Total Cross Section Measurements Research Articles

Measurement of the neutron total cross section of 9Be at the Back-n white neutron source of CSNS* *Supported by the National Key Research and Development Plan (2016YFA0401603), the National Natural Science Foundation of China (11675155, 11790321) and Foundation of President of China Academy of Engineering Physics (YZJJLX2016003)

The neutron total cross section data of 9Be are essential in the nuclear structure model research of light nuclei and nuclear power installations. The neutron total cross section of 9Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer (NTOX) based on the multi-cell fast fission chamber at the China Spallation Neutron Source (CSNS)-Back-n white neutron source (Back-n). The fission count-neutron energy distributions of 235U and 238U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW. The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV. The neutron total cross section of 9Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region. In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV, the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5% and 15%, respectively. In the resonance energy region, the measured resonance energies in our experiment were 0.63, 0.82, and 2.8 MeV, respectively. The results showed that the total cross section uncertainties of three Be samples were within 2.2% in the energy region below 1 MeV. The total cross section uncertainty of 30 mm Be from 235U was the smallest and less than 5% in the energy region of 0.3 eV−120 MeV. The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.

The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3

The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of ℒ = 2 × 1034 cm-2 s-1 was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of ℒ = 2 × 1034 cm-2 s-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector.

Total cross section measurements of electron scattering from NH3 in the intermediate-energy region

Total cross section measurements of electron scattering from NH3 in the intermediate-energy region

Measurement of the neutron-induced total cross sections of $$^\text {nat}$$Pb from 0.3 eV to 20 MeV on the Back-n at CSNS

Measurement of the neutron-induced total cross sections of $$^\text {nat}$$Pb from 0.3 eV to 20 MeV on the Back-n at CSNS

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

Nuclear radii from total reaction cross section measurements at intermediate energies with complex turning point corrections to the eikonal model

Total and Double Differential Scattering Cross-Section Measurements of Isotropic Graphite

Total and Double Differential Scattering Cross-Section Measurements of Isotropic Graphite

L-MM Auger electron emission from chlorinated organic molecules under proton impact: Angular distribution and total cross section measurement

We have measured the absolute cross section for L-MM Auger electron emission in chlorinated methanes and benzene chloride molecules in collision with keV energy protons. The measurements have been performed with four different chlorine containing organic molecules viz CCl4, CHCl3, CH2Cl2 and C6H5Cl. We have measured the angular distribution of chlorine L-MM Auger electrons at backward emission angles (90° – 150°). The angular distribution shows an isotropic character. We also studied the projectile energy dependence of the total L-MM Auger yield for proton energy ranging from 125 keV to 275 keV. Carbon K-LL Auger yield was also obtained in the same experiments.

Exploring the higher-order QED effects on the differential distributions of vacuum pair production in relativistic heavy-ion collisions

Extensive studies have been conducted in the past few decades to investigate potential signatures of higher-order QED effects in high-energy electromagnetic scattering processes. In our previous work, we have identified evidence of higher-order corrections in the total cross-section for the vacuum pair production in relativistic heavy-ion collisions. However, the presence of higher-order QED corrections cannot be unambiguously proven solely based on total cross-section measurements due to substantial experimental and theoretical uncertainties. The objective of this paper is to explore the sensitivity of specific differential observables in the vacuum pair production to higher-order QED effects in high-energy heavy-ion collisions. These investigations will provide guidance in determining the presence or absence of higher-order QED processes by conducting precise measurements in future experiments.

High-resolution and high-precision measurements of total cross section for electron scattering from CO$$_2$$

High-resolution and high-precision measurements of total cross section for electron scattering from CO$$_2$$

Measurement and analysis of the neutron-induced total cross-sections of 209Bi from 0.3 eV to 20 MeV on the Back-n at CSNS* *Supported by the National Natural Science Foundation of China (12375296), the Key Laboratory of Nuclear Data Foundation (JCKY2022201C153), the National Key Research and Development Plan (2022YFA1603303), and the Natural Science Foundation of Hunan Province of China (2021JJ40444, 2020RC3054)

The neutron-induced total cross-section of 209Bi is crucial for the physical design and safety assessment of lead-based fast reactors, and the quality of experimental data should be improved for evaluation and application. A recent experiment was conducted on the back-streaming white neutron beamline (Back-n) at the China Spallation Neutron Source (CSNS) using the neutron total cross-section spectrometer (NTOX). The neutron energy was determined using a fast multi-cell fission chamber and the time-of-flight technique. Two high-purity bismuth samples, 6 mm and 20 mm in thickness, were chosen for neutron transmission measurements and comparisons. The neutron total cross-sections of 209Bi, ranging from 0.3 eV to 20 MeV, were derived considering neutron flight time determination, flight path calibration, and background subtraction. A comparison of the experimental results with the data in the ENDF/B-VIII.0 library showed fair agreement, and the point-wise cross-sections were found to be consistent with existing experimental data. Special attention was given to the determination of resonance parameters, which were analyzed using the R -matrix code SAMMY and Bayesian method in the 0.5 keV to 20 keV energy range. The extracted resonance parameters were compared to previously reported results and evaluated data. This study is recognized as the first one where the neutron total cross-section of bismuth across such a broad energy spectrum is measured in a single measurement or experiment, and it provides valuable data for the assessment of related reaction information for evaluated libraries and the advancement of lead-bismuth-based nuclear systems.

