Our research has been supported by the National Science Foundation, Department of Homeland Security, Department of Energy, Defense Advanced Research Project Agency, Defense Threat Reduction Agency, Nuclear Regulatory Commission, and the industry.
Research Thrust 1: Nuclear Detection and Remote Sensing
Nuclear nonproliferation and security are some of the major challenges associated with the expansion of nuclear power. Both a sound nuclear policy and major advances in detection science and technology are needed to address those challenges. We are pursuing a set of research projects in collaboration with other academic departments, universities, and national laboratories, focusing on the development of advanced technology needed to safeguard nuclear technology and detect nuclear proliferation. Some of our recent projects include:
1) Remote discovery and monitoring of nuclear reactors using antineutrinos (Sponsor: DOE/NNSA)
We are part of the WATCHMAN scientific collaboration that consists of a consortium of universities and national laboratories in the US and UK, with the goal to demonstrate remote monitoring of individual reactor operations at a significant distance using scalable water-based technology. WATCHMAN plans to deploy a 6-kton water-based antineutrino detector called NEO at the Advanced Instrumentation Testbed (AIT) site. The AIT site consists of an underground laboratory in the Boulby mine in Northern England that is located 26 km away from the Hartlepool Reactor Complex. The project is supported by the NNSA’s Office of Defense Nuclear Nonproliferation, the DOE Office of Science, The Ministry of Defence, and The Science and Technologies Facilities Council.
2) Near-field reactor monitoring using antineutrinos (Sponsor: DOE/NNSA)
We are building and testing the first antineutrino directional detector that employs 6Li-doped pulse-shape-sensitive plastic called SANDD. The use of solid-state material enables fine-grained segmentation that leads to excellent spatial resolution. This, combined with particle ID sensitivity are not only critical to reconstructing the direction of antineutrino flux but could also potentially allow for aboveground detection of antineutrinos that would be immensely beneficial to both the physics and nonproliferation communities. Additionally, we are investigating the possibility of performing pulse shape discrimination using an alternative DAQ based on mass-produced ASICs with a low cost per channel, excellent timing characteristics, and scalability to thousands of channels. The work is conducted in collaboration with Lawrence Livermore National Laboratory (LLNL) and the University of Hawaii, and with the support of LLNL.
3) Active interrogation (Sponsor: DHS and DOE/NNSA)
Active interrogation techniques can provide highly accurate information about special nuclear material (SNM) in many safeguards and verification settings. With the support of the Department of Homeland Security, National Nuclear Security Administration, and the Consortium for Monitoring, Technology, and Verification, we have collaborated with partners at Los Alamos National Laboratory to conduct several experimental campaigns at the Device Assembly Facility at the Nevada National Security Site, MIT Bates Accelerator Laboratory, University of Notre Dame, and Institute for Nuclear Energy Research in Taiwan. We have been investigating novel methods for the detection and characterization of SNM, such as HEU, through the use of active interrogation neutron sources to induce delayed neutron signatures, which can provide calibration-free isotopic identification.
4) Magnetic microcalorimeters (Sponsor: DOE/NNSA)
We are collaborating with Lawrence Livermore National Laboratory to develop magnetic microcalorimeters (MMCs) optimized for decay energy spectroscopy. MMCs are cryogenic (~10 mK) radiation detectors comprised of a gold foil absorber in thermal contact with a magnetic sensor. Nuclear samples are embedded within the absorber; the energy from a single decay produces enough heat to change the distribution of atomic spins and hence the magnetic field within the sensor. This change in the magnetic field is directly proportional to the energy deposited within the absorber. MMCs measure the entire decay energy, including nuclear recoil, with 100% efficiency and high resolution (< a few keV) at energy scales of 5 MeV. The objective is to develop a novel method for identifying ratios of fissile isotopes to better than 1% uncertainty with shorter measurement time and at a lower cost in comparison to mass spectrometry. The collaboration will perform a precision measurement of the half-life of Sm-146. We aim to resolve the tension between past measurements of the half-life. This contributes to fundamental astrophysics, relevant for the chronology of early solar-system formation and dating of ancient supernovae.
