• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:

    公开号:SE539715C2
    申请号:SE1650846
    申请日:2016-06-15
    公开日:2017-11-07
    发明作者:Baltzer Peter
    申请人:Mb Scient Ab；
    IPC主号:
    专利说明:

    ANGULAR MODE TEST DEVICE The present invention relates to the field of electron spectrometry in general and to a test device for electron spectrometers in particular.
    Background of the Invention In Angular Resolved Photoelectron Spectroscopy (ARPES) it is necessary to test the spectrometer system i.a. at delivery to the user to ascertain that the performance meets the specifications. Also, in the angular mode operation the electron lens exhibits certain non-linearities that one may wish to eliminate by calibration.
    A prior art method for performing these tasks entails the use of a device 10 comprising a wire 14 and slits 18, an example of which is shown in Fig. la.
    Fig. 1 b shows the functioning of this prior art device 10 schematically. It comprises an electron source 12 generating an electron beam e- having a diameter of typically 1 mm. The electron beam irradiates a wire 14 of tungsten having a diameter of typically about 50 jam. The electron beam will cause emission of electrons from the wire spreading in all directions.
    In front of the wire 14 there is a screen 16 having a plurality of slits 18 extending transversely. The screen is positioned about 25 mm from the wire and is bent along a circular path such that the distance from the wire 14 to the screen 16 is equal for all angles.
    The slits are typically 0,25 mm and spaced apart with a pitch of 0,5 mm.
    The prior art device has some disadvantages. It uses the secondary emission which is strong only below 30 eV, see the diagram in Fig. lc. In this region the efficiency is thus fairly high. However, in the region above 30 eV the intensity is very low which means that the irradiation power has to be increased to extent where problems arise. Namely, heat evolves up to about 1000 degrees which generates evaporation of metal that deposit on surfaces in the vicinity, which generates considerable contact potential distortion in the shadow mask.
    At the right end of the energy scale there is the so called elastic peak which is not practically usable with this prior art device.
    The handling is relatively cumbersome due to the mechanical design comprising two independent parts, e.g. the electron source, and the wire with its attached shadow mask.
    Summary of the Invention The present inventor has now designed an angular mode test device that provides electrons of an energy that is the same as the desired energy, eliminates the contact potential related distortion, and is provided as a compact unit that is much easier to handle.
    Furthermore, the novel device is useable for developing the voltage tables that are used in operation of the spectrometer, which in the prior art systems is a very cumbersome and time consuming task.
    This novel angular mode test device is defined in claim 1 and comprises a housing (12); a source (14, 36) of primary electrons arranged inside the housing (12), said source comprising a filament (36); a surface (26) capable of elastically scattering electrons when the primary electrons impinges thereon; a hole (33) in the housing (12) provided so as to allow only electrons to pass there through; a mask (34) having a pattern (P) of holes the size of each hole being such as to define the angular distribution of the emitted bundle of electrons; and a variable voltage source (Vvar) connected between the housing and the filament (36) and the electron emitting surface (26).
    Preferred embodiments are defined in the dependent claims.
    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus not to be considered limiting on the present invention, and wherein Fig. 1 a shows a prior art device for angular mode testing; Fig. lb schematically shows the function of the prior art device of Fig. la; Fig. lc shows an energy spectrum for emitted electrons; Fig. 2 is a view in perspective view of the novel device with parts broken away; Fig. 3 shows in detail the important part of the device in magnification; Fig. 4 schematically illustrates the feature of accelerating the electrons; and Fig. 5 schematically illustrates the positioning of the device in a spectrometer.
    Detailed Description of Preferred Embodiments Fig. 2 illustrates the component parts of an embodiment of the angular mode test device, generally designated 10, in a perspective view with parts broken away.
    The shown embodiment comprises a mounting block 12 for housing an electron source 14. The mounting block has a lower interior space (not visible in Fig. 2) and an upper interior space 15. This upper interior space 15 can be closed off by a cover plate 16, suitably by means of bolts 18, to form a chamber. In this chamber the source 14 is mounted by means of a holder 14' such that the source 14 is clamped between the holder 14' and an inner wall of the mounting block 12. Details of the source 14 will be described in connection with Fig. 4.
    The mounting block 12 is suspended by a rod 20 mounted to a rod fastener 22, which in turn is attached to a mounting flange 24 attachable to the spectrometer main frame (not shown). The rod is hollow and carries electrical leads for energizing the source 14.
    Now the design of the crucial parts of the test device will be described with reference to Fig. 3 which shows the mounting block 12 in cross section.
    The mounting block 12, as already mentioned comprises an upper space 15 forming a compartment when closed off by the cover plate 16, but also a lower space 15'. In this lower space 15' the filament 36 of the source 14 is located.
    The source 14 thus comprises a filament, i.e. wire 36, suitably a tungsten wire. It is possible to use a standard halogen lamp with the glass bulb removed for this.
    The source 14 is located inside the mounting block 12 in a position such that metal atoms evaporated from the filament 36 cannot take a straight path out of the chamber. This is a very important aspect and will be described further below.