Progress in measurements of fission cross sections and total cross sections at CSNS Back-n white neutron source

The neutron-induced cross sections are of great significance for the design of nuclear devices and advanced reactors for the nuclear energy production. At CSNS Back-n white neutron source, new measurements of the fission cross sections and total cross sections are performed with two sets of Day-one spectrometers based on the multi-cell fast fission ionization chamber (FIC). The neutron-induced 236,238U fission cross sections relative to 235U from the fission threshold energy to 200 MeV were measured by using the TOF method and the Fast Ionization Chamber Spectrometer for Fission Cross Section Measurement (FIXM) in the single/double bunch mode of Back-n. The experimental uncertainties are analyzed in detail, and the results from the two modes are consistent. The measured 236,238U/235U fission cross section ratios are compared with previous experiments and evaluations. The 236,238U(n,f) cross sections are obtained based on the standard 235U fission cross section. The neutron total cross sections of carbon and aluminum in the energy region from 1 eV to 20 MeV have been measured by using the TOF method and transmission method based on the Neutron Total Cross Section Spectrometer (NTOX) in the double bunch mode. The total cross section results after unfolding are in good agreement with the previous measurements as well as the broadening of the ENDF/B-Ⅷ.0 evaluation with Gaussian function within the experimental uncertainty. The present results provide the experimental data for further measurements, relevant evaluations and the design of nuclear system.

Measurement of total and partial cross sections of the ^{90}Zr(p,gamma )^{91}Nb reaction with in-beam gamma -ray spectroscopy

The origin of many p-nuclei remains an unsolved problem in nuclear astrophysics. While photo-dissociation reactions in the gamma -process can explain the production of many p-nuclei, some, notably ^{92,94}Mo and ^{96,98}Ru are underproduced in network calculations. The ^{90}Zr(p,gamma )^{91}Nb reaction is part of a possible (p,gamma ) reaction chain for the production of the p-nucleus ^{92}Mo. Available data show a large disagreement between the different reported cross sections measurements for the ^{90}Zr(p,gamma )^{91}Nb reaction. We measured proton capture cross sections with an enriched ^{90}Zr target using in-beam gamma -ray spectroscopy for proton energies between 2.75 MeV and 5.1 MeV. The emitted gamma -rays were detected using the HORUS (High efficiency Observatory for gamma -Ray Unique Spectroscopy) detector array at the University of Cologne, Germany. To account for the possible contribution of the ^{91}Zr(p,n) reaction, an enriched ^{91}Zr was irradiated. We measured production cross sections for the ground and isomeric state of ^{91}Nb as well as partial cross section for up to ten high-energy primary transitions. The results are in good agreement with a former in-beam gamma -ray spectroscopy measurement by Laird et al.. We provide a possible explanation for the discrepancies between our data and other available measurements.

Total neutron cross-section measurement on CH with a novel 3D-projection scintillator detector

In order to extract neutrino oscillation parameters, long-baseline neutrino oscillation experiments rely on detailed models of neutrino interactions with nuclei. These models constitute an important source of systematic uncertainty, partially because detectors to date have been blind to final state neutrons. Three-dimensional projection scintillator trackers comprise components of the near detectors of the next generation long-baseline neutrino experiments. Due to the good timing resolution and fine granularity, this technology is capable of measuring neutron kinetic energy in neutrino interactions on an event-by-event basis and will provide valuable data for refining neutrino interaction models and ways to reconstruct neutrino energy. Two prototypes have been exposed to the neutron beamline at Los Alamos National Laboratory (LANL) in both 2019 and 2020, with neutron energies between 0 and 800 MeV. In order to demonstrate the capability of neutron detection, the total neutron-scintillator cross section as a function of neutron energy is measured and compared to external measurements. The measured total neutron cross section in scintillator between 98 and 688 MeV is 0.36 ± 0.05 barn.

Comparative assessment of different aluminum alloys for neutron beam window applications

The choice of an aluminum alloy window along a neutron beam requires careful consideration depending on the requirements of the instrument end station. The windows should generally be thin to minimize loss of neutrons from the beam due to scattering and absorption but still thick enough to be structurally sound for safety requirements. The microstructure of the material is dependent on the alloy and the preparation method and may introduce scattering artifacts or smearing of the instrument resolution that are not desirable. In this manuscript, SANS and total cross section measurements of several different aluminum alloys will be presented and compared in order to provide some useful insight to engineers working on future neutron instrument design.

ATHENA: An active target detector for the measurement of total cross sections

Experimentally determined cross sections are a critical input for accurately modeling the nuclear processes that take place in a variety of astrophysical environments. A new detector has been designed and constructed to measure the total cross section of nuclear reactions relevant for astrophysics. The Active Target High Efficiency detector for Nuclear Astrophysics (ATHENA) has been constructed and commissioned by a measurement of the 12 C + 12 C fusion reaction. As an active target detector with a segmented anode, efficient measurements of total cross sections over a wide energy range are possible.

