Alcatel

Alcatel Cit

Didier Pierrejean

Denis Perrillat-Amede

Guy Lemarquand

Bertrand B Seigeot

Francois Reverdy

Bruno Galland

Fr&eacute;d&eacute;ric Rouveyre

A system in accordance with the invention which generates electrons by means of a field-emission cathode comprises an array of electron-emitting micropoints associated with a grid and carried by a substrate with integral heater means for heating the micropoints to a temperature in the range approximately 300&deg; C. to approximately 400&deg; C. and maintaining them at that temperature during emission of electrons. The cathode can therefore function at higher residual air pressures with no risk of breakdown.

High-pressure operation of a field-emission cold cathode

In accordance with the invention, the ion source of a time-of-flight mass spectrometer includes an electron gun having an electron source and at least one electrode for conditioning the flow of electrons, followed by at least one microchannel wafer for generating a pulsed secondary electron beam containing a greater number of electrons from a pulsed primary electron beam. The secondary electron beam enters a gas ionization area of an ion gun which produces a flow of ions which is then passed through the flight tube in order to be analyzed by an ion detector. This provides a high-performance ion source which is compact, sensitive and easy to integrate.

Ion source for time-of-flight mass spectrometers for analyzing gas samples

The pulse mode electron generator of the invention includes a field emission cathode with electron-emitting micropoints associated with a grid biased by means for positively biasing the grid and an anode attracting electrons emitted by the cathode. The grid is biased by a permanent positive pre-bias voltage generator delivering a rest voltage which is slightly lower than the emission threshold voltage of the cathode and in series with a positive pulse voltage generator delivering a pulse component of sufficient value to exceed the emission threshold voltage of the cathode. This facilitates the pulse mode production of electrons and reduces the power consumption needed to produce the electrons.

Pulse mode electron generator

In a system in accordance with the invention for detecting leaks, a mass spectrometer is connected to the aspiration side of a secondary pump whose discharge side is connected to the aspiration side of a primary pump driven by a rotational drive system adapted to vary the rotation speed of the primary pump between at least two different rotation speeds. An aspiration inlet is selectively connected by control valves either to the aspiration side of the primary pump or to the aspiration side or an intermediate area of the secondary pump. Variation of the rotation speed of the primary pump is used to perform faster pre-evacuation before the test, to detect grosser leaks, to compensate for a high level of outgassing or to adapt the sensitivity of the device, and equally to eliminate helium background noise from the primary pump.

Variable speed primary pumping in a tracer gas leak detector

A micropoint type cold cathode comprises a substrate including an array of micropoints and a plate disposed parallel to the substrate carrying the points. The plate includes a hole facing each point and thereby constitutes a grid. An insulator fills the space between the substrate and the grid except at the location of the points. The nominal distance between the summit of a point and the face of the grid farthest from the substrate is zero, the nominal radius of curvature at the summit of each point is 25 nm and the nominal radius of the holes in the grid is 1.3 &mgr;m.

Micropoint type cold cathode

A mass spectrometer ionization cell includes a micropoint type cold cathode which emits electrons, an amagnetic material anode forming an ionization cage positively biased relative to the cathode and including an entry slot for emitted electrons facing the cathode, and an ion collector electrode which is held at a potential lower than that of the cathode. The electrode is disposed laterally of and outside the space between the cathode and the anode and extends from the cathode to the anode. An axial magnetic field is generated in the cathode-anode direction.

Ionization cell for mass spectrometers

A turbomolecular pump comprising a stator and a rotor, said rotor comprising a central shaft and a bell-shaped active portion, said stator comprising an outer portion and an inner portion that penetrates into the cavity of said bell-shaped active portion, and that supports the stator portion of the drive motor, the shaft of said rotor supporting the rotor portion of said drive motor, wherein said central shaft and the bell-shaped active portion of the rotor are made in one piece, without any assembly being necessary, and of a non-magnetic material, said shaft being provided with a central bore which receives the rotor portion of said drive motor, which portion is constituted by a cylindrical permanent magnet.

Turbomolecular vacuum pump

An electromagnetic bearing including a stator portion having sixteen magnetic cores facing the rotor portion. The sixteen cores are divided into four groups of four cores, and each group is equipped with suspension electric windings disposed such that the magnetic flux produced thereby is in the same direction in the first two cores of the group and in the opposite direction in the following two cores, each core in each group further being equipped with a position-detection electric coil, the coils on the four cores in any one group being connected together in series and powered by an AC electric current, the magnetic flux produced by the coils at any determined time being in opposite directions in the first two cores of any group, and also in opposite directions in the following two cores.

Electromagnetic bearing

A vacuum pump for producing a clean molecular vacuum, the vacuum pump comprising a stator (1A, 1B) and a rotor (2), the rotor being driven by a drive motor (6, 7, 8) integrated in the pump, the rotor being supported by magnetic bearings, and being bell-shaped fitting over an internal projection (3) protruding from the stator, the stator components (7, 8) of the drive motor and of the bearings (11B, 12B, 13B, 15, 16) being situated on the periphery of the internal projection (3), the rotor components (11A, 12A, 13A, 14) of the drive motor and of the bearings being situated on the internal periphery of the bell-shaped rotor (2), the vacuum pump being characterized in that a first gastight coating (29) made of non-magnetic material covers the projection (3) overlying the stator components of the motor and of the bearings, and in that similarly in the rotor a second gastight coating (30) made of non-magnetic material covers the rotor components of the drive motor and of the bearings.

Growing community of inventors

Villaz, France

Didier Pierrejean