Defence Research Establishment Valcartier Research Articles

Optical limiting threshold in carbon suspensions and reverse saturable absorber materials

I report on the measurement of threshold energy fluence for optical limiting of nanosecond and microsecond pulses in a high-performance carbon suspension known as Defence Research Establishment Valcartier carbon black suspension (CBS)-100. Thresholds as low as 24-mJ/cm(2) (nanosecond regime) and 100-mJ/cm(2) (microsecond regime) have been obtained. The measurement technique, based on an f/20 optical system and a small analysis aperture, has been tested by measurement of reverse saturable absorber materials and other carbon suspensions whose properties can be found in the technical literature. A factor of merit has emerged from these measurements that could be used to order by limiting performance the different types of carbon suspension. In this ordering, CBS-100 appears as the best choice in the set of suspensions tested for short and long pulses.

Metallic witness packs for behind-armour debris characterisation

For the experimental characterisation of behind-armour debris so-called metallic witness packs can be used. A metallic witness pack consists of an array of metallic plates interspaced by polystyrene foam sheets. To quantify the fragment mass and velocity from the corresponding hole area and position in the individual witness plates, perforation threshold curves must be available to provide the ballistic limit velocity for each plate as a function of the fragment mass. Furthermore, the relation between the fragment impact velocity and hole size should be known. This paper presents the results of a collaborative study between Defence Research Establishment, Valcartier (DREV) and TNO Prins Maurits Laboratory, The Netherlands. The first phase of this project is an experimental study to develop perforation threshold and hole-growth curves for two metallic witness pack configurations. In addition, it is shown that a hydrocode can be succesfully used to predict perforation threshold velocities.

Optimization of the Multi-Source Data Fusion System for Integration on the Canadian Patrol Frigate

Since 1991, the Research and Development (R&D) group at Lockheed Martin Canada (LM Canada) has been developing and demonstrating Level 1, 2, 3 and 4 data fusion, resource management and imaging technologies which will provide Observe-Orient-Decide-Act (OODA) decision making capabilities/tools in Naval and Airborne Command and Control (C2) for application on Canadian Patrol Frigates (CPF) and Canada’s CP-140 (Aurora) fixed wing aircraft. Over the last three years LM Canada, in collaboration with Canada’s Defence Research Establishment Valcartier (DREV), has also established a generic expert system infrastructure and has demonstrated that it is suitable for integrating these decision making technologies into real-time Command and Control System (CCS). The Multi-Source Data Fusion (MSDF) technology is the most mature among these decision making technologies and is likely to be integrated onboard a currently fielded CCS the soonest. Over the last two years the LM Canada R&D team has started the effort towards re-structuring and optimizing the proof-of-concept MSDF algorithms to establish a prototype which will be ready for integration on the existing platforms, specifically the CPF, and that can perform real-time tracking and identification by the end of the year 2000. This restructuring and optimization is occurring in phases.

Optical limiting with C_60 and other fullerenes

In view of a possible application in optical limiting devices for protection against laser radiation, at the Defence Research Establishment Valcartier we have studied the nonlinear transmission properties of fullerenes. The study involved C(60), C(70), C(76), C(84), several derivatives of C(60), and a variety of solvents. The nonlinear measurements were made with 7-ns pulses at 532 nm from a N-d:YAG laser. For optical limiting applications, solutions of C(60) yielded better results than the other fullerenes, with a solution of C(60) in chlorobenzene being marginally the best.

Analysis of the fascode model and its H_2O continuum based on long-path atmospheric transmission measurements in the 45–115-μm region

