Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J27/00—Ion beam tubes
  • H01J27/02—Ion sources; Ion guns
  • H01J27/16—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation
  • H01J27/18—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation with an applied axial magnetic field

Definitions

• the invention relates to an electron impact ion source according to the preamble of claim 1.
• the electron impact ion source allows the generation of highly charged ions, their extraction, serves as a source of UV, NUN, infrared rays and of characteristic X-ray radiation of highly charged ions
• the system consists of an electron gun, several cylindrical drift tubes, an electron collector, an extractor, a focusing magnet system and a system for generating ultra-high vacuum conditions in the system
• the electron beam creates an ion trap in the central part of the system, which holds the ions in the radial direction due to their space charge forces.
• the ions that are generated in the electron beam by electron impact ionization are generated by positive potentials at the ends of the drift tube structures according to ED Donets, USSR Inventors Certificate ⁇ o 248860, March 16, 1967, Bull OIPOTZ ⁇ o 23 (1969) 65
• the uploaded ions obtained can be extracted from the ion trap along the trap axis by lowering the trap potential at the last drift tubes.
• characteristic X-rays and other long-wave electromagnetic radiation emitted by the stored ions are in the meridian plane of the magnet system and perpendicular to it Radiated source axis
• the maximum achievable ion charge is a function of the ionization factor j ⁇ , i.e. the product of the electron current density j and the ion residence time ⁇ in the electron beam.
• the process that limits the achievement of the highest charge states is essentially the charge reversal processes of multiply charged ions on residual gas atoms.Therefore, devices based on the method described generate charged ions that Enable formation of a high-density electron beam under ultra high vacuum conditions
• cryogenic technology in conjunction with superconducting technology is used in EBIT systems.
• Superconducting Helmholtz coils with induction of the magnetic field from 3T to 5T are used here to focus the electron beam over the length of the ion trap, which in known systems does not exceed 25 mm
• the current density of the electron beam over the trap length is 2,000-5,000 A / cm 2 with a total length of the electron-optical system (cathode - electron collector) of more than 30 cm K the function of a powerful cryopump in the area of the ion trap to create a vacuum of> 10 "11 to 10 " 12 Torr
• cryogenic and ultra-high vacuum technology have an additional limiting effect
• a decrease in the electron current density to 200 to 500 A cm 2 leads to an increase in the time required to generate a certain ion charge state in the trap and thus to a decrease in the mean beam intensity for extracted multi-charged
• Magnetic fields of the strength 0.2 T to 0.5 T are required, which can be generated by permanent magnet systems based on modern magnetic materials
• the original cathode of the klystron with a maximum emissivity of 2.5 A / cm 2 is used.
• the ultra-high vacuum in the system is achieved after heating at 300 ° C using standard technology with the combination of a turbomolecular and an ion getter pump
• This system has a low electron current density in the beam (100 times lower than for superconducting EBIT). This is associated with a limitation to comparatively low ionic charge states such as Ar 16+
• the maximum current intensity in the electron beam focused by a longitudinal magnetic field for Brillouin focusing can be obtained if the magnetic field disappears at the location of the cathode in one
• the so-called Brillouin density of the electron flow is limited by thermal velocity components of the electrons as they exit the cathode (see also M Szilagyi, Electron and Ion Optics, Plenum Press, New York and London, 1988) and by aberrations in the anode lens for the aberrations is possible in the case of paraxial and laminar flows, ie for an electron gun with minimal divergence (compression) of the electron beam and thus for a maximally efficient cathode, ie for a cathode with maximum emission density
• the object of the invention is to create an effective electron impact ion source (WEBIT) without any cryogenic components and without superconductivity technology for the receipt of charged ions, X-ray and VUV spectroscopy on these ions and the extraction of the charged ions from the trap for the purposes of various scientific , technological and technical applications
• WEBIT electron impact ion source
• the object is achieved in connection with the features mentioned in the preamble of claim 1 in that the device for the axially symmetrical focusing of the electron beam consists of at least two rings that are radially magnetized in opposite directions and each of the rings encloses the electron beam, two rings that are radially magnetized in opposite directions are connected to form a uniform magnet system by magnetic conductors, the closing magnetic field denying the
• the cathode has a very high emissivity of> 25 A / cm 2 with a small cathode diameter, and a vacuum of 10 ⁇ 7 to 10 " ⁇ Torr in the area of the ions during the
• Magnetized permanent magnet blocks are advantageously assembled into rings and enclosed by magnetic conductors made of soft magnetic material, so that radial magnetization results
• the magnetized permanent magnet blocks cuboids made of hard magnetic materials such as Sm 5 Co or NdFeB are also advantageous, as a result of which the rings can be produced efficiently
• the ion trap to be opened and closed advantageously consists of a three-part drift tube mounted on a high-voltage insulator.
