Duoplasmatron with a small flow of gas at the outlet

 

(57) Abstract:

The invention relates to a charged particle sources and used in accelerator technology. The technical result is the decrease of the gas flow at the output of duoplasmatron when generating a continuous beam of charged particles. In duoplasmatron consisting of a discharge chamber, a cathode, an intermediate electrode, of an electromagnet, the anode channel emission of charged particles, have been added to the channel pumping, one end of which is connected to the channel emission of charged particles, the other with a vacuum pump, and the entrance emission of charged particles from the cathode is made in the form of a cone. Consequently, the proposed changes there is no flap that overlaps the channel emission of charged particles, and you can pump out unionised working gas, preventing its release from the source. The presence of the cone at the entrance of the channel emission contributes to the fact that the flow of ionized gas becomes component of velocity in the direction different from the direction along which the extraction beam current of charged particles. Deviating from it, the gas enters the channel pumping with large gas conductivity than the channel emission of paragenetic and applied in the field of accelerator technology.

Analogue of the invention is the ion cannon with high brightness beam [1]. The disadvantage is the dependence of the gas stream at the exit of the gun from the working gas pressure in the ionization chamber.

The prototype of the invention is a pulse duoplasmatron [2], consisting of a discharge chamber, a cathode, an intermediate electrode, of an electromagnet, the anode channel emission of charged particles, covered by a movable metal shutter which is opened only at the time of release of the beam current. K the prototype disadvantages include the fact that the source with the flap at the exit cannot be used to obtain a continuous beam.

The aim of the invention is to reduce gas flow at the output of duoplasmatron when generating a continuous beam of charged particles.

This objective is achieved in that in duoplasmatron with a small gas flow at the output, consisting of a discharge chamber, a cathode, an intermediate electrode, of an electromagnet, the anode channel emission of charged particles, have been added to the channel pumping, one end of which is connected to the channel emission of charged particles, the other with a vacuum pump, and the entrance channel emission of charged particles from the cathode is made in the form of STIC, and the flow of ionized gas at its input becomes component of velocity in the direction different from the axial axis of the source, along which the extraction beam current deviates from it, falls into the canal pumping with large gas conductivity than the channel emission of charged particles and is removed by a vacuum pump.

Thus, in duoplasmatron in the proposed design changes - log channel emission of charged particles from the cathode in the form of a cone and a complementary channel pumping, proposed by the United way, new physical properties. Namely, the output of the ion source is unobstructed, and it becomes possible to effect the separation in the direction of two different flows in the channel emission of charged particles flow of charge carriers and the flow of ionized gas with subsequent removal of the last vacuum pump through the channel pumping.

Widely known duoplasmatron sources of charged particles, which decrease the flow of gas ballast output is achieved by reducing the operating pressure in the field ionization or overlapping channel issue. Sources Cow, flow of charge carriers and the flow of ionized gas with subsequent pumping of the latter, was not found.

Analysis distinctive essential features and manifested through them, the properties associated with achieving a positive effect, suggests that the claimed technical solution meets the criterion of "substantial differences".

The drawing shows duoplasmatron with a small gas flow at the output, consisting of the discharge chamber 1, a cathode 2, an intermediate electrode 3, the electromagnet 4, the anode 5, cone 6, channel emission of charged particles 7, channel pumping 8, the vacuum pump 9.