5) Coherent elastic neutrino-nucleus scattering – CEνNS (Sponsor: DOE/NNSA)
CEνNS is a recently measured neutrino interaction with a relatively high cross-section. CEνNS would allow small detectors (~10’s of kg) to monitor nuclear reactors via their antineutrino signature for malicious activity, such as diversion of fissile material. We are collaborating with Lawrence Livermore National Laboratory to develop dual-phase (liquid and gas) argon CEνNS detectors. We aim to perform the first CEνNS measurement of reactor antineutrinos, to measure neutrinos below the IBD kinematic threshold (1.8 MeV), and to develop this technology and analysis methods for nonproliferation. In conjunction, we are investigating the possible vulnerability of neutrino detectors to “spoofing” signals malicious actors might produce and the steps nuclear regulators might take to ensure the validity of the neutrino signal. Additionally, CEνNS is a crucial tool in answering high-level fundamental physics questions and contributes to studies of sterile neutrinos, neutrino magnetic moment(s), solar nuclear fusion, and dark matter cosmology.
Research Thrust 2: Ultraintense Laser Science and Technology
In the past two decades, remarkable developments in laser technology occurred, resulting in peak power exceeding 1 Petawatt and focal spot intensities exceeding 10²² W/cm², establishing a new and promising field of relativistic optics and high-field science. Importantly, laser systems producing relativistic intensities have become available in university settings. Applications of such systems in nuclear engineering are numerous and include the production of intense pulses of X-rays, gamma-rays, and neutrons, as well as extremely high-current electron and ion beams. Such systems have been used for isotope production, inertial confinement fusion via fast ignition, studies of ultrafast dynamics in solids, and even for the demonstration of photon-photon scattering. Our current research activities include:
1) Laser spectroscopy for nonproliferation (Sponsor: DOE/NNSA)
Laser-based spectroscopy has several benefits for nuclear nonproliferation applications. One of which is the ability to excite isotopic, atomic, and molecular signatures. Another is, due to optical nonlinear effects, that one can overcome the diffraction limit and deliver energy to a remote (~km distance) target at high peak powers. We use high-intensity, ultrafast lasers at the Gérard Mourou Center for Ultrafast Optical Science to investigate the use of optical remote sensing via filamentation. We primarily focus on laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) of various materials relevant to nonproliferation. Our most recent projects have focused on identifying signatures from uranyl fluoride, the stress in biota through LIF, and uranium-containing compounds via LIBS. Other focuses are on understanding the filament plasma properties, and how to control and optimize the laser beam parameters to improve the production and collection of optical signals at a remote distance.
2) Remote optical detection of nuclear materials (Sponsor: DTRA)
Optical methods based on the detection of photons in the UV, visible, and IR spectral regions that originate from electronic transitions provide a modality for the detection of nuclear materials that can complement the traditional techniques based on ionizing radiation detection. The relative ease with which the electronic states can be excited in comparison to nuclear states, along with their typically larger population, results in generally stronger, more easily detectable signals with improved statistical significance. Optical photons can also readily propagate through the air over extended distances. We study the filamentation of ultrafast laser pulses in the air as a means to deliver high electric fields needed to excite and/or ionize remote targets at distances on the order of several tens to hundreds of meters. Our research of the fundamental science behind the filamentation phenomenon spans three interrelated areas: we investigate the nonlinear propagation of intense, high-peak-power, ultrafast laser pulses, the excitation and ionization of the propagation medium to form the filament channel, and, ultimately, the interaction of the filament with the target.
3) Optical instrumentation for advanced reactors (Sponsor: DOE, INL)
With the support of the U.S. Department of Energy and in collaboration with Ohio State University, Idaho National Laboratory, and private industry, we are investigating the linear and nonlinear optical properties of materials post-irradiation and thermal annealing to support the development of optical instrumentation for use in advanced reactors. We investigate these properties through spectroscopy and nonlinear optical techniques enabled by high-energy, nanosecond pulsed lasers. We further develop optical technologies for online testing of the fuel integrity in next-generation gas-cooled fast reactors.
4) Long-wave ultrafast coherent radiation sources (Sponsor: DOD/ONR)
Many laser-matter interaction processes, such as laser pulse filamentation, strong-field physics, and attosecond science, have strong wavelength dependence and favor longer wavelengths in the infrared spectral range, which has not been fully explored experimentally due to the lack of a laser source. With the support of the Office of Naval Research (ONR), we are investigating the use of Optical Parametric Chirped Pulse Amplification (OPCPA) to produce ultrashort, TW-class long-wave infrared pulses. We developed a seed source centered at 10 µm based on difference frequency generation in an AGS crystal, and a 2.75-µm pump source based on KTA parametric master oscillator power amplifier system to support the OPCPA development in GaSe crystals.
