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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Yrast structures of 98 Nb and 99 Mo

Neutron-rich nuclei in the A ≈ 100 mass region are interesting due to a rapid shape transition, especially pronounced in the Zr isotopes, and more recently observed in Nb isotopes. 98 Nb, with only one proton and one neutron outside the subshell closure nucleus of 96 Zr, is amenable to shell model calculations. To further examine the rapid shape transition the yrast structure of 98 Nb was established in this work. This was the only yrast structure missing from all immediate neighbors to 96 Zr. The yrast structure of 98 Nb was studied in the fission of the compound systems formed in three heavy-ion induced reactions, 24 Mg (134.5 MeV) + 173 Yb, 23 Na (129 MeV) + 176 Yb, and 18 O (91 MeV) + 208 Pb. Prompt γ-ray spectroscopy was accomplished using the Gammasphere array. Excitation energies up to 3 MeV were observed for the first time in 98 Nb. The yrast structure above the previously known (5) + isomer was established. In the process of studying 98 Nb the yrast structure of positive-parity states in 99 Mo was extended to 3.7 MeV excitation energy, the previously-known 99 Nb level scheme was enriched, and two new levels were added in the level scheme of 97 Zr. The coupling of the odd proton occupying the g 9/2 orbital to the yrast states in the core nucleus of 97 Zr can account for all observed states in 98 Nb. The yrast structure for the positive-parity states of 99 Mo is compared to the deformed ground-state bands of the 101 Ru isotone and of 98,100 Mo.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Stellar s-process neutron capture cross sections on 78,80,84,86 Kr determined via activation, atom trap trace analysis and decay counting

We present a detailed account of neutron capture experiments of astrophysical relevance on 78,80,84,86 Kr (n, γ) reactions at the border between weak and main s process. The experiments were performed with quasi-Maxwellian neutrons from the Liquid-Lithium Target (LiLiT) and the mA-proton beam at 1.93 MeV (2-3 kW) of the Soreq Applied Research Accelerator Facility (SARAF). The setup yields high-intensity approximate to 40 keV quasi-Maxwellian neutrons (3-5 x10 10 n/s) closely reproducing the conditions of s-process stellar nucleosynthesis. A sample of 100 mg of atmospheric, pre-nuclear-age Kr gas contained in a Ti spherical shell was activated in the LiLiT neutron field. The abundances of long-lived Kr isotopes ( 81,85g Kr) were measured by atom counting via atom trap trace analysis (ATTA) at Argonne National Laboratory and low-level counting (LLC) at University of Bern. This work is the first measurement of a nuclear cross section using atom counting via ATTA. The activities of short-lived Kr isotopes ( 79,85m,87 Kr) were measured by gamma-decay counting with a high-purity germanium detector. Maxwellian-averaged cross sections for s-process thermal energies are extracted. By comparison to reference values, our nucleosynthesis network calculations show that the experimental cross sections have a strong impact on calculated abundances of krypton and neighboring nuclides, in some cases improving agreement between theory and observations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

PIP2-BD: GeV Proton Beam Dump at Fermilab's PIP-II Linac

The PIP-II superconducting RF linac is currently under construction at Fermilab and is expected to be completed by the end of 2028. PIP-II is capable of operating in a continuous-wave mode and can concurrently supply 800 MeV protons to a mega-watt, GeV-scale beam dump facility and to LBNF/DUNE. Designs for proton accumulator rings are being studied to bunch the PIP-II protons into the short pulses needed for neutrino and low-mass dark matter experiments. PIP2-BD is a proposed 100-ton LAr scintillation-only experiment, whose detector design is inspired by CENNS-10 and CCM, that would have world-leading sensitivities to BSM physics, including low-mass dark matter produced in the PIP-II proton beam dump.

42 ENGINEERING↗
DOE OSTI2022

Experimental verification of TNSA protons and deuterons in the multi-picosecond moderate intensity regime

Ion acceleration from high intensity short pulse laser interactions is of great interest due to a number of applications, and there has been significant work carried out with laser energies up to a few 100 J with 10's of femtosecond to 1 ps pulse durations. Here, we report results from an experiment at the OMEGA EP laser, where laser energy and pulse length were varied from 100 to 1250 J and 0.7–30 ps, respectively, in the moderate (2 × 10 17 –2 × 10 18 W/cm 2 ) laser intensity regime. Ions and electrons were simultaneously measured from disk targets made of CH and CD by a Thomson parabola and a magnetic spectrometer, respectively. Measurements showed that the electron temperature, T e (MeV), has a dependence on the laser energy, E L (J), and pulse duration, τ L (ps), and its empirical scaling was found to be 0.015 × E L 0.90 τ L –0.48. The maximum proton and deuteron energies are linearly dependent on the electron temperature, (5.60 ± 0.26) × T e and (3.17 ± 0.18) × T e , respectively. A significant increase in proton numbers with the laser energy was also observed. Furthermore, the increase in the maximum proton energy and proton count with higher energy longer duration pulses presented in this article shows that such laser conditions have a great advantage for applications, such as the proton radiograph, in the moderate laser intensity regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Observation of deuteron and antideuteron formation from resonance-decay nucleons

