DE1179309B - High frequency ion source - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Kl .: HOIj

German: 21g -21/01

Number: 1179 309

File number: C18925 VIII c / 21 g

Filing date: May 2, 1959

Opening day: October 8, 1964

The invention relates to a high-frequency ion source for generating bundles of ionized Particles, such as those used for further treatment in particle accelerators, mass spectrometers, Arrangements for isotopic separation, etc. can be used.

In the known high-frequency ion sources, the particles are ionized by an electrical one High frequency field in a generally made of quartz or glass, especially aluminum and Sodium borosilicate glass, existing chamber. There are also means for generating a high vacuum in the chamber, for applying a high DC voltage to the two ends of the chamber and to the Supplying one end of the chamber with the gaseous substance to be ionized is provided.

Such high-frequency ion sources are also already known to be designed as a cavity resonator. This is preferably a coaxial cavity resonator with an ao Outer conductor and a waveguide lying within it, with inner conductor and outer conductor on are short-circuited at one end and open at the other end. In such a cavity resonator the actual discharge vessel is arranged at the open end of the same. Because on the open side that electric field in the resonator has an optimal value, it creates a particular problem, flashovers to avoid between the inner and outer conductor of the cavity resonator.

In a known high-frequency ion source, the open end of the coaxial resonator is through a small glass discharge vessel closed. Here is the distance between the inner and outer conductors chosen so large that an undesired discharge between the adjacent ends of the conductors is prevented. The resulting relatively long path for the ionization electrons requires however, an additional magnetic field to prevent the electrons from essentially leaving theirs to deviate parallel to the axis of the resonator running tracks. With this well-known Ion source, the additional magnetic field at the end of the cavity resonator is necessary to to achieve a satisfactory ionization yield.

The aim of the present invention is to design a cavity resonator for an ion source in such a way that that the disadvantages of the known devices are avoided, in particular one considerable increase in the concentration of the high-frequency field on the open side of the resonator High frequency ion source

Applicant:

Commissariat a l'Energie Atomique, Paris

Representative:

Dr. W. P. Radt and Dipl.-Ing. E. E. Finkener,

Patent attorneys, Bochum, Heinrich-König-Str. 12th

Named as inventor:
Siegfried Klein, Paris

Claimed priority:

France of May 3, 1958 (764 698)

The aim is to achieve an increase in the ion yield with the same output.

In the invention, it is made up of a high-frequency ion source assumed, which consists of a tube of dielectric material, in the facilities for generating a high vacuum in the pipe, devices for applying a high DC voltage at the two ends of the tube, means for supplying the gaseous to be ionized Substance are provided at one end of the tube and which contains a cavity resonator made of an outer conductor and an inner conductor arranged inside and coaxially to it is constructed, with the two conductors short-circuited at one end, but at the other end are open.

In such a high-frequency ion source, the invention is that the tube to which the Has a bulge in the form of a flattened onion or tuber end facing away from the gas supply and the bulge at the open end of the coaxial cavity resonator is strongest at the location Concentration of the electrical field lines is arranged so that the inner conductor rests against the tube from the end at which the gas flows in to the bulge that surrounds the outer conductor is terminated by two electrically conductive plates, one of which is short-circuited to the The end of the cavity resonator is attached to the inner conductor and carries this and the other the open end of the cavity resonator with a central opening for the ions to exit is provided and from the end of the inner conductor

409 690/236

will. Parts 3 and 4 are made of an anti-ion bombardment resistant metal made such. B. platinum, stainless steel or aluminum.

The other conical end 26 of the tube 1 carries the device T for the purpose of supplying the gas or vapor to be ionized, which is designed in the form of a chamber 27 which has a conical opening 28 at one end 26 and a hollow electrode at the other end 5 has, by which, how

on which the bulge lies is spaced apart from the order of magnitude of the thickness of the bulge. In order to achieve a further increase in the intensity of the high-frequency field, the invention provides also suggest that the cavity resonator by means of capacitive coupling through the high-frequency power source is excited. According to a further feature of the invention, the high-frequency power source consists of an oscillator tube with a cathode, a

Control grid and an anode, the two io represented by the arrow F , the gas to be ionized

last tube component is introduced with one of the assignments. In the chamber 27 there is one

are connected by three capacitors, the other quartz disk 29 for the purpose of increasing the breakdown

Assignments associated with the inner waveguide voltage.

