Keith S. Pickens

The mass spectrometer for planetary exploration (MASPEX)

The MASPEX instrument is a high-resolution, high-sensitivity time-of-flight mass spectrometer developed for planetary applications. Its high-resolution (25,000 mMm at 10% peak height) allows the unambiguous determination of volatile isotopes of methane, water, ammonia, carbon monoxide, molecular nitrogen, carbon dioxide, and low order (C2, C3, and C4) organic compounds in complex mixtures. The use of cryotrapping boosts MASPEXs sensitivity by up to 10,000 times the ambient performance enabling the measurement of trace compounds including organic compounds and the noble gases argon, krypton, xenon, and their isotopes. Such capabilities are ideal for the study of astrobiology and solar system formation in a diverse range of planetary objects including asteroids, comets, and icy satellites. A highly sensitive electron impact ionization source (>105 ions per extracted ion packet) operating at 2000 extractions per second in conjunction with the time-of-flight mass analyzer, which produces a complete mass spectrum from every ion extraction, enables the rapid acquisition of high precision measurements over a wide range of mass. This is particularly important for applications such as atmospheric probes that have a limited operating period and also for providing high temporal/spatial resolution for flyby or orbital missions. Over ten years of development funded by Southwest Research Institute and NASA have resulted in a Technology Readiness Level of 6 suitable for applications to Discovery, New Frontiers, and Flagship missions. Several promising applications will be discussed in this presentation including the recent selection of MASPEX for the Europa mission payload, and applications to three Discovery 2015 proposals including a mission to Enceladus (ELF), comet Hartley 2 (PRIME), and to the main belt comet Read (Proteus). Other new applications to be discussed include upcoming New Frontiers opportunities for probes, landers, and sample return missions.

Microchannel Plate Detector Detection Efficiency to Monoenergetic Electrons Between 0.4 and 2.6 MeV

An unshielded microchannel plate detector was irradiated by an electron beam to determine the detection efficiency of electrons to create a detector signal or counts. Tested electron energies spanned a range of 400 kiloelectron volts to 2.6 million electron volts (MeV). Detection efficiency was found to decrease as the electron energy increased and ranged between 0.18 and 0.05 counts per incident electron, at 0.4 and 2.6 MeV, respectively. Simulations of beam losses over the experimental geometry were performed with MCNP6, and found to be similar in magnitude and possess a similar dependence over incident electron energy as the experimentally determined beam loss from beam current measurements. Detection efficiency as a function of incident angle of the electrons was also tested and relatively insignificant changes were observed. For the three beam energies and angles tested, deviation of the measured detection efficiency was 16%-22% (basically within the overlapping error bars of each measurement).

Comparison of Radiation Induced Noise Levels in Two Ion Detectors for Shielded Space Instruments in High Radiation Fields

Radiation shielding performance and radiation induced noise levels in ion detection instruments were investigated for a high radiation field. The intensity of primary and secondary radiation behind simple shields of aluminum and tantalum were determined by Monte Carlo computer simulations. Two ion detectors were evaluated: a micro-channel plate and a custom discrete dynode electron multiplier. Europa, an icy moon of Jupiter, was selected because it is one of the most intense radiation environments in our solar system. Based on the combination of computer simulation results and experimental measurements of detector responses to electron and photon radiation, the relative radiation induced background noise was assessed to inform further instrument design considerations and performance optimization, such as anticipated signal-to-noise ratio and minimum detectable concentrations for mass spectroscopy during specific missions. Radiation detection efficiencies between the two detectors were comparable for photons and higher energy electrons, but significant differences were found for electrons with energies less than 0.5 MeV. Higher radiation induced count rates are expected for the micro-channel plate detector owing to its larger cross-sectional area. Superior instrument performance is anticipated for the custom discrete dynode electron multiplier detector in high radiation environments with the same or slightly less shielding.

Image Processing and Artificial Intelligence for Detection and Interpretation of Ultrasonic Test Signals

Detection of flaws is an important industrial concern. For example, aircraft and nuclear-power reactor owners and regulatory authorities need effective means of detecting flaws that could pose a threat to public safety. Operators of costly equipment require information on service-induced flaws to be able to make run-or-retire decisions. As the cost of parts and concerns for public safety increase, the importance of flaw detection and size estimation has likewise escalated.