An experimental study performed to evaluate the atmospheric transmission model FASCODE and its water vapor continuum [Clough, Kneizys, and Davies (CKD) model, Atmos. Res. 23, 229-241 (1989)] in the 850-2250-cm-(1) spectral region is presented. The analysis is based on a comparison between model calculations and transmission measurements carried out at the Defence Research Establishment Valcartier over a 5.7-km horizontal path for a wide range of ambient temperature (from -8.6 to 29.4°C) and humidity (from 1.16 to 14.2 g/m(3)) conditions. The agreement between measurements and calculations is good on the average. However, there are three specific spectral intervals where the differences cannot be explained by experimental errors. For summer conditions, it is shown that FASCODE overestimates the transmittance by approximately 3-6% (absolute terms) in the 850-950-cm(-1) region. For winter conditions, measurements are higher than calculations by as much as a factor of 2 at the edges of the 6.3µm absorption band of water vapor, namely near 1250-1380 cm(-1) and 1800-2000 cm(-1). The continuous nature of these differences is interpreted as anomalies that are due to the broadening coefficients of the water vapor continuum (CKD model). A set of coefficients is derived from experimental spectra and compared with coefficients from the CKD model. The results suggest that first the self-broadening coefficients at high temperature, C¯(s)(ν, 296), need to be increased by 10-16% near 850-950 cm(-1) and second the foreign broadening coefficients, C¯(ν), need to be decreased by approximately a factor of 2 near 1250-1380 cm-(1) and 1800-2000 cm(-1) to recover a good model-measurement agreement in these three spectral intervals. A modified continuum (based on coefficients derived from transmittances) has been implemented in FASCODE and used to analyze emission spectra from the High-Resolution Interferometer Sounder instrument. The modified continuum reduces the discrepancy by almost a factor of 5 near 1350 cm(-1).

Range-gated underwater laser imaging system

A careful analysis of a scattering and absorption database of the waters off the coasts of Canada shows that a laser-assisted camera system will have a significantly improved viewing performance over conventional systems. The laser underwater camera image enhancer system is a range-gated laser system that can be mounted on a remotely operated vehicle. The system uses a 2-kHz diode-pumped frequency-doubled Nd:YAG laser as an illumination source. The light is collected by a 10-cm-diam zoom lens. The detector is a gated image intensifier with a 7-ns gate and a gain that is continuously variable from 500 to 1,000,000. The system has been tested in a water tank facility at Defence Research Establishment Valcartier and has been mounted on the HYSUB 5000 remotely operated vehicle for sea trials. In the strongly scattering waters typical of harbor approaches, this system has a range of from three to five times that of a conventional camera with floodlights.

Remote biodetection performance of a pulsed monostatic lidar system

A monostatic pulsed lidar system called the laser cloud mapper was operated at the lidar range facility at the Defence Research Establishment Valcartier for 2 weeks during the autumn of 1990 to determine and assess its sensitivity for the remote detection of airborne biological organisms. The methodology called for the measurement of the depolarization of the lidar return signals that were backscattered from a biological aerosol cloud introduced into a large outdoor aerosol chamber. The test aerosol was produced by aerosolization of bacterial spores suspended in tap water; the relative concentration (by volume) of the bacterial material in tap water was varied from 1.0 to 0.001%. The detection performance of the laser cloud mapper is characterized through the ordered statistics of the depolarization ratio (e.g., sample distribution functions, quantile-quantile plots, and shift functions). In addition, a robust detection statistic based on the a-trimmed mean has been considered and the bootstrap-resampling method has been utilized to estimate uncertainties or confidence limits for this statistic. The receiver-operating characteristic curves of the laser cloud mapper (i.e., the probability of detection, <p>P</p>(D), versus the probability of false alarm, P(FA)) for both the empirical distribution function and the linearly thresholded, trimmed mean-level detectors are presented as a function of the source concentration of the test aerosol.

The effect of high spin on the performance of tracer compositions

AbstractA unique tracer evaluation facility has been put into operation at the Defence Research Establishment, Valcartier (DREV), in order to characterize tracer compositions loaded in 5.56 mm envelopes. The effect of rotational speeds up to 300,000 rpm on the performances of two tracer compositions and the standard Belgian L‐110 tracer was studied in this facility. The trace duration decreased substantially with any increase in spin speed. The luminous output was observed generally to be weak at low rotational speeds and to increase with any rise in spin over 150 krpm. The formation of a convex surface of combustion in the composition under spin and the degree of obstruction of the projectile mouth by the combustion residues are postulated to explain such behaviours.

