Side branch resonance can cause standing waves in the main line. The main line standing wave modifies the acoustic boundary condition between the side branch and the main line. This interaction leads to drift in the side branch resonant frequency, and to sensitivity in the side branch and main line resonant amplitude as a function of branch position along the main line standing wave. In many cases the mainline standing wave is not stationary, leading to temporal modulation of the side branch frequency and amplitude. These features are examined using novel signal interrogation techniques that expose frequency and amplitude variation in time. Data from a low pressure air test facility are used to reinforce the theory and demonstrate the system behavior. Finally, the connection between the dynamic pressure signal features and methods for main line and branch component endurance prediction is developed. Components such as steam dryers, safety relief valves, and heat exchangers would be candidates for endurance prediction using these methods.

Abstract. Trailer-based search platforms for detection of radiological and nuclear threats are often based upon coded aperture gamma-ray imaging, because this method can be rendered insensitive to local variations in gamma background while still localizing the source well. Since gamma source emissions are rather easily shielded, in this work we consider the addition of fast neutron counting to a mobile platform for detection of sources containing Pu. A proof-of-concept system capable of combined gamma and neutron coded-aperture imaging was built inside of a trailer and used to detect a 252 Cf source while driving along a roadway. Neutron detector types employed included EJ-309 in a detector plane and EJ-299-33 in a front mask plane. While the 252 Cf gamma emissions were not readily detectable while driving by at 16.9 m standoff, the neutron emissions can be detected while moving. Mobile detection performance for this system and a scaled-up system design are presented, along with implications for threat sensing.