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Tang, Zhaowen

Publications and source records attributed to Tang, Zhaowen.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Development of Material Studies at the LANL UCN Facility Focusing on Actinide Hydriding and Fission Damage

The aging of as-built actinide surfaces in static and dynamic environments is a complex problem of high importance to LANL’s core mission. Many standard material science tools used to study this problem are ideal for highly controlled, lab-made samples. The goal of this work is to use ultracold neutrons to bridge the gap between lab made and as-built surface aging studies. This capability is unique to LANL and will support our core mission.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Scintillation characteristics of the EJ-299-02H scintillator

Here a study of the dead layer thickness and quenching factor of a plastic scintillator for use in ultracold neutron (UCN) experiments is described. Alpha spectroscopy was used to determine the thickness of a thin surface dead layer to be 630 ± 110 nm. The relative light outputs from the decay of 241 Am and Compton scattering of electrons were used to extract Birks’ law coefficient, yielding a kB value of 0.087 ± 0.003 mm/MeV, consistent with some previous reports for other polystyrene-based scintillators. The results from these measurements are incorporated into the simulation to show that an energy threshold of (∼9 keV) can be achieved for the UCNProBe experiment. This low threshold enables high beta particle detection efficiency and the indirect measurement of UCN. The ability to make the scintillator deuterated, accompanied by its relatively thin dead layer, gives rise to unique applications in a wide range of UCN experiments, where it can be used to trap UCN and detect charged particles in situ.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Project ν x B: Novel Application of Neutrinos to Evaluate U.S. Nuclear Weapons Performance

In this white paper, we discuss the feasibility of diagnosing a nuclear explosion using a neutrino detector. This idea was first proposed by Reines and Cowan to observe the then hypothesized neutrino. Since then, the neutrino was discovered and over the decades the field of neutrino research has matured and many properties of the neutrino have been measured such as interaction cross sections, masses, abundances, etc. The neutrino has been observed from the sun, supernova, nuclear reactors, accelerators, and even the Earth’s core. Interestingly, one of the most prolific sources of neutrinos, a man-made nuclear explosion, has yet to be detected.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Proposal to Develop Neutrino Diagnostics for Nuclear Weapons Tests

A nuclear weapon test would be a prolific source of neutrinos in a relatively short time window (<1 s). These neutrinos could be easily detected at distances of 10s of meters or more by detector technology that has been developed for studying neutrino interactions from nuclear reactors. Such a concept was already proposed at LANL in the 50’s but was finally reject for a more controlled experiment at a nuclear reactor – this latter method went on to win the 1995 Nobel prize in physics for the detection of the neutrino. However, times have changed and revisiting this concept could have new unappreciated applications.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2022

Fill and dump measurement of the neutron lifetime using an asymmetric magneto-gravitational trap

The past two decades have yielded several new measurements and reanalysis of older measurements of the neutron lifetime. These have led to a 4.4 standard deviation discrepancy between the most precise measurements of the neutron decay rate producing protons in cold neutron beams and the most precise lifetime measured in neutron storage experiments. Measurements using different techniques are important for investigating whether there are unidentified systematic effects in any of the measurements. In this paper we report a new measurement using the Los Alamos asymmetric magnetogravitational trap where the surviving neutrons are counted external to the trap using the fill and dump method. The new measurement gives a free neutron lifetime of $τ_n$ = 876.3(2.4) stat (0.8) syst . Although this measurement is not as precise, it is in statistical agreement with previous results using in situ counting in the same apparatus.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Gold leaf phantom development for the assessment of proton radiographic sensitivity limits simulating gold nanoparticle tagged tumors

Proton radiography may guide proton therapy cancer treatments with beam’s-eye-view anatomical images and a proton-based estimation of proton stopping power. However, without contrast enhancement, proton radiography will not be able to distinguish tumor from tissue. To provide this contrast, functionalized, high-Z nanoparticles that specifically target a tumor could be injected into a patient before imaging. We conducted this study to understand the ability of gold, as a high-Z, biologically compatible tracer, to differentiate tumors from surrounding tissue. We indicate that AuNP-enhanced proton radiography might be a feasible technology to provide image-guidance to proton therapy, potentially reducing off-target effects and sparing nearby tissue. These data can be used to develop treatment plans and clinical applications can be derived from the simulations.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Dark field proton radiography

A pre- and post-collimation scheme has been applied to high energy proton radiography to establish a dark field condition, which defaults to a state of no transmission until a scatterer is placed at the object plane. This technique, dark field proton radiography, provides two additional capabilities to a standard proton radiography setup. First, protons with a high degree of angular dispersion are removed from the beam, reducing the effects of chromatic aberrations and decreasing noise. Second, protons below the same threshold are removed from the beam downstream of the objects, effectively making the transmission highly sensitive to small amounts of scatter at the object plane. Finally, initial results indicate that the system is highly sensitive to the presence of thinner materials and improves sensitivity to subtle areal density variations in thick objects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Image quality indicator and dechromator setup for static LANSCE proton radiography experiment

This document describes a static geometry consisting of a sphere of gold and Ti-6Al-4V alloy, along with an energy-loss matching dechromator composed of polycarbonate, to field with the X3 electromagnetic magnifying lens at LANSCE during the next beam cycle. This static configuration will allow us to: (1) characterize the system’s resolution at the material interface between the gold and titanium alloy, and test the image quality for fine features associated with the screws used to fasten the titanium alloy hemispheres; (2) tune our models of proton scattering and imaging for these materials; and (3) test a procedure to align the polycarbonate dechromator and the sphere within the proton beamline. The data will also be suitable for validation of the software options available for proton radiography simulations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions 10 B (n,α0γ) 7 Li (6%) and 10 B(n,α1γ) 7 Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts α, 7 Li and γ (electron recoils). A signal-to-noise improvement on the order of 10 4 over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m 2 . The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Monte Carlo calculation and verification of the geometrical factors for the NPDGamma experiment

The NPDGamma experiment measures the parity-violating asymmetry in gamma-ray emission in the capture of polarized neutrons on liquid parahydrogen. The sensitivity to the asymmetry for each detector in the array is used as a parameter in the extraction of the physics asymmetry from the measured data. The detector array is approximately cylindrically symmetric around the target and a step-wise sinusoidal function has been used for the sensitivity in the previous iteration of the NPDGamma experiment, but deviations from cylindrical symmetry necessitate the use of a Monte Carlo model to determine corrections to the geometrical factors. For the calculations, source code modifications to MCNPX were done in order to calculate the sensitivity of each cesium iodide detector to the physics asymmetry. We describe the MCNPX model and results from calculations and how the results are validated through measurement of the parity violating asymmetry of gamma-rays from neutron capture on chlorine.

Grammer, K. B.↗
DOE OSTI2018

Search for the Neutron Decay n → X + γ , Where X is a Dark Matter Particle

Fornal and Grinstein recently proposed that the discrepancy between two different methods of neutron lifetime measurements, the beam and bottle methods, can be explained by a previously unobserved dark matter decay mode, n→X+γ. We perform a search for this decay mode over the allowed range of energies of the monoenergetic γ ray for X to be dark matter. A Compton-suppressed high-purity germanium detector is used to identify γ rays from neutron decay in a nickel-phosphorous-coated stainless-steel bottle. A combination of Monte Carlo and radioactive source calibrations is used to determine the absolute efficiency for detecting γ rays arising from the dark matter decay mode. Lastly, we exclude the possibility of a sufficiently strong branch to explain the lifetime discrepancy with 97% confidence.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