High-energy hadronic collisions generate environments characterized by temperatures above 100 MeV (refs.), about 100,000 times hotter than the centre of the Sun. At present, it is therefore unclear how light (anti)nuclei with mass number A of a few units, such as the deuteron, 3 He or 4 He, each bound by only a few MeV, can emerge from these collisions. Here, the ALICE Collaboration reports that deuteron–pion momentum correlations in proton–proton (pp) collisions provide model-independent evidence that about 90% of the observed (anti)deuterons are produced in nuclear reactions following the decay of short-lived resonances, such as the Δ(1232). These findings, obtained by the ALICE Collaboration at the Large Hadron Collider, resolve a gap in our understanding of nucleosynthesis in ultrarelativistic hadronic collisions. Apart from offering insights on how (anti)nuclei are formed in hadronic collisions, the results can be used in the modelling of the production of light and heavy nuclei in cosmic rays and dark-matter decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Search for Low mass Higgs Portal Scalars at the MicroBooNE Detector in the NuMI Beam

The MicroBooNE experiment exploits Liquid Argon Time Projection Chamber (LArTPC) technology to detect neutrinos from two beams at Fermilab, Chicago: on-axis Booster Neutrino Beam (BNB) and the off-axis Neutrinos at the Main Injector (NuMI) beam. While the aim of the experiment is to study the low-energy excess of electron neutrino events observed by the MiniBooNE experiment, to search for eV-scale sterile neutrinos and to characterise neutrino interactions on argon, it could also be exploited to probe Beyond Standard Model (BSM) Physics. This thesis presents a BSM search for low-mass Higgs Portal Scalars at MicroBooNE in the NuMI beam using data collected during the Run 1 and Run 3 data-taking periods with a total exposure corresponding to $7.01 \times 10^{20}$ protons on target (POT). The Higgs Portal Model is an extension to the Standard Model in which a dark-sector scalar, $S$, mixes with the Higgs boson with mixing angle $\theta$ and acquires a coupling to the Standard Model fermions via the Higgs Yukawa coupling. We search for low-mass Higgs Portal scalars, in the mass range $100-200$ MeV, at MicroBooNE via the production channel $K \rightarrow \pi + S$, where scalars are produced from kaons decaying at rest in the NuMI target and beam dump, as well as kaons decaying in flight in the decay pipe of the NuMI beam. In the MicroBooNE detector, we search for the decay channel $S \rightarrow e^+e^-$, which is the only decay channel available to the scalars in the mass range of our search. The results are expressed as limits, at the 95\% confidence level, on the scalar-Higgs mixing angle $\theta$ for scalars in the mass range $100-200$ MeV.Date of Award1 Aug 2023Original languageEnglishAwarding InstitutionThe University of ManchesterSupervisorStefan Soldner-Rembold (Supervisor) & Justin Evans (Supervisor)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Searches for Sub-GeV Dark Matter with NOvA and LDMX and Performance Studies of the Cosmic-Ray Veto for Mu2e

The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus to within about an MeV to 100 TeV. Most of the stable constituents of known matter have masses in the lower range, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well. Non-gravitational couplings of dark matter to Standard Model particles would make it possible to produce dark matter at accelerators. Through 120 GeV proton-nucleus collisions, NOvA is effectively a beam dump experiment for producing and detecting dark matter. This thesis presents a search for dark matter – electron scattering in the NOvA near detector from sub-GeV dark matter produced at the target. A future search for sub-GeV dark matter with the Light Dark Matter eXperiment (LDMX) is discussed, along with a study of LDMX's expected sensitivity to visibly decaying dark photons. Additionally, performance studies of the Mu2e cosmic ray veto (CRV) are presented. A calibration procedure for the CRV counters is discussed, along with tests of the efficiency, position resolution, and light yield decline of the CRV counters.

