SU1689818A1 - Source of collimated x-ray radiation - Google Patents

Abstract

The invention relates to the field of X-ray technology and can be used in X-ray tomography and lithography. The purpose of the invention is to increase the intensity of a collimated photon beam. The source of collimated x-ray and gamma radiation consists of a source of electrons 1 and a target including two plates 2, 3, installed one after the other with a gap 4 of size d, which satisfies the condition of multiple total external reflection of the air defense of the excited measurement from the walls of plates 2 and 3. The thickness of the upper plate 2 should not be less than & / K, where & - the critical angle of air defense, K - the attenuation index of the radiation with the energy of the excited photons Ea. 1 il. "Le about 00 h 00 00

Description

This invention relates to X-ray technology and can be used in X-ray tomography and lithography.

A tomographic emitter is known, in which a narrowly collimated X-ray X-ray beam with a simultaneously small optical focus is obtained using a system of focusing the electron beam on the anode of the tube and selecting the appropriate shape of the cathode 2.

The closest technical solution to the invention is a collimated x-ray source containing an electron source, a target and a collimator, the channel of which is formed by plates whose polished surfaces are tightly compressed.

The disadvantage of the prototype is that its intensity is limited by the intensity of the x-ray tube located outside the collimating device and the size of the channel made in the collimator.

The purpose of the invention is to increase the intensity of a collimated photon beam.

The drawing shows a schematic diagram of the source.

The source of collimated x-ray radiation contains a source of electrons 1 and a target consisting of two plates 2 and 3 with polished surfaces, between which when pressed closely, a slot (channel) of 4 micron and submicron sizes is formed,

The radiation source operates as follows.

An electron beam enters the plate 2 from above, the flux density of which is equal to p el ./ (cm2 sec), and the electron energy E must be such that after the passage of the electron plate 2 its energy is not less than the excitation potential of the corresponding characteristic line X-rays in the target, or not less than the required bremsstrahlung photon energy. The distance between the plates d, the thickness of the plate 2 is not less than the value of f 6k, where 1 / R, R is the attenuation rate of radiation with energy Ea by the target material; Qu is the critical angle of total external reflection of photons from the channel walls. Radiation generation occurs in the surface layer of the channel walls. The number of quanta with the energy Ea formed in this layer, the volume element of which is LxLydz, where Lx, Ly is the transverse and longitudinal dimensions of plate 2; dz layer thickness is:

 dN (p Na Ok (E1) LyLxdz (1)

where NA is the concentration of atoms in the target;

E1 is the electron energy at a depth Z from the upper surface of plate 2;

Ox (E1} is the X-ray yield cross section.

If the slip angle of quanta is less than critical, Ok, where o) p is the plasma frequency of electrons in the target material; ti is Planck's constant, then the photons, having passed through plate 2, are captured by slit 4, move in it in the mode of total external reflection and come out in the form of a beam 5 with a divergence of no more than 2 Ok. The quanta which are formed in the near-surface layer thickness h f v. The characteristic radiation, excited by electrons, propagates into the solid angle 4l: glad, therefore the number of quanta NI with energy Ea. captured by channel 4, equals:

N pNAObCE LyU c- -, (2)

where Q - 6y 2 6k is the divergence of the radiation in the y direction.

The number of quanta NI is increased by 2 times, if the electron energy is sufficient to generate radiation in a layer of thickness h of plate 3. The number of bremsstrahlung quanta entering the channel depends on the angle of incidence of the electron on plate 2.

When using the proposed device as a target of tungsten

wafers for obtaining K # radiation of tungsten, the parameter d takes the following value: Ea 57.98 keV, Ir 80.2 eV, k 53.27 cm 1, $ 9-U 9, & 1.38 10 3rad, l 0.26 µm, d lMKM, 1x 7.7 cm, (.

When silicon wafers are used as targets, the following value of the parameter d is obtained: Ea - 1.74 keV, Schr 31zV. k-755CM-1, / 9 4.28 1.78-, h 0.24 microns, d 10 microns, Lx 2 cm, d 37.

Thus, as a result of the implementation of the proposed device, a collimated beam of x-rays and gamma quanta is obtained, while the intensity of the beam s is 10-100 times higher than the intensity of the beam, which is obtained in the device selected as a prototype.

Claims (1)

Invention Formula The source of collimated X-ray radiation, containing the source of electrons, the target and the collimator, the channel of which is formed by plates, is polished whose surfaces are tightly compressed. ionization energy loss characterized in that, in order to dX K increase the intensity of the collimated electron in the target material; the photon beam, the target and the collimator Eu — the photon energy is combined, and the source of electrons is set-5 the longitudinal dimensions of the collimator are not outlined on the outside of one of the plates, the values 1 / a, where attenuation of radiation in the channel of the collimatospinum as photons move in the full external reflection from the channel walls, and  I dE I 1 region of radiation generation in the target I d) T I dX; divided from the edges of the target by an absorber layer, where Eo is the electron energy at the entrance to the front line. The size of which exceeds, .nk “the mean free path of the photo Ш6НЬ | . new in the material of the plates.