Early in the next century, several space missions are planned with the goal of landing craft on asteroids, comets, the Moon, and Mars. To increase the scientific return of these missions, new methods are needed to provide (1) significantly more analyses per mission lifetime, and (2) expanded analytical capabilities. One method that has the potential to meet both of these needs for the elemental analysis of geological samples is laser-induced breakdown spectroscopy (LIBS). These capabilities are possible because the laser plasma provides rapid analysis and the laser pulse can be focused on a remotely located sample to perform a stand-off measurement. Stand-off is defined as a distance up to 20 m between the target and laser. Here we present the results of a characterization of LIBS for the stand-off analysis of soils at reduced air pressures and in a simulated Martian atmosphere (5–7 torr pressure of CO2) showing the feasibility of LIBS for space exploration. For example, it is demonstrated that an analytically useful laser plasma can be generated at distances up to 19 m by using only 35 mJ/pulse from a compact laser. Some characteristics of the laser plasma at reduced pressure were also investigated. Temporally and spectrally resolved imaging showed significant changes in the plasma as the pressure was reduced and also showed that the analyte signals and mass ablated from a target were strongly dependent on pressure. As the pressure decreased from 590 torr to the 40–100 torr range, the signals increased by a factor of about 3–4, and as the pressure was further reduced the signals decreased. This behavior can be explained by pressure-dependent changes in the mass of material vaporized and the frequency of collisions between species in the plasma. Changes in the temperature and the electron density of the plasmas with pressure were also examined and detection limits for selected elements were determined.
The implementation of hand-held ion mobility spectrometers (IMS) requires the development and evaluation of miniature drift cells providing high sensitivity while maintaining reasonable resolution. This manuscript describes the construction of a miniature IMS designed for such an application and its characterization by evaluation of the detection limits and resolution of the system with seven explosive compounds including trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl), nitroglycerin (NG), 2,4-dinitrotoluene (2,4 DNT), and 2,6-dinitrotoluene (2,6 DNT).
ARA is currently developing technologies to improve food safety and food defense preparedness. One technology is Laser-Induced Breakdown Spectroscopy (LIBS), a tool developed by ARA for detecting pathogens in food.
Laser‐induced breakdown spectroscopy (LIBS) is a novel method of elemental analysis based on a laser‐generated plasma. Pulses from a laser are focused on a sample to atomize a small amount of material resulting in the formation of a microplasma. Because of the high plasma temperature, the resulting atoms are electronically excited to emit light. The plasma light is spectrallyresolved and detected to determine the elemental composition of the sample based on the unique emission spectrum of each element. Because of the simplicity of the method, it is suited for analyses that cannot be carried out using conventional methods of atomic emission spectroscopy (AES). This is particularly true for measurements that must be conducted outside of an analytical laboratory. A particular advantage of LIBS is the ability to analyze most types of samples without any preparation. This means that samples can be interrogated in situ, providing rapid measurement capability and permitting the method to be used in the analysis of gases, liquids, and solids in a variety of different sampling configurations. Although LIBS provides sensitive detection for many elements, it is not an ultrasensitive detection technique. In addition, under field conditions, the method typically does not provide the high accuracy and precision offered by laboratory‐based methods of AES.
Mean-variance analysis is described as a method for characterization of the read-noise and gain of focal plane array (FPA) detectors, including charge-coupled devices (CCDs), charge-injection devices (CIDs), and complementary metal-oxide-semiconductor (CMOS) multiplexers (infrared arrays). Practical FPA detector characterization is outlined. The nondestructive readout capability available in some CIDs and FPA devices is discussed as a means for signal-to-noise ratio improvement. Derivations of the equations are fully presented to unify understanding of this method by the spectroscopic community.
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