Thomson-cgr

Thomson-csf

Claude Prevot

Rene Chesneau

Bernard Rigeade

Jacques Sireul

Robert Encellaz

Michel Rincent

Guillaume Lebbolo

Jean Miscopein

The disclosure relates to the protection circuits interposed between a DC supply and a load circuit to protect the load circuit against short-circuits or reversals in polarity of the supply. The protection is obtained by means of a MOS power transistor connected between the supply and the load circuit. This transistor is turned on if it receives a voltage Vg from a bias circuit through a control circuit. The bias circuit delivers the voltage Vg only if the voltage given to it by the supply is sufficient while the control circuit turns the power transistor off if the output of the supply gets short-circuited or gives a voltage with reversed polarity.

Protection circuit for DC supply

A mandrel for holding gradient coils in an instrument that measures nuclear magnetic resonance is fastened directly to the magnet of this instrument. It is shown that this arrangement can be used to reduce the output of noise while, at the same time, making it easy to adjust the position of the mandrel. The device comprises two sets of brackets fastened by their struts, on either side of the magnet, to the end rings of the magnet. Each bracket exerts a holding force on the mandrel.

Device to fasten and adjust a mandrel for holding gradient coils

The object of the invention is an improved gradient coil. The improvement consists in making steps in the saddle-shaped conductors that form the coil in order to modify local distortions in the magnetic field produced. It is shown that the correction thus made has little effect on the rest of the field of distribution.

Gradient coil for image formation devices using nuclear magnetic

A high frequency antenna is provided for an apparatus measuring nuclear magnetic resonance, of the type whose radiating means comprise conductors forming high frequency resonators with a metal casing. They are frequency tuned by adjustment capacitors situated at their ends. For simplifying the frequency tuning of two paired resonators through which flow currents in phase opposition, it is proposed to join together galvanically two ends of these two resonators by a high frequency line section whose length is substantially equal to half the wave length of the energization wave to be emitted. The frequency matching of the antenna may be made by adjusting simultaneously all the adjustment capacitors by means of a common control knob. Coupling of the energization energy is provided magnetically in the middle of this high frequency line section.

High frequency antenna for a nuclear magnetic resonance measuring

A gradient coil is provided for a nuclear magnetic resonance image forming apparatus, the gradient coil being formed of four identical arrangements symmetrical with respect to the centre of a predetermined examination space. These arrangements comprise conductors formed in the shape of a saddle. In a particular embodiment for each arrangement two groups of conductors are provided. They may moreover be superimposed. In the invention, the conductors are flat conductors. Preferably their section is rectangular, the large side being greater than or equal to two and a half times the small side. The choice of flat conductors reduces the self-inductance of the system thus constructed. Finally, it is the necessary driving power which is reduced for establishing a field gradient. The temperature behavior of the whole of the apparatus is improved thereby.

Gradient coil for nuclear magnetic resonance image forming apparatus

The invention provides a device for creating an excitation field in an apparatus using nuclear magnetic resonance. The structure for creating this field comprises a number of conductors spaced evenly apart at the periphery of a circular cylinder. What characterizes the invention is that, for producing a homogeneous field inside this cylinder, it is sufficient to cause a current to flow through these conductors whose intensity is proportional to the cosine of the angle which locates this conductor with respect to a reference axis system.

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Antony, France

Claude Prevot