Electric lamp and discharge devices: systems – Cathode ray tube circuits – Combined cathode ray tube and circuit element structure
Patent
1991-02-06
1993-09-14
Pascal, Robert J.
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Combined cathode ray tube and circuit element structure
315 535, H01J 2306
Patent
active
052452506
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method of controlling a charged particle beam, such as an electron beam or an ion beam in an emittance for use in, for example, an electron beam apparatus such as an electron accelerator or an electron microscope for controlling the charged particle beam.
2. State of the Art
Generally, in an electron beam apparatus such as an electron microscope, energy of transverse thermal motion would occur within a transverse plane which is perpendicular to the direction of a beam generated by an electron gun. The transverse thermal motion can be replaced by the term "emittance" which is used in the particle optics art and which is defined as a product of an inclination angle with respect to the axial direction of the electron beam and spatial spread of the electron beam along the direction of the inclination projected on the transverse plane. Such a magnitude of the emittance determines the upper limit of a resolution of an electron microscope.
As will be obvious even from the above-mentioned fact, in order to get an electron beam of high quality, it is required to minimize an emittance of the electron beam as well as to make energy uniform by cooling the electron beam. However, a method of improving an emittance in an electron beam apparatus has not been proposed at all so far.
It is an object of the present invention to resolve this problem and to momentarily cool an electron beam regardless of a pulsed beam or a continuous beam.
SUMMARY OF THE INVENTION
The invention is applicable to use in an electron beam apparatus, such as an electron accelerator or an electron microscope. According to an aspect of this invention, the apparatus comprises magnetic field generating means formed by a solenoid having a solenoid axis for generating a magnetic field along a predetermined axial direction, beam generating means for generating a charged particle beam, such as an electron beam, and introducing said charged particle beam along a traveling direction which is extended along said predetermined axial direction, and radio frequency wave injecting means located within the magnetic field generating means for injecting a radio frequency wave in a direction parallel to the predetermined axial direction so that a cyclotron maser beam, referred to herein as a maser, is generated in the charged particle beam to reduce charged particle beam emittance. With this structure, kinetic energy of the charged particle beam is forcibly radiated in the form of the electron cyclotron maser on a plane transverse to the traveling direction of the charged particle beam. In addition, the radio frequency may be injected, or projected, in a direction opposite to or identical with the traveling direction of the charged particle beam, referred to in the following exemplary embodiments as an electron beam.
Furthermore, an apparatus according to another aspect of this invention assures stimulation of the charged particle beam, after a part of the energy has been converted into cyclotron gyration by obliquely accelerating electrons with respect to the axial direction of the electron beam or by making use of deflection magnets, with improved emittance being achieved by means of cyclotron maser.
More particularly, a solenoid magnetic field generating section is disposed within the electron beam apparatus, and in this section, a solenoid magnetic field B.sub.o (tesla) is generated in the axial direction of the electron beam. Thereby, electrons make a cyclotron gyration at an angular frequency of .omega..sub.c */.gamma..sub..perp. =eB.sub.o /m.sub.o .gamma..sub.195 within the transverse plane, where .omega..sub.c * is given by eB.sub.o /m.sub.o and is representative of a cyclotron gyration angular frequency. Here, e and m.sub.o denote charge and rest mass, respectively, of an electron. In the following, it is assumed that all the physical quantities are given in practical units. Here, .gamma..sub..perp. denotes the relativistic energy factor of the transverse motion, where c r
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European Search Report EP 90 91 0931; Search completed Jul. 10, 1991.
Lee Benny T.
Pascal Robert J.
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