Thermal Cross Section Measurements At The RPI LINAC

Recently, a cold moderator was designed and developed for use at the Rensselaer Polytechnic Institute Linear Accelerator (RPI LINAC). This cold moderator proved to easily and safely couple to an existing neutron producing target, while enhancing neutron flux below 0.02 eV by up to a factor of 8 by cooling polyethylene down to 29 K. This cold moderator capability allowed for significantly improved counting statistics below 0.02 eV not previously possible due to a poor signal to background ratio. Additionally, testing was performed to characterize the energy resolution of the new cold moderator system and found the system easily capable of resolving resonances in Ta-181 at 4 and 10 eV, while also clearly resolving the Bragg edges found in Be metal below 0.01 eV. Following the design and development of a cold polyethylene moderator, a series of thermal total cross section measurements were performed for polyethylene, polystyrene, Plexiglas and yttrium hydride in the thermal region. These measurements serve to help validate thermal scattering law (TSL) evaluations in the 0.0005 – 1 eV energy range. For polyethylene and polystyrene, two sets of experiments were performed – one with the Enhanced Thermal Target (ETT) and another with the ETT plus the new cold moderator capability (ETTC). The yttrium hydride and Plexiglas measurements were only performed with the ETTC. The measurements for polyethylene help to validate the data processing methodology when using the ETTC, while extending the measured range of polyethylene down to 0.0005 eV. Two different Plexiglas, Plexiglas G and Plexiglas G-UVT, and two different concentrations of yttrium hydride, H/Y = 1.85 and 1.68, were measured. Overall, all materials had generally good agreement with their ENDF/B-VIII.0 TSL evaluations, though some discrepancies were noticed. In the case of the yttrium hydride, the high energy oscillations in the hydrogen cross section and the low energy Bragg edges in the yttrium cross section were clearly seen. These measurements represent the first total cross section measurements that encompass the entire thermal region from 0.0005 – 1 eV for polystyrene and yttrium hydride.

Uncertainty estimation in neutron TOF measurements with ANNRI

To improve data accuracy of neutron-capture and total cross sections of minor actinides and long-lived fission products, the time-of-flight experimental instrument named ”Accurate Neutron-Nucleus Reaction measurement Instrument” was constructed, and neutron time-of-flight experiments have been performed with an intense pulsed-neutron beam at MLF in J-PARC. Detailed analysis methods and deduced uncertainties for capture and total cross-section measurements are presented using an example of the experiments of 243Am. The deduced uncertainties are categorized into five types.

Neutron capture and total cross-section measurements on 94,95,96Mo at n_TOF and GELINA

Capture and total cross section measurements for 94,95,96Mo have been performed at the neutron time-of-flight facilities, n_TOF at CERN and GELINA at JRC-Geel. The measurements were performed using isotopically enriched samples with an enrichment above 95% for each of the 94,95,96Mo isotopes. The capture measurements were performed at n_TOF using C6D6 detectors and a new sTED detector. The transmission measurements were performed at a 10 m station of GELINA using a 6Li glass neutron detector. Preliminary results of these measurements are presented.

Experimental validation of thermal scattering evaluations

In order to test the performance of new neutron thermal scattering law (TSL) evaluations it is desirable to have experimental data that is highly sensitive to the TSL and provides high fidelity information on the energy dependent performance of TSL evaluations. Three relevant experiments are discussed including: accurate thermal total cross section measurements, thermal neutron die-away experiments, and neutron leakage experiments. The experimental setups and results are reviewed and examples provided for some moderators including polyethylene, Plexiglas, and YHx. For the experiments preformed thus far, there is generally good agreement between the measured total cross section and simulations using current TSL evaluations, however in certain energy ranges differences were observed. Similarly neutron die-away and leakage measurements for samples at room temperature are in good agreement with data computed from TSLs, however leakage measurements for polyethylene at 29K show discrepancies with TSL evaluations.

Total thermal neutron cross section measurements of hydrogen dense polymers from 0.0005–20 eV

Hydrogen dense polymers, specifically polyethylene, polystyrene, and Plexiglas, have served as neutron moderator and reflector materials in hundreds of separate critical benchmark experiments because of their low cost and abundance of hydrogen. In order to accurately model and simulate these critical benchmarks, the thermal scattering law (TSL) evaluation that governs how neutrons will thermalize must be well understood and rigorously validated. To support this validation, researchers at Rensselaer Polytechnic Institute performed total neutron cross section measurements for high-density polyethylene & polystyrene over the energy range 0.0005–20 eV and for Plexiglas G & Plexiglas G-UVT over the energy range 0.0005–3 eV. Comparisons were made between the measured cross section and that predicted by the ENDF/B-VIII.0 and Oak Ridge National Laboratory/European Spallation Source/Rensselaer Polytechnic Institute TSL evaluations for polyethylene, Plexiglas, and polystyrene, as available. These experiments represent the first total neutron cross section measurements for polystyrene.