Horoho, Tyler Gregory [Virginia U.] (ORCID:0000000↗
DOE OSTI2024

Radiation damage study of POCO ZXF-5Q graphite for neutrino production targets using 4.5 MeV helium ions

To address the challenges of increased beam power and target survivability associated with next-generation particle production beam lines, high dose, high-energy proton beam conditions are simulated using irradiation from low-energy ion beams. A low-energy ion irradiation study of POCO ZXF-5Q graphite under conditions similar to those of the NuMI NT-02 neutrino production target at the Fermi National Accelerator Laboratory is reported. Helium ion irradiation was performed at 100 ∘ C to a maximum damage level of 0.9 displacements per atom (DPA). Irradiation induced hardening, swelling of the irradiated region, inter-plane lattice expansion, and intraplane lattice contraction with increasing ion fluence was observed using micromechanical (nanoindentation, atomic force microscopy) and electron microscopy (high-resolution imaging, selected area diffraction) characterization. Similar changes were also observed in post irradiation examination of the NT-02 target indicating that ion irradiation can be a valuable tool for estimating radiation damage in proton beam targets. Caution must be exercised though, because the hardening, lattice alteration, and swelling occur to different magnitudes for a given damage level. The observed hardening and embrittlement were greater for ion irradiated graphite. For He ion irradiated samples the lattice spacing changes were smaller at low damage levels (78% less expansion and 71% less contraction at 0.1 DPA) and larger at high damage levels (38% more expansion and 5% more contraction at 0.9 DPA) relative to that observed in the NT-02 target. The magnitude of swelling was 8.5× greater under ion irradiation which is influenced by the differing damage gradients and inclusion of implanted He ions in the region of interest.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Neutrino-portal dark matter detection prospects at a future muon collider

With no concrete evidence for nongravitational interactions of dark matter to date, it is natural to wonder whether dark matter couples predominantly to the Standard Model (SM)’s neutrinos. Neutrino interactions (and the possible existence of additional neutrinophilic mediators) are substantially less understood than those of other SM particles, yet this picture will change dramatically in the coming decades with new neutrino sources. One potential new source arises with the construction of a high-energy muon collider (MuCol); due to muons’ instability, a MuCol is a source of high-energy collimated neutrinos. Importantly, since the physics of muon decays (into neutrinos) is very well-understood, this leads to a neutrino flux with systematic uncertainties far smaller than fluxes from conventional high-energy (proton-sourced) neutrino beams. In this work, we study the capabilities of a potential neutrino detector, “ MuCol ν ”, placed ∼ 100 m downstream of the MuCol interaction point. The MuCol ν detector would be especially capable of searching for a neutrinophilic mediator ϕ through the mononeutrino scattering process ν μ N → μ + ϕ X , exceeding searches from other terrestrial approaches for m ϕ in the ∼ few MeV- ten GeV range. Even with a 10 kg-yr exposure, MuCol ν is capable of searching for well-motivated classes of thermal freeze-out and freeze-in neutrino-portal dark matter. Published by the American Physical Society 2025

Adhikary, Jyotismita (ORCID:0000000253894170)↗
DOE OSTI2020

RECENT RESULTS AND OPPORTUNITIES AT THE IOTA FACILITY

The Integrable Optics Test Accelerator (IOTA) was recently commissioned as part of the Fermilab Accelerator Science and Technology (FAST) facility. The IOTA ring was briefly operated with electrons at 47 MeV followed by a 6-months run with 100 MeV electrons. The main goal of the first runwas to study beam dynamics in the integrable lattices with elliptical nonlinear magnets and in the quasi-integrable case with profiled octupole channel. The flexibility of the IOTA ring allowed a wide range of complementary studies, such as experiments with a single electron; studies of fluctuations in undulator radiation and operation with low emittance beams. Over the next year the proton injector will be installed and two runs carried out. One run will be dedicated to the refinement of nonlinear experiments and another will be dedicated to the proof-of-principle demonstration of Optical Stochastic Cooling.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Letter of Intent: Muonium R&D/Physics Program at the MTA

With the planned turn-on of the PIP-II 800 MeV superconducting proton linac, Fermilab will potentially become the world's best laboratory at which to carry out fundamental muon measurements, sensitive searches for symmetry violation, and precision tests of theory. In preparation, we propose to develop the techniques that will be needed. An R&D and physics program is proposed at the Fermilab MeV Test Area to use the existing 400 MeV Linac to demonstrate the efficient production of a slow muonium beam using $\mu^+$ stopped in a ~100 $\mu$m-thick layer of superfluid helium, and to use that beam to measure muonium gravity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Photonuclear Production of 67 Cu From Gallium

