Detonation velocity measurements with uniform fibre Bragg gratings.

In this paper we demonstrate a simple and new fibre optic technique for measuring detonation velocities using uniform fibre Bragg gratings. We compare this new system with chirped fibre Bragg grating diagnostics and show how coherent source illumination can yield spatial uncertainties below ±10 µm - a percentage error that is an order of magnitude lower than the broadband ASE methods we have tested.

Optimised Chirped Fibre Bragg Gratings for Detonation Velocity Measurements.

Over the last decade, the use of chirped fibre Bragg gratings (CFBGs) in detonation velocity experiments has been steadily increasing. In this paper, we show how CFBG design parameters-chirp-rate, reflectivity and apodisation-affect linearity in detonation velocity tests. It is found that the optimal CFBG detonation velocity probe should have a high chirp-rate, a low reflectivity and no apodisation. As a further demonstration of these findings, we measure detonation velocity with a 24 cm optimised CFBG; the longest CFBG test of this kind so far.

Detonation Velocity Measurements Using Rare-Earth Doped Fibres.

In this paper, a simple detonation velocity measurement scheme is presented, which exploits the length-dependent amplified spontaneous emission (ASE) power emitted by off-the-shelf Er-doped fibres. This measurement scheme is first calibrated using cutback tests, so that minimal processing is required between data collection and velocity readout. We then demonstrate the use of this method in an explosive cylinder test and achieve a spatial resolution of approximately ±2 mm, owing to its implementation in a helical geometry. Alongside the standard Er fibres, a specially made, high-concentration Er/Yb-doped fibre is also calibrated, which demonstrates a potential spatial resolution approaching ±20 µ m.

Development of U.S. EPA method 527 for the analysis of selected pesticides and flame retardants in the UCMR survey.

Method 527 was developed to address the occurrence monitoring needs of the U.S. Environmental Protection Agency (EPA) under its second unregulated contaminant monitoring rule (UCMR 2). This method includes a wide range of semivolatile organic contaminants, including pesticides that were deferred during the first UCMR, flame retardants, and pyrethroid pesticides. This paper discusses the rationale for selection and inclusion of the various contaminants included in Method 527 and describes the challenges associated with developing analytical methods that will be used for the occurrence monitoring of such a diverse group of organic molecules. Method 527 employs solid-phase extraction with analysis by gas chromatography/ mass spectrometry (GC/MS). The final method preservation scheme requires the storage of samples in amber bottles buffered at pH 3.8 using citric acid to prevent degradation from acid-catalyzed hydrolysis and from UV light. Citric acid is also an effective antimicrobial reagent, preventing this mode of loss during storage. Ethylenediaminetetraacetic acid (EDTA) is added to remove transition metals such as copper, which was determined to degrade target analytes upon storage. Finally, free available chlorine (FAC), which is present in many finished waters and found to degrade a number of the targets, is removed using ascorbic acid. The final method meets all of the EPA UCMR survey requirements for sample storage, precision, accuracy, and sensitivity and will be proposed for use under the UCMR 2.