5) Nuclear photonics (Sponsor: NSF)
The University of Michigan is re-asserting its national and international leadership in intense laser-based radiation sources. The National Science Foundation’s facility called ZEUS (Zettawatt-Equivalent Ultrashort pulse laser System) is under construction in the Gérard Mourou Center for Ultrafast Optical Science and will house the nation’s most powerful laser. When interacting with matter, the 3-Petawatt ZEUS pulses will produce X rays, gamma rays, neutrons, electrons, positrons, and exotic particles with energies that rival large scientific particle accelerator facilities. We are exploring the production and use of this high-energy radiation and particle beams for nuclear physics studies and applications.
Low-dose shielded nuclear materials detection (Sponsor: NSF/DHS)
With the support of the Academic Research Initiative program of the National Science Foundation and the Department of Homeland Security, we explored methods to detect shielded nuclear materials via active interrogation. In this multi-particle method, we used monoenergetic photons and/or neutrons to perform transmission imaging or induce photofission. We developed new solid-state glass-plastic composite neutron detectors to facilitate the detection of fast neutrons.
Radiation sensors and radiation hard electronics based on graphene and other 2D materials (Sponsor: NSF/DHS and DTRA)
With the support of the Academic Research Initiative program of the National Science Foundation and the Department of Homeland Security, we investigated non-traditional detection methods and detector architectures based on graphene, a material with numerous favorable properties for potential use in radiation detection. With the support of the Defense Threat Reduction Agency, we studied the radiation effects on other novel 2-dimensional materials for applications such as radiation-hard electronics.
Directional neutron detection (Sponsor: DOE/NNSA)
In collaboration and with the support of Lawrence Livermore National Laboratory and the Department of Energy we investigated the use of time projection chambers, sophisticated detectors used in particle and nuclear physics research, as high-performance directional neutron detectors for nonproliferation applications and for accurate measurement of fission cross-sections.
Fission distribution anisotropy studies by use of the surrogate reaction method (Sponsor: LLNL)
The surrogate reaction method is highly suitable for measurements of short-lived nuclides. We are studying the low-energy fission anisotropy of Pu-239, U-235, and U-238 prevalent in surrogate reactions. In conjunction with microscopic cross-section models, this work can extend the validity of the surrogate method to measure cross-sections of short-lived isotopes to energies <1 MeV for nearly any actinide. This work was conducted in collaboration with Lawrence Livermore National Laboratory and Texas A&M University.
Mid-infrared ultrafast sources for accelerator applications (Sponsor: DARPA)
Compact dielectric structures pumped by ultrafast lasers could enable compact, high-efficiency accelerators and radiation sources for medical, scientific, and security applications. Within the UCLA-led GALAXIE consortium, we developed mid-infrared sources of radiation based on nonlinear optical mixing processes. The goal of the project was the development of an ultra-bright compact X-ray source phase-contrast medical imaging.
Laser-based radiation sources based on microstructures (Sponsor: DTRA)
We pursued novel, high-risk approaches to particle acceleration with the aim to allow low-power ultrafast laser systems to achieve large acceleration gradients and replace traditional particle accelerators. These methods could enable the production of X-rays, gamma-rays, and neutrons for active nuclear interrogation and medical applications.
Femtosecond laser spectroscopy for nuclear forensics (Sponsor: DHS)
Nuclear forensics is an area of increasing importance in the present climate of post-Cold War nuclear threats. In collaboration with ANL, LBNL, and LLNL we investigated the potential of laser spectroscopy using shaped femtosecond pulses to enhance the sensitivity and speed of nuclear forensics techniques.
Quantum remote sensing (Sponsor: DOE/NNSA, DARPA)
Advanced technology is needed to support areal surveillance for the detection of proliferation activities. We explored a novel class of sensors based on nonclassical manipulation of light to demonstrate imaging resolution that exceeds that of classical imaging systems.
Advanced pulse shaping techniques (Sponsor: DARPA)
With the support of the Defense Advanced Research Project Agency, we investigated the use of phase-sensitive parametric interactions to produce complex shapes of ultrashort laser pulses needed to support applications in ultrafast and materials science, nuclear fusion, and particle accelerators.