Polymer‐Bonded Coloured Smoke Compositions

AbstractPolymer‐bonded smoke compositions offers numerous advantages over conventional pressed smoke mixtures such as improved mechanical properties and safety in handling. The Defense Research Establishment Valcartier (DREV) has developed pour‐castable coloured smoke compositions using a well known hydroxy‐terminated polybutadiene prepolymer cured with a commercially available diisocyanate. These smoke formulations consist of ingredients typically found in pressed powder mix, but dispersed in a polymeric binder. A granulated dye is utilized to provide the low viscosities required for pour‐casting. The necessary ingredients and processing techniques as well as the properties and inherent advantages of such compositions are described.

Primitive functions for graphics in APL

article Free Access Share on Primitive functions for graphics in APL Author: D. S. Galbraith Defence Research Establishment Valcartier, Courcelette, Canada Defence Research Establishment Valcartier, Courcelette, CanadaView Profile Authors Info & Claims ACM SIGAPL APL Quote QuadVolume 7Issue 1Summer 1976 pp 27–36https://doi.org/10.1145/585968.585972Online:01 April 1976Publication History 6citation96DownloadsMetricsTotal Citations6Total Downloads96Last 12 Months2Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Growth Characteristics of Turbulent Wakes

Recent advances in the experimental study of hypersonic wakes at the Defence Research Establishment Valcartier have led to spatially resolved measurements of the behavior of the important physical variables which characterize the wake. Previous measurements pertained mainly to the wake growth, and they were achieved by an integrated-type technique using a schlieren system under test conditions different from those utilized at this establishment. To assist in relating the new measurements with the earlier ones, and to provide a basis for comparing growth results obtained from the spatially resolved measurements, schlieren films of model wakes taken during this program have been utilized to obtain wake growth data at the same velocities and pressures as those of the spatially resolved measurements. Both cone and sphere wakes have been investigated. Results show that the effect of P∞D (pressure times body diameter) on wake growth is negligible, while the Mach number has a strong effect. Turbulent wake growth can be described by the expression: [Formula: see text], where both the wake width Dw and the axial distance X have been normalized by the drag diameter [Formula: see text]. The factor C is a function of the Mach number M∞: C = 0.56 + 0.032 M∞.

Experimental Study of Wakes Produced by Hypersonic Cones in Free Flight

This paper describes an experimental study of the wakes produced by hypersonic cones flying at a velocity of 15 000 ft/s in Range 3 at the Defence Research Establishment Valcartier (DREV). Three basic cone shapes have been flown: 0.7 in. base diameter, 20° included angle cones with sharp and blunted noses, and a 1.0 in. base diameter, 44° included angle sharp nose cone. Because of the complexity of the flow field generated by these cones usually flying at some angle of attack, the experimental study was limited to one set of ambient conditions, namely, a cone velocity of 15 000 ft/s and an ambient pressure of 100 Torr of air.The measurement of the wake velocity distribution by means of the sequential spark technique constituted the backbone of the experimental program on cone wakes. The technique is based on the formation of an ionized luminous path in the wake by a first spark and on the periodic reillumination of the displaced ionized path by successive sparks. Over 100 profiles of velocity were measured behind the cone shapes. Additional diagnostic tools for this study included the photoattitude and velocity measurement system of the range which was used to determine the flight history and to measure the drag coefficient of the models and also the schlieren technique which was used to measure wake growth and deflection. A wealth of original data has been obtained on the behavior of the wake generated by the three different conical models. The measurements have revealed the presence of an asymmetry in the transverse profile of axial velocity and the presence of a lateral velocity component in the wake of high lift to drag ratio cones flying at angle of attack. The variation of the wake axis and wake front velocity with axial distance has been derived and shows good agreement with other theoretical and experimental results. Due to the presence of angles of attack of different amplitude and orientation, it was not possible to determine the transverse distribution of the mean axial velocity. Nevertheless, these results should contribute to a better understanding and also to an accurate modeling of the wake of cones.

Double Discharge Excitation for Atmospheric Pressure CO2 Lasers

The problems encountered in the electrical excitation of pulsed CO2 lasers operating at atmospheric pressure are briefly reviewed, with some solutions developed at the Defence Research Establishment Valcartier, and their limitations. A new approach, based on a double transverse discharge technique, has permitted the design of a 3.8 m long laser which delivered up to 9 J/pulse with a peak power of 12 MW. An output energy density of 5.5 mJ/cm3 of excited gas has been achieved.