A current-driven wiggler is the cornerstone of an innovative, compact, high-efficiency, transportable tunable free-electron laser (FEL), the feasibility of which is currently being evaluated by Thomson-CSF. The salient advantages are: compactness of the FEL, along with the possibility to accelerate the beam through several successive passes through the accelerating section (the number of passes being defined by the final wavelength of the radiation; i.e. visible, MWIR, LWIR); the wiggler can be turned off and be transparent to the beam until the last pass. Wiggler periodicities as small as 5 mm can be achieved, hence contributing to FEL compactness. To achieve overall efficiencies in the range of 10% at visible wavelengths, not only the wiggler periodicity must be variable, but the strength of the magnetic field of each period can be adjusted separately and fine-tuned versus time during the macropulse, so as to take into account the growing contribution of the wave energy in the cavity to the total ponderomotive force. The salient theoretical point of this design is the optimization of the parameters defining each period of the wiggler for each micropacket of the macropulse. The salient technology point is the mechanical and thermal design of the wiggler which allows the required high currents to achieve magnetic fields up to 2T.

Using thoracoscopy lung biopsy we investigated the bacteriological diagnostic yield in immunodepressed and/or infected NZ rabbits. 84 rabbits were used: 18 controls, 30 immunodepressed rabbits and 36 rabbits immunodepressed and then infected with Aspergillus fumigatus. Candida albicans or B.C.G. The thoracoscopy technique was the one we designed for humans, the instruments were adapted to the size of animals. Thoracoscopy biopsy results were compared to those of surgical biopsies made in the same animals. The results of both techniques were similar: indeed, the sensitivity of thoracoscopy biopsy was 88.9% in immunodepressed rabbits (versus 100% with surgical biopsies), 86% in the group of rabbits infected with B.C.G. (versus 86%), 90.1% in rabbits infected with Aspergillus fumigatus (versus 100%) and 88.9% in rabbits infected with Candida albicans (versus 100%). The indications for thoracoscopic lung biopsy in immunodepressed patients with infectious lung diseases are drawn from these experimental data, from our experience and the known mortality and morbidity of surgical lung biopsy.

A nonlinear theory of noise in a Read diode which takes account of the coupling between low and high frequencies has been developed. At high levels, the components of the driving noise voltage of the diode, in phase and out of phase with the signal, have unequal values and are correlated.

The linear theory of the noise of Read diodes is extended to the case of different ionizing coefficients for electrons and holes and a finite multiplication factor. It is shown that the noise is smallest when the carriers injected in the avalanche region are of the less strongly ionizing type.

Preliminary results on the noise behavior in the "M" carcinotron are given. The aim of this study was not to construct a low noise oscillator but rather to obtain information concerning the space charge effects in the "M" carcinotron. An attempt was made to measure the noise as a function of frequency but no systematic behavior could be found. As a function of anode voltage the noise had more or less pronounced maxima and minima. The noise power varied in a range of 2 or 4 and at some points even in a range of 10. No studies have yet been made to compare measured noise in the "M" carcinotron with theoretical results, or to see if the noise is coherent with the sole current noise. Up to now no attempt has been made to construct "M" carcinotrons with low noise power.