The effect of evaluation time variance on asynchronous Particle Swarm Optimization

Optimizing computationally intensive models of real-world systems can be challenging, especially when significant wall clock time is required for a single evaluation of a model. Employing multiple CPUs is a common mitigation strategy, but algorithms that rely on synchronous execution of model instances can waste significant CPU cycles if there is variability in the model evaluation time. In this paper, we explore the effect of model run time variance on the behavior of PSO using both synchronous and completely asynchronous particle updates. Results indicate that in most cases, asynchronous updates save considerable time while not significantly impacting the probability of finding a solution.

Microchannel plate detector detection efficiency to monoenergetic electrons between 3 and 28 keV

An unshielded microchannel plate (MCP) detector with an ultrafine pore diameter of 2 μm was irradiated by an electron beam to determine the detection efficiency of electrons for creating detector signals, or counts. Tested electron energies spanned a range of 3 kiloelectron volts (keV) to 28 keV. Higher detection efficiencies were measured at the lower end of this energy range, 0.376 counts per incident electron at 3 keV down to 0.155 at 15 keV with an increase to 0.217 at 18 keV and then another decrease down to 0.15 counts per incident electron at 28 keV. The increase at 18 keV is attributed to primary electron interaction with the L shell electrons of lead (Pb), leading to an increase in secondary electron and X-ray generation within the MCP and thus an increase in detection efficiency. For the electron beam directed normal to the MCP surface, the lowest efficiency of 0.15 counts per incident electron was observed at 28 keV. Detection efficiency was also tested as a function of incident angle with angular steps of 5°. Detection efficiency was more sensitive to the angle of incidence as the incident electron energy decreased. The detection efficiency at 3 keV decreased from 0.376 counts per electron at the zero degree angle (normal incidence to MCP surface) to 0.027 counts per electron at an incident angle of 50° (average in both orientations). At 28 keV, the decrease in detection efficiency as a function of increasing angle was less pronounced, ranging from 0.15 counts per electron at zero degrees to 0.08 counts per electron at 50° (average in both orientations). Experimental data showed lower detection efficiencies compared with previously published data.

Parallelization of the Synthetic Aperture Focusing Technique for Ultrasonic Testing

A new parallel implementation of the synthetic aperture focusing technique for ultrasonic testing (SAFT-UT) has been developed. This algorithm runs on small, inexpensive workstations, which are easily transported to a testing site. The performance is achieved in realtime, in that data can be processed as fast as it is acquired. The SAFT-UT technique is reviewed, and details of the new implementation are discussed. Performance data are presented for two platforms, a shared-memory parallel processor and a distributed-memory parallel processor.

Application of Large-Scale Analysis Techniques to a Man-Portable Limited-Scope Environment

New computer-assisted ultrasonic inspection techniques are occurring on both small PC-based and larger minicomputer/workstation-based systems. The bigger systems can address large-scale inspection problems through the acquisition of multigigabytes of data and the use of sophisticated analysis and visualization techniques [1,2]. With these benefits, however, come greater bulk, complexity, and cost. Smaller systems excel in applications requiring man portability. Optimally a combination of the two technologies would provide the sophisticated analysis techniques of the large systems with the smaller size and lower cost PC. The EDAS Model 100 ultrasonic inspection system, described in this paper, achieves this synthesis.

A Cryogenic Eddy Current Microprobe

In nondestructive eddy current testing (ET), wire coils are excited to induce electric currents in conducting test specimens. The distribution of these eddy currents is altered by the presence of flaws in the material or by changes in material properties. The distribution changes are then sensed by one or more detector coils.

A Second-Generation System for Detection and Characterization of Steam-Turbine Rotor Flaws

Detection and characterization of steam-turbine rotor flaws are of prime concern in decisions affecting life extension. Rotors represent large capital investments where life extension can provide significant returns, especially if a forced outage or catastrophic failure is avoided. Nondestructive evaluation (NDE) of flaws has proven to be a valuable tool in extending the life of rotors.