The source operates as follows. The electric discharge in the discharge chamber 1 burns between the cathode 2, the intermediate electrode 3 and the anode 5. The plasma output duoplasmatron comes through the channel of the emission of charged particles 7. The electromagnet 4 generates a magnetic field, contrairwise plasma in the area of the intermediate electrode is the anode. Everything happens in accordance with the well-known process of duoplasmatron. In the prototype, and the analogue of the ionized gas from the discharge chamber 1 through the channel emission of charged particles 7 is output to the source and load accelerating structure, wkhuds is the gas pressure in the source 1-2 Torr and the diameter of the channel emissions of the order of 1.5-2.0 mm [3], the magnitude of the gas flow from a source operating in generation mode continuous beam, up to several hundred thousand PAL/s, which is absolutely unacceptable for the effective acceleration of the ion current. In the proposed invention the value of the flow will be reduced as follows. Tube current of the ballast gas, moving along the walls of the cone 6 (see drawing), gain direction in which they enter the channel emission of charged particles 7 on the trajectories having different angles of inclination to the Central axial axis of the source, along which is the extraction of the charged particle beam current. On the stretch of the canal, issue 7 behind the focus point that is defined by the geometry of the input cone 6, the gas flow forms a diverging cone that prevents direct passage of neutral gas molecules through the channel to the source output. As a result of artificially generated direction most of the molecules entering the channel pumping 8 are removed by a vacuum pump 9. On the charged particles of the plasma electric field acts on the part of the accelerating electrodes, which sets their direction of movement along the Central axial axis of the source. Since the channel emission of charged particles 7 them the gas molecules, the flow rate Q from the discharge chamber of the source through the channel issue for viscous flow regime of the jet through a small aperture is calculated according to [4]

< / BR>
where P is the gas pressure in the source, F is the square of the aperture of the channel issue 7 (see the drawing), is the ratio of the pressures at the ends of this channel, the adiabatic exponent, M is the molecular mass of the gas, T is the temperature of the gas, R is the universal gas constant.

The value of the gas stream, which can be removed through the channel 8 when pumping viscous flow regime for a long pipeline, according to [4]

< / BR>
where r is the radius of the channel pumping 8 (see drawing), P1and P2is the gas pressure at the ends of the channel, L is its length, is the dynamic viscosity of the gas. Comparison of expressions (1) and (2) shows that with the proper choice of values (F, r, L) ratio of the gas flow in the channel emission of charged particles 7 to the stream removed through the channel pumping 8, can approach 1 with the desired accuracy, making the opaque anode gas.

Optimized proposed, the design of the anode AI allows you to pump out the bulk of the unused discharge of the working gas pump, and thereby reduces the flow of neutrals at the output of a Duo who's particles of 1 mm at an operating pressure of hydrogen in the discharge chamber 2 Torr and pumping gas only at a rate of 8 l/s through shestimillimetrovye channel 8 (see the drawing), has allowed to reduce the amount of gas flow, notcause in the outer volume of duoplasmatron, compared to a case when the pump 9 is turned off 4 times.

Since in the invention the diameter of the channel emission of charged particles does not change, and the magnitude of the leakage source is governed by the efficiency of the pumping of ballast gas through the channel 8, it becomes possible to control the leakage of gas from the source without changing the operating pressure in the discharge chamber. Thus, it remains a work mode duoplasmatron and there is no loss of current magnitude and quality of the beam at the exit of the ion source. In the present invention, unlike the prototype, there are no moving mechanical parts of the valve flap in the anode blocking the exit of the source. This allows you to use it in a wide frequency spectrum of the pulse generation beam current when generating bunches of ions with a low duty cycle up to obtain continuous beam of charged particles. This defines a high reliability in operation and long service life. Well-known advantages of using basacally cathodes, compared with hot, when the capacity of the source. But working with cold cathodes requires to maintain the gas pressure in the source of a few Torr, which prevents their use in a continuous mode of generation. The present invention removes this obstacle. The source of charged particles is more convenient and simple in operation.

References

1. Kutorga N. N., Sevastyanova C. S., Teplyakov Century A. Ion gun with high brightness beam. Proceedings of the Second all-Union conference on charged particle accelerators. 1972. C. 88-90.

2. Copyright certificate 431576, 1974. A pulsed ion source (Batalin C. A. Bulletin OPTS, N 21, 1975.

3. Kapczinski I. M. and others to Develop new components and operation of a linear accelerator And a-2. Preprint N 10, M, ITEP, 1975.

4. Frolova E. C. Handbook of vacuum technology. M., 1985. C. 22-53.

Duoplasmatron with a small gas flow at the output, consisting of a discharge chamber, a cathode, an intermediate electrode, an electromagnet that generates a magnetic field, contrairwise plasma in the area of the intermediate electrode is the anode, the anode channel emission of charged particles, characterized in that it additionally introduced channel pumping, gas conductivity which exceeds gastic, the other with a vacuum pump, and the entrance channel emission of charged particles from the cathode is made in the form of a cone.

 

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