Copper-67 is a radioisotope of interest for medical imaging and therapy as well as for under- standing stellar and interstellar evolution pertaining to the formation of proton-rich nuclei. Since 67 Cu decays 100% to 67 Zinc, understanding this reaction can shed light on the abundance of this and other p-nuclei elements in the universe. Here, the photonuclear production of 67 Cu from 71 Ga and natural gallium is examined as an alternative to its photoproduction from zinc. Two research and development production runs were performed at Thomas Jefferson National Accelerator Facility using an electron linac. During the first run, an 805-W, 30.9-MeV beam was used to irradiate a 1-mm tungsten radiator to create a bremsstrahlung flux. The resulting gamma photons irradiated 50.9 g of natural gallium encased in a graphite crucible for 24.2 h; 7.02 Bq/W∙s∙kg of 67 Cu activity was produced. During the second run, a 4380-W, 31.5-MeV beam was used for 12.0 h on the same target containing 60 g of natural gallium; 6.41 Bq/W∙s∙kg of 67 Cu activity was produced. Because of the difficulties in spectroscopically differentiating 67 Cu from 67 Ga, prior to each run, an isotopically pure 71 Ga disk was irradiated using a 100-W beam for 1 h, at the same respective energies. Finally, these baseline irradiations allowed for separation of 67 Cu from 67 Ga in the spectroscopic measurements of the natural gallium targets.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2022

The influence of nitrogen and nitrides on the structure and properties of proton irradiated ferritic/martensitic steel

The 12Cr1MoWV (wt%) ferritic/martensitic steel HT9 is a candidate material for fuel cladding in advanced nuclear reactors, such as the Versatile Test Reactor currently under development. As such, understanding the relationship between microstructure and mechanical properties in the context of irradiation environments for these steels is critical. N content, and more specifically interstitial N, has been hypothesized to be detrimental to irradiated properties at lower temperatures (less than 0.3T m ) to a total of 6 dpa; however, in this work at a dose of 1 dpa the irradiated microstructure was improved with added N, leading to less irradiation hardening. Three variants of HT9 were irradiated with 1.5 MeV protons to a dose of 1 dpa at 300°C. The HT9 variants included Low (10 ppm), Mid (190 ppm), and High (440 ppm) N alloys that were otherwise nearly identical. Changing the N content had a variety of effects on the irradiated defect structures. As N content increased, the average dislocation loop diameter decreased, while the number density of loops increased. Additionally, extensive Ni clustering was observed on dislocations and interfaces. The Mid and High N specimens exhibited significantly less hardening (ΔHV≃100) relative to the Low N specimen (ΔHV≃160). The decrease in hardening is attributed to vanadium carbonitride acting as a sink for Ni clusters that would otherwise form on dislocations. Under the irradiation conditions used, these results suggest increasing the N content in HT9 may have a desirable effect on the irradiated structure and properties at the dose studied, as well as the swelling resistance at higher doses. In other words, N content appears to be a powerful tool for tailoring the self-interstitial atom cluster mobility in F/M steels for different temperature and dose applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Proton beam dynamics in bare IOTA with intense space-charge

We are commissioning a 2.5-MeV proton beam for the Integrable Optics Test Accelerator at Fermilab, allowing experiments in the strong space-charge regime with incoherent betatron tune shifts nearing 0.5. Accurate modelling of space-charge dynamics is vital for understanding planned experiments. We compare anticipated emittance growth and beam loss in the bare IOTA configuration using transverse space-charge models in Xsuite, PyORBIT, and MADX simulation codes. Our findings reveal agreement within a factor of 2 in core phase-space density predictions up to 100 synchrotron periods at moderate beam currents, while tail distributions and beam loss show significant differences.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Performance of the AstroPix Prototype Module for the Barrel Imaging Calorimeter at the ePIC Detector and in Space-Based Payloads

AstroPix is a high-voltage CMOS (HV-CMOS) monolithic active pixel sensor originally developed to enable precision gamma-ray imaging and spectroscopy in the medium-energy regime (~100 keV–100 MeV) based on the groundwork laid by ATLASpix and MuPix. It features a 500 μm pixel pitch, in-pixel amplification and digitization, and low power consumption (~3-4 mW/cm2), making it scalable for large-area, multilayer telescope detector planes. The detectors have a designed dynamic range of 25 keV to 700 keV. With these features, AstroPix meets the requirements of future space-based high-energy telescopes and the imaging layers of the Barrel Imaging Calorimeter (BIC) in the Electron-Proton/Ion Collider (ePIC) detector at the future Electron-Ion Collider (EIC). For the space-based payload, AstroPix is being integrated into sounding rocket and balloon payloads to demonstrate the technical readiness of the devices. For BIC, AstroPix-based imaging layers interleaved within the lead/scintillating-fiber (Pb/SciFi) sampling calorimeter provide granular shower imaging, enabling key performance features such as electron/pion or gamma/neutral pion separation. As part of the ongoing detector R&D efforts, we have been testing various AstroPix_v3 configurations: the single chip, a quad-chip assembly, a three-layer stack of quad chips, and a 9-chip module that represents the smallest prototype unit of the BIC imaging layer. This presentation will highlight recent performance test results from these AstroPix detector configurations.

