Today manufacturers propose echographic systems with a resolution ranging from 100 microm down to 30 microm. This requires ultrasonic frequencies ranging from 20 to 60 MHz. However, when associated with an increase in the attenuation of the wave in the media this limits the applications to superficial exploration. High frequencies also bring special technological limitations mainly in the fields of transducers, electronics, and acoustic coupling. Although high-resolution echography has long remained marginal and been used for the exploration of the skin or the anterior chamber of the eye, new powerful and easy-to-use devices have recently appeared on the market. With these new products, new applications have also appeared such as the exploration of the oral cavity or small laboratory animals (mice).

Since 1993, a joint research programme on electric energy gun technology is being pursued by France, Germany and the Netherlands.Research and technology development is being performed jointly in six subprograms. Next to operational aspects and system studies, railgun, coilgun and electrothermal gun launch is investigated. To power these future gun weapon systems, research on both energy storage, switching, pulse forming networks and hypervelocity projectiles is being performed, too.This trilateral programme is characterised by complementary research executed in the nations mentioned. Besides institutes and military services, both universities and industry contribute to the programme. Research and technology spans the development of the technology base of new physical concepts and the development of proof of principle demonstrators.An overview is presented concerning the status and results of the subprograms. It is focused on the merit of hypervelocity for different military missions, gun system integration aspects, experimental and theoretical study results of the three fundamental concepts of launching obtained with 3D-computer codes, with small and large (up to 30 MJ) launch facilities, with pulse forming networks, energy storage and solid state switching, and with hypervelocity projectiles of different design. Recently, study of ignition control of gun propellants by a plasma-jet has been started, too.Finally, anticipated development of the way ahead of the trilateral programme is highlighted.

Objective: This paper investigates the problems, advantages and potential applications of 20 MHz ultrasonic devices. Method: Aqueous gel and a thin appropriate membrane to enclose the front tip were used with 20 MHz probes without obvious decrease in resolution and sensitivity compared to the results obtained without a membrane and this considerably facilitates their routine use. Results: Many applications with linear scanning were evaluated in dermatology, ophthalmology (investigations of the anterior chamber of the eye, checking of corneal grafts), stomatology (detection and evaluation of periodontal disease) and in the field of measurement of very low velocities in small vessels by means of a duplex probe comprising two 20 MHz transducers: an imaging transducer and an inclined blood flow measurement transducer. Velocity profiles (velocities less than 0.50 mm/s) were measured in 100–300 μm diameter vessels using a cross-correlation method. Conclusion: The use of 20 MHz frequency limits resolution but we have shown that this frequency allows the development of easy to handle probes.

Today the energy storage systems are still encumbering, therefore it is useful to think about the optimization of a railgun system in order to achieve the best performance with the lowest energy input. The important parameters in lowering electrical input energy are:the ratio of the projectile mass and the payload mass which has to be near unity, the inductance gradient L' of the rails which has to be high, the resistive losses in the rails and in the pulse forming network which have to be minimal, In this paper we present an overview of what can be done to enhance the efficiency of a rail launcher fed by capacitor banks adjusting the rails design, the launcher caliber and length in view to accelerate payloads of several kilograms up to velocities of a few km/s with the minimum of charged electrical energy.

We present the ISL 50 mm 3 MJ railgun as an illustrative example in order to discuss some specific technical aspects in the case of a nonstiff bore railgun. The lack of ultra-stiffness admits low-weight barrel constructions but requires a special consideration of the interaction between the rails on one hand and the projectile and current input connections on the other. This interrelationship has to be taken as a combined problem; therefore we deal with the repulsive rail forces, recoil forces, contact loads and the structural response of the supporting housing and discuss some of the resulting problems.< >

We present a few results from operational research considerations in order to highlight the advantage of higher muzzle velocities which can be obtained by electrically driven guns. Moreover we will give a brief description of the joint French-German research program on Electromagnetic Launch Technology.

A stratified methodology for water sampling on tidal flats was adopted in 1988 and 1989 in the Bay of Somme.

ISL-EMA railguns are driven by capacitors and equipped with spark gaps as main switches and semiconducting diodes as crowbar switches. We report on investigations to replace the spark gaps by thyristors. First tests with the application of phase-controlled thyristors showed that the decices should have a fine structured gate at their disposal to enable the high current rate typical for pulsed power applications. Because of this, experiments were made with a pulse power thyristor developed by ABB and with a modified fast switching thyristor. The pulse power thyristor has the gate structure of a GTO device, but in contrast to a GTO, it is not possible to switch it off. Furthermore a modified fast switching thyristor was investigated due to pulse power applications. The device has a blocking voltage of 3 kV and, in contrast to a normal fast switching thyristor, it is not irradiated. By this step the charge carrier lifetime can be increased.

An overview of the ISL activities on electromagnetic accelerations is presented. A railgun system with a 15 mm round-bore barrel and a length of 1.5 m has been designed and tested. The railgun is powered from a 500 kJ capacitor bank. Using a 2.5 μH variable storage inductor, the maximum current reaches 450 kA. An He light gas injector preaccelerates the projectile up to a velocity of 500 m/s. A 3.5 g projectile driven by a plasma armature can be accelerated up to 5000 m/s. The first experimental results obtained with this facility are presented and compared with the results of numerical simulations

In order to record x-ray diffraction patterns with exposure times of less than 200 ns, an image intensifier is used along with a flash x-ray tube. Examples of x-ray diffraction patterns are given and records are shown which have been taken in the case of rapid dynamic changes such as the electric explosion of a metal foil.