145 research outputs found
Magnetic Moment of the Fragmentation Aligned 61Fe(9/2)+ Isomer
We report on the g factor measurement of the isomer in (). The isomer was produced and spin-aligned via a projectile-fragmentation
reaction at intermediate energy, the Time Dependent Perturbed Angular
Distribution (TDPAD) method being used for the measurement of the g factor. For
the first time, due to significant improvements of the experimental technique,
an appreciable residual alignment of the isomer has been observed, allowing a
precise determination of its g factor: . Comparison of the
experimental g factor with shell-model and mean field calculations confirms the
spin and parity assignments and suggests the onset of deformation due
to the intrusion of Nilsson orbitals emerging from the .Comment: 4 figures. Submitted to Phys. Rev. Let
Energy measurement of prompt fission neutrons in 239Pu(n,f) for incident neutron energies from 1 to 200 MeV
Prompt fission neutron spectra in the neutron-induced fission of 239Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Preliminary results are discussed and compared to theoretical model calculation
A compact fission detector for fission-tagging neutron capture experiments with radioactive fissile isotopes
In the measurement of neutron capture cross-sections of fissile isotopes, the fission channel is a source of background which can be removed efficiently using the so-called fission-tagging or fission-veto technique. For this purpose a new compact and fast fission chamber has been developed. The design criteria and technical description of the chamber are given within the context of a measurement of the 233U(n, ) cross-section at the n_TOF facility at CERN, where it was coupled to the n_TOF Total Absorption Calorimeter. For this measurement the fission detector was optimized for time resolution, minimization of material in the neutron beam and for alpha-fission discrimination. The performance of the fission chamber and its application as a fission tagging detector are discussed.French NEEDS/NACRE ProjectEuropean Commission within HORIZON2020 via the EURATOM Project EUFRA
Discovery and Cross-Section Measurement of Neutron-Rich Isotopes in the Element Range from Neodymium to Platinum at the FRS
With a new detector setup and the high-resolution performance of the fragment
separator FRS at GSI we discovered 57 new isotopes in the atomic number range
of 60: \nuc{159-161}{Nb}, \nuc{160-163}{Pm}, \nuc{163-166}Sm,
\nuc{167-168}{Eu}, \nuc{167-171}{Gd}, \nuc{169-171}{Tb}, \nuc{171-174}{Dy},
\nuc{173-176}{Ho}, \nuc{176-178}{Er}, \nuc{178-181}{Tm}, \nuc{183-185}{Yb},
\nuc{187-188}{Lu}, \nuc{191}{Hf}, \nuc{193-194}{Ta}, \nuc{196-197}{W},
\nuc{199-200}{Re}, \nuc{201-203}{Os}, \nuc{204-205}{Ir} and \nuc{206-209}{Pt}.
The new isotopes have been unambiguously identified in reactions with a
U beam impinging on a Be target at 1 GeV/u. The isotopic production
cross-section for the new isotopes have been measured and compared with
predictions of different model calculations. In general, the ABRABLA and COFRA
models agree better than a factor of two with the new data, whereas the
semiempirical EPAX model deviates much more. Projectile fragmentation is the
dominant reaction creating the new isotopes, whereas fission contributes
significantly only up to about the element holmium.Comment: 9 pages, 4 figure
Status of QUBIC, the Q&U Bolometer for Cosmology
The Q&U Bolometric Interferometer for Cosmology (QUBIC) is a novel kind of
polarimeter optimized for the measurement of the B-mode polarization of the
Cosmic Microwave Back-ground (CMB), which is one of the major challenges of
observational cosmology. The signal is expected to be of the order of a few
tens of nK, prone to instrumental systematic effects and polluted by various
astrophysical foregrounds which can only be controlled through multichroic
observations. QUBIC is designed to address these observational issues with a
novel approach that combines the advantages of interferometry in terms of
control of instrumental systematics with those of bolometric detectors in terms
of wide-band, background-limited sensitivity.Comment: Contribution to the 2022 Cosmology session of the 33rd Rencontres de
Blois. arXiv admin note: substantial text overlap with arXiv:2203.0894
QUBIC VI: cryogenic half wave plate rotator, design and performances
Inflation Gravity Waves B-Modes polarization detection is the ultimate goal
of modern large angular scale cosmic microwave background (CMB) experiments
around the world. A big effort is undergoing with the deployment of many
ground-based, balloon-borne and satellite experiments using different methods
to separate this faint polarized component from the incoming radiation. One of
the largely used technique is the Stokes Polarimetry that uses a rotating
half-wave plate (HWP) and a linear polarizer to separate and modulate the
polarization components with low residual cross-polarization. This paper
describes the QUBIC Stokes Polarimeter highlighting its design features and its
performances. A common systematic with these devices is the generation of large
spurious signals synchronous with the rotation and proportional to the
emissivity of the optical elements. A key feature of the QUBIC Stokes
Polarimeter is to operate at cryogenic temperature in order to minimize this
unwanted component. Moving efficiently this large optical element at low
temperature constitutes a big engineering challenge in order to reduce friction
power dissipation. Big attention has been given during the designing phase to
minimize the differential thermal contractions between parts. The rotation is
driven by a stepper motor placed outside the cryostat to avoid thermal load
dissipation at cryogenic temperature. The tests and the results presented in
this work show that the QUBIC polarimeter can easily achieve a precision below
0.1{\deg} in positioning simply using the stepper motor precision and the
optical absolute encoder. The rotation induces only few mK of extra power load
on the second cryogenic stage (~ 8 K).Comment: Part of a series of 8 papers on QUBIC to be submitted to a special
issue of JCA
New experimental approaches to investigate the fission dynamics
Abstract. The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of 208 Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point
- …