are discussed. The advantages which ELI-NP provides for all these experiments compared to the existing facilities are discussed.
The dipole polarizability of stable even-mass tin isotopes 112,114,116,118,120,124Sn was extracted from inelastic proton scattering experiments at 295MeV under very forward angles performed at RCNP. ...Predictions from energy density functionals cannot account for the present data and the polarizability of 208Pb simultaneously. The evolution of the polarizabilities in neighboring isotopes indicates a kink at 120Sn while all model results show a nearly linear increase with mass number after inclusion of pairing corrections.
Reduced transition probabilities have been extracted between excited, yrast states in the N=Z+2 nucleus 94Pd. The transitions of interest were observed following decays of the Iπ=14+, Ex=2129-keV ...isomeric state, which was populated following the projectile fragmentation of a 124Xe primary beam at the GSI Helmholtzzentrum für Schwerionenforschung accelerator facility as part of FAIR Phase-0. Experimental information regarding the reduced E2 transition strengths for the decays of the yrast 8+ and 6+ states was determined following isomer-delayed Eγ1−Eγ2−△T2,1 coincidence method, using the LaBr3(Ce)-based FATIMA fast-timing coincidence gamma-ray array, which allowed direct determination of lifetimes of states in 94Pd using the Generalized Centroid Difference (GCD) method. The experimental value for the half-life of the yrast 8+ state of 755(106) ps results in a reduced transition probability of B(E2:8→+6+) = 205−25+34 e2fm4, which enables a precise verification of shell-model calculations for this unique system, lying directly between the N=Z line and the N=50 neutron shell closure. The determined B(E2) value provides an insight into the purity of (g9/2)n configurations in competition with admixtures from excitations between the (lower) N=3pf and (higher) N=4gds orbitals for the first time. The results indicate weak collectivity expected for near-zero quadrupole deformation and an increasing importance of the T=0 proton-neutron interaction at N=48.
New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4
π
instrument. AGATA is a high-resolution
γ
-ray spectrometer, solely built from ...highly segmented high-purity Ge detectors, capable of measuring
γ
rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual
γ
-ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.
Response of the FAst TIMing Array (FATIMA) for DESPEC at FAIR Phase-0 Chishti, M.M.R.; Jazrawi, S.; Shearman, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2023, Letnik:
1056
Journal Article
Recenzirano
The Monte-Carlo simulated response for γ-ray detection of the FAst TIMing Array (FATIMA) for exploitation within the DEcay SPECtroscopy (DESPEC) experimental system at the FAIR Phase-0 facility at ...Darmstadt, Germany is presented. In this configuration, FATIMA consisted of 36 LaBr3(Ce) detectors surrounding the AIDA, position-sensitive charged-particle active stopper. The decay of the Iπ=8+ isomer-fed decay cascade in 96Pd, measured in the first DESPEC experiment at the FAIR-0 facility was used to validate the simulations. The experimental data yielded in-situ full-energy peak efficiency values for FATIMA of 11.2(11)%, 6.8(7)%, 3.8(4)% and 2.1(4)% at 106, 325, 684 and 1415 keV respectively, consistent with the values derived from the simulated response.
.
Starting from the Skyrme interaction
f
-
together with the density-dependent pairing interaction, we study the
g
factors for the
2
1
,
2
+
excitations of
88, 90
Sr and
90, 92
Zr. The coupling ...between one- and two-phonon terms in the wave functions of excited states is taken into account within the finite-rank separable approximation. Using the same set of parameters we describe available experimental data and give the prediction for
90
Sr,
g
(
2
2
+
)
=
+
0
.
03
in comparison to
+
0
.
31
in the case of
92
Zr.
Precise measurements of the lifetimes of the first excited 2+ states in the stable even-A Sn isotopes 112–124Sn have been performed using the Doppler shift attenuation technique. For the isotopes ...112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously reported values and indicate a shallow minimum at N=66. The observed deviation from a maximum at mid-shell is attributed to the obstructive effect of the s1/2 neutron orbital in generating collectivity when near the Fermi level.
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