38 research outputs found
Direct Determination of Fission-Barrier Heights Using Light-Ion Transfer in Inverse Kinematics
We demonstrate a new technique for obtaining fission data for nuclei away
from -stability. These types of data are pertinent to the astrophysical
\textit{r-}process, crucial to a complete understanding of the origin of the
heavy elements, and for developing a predictive model of fission. These data
are also important considerations for terrestrial applications related to power
generation and safeguarding. Experimentally, such data are scarce due to the
difficulties in producing the actinide targets of interest. The
solenoidal-spectrometer technique, commonly used to study nucleon-transfer
reactions in inverse kinematics, has been applied to the case of
transfer-induced fission as a means to deduce the fission-barrier height, among
other variables. The fission-barrier height of U has been determined
via the U(,) reaction in inverse kinematics, the results of
which are consistent with existing neutron-induced fission data indicating the
validity of the technique
First Results from The GlueX Experiment
The GlueX experiment at Jefferson Lab ran with its first commissioning beam
in late 2014 and the spring of 2015. Data were collected on both plastic and
liquid hydrogen targets, and much of the detector has been commissioned. All of
the detector systems are now performing at or near design specifications and
events are being fully reconstructed, including exclusive production of
, and mesons. Linearly-polarized photons were
successfully produced through coherent bremsstrahlung and polarization transfer
to the has been observed.Comment: 8 pages, 6 figures, Invited contribution to the Hadron 2015
Conference, Newport News VA, September 201
Observation of Coherent Elastic Neutrino-Nucleus Scattering
The coherent elastic scattering of neutrinos off nuclei has eluded detection
for four decades, even though its predicted cross-section is the largest by far
of all low-energy neutrino couplings. This mode of interaction provides new
opportunities to study neutrino properties, and leads to a miniaturization of
detector size, with potential technological applications. We observe this
process at a 6.7-sigma confidence level, using a low-background, 14.6-kg
CsI[Na] scintillator exposed to the neutrino emissions from the Spallation
Neutron Source (SNS) at Oak Ridge National Laboratory. Characteristic
signatures in energy and time, predicted by the Standard Model for this
process, are observed in high signal-to-background conditions. Improved
constraints on non-standard neutrino interactions with quarks are derived from
this initial dataset
First Measurement of Coherent Elastic Neutrino-Nucleus Scattering on Argon
We report the first measurement of coherent elastic neutrino-nucleus
scattering (\cevns) on argon using a liquid argon detector at the Oak Ridge
National Laboratory Spallation Neutron Source. Two independent analyses prefer
\cevns over the background-only null hypothesis with greater than
significance. The measured cross section, averaged over the incident neutrino
flux, is (2.2 0.7) 10 cm -- consistent with the
standard model prediction. The neutron-number dependence of this result,
together with that from our previous measurement on CsI, confirms the existence
of the \cevns process and provides improved constraints on non-standard
neutrino interactions.Comment: 8 pages, 5 figures with 2 pages, 6 figures supplementary material V3:
fixes to figs 3,4 V4: fix typo in table 1, V5: replaced missing appendix, V6:
fix Eq 1, new fig 3, V7 final version, updated with final revision
Probing the quadrupole transition strength of C15 via deuteron inelastic scattering
Deuteron elastic scattering from C and inelastic scattering reactions to the first excited state of C were studied using a radioactive beam of C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length Ύd = 1.04(11) fm has been extracted from the differential cross sections of inelastic scattering to the first excited state. The ratio of neutron and proton matrix elements Mn/Mp = 3.6(4) has been determined from this quadrupole transition. Neutron effective charges and core-polarization parameters of C were determined and discussed. Results from ab initio no-core configuration interaction calculations were also compared with the experimental observations. This result supports a moderate core decoupling effect of the valence neutron in C similarly to its isotone O, in line with the interpretation of other neutron-rich carbon isotopes.Deuteron elastic scattering from 15C and inelastic scattering reactions to the first excited state of 15C were studied using a radioactive beam of 15C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length Ύd = 1.04(11) fm has been extracted from the differential cross sections of inelastic scattering to the first excited state. The ratio of neutron and proton matrix elements Mn/Mp = 3.6(4) has been determined from this quadrupole transition. Neutron effective charges and core-polarization parameters of 15C were determined and discussed. Results from ab-initio no-core configuration interaction calculations were also compared with the experimental observations. This result supports a moderate core decoupling effect of the valence neutron in 15C similarly to its isotone 17O, in line with the interpretation of other neutron-rich carbon isotopes
Study of the Isomeric State in N Using the N(,He) Reaction
The isomeric state of N was studied using the
N(,He)~proton-removal reactions at \mbox{11.8~MeV/} in
inverse kinematics. The N beam, of which 24% was in the isomeric state,
was produced using the ATLAS in-fight facility and delivered to the HELIOS
spectrometer, which was used to analyze the He ions from the
(,He) reactions. The simultaneous measurement of reactions on both the
ground and isomeric states, reduced the systematic uncertainties from the
experiment and in the analysis. A direct and reliable comparison of the
relative spectroscopic factors was made based on a Distorted-Wave Born
Approximation approach. The experimental results suggest that the isomeric
state of N is an excited neutron-halo state. The results can be
understood through calculations using a Woods-Saxon potential model, which
captures the effects of weak-binding.Comment: 8 pages, 7 figur
Monitoring the SNS basement neutron background with the MARS detector
We present the analysis and results of the first dataset collected with the
MARS neutron detector deployed at the Oak Ridge National Laboratory Spallation
Neutron Source (SNS) for the purpose of monitoring and characterizing the
beam-related neutron (BRN) background for the COHERENT collaboration. MARS was
positioned next to the COH-CsI coherent elastic neutrino-nucleus scattering
detector in the SNS basement corridor. This is the basement location of closest
proximity to the SNS target and thus, of highest neutrino flux, but it is also
well shielded from the BRN flux by infill concrete and gravel. These data show
the detector registered roughly one BRN per day. Using MARS' measured detection
efficiency, the incoming BRN flux is estimated to be
for neutron energies
above ~MeV and up to a few tens of MeV. We compare our results with
previous BRN measurements in the SNS basement corridor reported by other
neutron detectors.Comment: Submitted to JINS
COHERENT Collaboration data release from the measurements of CsI[Na] response to nuclear recoils
Description of the data release 10.13139/OLCF/1969085
(https://doi.ccs.ornl.gov/ui/doi/426) from the measurements of the CsI[Na]
response to low energy nuclear recoils by the COHERENT collaboration. The
release corresponds to the results published in "D. Akimov et al 2022 JINST 17
P10034". We share the data in the form of raw ADC waveforms, provide benchmark
values, and share plots to enhance the transparency and reproducibility of our
results. This document describes the contents of the data release as well as
guidance on the use of the data