Kim, Bobae (ORCID:0000000295396815)↗
DOE OSTI2022

Two-particle Bose–Einstein correlations in ${ pp }$ collisions at $\mathbf {\sqrt{s} = 13}$ TeV measured with the ATLAS detector at the LHC

This paper presents studies of Bose–Einstein correlations (BEC) in proton–proton collisions at a centre-of-mass energy of 13 TeV, using data from the ATLAS detector at the CERN Large Hadron Collider. Data were collected in a special low-luminosity configuration with a minimum-bias trigger and a high-multiplicity track trigger, accumulating integrated luminosities of 151 μb -1 and 8.4 nb -1 , respectively. The BEC are measured for pairs of like-sign charged particles, each with |η|<2.5, for two kinematic ranges: the first with particle p T >100 MeV and the second with particle p T >500 MeV. The BEC parameters, characterizing the source radius and particle correlation strength, are investigated as functions of charged-particle multiplicity (up to 300) and average transverse momentum of the pair (up to 1.5 GeV). The double-differential dependence on charged-particle multiplicity and average transverse momentum of the pair is also studied. The BEC radius is found to be independent of the charged-particle multiplicity for high charged-particle multiplicity (above 100), confirming a previous observation at lower energy. This saturation occurs independent of the transverse momentum of the pair.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Charge collection study with the ATLAS ITk prototype silicon strip sensors ATLAS17LS

The inner tracker of the ATLAS detector is scheduled to be replaced by a completely new silicon-based inner tracker (ITk) for the Phase-II of the CERN LHC (HL-LHC). The silicon strip detector covers the volume 40 < R < 100 cm in the radial and | z | < 300 cm in the longitudinal directions. The silicon sensors for the detector will be fabricated using the n + -on-p 6-inch wafer technology, for a total of 22,000 wafers. Here, intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics (HPK). The charge collection properties were examined using penetrating 90 Sr β -rays and the ALIBAVA fast readout system for the miniature sensors of 1 cm × 1 cm in area. The samples were irradiated by protons in the 27 MeV Birmingham Cyclotron, the 70 MeV CYRIC at Tohoku University, and the 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor for fluence values up to 2 × 10 15 n eq /cm 2 . The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for the ITk. Sensors with two active thicknesses, 300 μ m (standard) and 240 μ m (thin), were compared and the difference in the charge collection was observed to be small for bias voltages up to 500 V. Some samples were also irradiated with gamma radiation up to 2 MGy, and the full depletion voltage was found to decrease with the dose. This was caused by the Compton electrons due to the 60 Co gamma radiation. To summarize, the design of the ATLAS17LS and technology for its fabrication have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors already delivered in January of 2020.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Dispersion calibration for the National Ignition Facility electron–positron–proton spectrometers for intense laser matter interactions

Electron–positron pairs, produced in intense laser–solid interactions, are diagnosed using magnetic spectrometers with image plates, such as the National Ignition Facility Electron–Positron–Proton Spectrometers (EPPSs). Although modeling can help infer the quantitative value, the accuracy of the models needs to be verified to ensure measurement quality. The dispersion of low-energy electrons and positrons may be affected by fringe magnetic fields near the entrance of the EPPS. We have calibrated the EPPS with six electron beams from a Siemens Oncor linear accelerator (linac) ranging in energy from 2.7 MeV to 15.2 MeV as they enter the spectrometer. A Geant4 Tool for Particle Simulation Monte Carlo simulation was set up to match depth dose curves and lateral profiles measured in water at 100 cm source–surface distance. An accurate relationship was established between the bending magnet current setting and the energy of the electron beam at the exit window. The simulations and measurements were used to determine the energy distributions of the six electron beams at the EPPS slit. Furthermore, analysis of the scanned image plates together with the determined energy distribution arriving in the spectrometer provides improved dispersion curves for the EPPS.

47 OTHER INSTRUMENTATION↗