CN1270158C - Simple x-ray interferometer - Google Patents

Abstract

The present invention relates to a simple x-ray interferometer which is characterized in that the x-ray interferometer is composed of an X-ray source, two plane glass plates, a sample and a detector. The two plane glass plates are arranged in a slight incidence mode in the X-ray advanced direction of the X-ray source. An included angle between the two plane glass plates is 1', X-rays are respectively reflected by the two plane glass plates, wherein after passing through a sample, one reflected X-ray is intersected with another reflected X-ray. After the two X-rays are mutually interfered, the detector is used for detection. The present invention has the advantages of simple structure, low cost and reliable use.

Description

Simple and easy X ray interferometer

Technical field:

The present invention relates to interferometer, particularly a kind of easy X ray interferometer, this interferometer can be used for testing synchrotron radiation source and microfocus X-ray tube spatial coherence etc.

Background technology:

X ray essence is the same with visible light all to be electromagnetic radiation, and X ray also has wave-particle duality, and its particulate nature comprises photoelectric effect, incoherent and coherent scattering, gas ionization etc.Its undulatory property comprises: phase velocity, position phase, reflection, refraction, diffraction, interference and polarization etc.Since X ray was found, people utilized these characteristics always, were engaged in the various activities that are beneficial to man, for example widely known XCT imaging technique.

X ray short wavelength's character makes its refractive index in material be one and is slightly smaller than 1 amount, therefore can not use be similar to the optical element that uses in the visible light usually, makes x-ray imaging focusing and beam splitting or the like.

Because X ray wavelength ratio visible light much shorter, when carrying out the precision detection with it, resolution is than the high 2-4 of a visible light magnitude in theory.Therefore, utilize X ray can carry out the research of high resolving power interferometry.Again because the temporal coherence of existing x-ray source is relatively poor, Δ λ/λ ≈ 10 for example ^-4, therefore, temporal coherent length only is a micron dimension, these all are that the making of X ray interferometer brings difficulty.

Nineteen sixty-five, first X ray interferometer that the U.Bonse of U.S. Cornell university and M.Hart are developed into, it is to be made of three blocks of parallel monocrystalline silicon, as shown in Figure 1, based on the crystal diffraction principle, first crystal is used as beam splitter, second crystal is compound with this two beam X-ray, since X ray wavelength ratio visible light want much shorter, the interference fringe that their form is too close, so that Direct observation with the naked eye, the 3rd crystal then solved this difficult problem, it becomes very little with the angle between two beam X-rays, and is almost parallel, with striped under the egative film record.This interferometer almost is aplanatic, so it successfully is applied to the research of hard X ray phase contrast imaging.The shortcoming of this interferometer maximum is to need three high-quality crystal, and not only crystal plane direction wants consistent, and three crystal will be parallel to each other, and this has brought difficulty for crystal growth and processing undoubtedly.

Summary of the invention:

The technical problem to be solved in the present invention is at the existing shortcoming of above-mentioned technology formerly, a kind of easy structure X ray interferometer is proposed, it be as long as two glass plates, x-ray source and ccd detector just can constitute, have simple in structure, cost is low, the service-strong advantage.

The foundation of technical solution of the present invention is as follows:

According to Electromagnetic theory, the amplitude reflectivity of X ray on minute surface can be provided by the Fresnel formula.X ray incides refractive index from vacuum and is as a result Dielectric surface, then

To vertically polarized wave:

$r_s=\frac{\sin \mathrm{\θ}-{({\tilde{n}}^2-{\cos }^2\mathrm{\θ})}^{1/2}}{\sin \mathrm{\θ}+{({\tilde{n}}^2-{\cos }^2\mathrm{\θ})}^{1/2}}$

To horizonally-polarized wave:

$r_p=\frac{-{\tilde{n}}^2\sin \mathrm{\θ}+{({\tilde{n}}^2-{\cos }^2\mathrm{\θ})}^{1/2}}{{\tilde{n}}^2\sin \mathrm{\θ}+{({\tilde{n}}^2-{\cos }^2\mathrm{\θ})}^{1/2}}$

Wherein θ is a grazing angle.For normal incidence situation (θ=90 °), more than two formulas obtain identical value, and reflection strength

$R={\mathrm{rr}}^{*}={\left(\frac{1-\tilde{n}}{1+\tilde{n}}\right)}^2\≈\frac{{\mathrm{\δ}}^2{+\mathrm{\β}}^2}{4}$

Because δ and β value are all very little, therefore as can be seen, for general normal incidence situation, specular reflectance almost can be ignored.

In ordinary optical, we know, when light by optically denser medium when optically thinner medium is propagated, if incident angle surpasses certain value, light will be by total reflection, the angle that total reflection just in time takes place is called the cirtical angle of total reflection.