The largest part of the tube 1 is in one

because between the two assignments of the three con - 15 Koaxialleitungsresonator R, which consists of a

capacitors is arranged. The dielectric sheet is tube surrounding the inner conductor 7 and an outer

According to the further invention, a mica sheet with a conductor 6 is made. One at 30 to the outer conductor 6

a thickness of about 0.1 mm. The soldered metal plate 8 closes the outer conductor 6

The main advantage of the side according to the invention. The plate 8 has a bore 31 for the applied bulging of the tube at the open 20 passage of the end in the annular extension 2 of the cavity resonator can be seen in it, produced ions which the tube 1 in the direction of the that this makes it possible to leave an arrow /. Vacuum seals 32 and 33 very large tension difference between the two rubber are between the plate 8 and the ring adjacent Ends of the conductors of the cavity resonance-shaped extension 2 and between the plate 8 to adjust the gate. In this way one gets arranged on 25 and the wall 25. In the same way will a very limited space an extraordinarily the other end of the outer conductor 6 by a strong high-frequency field, whereby the ionization metal plate 34 closed, which at 30 a to the the particle is significantly favored. The outer conductor 6 is soldered and in its center to A sleeve 35 is bored radially to the longitudinal axis of the cavity resonator, into which a sleeve stretching bulge made of dielectric material 30, the tubular parts 1 and 7 are inserted. the prevents in a simple way any undesirable Ent- Parts 6, 7, 8, 34, 35 are made of highly conductive materials, charge between the two conductors of the resonator. such as B. Copper.

As a result of the small extent of the ionization pump devices shown at P are with

zone is the use of an additional magnet - the space 50 and over the openings 4 a of the part 4

field superfluous, since a deviation of the particles 35 with the discharge vessel 1 in connection and hold

practically does not occur on the short distance. a vacuum of the order of 10 ^-3 to

The high-frequency ion source according to the invention is 10 ~ ⁴ mm Hg in the part of the discharge vessel 1

dung is particularly suitable for the ionization of upright, in which the ionization takes place. The elec-

Gases, e.g. B. hydrogen, deuterium, helium, nitrogen Irish part of the ion source is shown on the basis of FIG. 2

fabric, or steaming, e.g. B. light metals, such as lithium 40 explained.

and sodium. It is preferably used to generate the high frequency generator has an oscillator of Bundling of ionized particles for the storage tube 9, the formwork according to a three-point circuit a particle accelerator with high ion tet is. It works at one frequency in size yield (on the order of about 10 mA order of 150 MHz and delivers a power of at a high frequency power of about 75 W) loading 45 about 75 to 100 W. The oscillator tube 9 can, for. B. it's correct. be a tetrode, the anode 11 of which is out of the line

Further details of the invention are fed to 10 with the anode voltage + HT ₁ ,

Hand drawing illustrated embodiments whose screen grid 14 through the line 13 with the

explained. Screen grid voltage + HT., Is fed, whose

F i g. 1 is a cross-sectional view of a preferred cathode 38 through the filament wires 39

Embodiment of an ion source according to which Er is supplied, and the line 19, which is connected to the one finding without the devices for the electrical supply of the same;

F i g. 2 shows the electrical supply to the ion source according to FIG. 1;

F i g. 3 shows schematically the cavity resonator and the manner in which it is excited;

F i g. 4 shows the equivalent circuit diagram for the cavity resonator.

The in F i g. 1 shown ion source has a 60 hand over a resistance 17 of a few thousand tubular discharge vessel 1, which in general ohms and the rod 44 with the capacitor 18 mean consists of glass or quartz and its bound, which through the conductor 44 a with the Leieines At the end 24 an annular enlargement 2 is connected to 19, d. H. high frequency with shows which z. B. a volume in the size of the cathode of the oscillator tube. Eventually the Order of one cubic centimeter. The end 65 anode voltage through the rod 37 to the condensers 24 of the tube is supported on a ring 3, which wel- sator 12 is applied.

rather of a lead in a recess 25 α These three capacitors 12, 16, 18 are used for

the wall 25 held the conical part 4 supported blocking the various on the electrodes of the

Heating line 39 is connected to the negative pole - HT of the anode voltages. Choke coils 40 prevent the high-frequency currents generated by the tube 9 from flowing back, while capacitors 41, 42 prevent the direct current from flowing directly into the line 19. The control grid 15 of the tube 9 is on the one hand directly through the rod 43 with the capacitor 16 and on the other hand

Claims (1)

