ZelTech scientists have more than 30 years of experience working in the field of nuclear detonation detection. We specialize in gamma ray, x-ray, optical, and electromagnetic pulses produced by nuclear explosions in the atmospheric and space. Our experience encompasses a wide range of scientific and technical support to include:

• Design and implementation of the sensors
• Data analysis and interpretation
• Development of computational models for nuclear phenomenology propagation
• Development of sensor models
• Complex first principles source term modeling and simulation

ZelTech is an active and productive member of the nuclear detection community with our many of our scientists sitting of Expert Panels helping shape emerging technology directives and policy for our customers and their programs.

Technical Nuclear Forensics

ZelTech scientists are subject matter experts (SMEs) in nuclear phenomenology such as gamma rays, Teller light, and electromagnetic pulse (EMP) as they relate to the science of Nuclear Forensics. We perform the following technical support services for our Nuclear Forensics customers:

• Analysis and interpretation of data from prototype sensors
• Assessments of analysis tools and ability to extract information relevant to forensics
• Execution and development of nuclear first-principles models
• Complex algorithm development supporting data analysis and nuclear forensics

Nuclear Weapons Effects

ZelTech’s SMEs have combined experience of over 50 years in nuclear weapons phenomenology, predictive modeling, and sensor performance assessments in the areas of treaty monitoring, nuclear forensics, and weapon effects. ZelTech has a number of computational tools based on the EM-1 Handbook, as well as, our own source models used to calculate such things as:

• Peak overpressure along with time of arrival associated with airblasts as a function of range, yield, and height of burst
• Nuclear EMP through source region, total, and peak electric field strength calculations as a function of range and yield

ZelTech SMEs also have a strong understanding of the historic foundation that forms the EM-1 Handbook and related weapons effects calculations and apply this knowledge of historic data in support of our DOD customers.

ZelTech’s M&S Group carries out fluid mechanics and ocean hydrodynamics, as well as underwater acoustics, work using a combination of state-of-the-art modeling and reduced physics models. We study and provide research and development on subjects such as:

• Internal waves/tides
• Potential flows
• Stratified flows
• Surface waves
• Fate and transport
• Coastal circulation
• Nonhydrostatic and hydrostatic 1D, 2D, and 3D modeled flows
• Radiated flows and waves from moving or static submerged objects  

ZelTech’s expertise includes not only assessing the physical processes themselves, but also in the development of the algorithms.  ZelTech’s M&S Group provides expertise in: 

• Finite-difference, finite-volume, and spectral methods as they apply Reynolds averaged (time) and Large-Eddy Simulation (LES) (space) frameworks
• Numerical modeling schemes
• Complex algorithm development running on individual desktop workstations and parallel computing clusters

ZelTech Nuclear EMP (ZT-HYDROFLASH™) and Lightning Discharges 

The detonation of a nuclear weapon in the atmosphere leads to the generation of an Electromagnetic Pulse (EMP) that can be detected remotely for the purposes of identification, geolocation, and characterization. ZelTech’s ZT-HYDROFLASH™ software addresses scientists’ need to simulate the physical processes that lead to production of EMP at all heights of burst. ZT-HYDROFLASH™ has been used on several projects and encompasses:  

• The same physics inherent to the formation of electrical discharges in the atmosphere
• ZT-HYDROFLASH™ is a 2-D hydrodynamic software that solves the fluid equations for electron and ion transport in the atmosphere and the coupled Maxwell equations using algorithms extracted from the Conservation Law (CLAW) package for solving multi-dimensional hyperbolic equations with finite volume techniques
• Simulations include the ground, atmospheric gradient, and an azimuthal applied magnetic field as a first approximation to the geomagnetic field
• ZT-HYDROFLASH takes advantage of multiprocessor systems by using domain decomposition together with the Message Passing Interface (MPI) protocol for parallel processing
• Post processing with IDL produces snapshots of key parameters across the simulation volume and movies to better visualize the temporal development of the EMP or lightning discharge.
• Can also be used to simulate lightning and high-altitude discharges such as cloud-to-ground lightning, sprites, jets, and elves.

Lightning Monitoring

Lightning is a major source of optical, radio frequency (RF), and X-ray impulses. Our experience includes understanding the fundamental nature of thunderstorm electrical discharges in order to characterize sensor backgrounds. We have developed 2-D, first principles models of various types of lightning discharges that include the relativistic mechanism of runaway breakdown. Our research has focused on: 

• Modeling sprites, blue jets, elves, halos, and intra-cloud lightning
• Precise mechanism that initiates lightning
• Role of runaway breakdown in the lightning process
• Manner in which stepped leaders propagate to ground in a cloud-to-ground discharge
• Validation of modeled data through collaborations with the lightning community

Cosmic Rays

Cosmic rays are the primary source of ionization in the lower atmosphere below ~ 50 – 60 km.  The primary energetic electrons, secondary low energy electrons, and the positive and negative ions produced ultimately by Cosmic rays contribute to the overall lightning process and the global electrical circuit in various ways.  High energy electrons seed the runaway breakdown mechanism and may play a key role in initiating lightning discharges.  The secondary electrons and ions define the conductivity of the upper atmosphere which in turn affects the onset of high-altitude discharges such as sprites, blue jets, elves etc. Our experience includes:

• Understanding the role played by Cosmic rays in preconditioning the atmosphere for the development of lightning discharges of all forms and for driving or establishing the conducting elements that compose the global circuit.
• Understanding the role of Cosmic rays in climate change, a subject generally referred to as cosmoclimatology.

Radio Wave Propagation

The electromagnetic impulses produced by lightning and anthropogenic activity are generally detectable from space. The propagation of these broadband signals through the Earth’s ionosphere leads to significant temporal and spatial distortions that can be exploited to provide diagnostic information about the ionospheric plasma. ZelTech’s scientists’ experience includes researching and developing:

• First principles, trans-ionospheric radio wave propagation models
• Broadband measurements of both lightning and EMP simulators in an effort to determine and monitor key properties of the ionosphere
• Improving in-house modeling capability to include 3-D full wave solutions of Maxwell’s equations to accurately characterize ionospheric irregularities and disturbances and their effect on broadband signals