When incident X-rays incides mirror surface to omit the incident mode, because $\tilde{n}<1,$ When it when vacuum incides certain material, " total reflection " may take place.According to the Snell law $\sin \mathrm{\&phi;}=\tilde{n}\sin {\mathrm{\&phi;}}^{\&prime;},$ Wherein φ and φ ' are respectively incident angle and refraction angle.Replace φ ' with glancing incidence θ=90 °-φ, then when grazing angle less than a certain critical angle θ _cThe Shi Fasheng total reflection, and can obtain ${\mathrm{\&theta;}}_c={\cos }^{-1}\tilde{n}.$ If ignore absorption, this moment n=1-δ, thereby obtain:

sinθ _c＝(2δ) ^1/2

θ _c≈(2δ) ^1/2

$\mathrm{\&delta;}=\frac{r_0}{\mathrm{\&pi;}}{\mathrm{\&lambda;}}^2\mathrm{Nf}$

${\mathrm{\&theta;}}_c={\mathrm{\&lambda;}}_c{\left(\frac{r_0}{\mathrm{\&pi;}}{N}_{\mathrm{at}}f\right)}^{1/2}$

R in the formula ₀Be the classical radius of electronics, f is single proton free electron number, and N is an atomicity density.λ _cBe called critical wavelength.When δ＞＞during β, acute variation takes place in critical angle place in reflectivity, grazing angle is during less than critical angle, reflectivity is near 100%.

Can draw a conclusion from above discussion: when X ray when inciding a certain minute surface less than critical angle, can produce total reflection.Around this principle, our concrete technical scheme is as follows:

A kind of simple and easy X ray interferometer, it is characterized in that it is made up of x-ray source, first glass plate, second glass plate, sample and detector: on the direction that the X ray of x-ray source advances, first glass plate and second glass plate on two planes placed on glancing incidence ground, the angle of this two flat glass plate is 1 "; these two flat glass plates reflect X ray respectively; wherein the X ray of a branch of reflection after also interfering mutually with the X ray of another bundle reflection is crossing, detects with detector behind sample again.

Said x-ray source is a synchrotron radiation source, or the X-ray tube of a microfocus.

Said two glass plates all are k ₉Glass plate, surface smoothness and flatness assurance X ray corrugated are reflected undistortedly.

Said sample is a biosome to be measured, perhaps other material.

Said detector is the device that can accept and write down the X ray interference fringe.Technique effect of the present invention is as follows:

The present invention adopts two angles 1 " about glass plate almost under the condition of parallel placement, the X ray glancing incidence is to these two glass plates, the two beam X-ray angles that their produce total reflection are 1 ", after these two groups of X ray intersect, produce interference fringe, without any need for crystal, very simple.

Simple and easy X ray interferometer of the present invention is compared with technology formerly, has simple in structurely, without any need for beam splitter and crystal, owing to be total reflection, can make full use of X-ray beam.

Description of drawings:

Fig. 1 is X ray interferometer in the technology formerly.

Fig. 2 is a simple and easy X ray interferometer schematic diagram of the present invention.

Embodiment

Simple and easy X ray interferometer of the present invention as shown in Figure 2, as seen from the figure, the simple and easy X ray interferometer of the present invention, it is by x-ray source 1, first glass plate 2, second glass plate 3, sample 4 and detector 5 formed: on the direction that the X ray of x-ray source 1 advances, first glass plate 2 and second glass plate 3 on these two planes placed on glancing incidence ground, the angle of this first surface glass plate 2 and second glass plate 3 is 1 "; this first glass plate 2 and second glass plate 3 will reflect X ray; wherein the X ray of a branch of reflection is behind sample 4; after also interfering mutually with the X ray of another bundle reflection is crossing, detect with detector 5 again.

Described x-ray source 1 is a synchrotron radiation source, and its output wavelength is limited to the X ray zone with monochromator, is about 1 .

Described first glass plate 2 and second glass plate 3 all are k ₉Glass is of a size of 20 * 20mm, and surface smoothness reaches the minute surface level.

Said sample 4 is phase objects, as the liver of mouse.

Said detector 5 is CCD receivers, and signal is sent in the computing machine and goes.

The principle of work and the basic process of simple and easy X ray interferometer of the present invention are as follows:

When the X ray glancing incidence after first glass plate 2 and second glass plate 3, produce total reflection, wherein a beam X-ray is through sample, contain sample message and another beam X-ray and intersect the generation interference, conoscope image is received by CCD5, and the distance of interference fringe depends on the angle of cut of two beam X-rays, adjust the angle of described first glass plate and second glass plate, the distance of interference fringe can be changed, when the angle of two glass plates becomes big, the X ray hologram can be obtained.

Claims (4)

1, a kind of simple and easy X ray interferometer, it is characterized in that it is by x-ray source (1), first glass plate (2), second glass plate (3), sample (4) and detector (5) are formed: on the direction that the X ray of x-ray source (1) advances, be arranged to glancing incidence ground and place first glass plate (2) and second glass plate (3) on two planes, the angle of this first glass plate (2) and second glass plate (3) is 1 "; first glass plate (2) and second glass plate (3) reflection X ray; wherein the X ray of a branch of reflection is behind sample (4); after also interfering mutually with the X ray of another bundle reflection is crossing again, detect with detector (5).

2, simple and easy X ray interferometer according to claim 1 is characterized in that said x-ray source (1) is a synchrotron radiation source, and its output wavelength is limited to the X ray zone with monochromator, is 1 .

3, simple and easy X ray interferometer according to claim 1 is characterized in that described first glass plate (2) and second glass plate (3), all is a k ₉Glass is of a size of 20 * 20mm, and surface smoothness reaches the minute surface level.

4, simple and easy X ray interferometer according to claim 1 is characterized in that described detector (5) is a CCD receiver, and signal is sent in the computing machine and goes.