5 6 Oscillator tube lying DC voltages. The patent claims: Dielectric between the assignments of this con capacitors is a single mica sheet 36 for all 1st high-frequency ion source, consisting of three capacitors with a thickness of about a tube made of a dielectric material, 0.1 mm. 5 devices for generating a high vacuum With the help of the Cu rods 20, 21, 22, which with the in the tube, facilities for creating a Inner conductor 7 and the assignments of the capacitors high DC voltage to the two ends of the 12, 16, 18 are connected, the high-frequency tube, means for feeding one voltage on the coaxial line resonator over- to ionized gaseous substance to the one wear. The shield 23 of the HF generator io the end of the tube and made of a cavity resonator can be grounded. nator, which consists of an outer conductor and a In order to suck off the ions, connection is made between the electrode inside it and coaxially to it. trode 5 (positive pole + HT ₀ ) and the plate 8 (nega- tive inner conductor is built up and where tiver pole -HT ₀ ) a high DC voltage is applied. these two conductors short-circuited at one end The switching elements and voltages of Fig. 2 15 sen and are open at the other end, thereby can have the following values: marked that the pipe (l) on the the end (24) facing away from the gas supply has an outlet 1 + / UU V bulge (2) in the form of a flattened branch ₂ +1500 V at or tuber and this bulge -HT OV ao at the open end of the coaxial cavity resonance- 41 ι 500 pF ^{tors at the m} o ^rt strongest concentration of elec- 42 6 οπή _o p Irish field lines is arranged that the interior _. _- ^. _TT head (7) the pipe (1) adjacent to this from ^Frec l ^{ueilz 150 MHz from} the end where the gas flows in to 17 20 000 Ohm ₂₅ bulge surrounds that the outer conductor (6) + HT ₀ +20 000 V through two electrically conductive plates (8, 34) -HT +15,000 V is closed, one of which is closed at the short end of the ⁰ cavity resonator in the manner previously described to vibrations the inner conductor is attached to the these and transmits and conditions excited Koaxialleitungsresonator 30 shows the other at the open At the end of the cavity, a field line course 46, as shown in FIG. 3 is a resonator with a central opening for the is. In the area S between the free end exit of the ions is provided and from which of the inner conductor 45 and the opposite wall end (45) of the inner conductor, on which the outer conductor has the electrical field strength indentation (2) lies, a distance (i.e. ) from the maximum. At this point the capacitance is also concentrated while having the order of magnitude of the thickness (e) of the bulge of the coaxial line resonator. the inductance is distributed over the entire remaining parts 2. Ion source according to claim 1, thereby gedes Koaxialleitungsresonators distributed. indicates that the cavity resonator (R) F i g. 4 shows the equivalent circuit diagram for the coaxial by means of capacitive coupling through the high-power resonator, which is excited as a parallel circuit of a frequency current source (9). Inductance L with a capacitance C, which is concentrated at the location S 3. Ion source according to claim 2, can be represented. G indicates that the high-frequency power source HF generator for exciting this parallel resonance (9) from an oscillator tube with a cathode circle. This ion source works as follows: (38), a control grid (15) and an anode The gas to be ionized or the 45 to be ionized (11) consists of the last two tubular construction steam coming through the electrode 5 into the part with one each the coverings of three condensation charge vessel and is essentially connected in the ring sators (12,16,18) whose other shaped extension 2, which is located at the location of the largest coverages with the inner waveguide (7) verField strength S, is ionized. The degree of ionization is bound, with a single sheet of a di being at least 70%. The ionized gas is now 50 electrics (36) in each case between the two with the help of the suction voltage and focusing electrodes of the three capacitors arranged in a known manner as a beam / from net. brought out of the ion source. 4. ion source according to claim 3, characterized in that The high degree of ionization of the gas or vapor characterizes that the dielectric sheet is a at the location of the annular extension 2 is reached 55 mica sheet with a thickness of about 0.1 mm. by concentrating the lines of force of the elec- tric field in the area and due to the low Losses of a cavity resonator with considered publications: Maximum frequencies compared to the vibrating »Helv. Phys. Acta ", Vol. 30, 1957, H. 4, p. 292 circles with concentrated switching elements. The A 60 to 296; Conducting the ionization can also be done easily, "The Rev. of Scient. Instr. «, Vol. 19, 1948, No. 12, because of the low losses, there is a strong span p. 905 to 910; excessive elevation occurs. Another very essential M. v. Ardenne, »Tables of Electron Physics, The real advantage of this ion source is that Ion Physics and Ubermicroscopy ", Vol. I, 1956, the ionization zone ^ is adjacent to the suction zone. 65 Berlin, p. 538, H. III. 1 sheet of drawings 409 690/236 9.64 © Bundesdruckerei Berlin