• a controllable acceleration potential is applied to the middle part and an adjustable trap potential is applied to the two outer parts
• the middle part of the drift tubes is provided with a number of elongated holes or other suitable openings running along the axial electron beam, which enable efficient pumping in the area of the ion trap
• a vacuum recipient with four flanges in which two flanges lying opposite one another form a first axis and two further flanges form a second axis, the first and second axes crossing, on the first axis electron gun, drift tubes, electron collector and Extractors are arranged in this order, and along the second axis on a flange High-voltage bushing for positioning the drift tubes in the course of the first axis and a vacuum pump can be connected to the other flange.
• Other solutions with more or fewer flanges are possible
• the magnetic conductors advantageously pierce the vacuum recipient on both sides of the second axis parallel to the first axis and form a seat for the rings there.
• the part of the magnetic conductor protruding into the vacuum recipient is angled in a 1-shape and magnetically short-circuited with the drift tubes
• an electron gun with minimal divergence (compression) of the electron beam and thus with a maximally efficient cathode, i.e. a cathode with maximally high emission density, is used
• the advantage of the invention is that highly charged ions can be generated efficiently without cryogenic technology
• Fig. 1 is a schematic representation of the invention
• Fig. 2 shows an advantageous embodiment of the invention in a schematic sectional view
• FIG. 3 shows a section A-A corresponding to the representation in Fig. 2nd
• FIG. 4 shows a detailed representation corresponding to FIG. 3
• Electron gun 3 with cathode 14, three drift tubes 4, 15, 4, an electron collector 5, and an extractor 6 are arranged on axis 16 in this order.
• Two oppositely radially magnetized rings 2 enclose axis 16 input and output of the drift tube structure 4, 15 and thus the electron beam that can be generated
• the rings 2 contain a number of permanent magnet blocks 8, with which the rings 2 receive a radial magnetization.
• an electron impact ion source which consists of a vacuum recipient 1, a magnetically focusing system 2, an electron gun 3, a drift tube structure 4, 15 mounted on a high-voltage insulator, and under certain circumstances the high-voltage insulator can be dispensed with, an electron collector 5 and an extractor 6.
• pole shoes 7 made of soft magnetic material for field formation in the region of the ion trap are mounted in its interior
• the magnetic field is generated by two rings 2 made of radially magnetized permanent magnet blocks 8, which are connected to one another by a system of magnetic conductors 7, 9 made of soft magnetic material.
• the individual magnetic elements have the shape of simple cuboids, which makes it possible without difficulty to use modern hard magnetic materials such as To use Sm 5 Co or NdFeB
• the rings 2 are located outside the vacuum recipient 1 and can therefore be dismantled during the time the device is heated to obtain ultra-high vacuums. This special feature of the system makes it possible to forego temperature limits in the heating process due to the relatively low Curie temperatures of modern hard magnetic materials
• the distances between the location of the characteristic X-ray radiation or the VUV radiation and possible detectors as well as the distances to the required vacuum pumps can be kept to a minimum.As a result, the system has a maximum large solid angle (and thus has maximum detection effectiveness) during the registration of the characteristic X-ray radiation or the VUV radiation and a maximum pumping speed during vacuum generation
• the electron gun 3 differs by its geometrical dimensions, here in particular by the cathode diameter, which is chosen with the aim of reducing the angular divergence of the electron beam and of achieving a paraxial current This is achieved through the use of highly effective emitting cathode materials, such as are known as monocrystalline boron-lanthanum cathodes
• an electron current density of 200 A / cm 2 For comparison with known EBIT and EBIS systems, at least the following parameters are achieved: an electron current density of 200 A / cm 2 , an electron current of 50 mA and an electron energy of 30 keV
• the compression level of the electron beam in the electron gun 3 is 4 (ie the ratio of the cathode radius to the radius of the electron beam in the cross-over is equal to 2).
• the values given were for a Brillouin field value of 250 mT and for a cathode sensitivity of 25 A / cm 2 received

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Electron Sources, Ion Sources (AREA)
• Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
• Dental Preparations (AREA)
• Luminescent Compositions (AREA)
• Particle Accelerators (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1999
  • 1999-10-08 DE DE19949978A patent/DE19949978A1/de not_active Withdrawn
• 2000
  • 2000-10-06 EP EP00982966A patent/EP1222677B1/fr not_active Expired - Lifetime
  • 2000-10-06 WO PCT/DE2000/003525 patent/WO2001027964A2/fr active Application Filing
  • 2000-10-06 DE DE50015866T patent/DE50015866D1/de not_active Expired - Lifetime
  • 2000-10-06 AT AT00982966T patent/ATE458260T1/de not_active IP Right Cessation
  • 2000-10-06 AU AU19927/01A patent/AU1992701A/en not_active Abandoned
  • 2000-10-06 US US10/110,261 patent/US6717155B1/en not_active Expired - Lifetime
  • 2000-10-06 DE DE10083121T patent/DE10083121D2/de not_active Expired - Lifetime
  • 2000-10-06 JP JP2001530888A patent/JP4886138B2/ja not_active Expired - Fee Related

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