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Strecker, Kevin E.

Publications and source records attributed to Strecker, Kevin E..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Imaging Spectroscopy: A Novel Use for the Velocity Mapped Ion Imaging Technique.

The ability to measure the velocity of neutral atoms and molecules with a precision of several meter/sec provides an opportunity to measure subtle perturbations on electronic states with high resolution. Using Velocity Mapped Ion Imaging we are able to measure induced perturbations of electronic states such as broadening and magnetic and electric field splittings . We demonstrate this ability utilizing the 5s[3/2] 2 → 5p[5/2] 3 cycling transition at 811.5 nm in metastable Kr atoms to investigate the saturation broadening caused by Rabi cycling on a resonant transition with MHz resolution. In addition we investigate the lifetime broadening associated with ionization from the cycling states and the Zeeman splitting of the states. We discuss the inherent limits to resolution obtained with this technique.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Sensitive Multi-Species Emissions Monitoring: Infrared Laser-Based Detection of Trace-Level Contaminants

This report summarizes our development of spectroscopic chemical analysis techniques and spectral modeling for trace-gas measurements of highly-regulated low-concentration species present in flue gas emissions from utility coal boilers such as HCl under conditions of high humidity. Detailed spectral modeling of the spectroscopy of HCl and other important combustion and atmospheric species such as H 2 O, CO 2 , N 2 O, NO 2 , SO 2 , and CH 4 demonstrates that IR-laser spectroscopy is a sensitive multi-component analysis strategy. Experimental measurements from techniques based on IR laser spectroscopy are presented that demonstrate sub-ppm sensitivity levels to these species. Photoacoustic infrared spectroscopy is used to detect and quantify HCl at ppm levels with extremely high signal-to-noise even under conditions of high relative humidity. Additionally, cavity ring-down IR spectroscopy is used to achieve an extremely high sensitivity to combustion trace gases in this spectral region; ppm level CH 4 is one demonstrated example. The importance of spectral resolution in the sensitivity of a trace-gas measurement is examined by spectral modeling in the mid- and near-IR, and efforts to improve measurement resolution through novel instrument development are described. While previous project reports focused on benefits and complexities of the dual-etalon cavity ring-down infrared spectrometer, here details on steps taken to implement this unique and potentially revolutionary instrument are described. This report also illustrates and critiques the general strategy of IR- laser photodetection of trace gases leading to the conclusion that mid-IR laser spectroscopy techniques provide a promising basis for further instrument development and implementation that will enable cost-effective sensitive detection of multiple key contaminant species simultaneously.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Acoustic detector for fission neutrons

We report here on the progress towards the development of an acoustic neutron detector. The goal is to make a detector that is passive, low cost, and scalable to large areas. We will discuss the potential for this detector to be blind to gamma radiation and the potential for high-efficiency fast neutron imaging. The detector signals are based on the generation of ei ther bubbles or thermo-acoustic shock in a liquid due to energy deposition from a neutron. The interaction of a neutron with a hydrogen rich fluid will primarily be a neutron-hydrogen collision. As they are nearly identical in mass, the most probable scattering event is an elastic event, depositing approximately half of the collision energy into the hydrogen atom. For fission neutrons this energy is in the 1-15 MeV range. The excited hydrogen atom (proton) rapidly thermalizes with the fluid establishing a thermo-acoustic signature which we then monitor with a hydrophone submerged in the fluid. Further, if the fluid is near a phase transition, the de position on energy from the neutron can form a bubble. The formation and collapse of the bubble will create a shockwave which is then detected using a hydrophone submerged in the fluid. Here we will describe: the generation and propagation of acoustic-shock waves, the design and construction of an acoustic detection cell, and the callibration of the cell using photo-acoustic spectroscopy. We will discuss tests preformed using both cosmogenic neutrons and a Californium 252 source, and conclude with a discussion on future implementation of the acoustic neutron detector.

Chandler, David W.↗