41st Annual INMM, New Orleans, LA Dynamic IR Imaging of Nuclear Weapon Platforms for Treaty Verification Marc L. Simpson 1, Ralph B. Dinwiddie 2, Ned E. Clapp 3, Brian Damiano 1, Mike J. Maston 4, and Chuck R. Schaich 1 Oak Ridge National Laboratory 1 Instrumentation and Controls Div., 2 Metals and Ceramics Div., 3 Engineering Technology Div., 4 National Security Program Office July 18, 2000 Support by DTRA Arms Control Technology Division

41st Annual INMM, New Orleans, LA Passive Thermal Measurements Have Had Limited Applicability to Subsurface Characterization Conventional applications target surface bulk temperature or temperature gradients Camera sensitivities in the 15º mK range Highly dependent on surface emissivity

41st Annual INMM, New Orleans, LA Our Approach Uses Dynamic Thermal IR Imaging to Extract Subsurface Feature Information Active heating or cooling of the object Measures changes over time in surface thermal properties due to subsurface features Thermal diffusivity, subsurface defects, and embedded structures can be characterized B61 casing Aluminum disk Dynamic IR thermal image through ¾” stainless steel

41st Annual INMM, New Orleans, LA Recent Experiments Have Targeted Sensitivity of Approach to Embedded Heat Source Aluminum Disk B61 casing Heating cartridge Section of casing cooled with liquid nitrogen for 60 sec. Time series IR measurements taken at applied power levels of 0, 4, 8 and 12 watts

41st Annual INMM, New Orleans, LA The Presence of the Heated Internal Disk is Difficult to Detect Without Image Analysis Disk IR signature two minutes after the start of a one minute cool-down Disk 12 Watts Outside of B61 casing cooled for 60 seconds with 4 liters of liquid nitrogen

41st Annual INMM, New Orleans, LA The Internal Disk is Clearly Evident After Image Subtraction and Contrast Enhancement 12 Watts Image taken at 7 min. minus the image taken at 2 min. Disk No Disk

41st Annual INMM, New Orleans, LA 0 Watts 4 Watts 8 Watts 12 Watts 9-2 min.7-2 min. Heater Power has a Significant Effect on the IR Signature of a Cooled BG61-11 Shell Casing

41st Annual INMM, New Orleans, LA Karhunen-Lo  ve Decomposition Is Used to Extract Spatial Information in Spatio-temporal Systems Used in applications such as flame dynamics or combustion Eigenvectors generated from a time series of 2-D images Principal decomposition using eigenvectors represents evolving spatial components In our case, spatial component is the surface thermal gradient due to the subsurface disk and heating element Disk

41st Annual INMM, New Orleans, LA Initial Results from Karhunen-Lo  ve Decomposition Show Some Dependence on Applied Power 0 Watts 4 Watts 8 Watts 12 Watts Results using 2nd Eigenmode

41st Annual INMM, New Orleans, LA Wavelet Analysis Uses Both Spatial Frequency and Time Dependence to Extract Information Used in applications as varied as fingerprint image compression to pattern recognition Practical effect of allowing us to detect signatures that are ordinarily obscured by background clutter Coefficients from wavelet analysis are grouped into subsets representing noise, bias, and signatures of interest Image reconstructed from subsets representing features of interest x dimension y dimension Wavelet representation of differential thermal image (axes represent increasing spatial frequencies to right and up)

41st Annual INMM, New Orleans, LA Raw image  T=0 Difference images  T>5 minutes Wavelet Analysis of Difference Images Shows Strong Dependence on Power Image energy calculated within disk region Reconstructed wavelet image from subset of coefficients

41st Annual INMM, New Orleans, LA Instrument Air Super-cooled air Hot air Vortex coolers Final Measurements Showed Feasibility of Limited Cooling by Controlling Emissivity

41st Annual INMM, New Orleans, LA Dynamic IR Imaging is a Viable Alternate Technology for Nonproliferation Uses the time response of a weapons casing to temperature variations Measurements made with commercially available mid-IR cameras Potential for generating 2 independent parameters: internal structure and source power Complements existing technologies for weapons characterization Technique extensible to vortex coolers that use room temperature instrument air