    In the lower space 15' inside the mounting block 12 there is provided a diffuse reflector 26 in the form of a slanting surface. In the shown embodiment it has a slant angle of 45°. The angle is in no way critical, and the surface could in principle be horizontal or vertical or any angle there between. This surface is in the shown embodiment provided by a pin 28 mounted in the mounting block 12 inside the chamber. The slanting surface 26 will emit elastically scattered electrons when electrons from the filament impinges thereon. The emitted electrons from said surface will be distributed in all directions.
    The chamber formed by the lower space 15' has a front wall 17f and a rear wall 17r. In the front wall 17f there is an aperture 30 in which there is mounted a foil 32, in the centre of which there is a small hole 33. Some of the electrons scattered from the slanting surface 26 will exit through the small hole 33 and form a cone of electrons that will hit a mask 34 arranged so as to receive the electrons exiting through the small hole 33. This hole 33 typically has a diameter of about 50 jam, but the size could vary depending on desired angular resolution which is given as Image available on "Original document" Practical limits for the diameter could be from 20 to 100 jam.
    The mask is provided with a pattern P of holes so as to define the angular distribution of the emitted bundle of electrons.
    One important feature of the present device is that there is no line-of-sight from the filament 36 to the small hole 33. In this way evaporated metal is prevented from reaching the hole 33 and cannot therefore exit from the chamber either. This is crucial since the evaporated metal would otherwise contaminate the mask 34 and the lens. In order to provide for this blockage of the line-of-sight the wall 17f is made relatively thick and the aperture 30 in the wall is given a diameter so as to shield off said line-of-sight from filament 36 to hole 33.
    Another important difference between the above device and the device according to prior art is that in the present device there is provided for variable acceleration of the electrons emitted from the filament 36 towards the surface 26. This is achieved by providing a variable voltage source Vvarcapable of applying a voltage Ua between the surface 26 and the filament 36, see Fig. 4, schematically illustrating the filament 36 and the slanting surface 26. The voltage Ua typically can vary between 0 and lkV which means that the energy of an electron typically can be between 0 and 1 keV when it reaches the surface 26. A practically usable upper extreme voltage could be 10 kV.
    This means that electrons emitted from the surface 26 will have energies defined by the voltage Ua. If one varies the voltage the energies of course vary in the same manner, and thus it becomes possible to provide electrons in the entire interval from 0 up to say 1 keV with large intensities, which is not possible with the prior art test device.
    The angular mode test device 10 described above is placed in an electron spectrometer ES (schematically indictated with broken lines), with the lens operated in angular mode at a location where a sample normally is provided, i.e. at the focal point E of a lens L, schematically illustrated in Fig. 5.
    The spectrometer ES comprises a control unit CU for its operation, i.e. for setting voltages to lens elements etc., and is also adapted to run the test device 10 synchronously with the operation of the spectrometer.
    权利要求:
    Claims (9)
    [1] 1. Angular mode test device for electron spectrometers, comprising a) a housing (12); b) a source (14, 36) of primary electrons arranged inside the housing (12), said source comprising a filament (36); c) a surface (26) capable of elastically scattering electrons when the primary electrons impinges thereon; d) a hole (33) in the housing (12) provided so as to allow only electrons to pass there through; e) a mask (34) having a pattern (P) of holes the size of each hole being such as to define the angular distribution of the emitted bundle of electrons; f) a variable voltage source (Vvar ) connected between the housing and the filament (36) and the electron emitting surface (26) .
    [2] 2. Device according to claim 1, wherein the filament (36) in the source of primary electrons is made of tungsten.
    [3] 3. Device according to claim 1, wherein the surface capable (26) of scattering electrons comprises a metal, preferably copper.
    [4] 4. Device according to claim 1, wherein the surface (26) capable of scattering electrons has an orientation selected from any orientation ranging between horizontal and vertical, preferably it is oriented at a slanting angle of 30 - 50 degrees, most preferred about 45 degrees from the horizontal.
    [5] 5. Device according to claim 1, wherein the variable voltage source (Vvar ) is configured to enable acceleration of electrons emitted from the source of primary electrons towards the surface (26) capable of emitting electrons.
    [6] 6. Device according to claim 5, wherein the variable voltage source (Vvar ) is configured to provide an acceleration voltage in the interval 0 to 10 keV, preferably from about 20 eV up to about 1 keV.
    [7] 7. Device according to claim 1, wherein the diameter D of the hole (33) is dependent on the angular resolution and suitably D is 3 jam < D < 100 jam, preferably the diameter D is about 50 jam.
    [8] 8. Device according to claim 7, wherein the hole (33) is provided in a foil (32), the foil being mounted in an aperture (30) in the wall (17f) of the housing (12)
    [9] 9. Device according to claim 8, wherein a line-of-sight from the filament (36) to the hole (33) is blocked, by adapting the thickness of the wall (17f) of the housing (12) and the inner diameter of the aperture (30).
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    同族专利:
    公开号 | 公开日
    SE1650846A1|2017-11-07|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1650846A|SE1650846A1|2016-06-15|2016-06-15|Angular mode test device|SE1650846A| SE1650846A1|2016-06-15|2016-06-15|Angular mode test device|
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