CN1381718A - Recorder of X-ray photoelectronic hologram - Google Patents

Abstract

A recorder of X-ray photoelectronic hologram for quickly real-time observing the 3D ultramicro structure of biological specimen in the natural state is disclosed. Its record method includes such steps as focusing X ray by waveband plate, filtering by pinhole diaphragm, overlap interference of the object beam passing through the opaque or semi-transparent part of specimen with the reference beam passing through its transparent part, converting the X-ray holography to photoelectronic interference field by photoelectronic cathode, accelerating, amplifying, sending to the computer, data processing and reproducing image.

Description

The pen recorder of x-ray photoelectron hologram

Technical field:

The invention relates to a kind of device that writes down the x-ray photoelectron hologram, particularly relate to a kind of record of hologram of photocathode photoelectron amplification.

Background technology:

In recent years, because the appearance of synchrotron radiation source fast development and high brightness x-ray laser has promoted the development of X ray holography greatly.Formerly in the technology, the device of record X ray hologram has two kinds:

Lid cypress coaxial X ray hologram recording apparatus (referring to technology [1] J.Opt.Soc.Am. (A) formerly, 1990,7 (10): 1847-1861).Fig. 1 is for covering the coaxial X ray hologram recorder of cypress structural representation.Polychrome synchrotron radiation X-ray source 1 is after the monochromator filtering of convergent wave strap 2 and pin hole light hurdle 3 compositions, obtain quasi monochromatic X ray, wherein a part be used to provide to testing sample 4 illumination as the thing bundle, be used for reference to bundle without another part of testing sample 4 disturbances.The thing bundle is with event is called coaxial X ray holography on same axis with reference to restrainting.Polymethylmethacrylate (PMMA) 5 is as the recording medium recording hologram with photoresist, with high-resolution transmission electron microscope or atomic force microscope hologram is read amplification then, carry out digitizing with microdensitometer again and be input to computing machine and carry out digital reconstruction.The best result that this recording mode obtains, resolution reach 40nm (referring to technology [2]: M.Hwells formerly, C.Jacobsen, et al., Science, 238,1987,514).

2. there is not lens Fourier transform X ray hologram recording apparatus.(referring to technology [3]: Science formerly, 1992,256:1009-1012).By the relevant X-ray beam of x-ray source 1 outgoing, after convergent wave strap 2, its zero order wave testing sample 4 that is used for throwing light on, its first-order diffraction ripple focuses on and produces with reference to point source, testing sample 4 with reference to point source at grade.On this plane, place a pinhole diaphragm 3, rise and cut apart filter action.Meeting in thing light and the reference light zone behind the certain distance of diaphragm back overlaps produces interference fringe, is scribbled charge-coupled device (CCD) 7 records of XRF powder.The data of record are directly imported computing machine and are carried out digital reconstruction after the A/D conversion.Before CCD, place a diaphragm 6, stop the direct irradiation of zero order light to CCD7.

The shortcoming that above-mentioned two kinds of hologram recording apparatus mainly exist is:

1. cover the coaxial X ray hologram recording apparatus of cypress, though the light path that adopts is simple, light requirement is learned element, also need not meticulous adjustment light path.But it is very high to the resolution requirement of recording medium.Because obtain higher holographic imaging resolution, then recording medium need write down senior time very meticulous interference fringe.If improve then its sensitivity meeting decline of resolution of photoresist, this just needs to increase exposure.And the increase of time shutter very easily causes recording medium to be damaged by electron beam.In addition, because it is too little to be recorded in the spacing of the holographic interference fringes on the photoresist, need the amplification of reading through high-resolution follow-up equipment such as transmission electron microscope or atomic force microscope, transcribe on film, with microdensitometer the image on the film is carried out digitizing again and is converted to data file, just can be input to computing machine and carry out digital reconstruction, like this hologram through repeatedly process, amplify, process such as developing and printing, digitized processing, introduce very big noise, reduced signal to noise ratio (S/N ratio) and image quality.Therefore covering the coaxial X ray holographic apparatus of cypress is difficult to obtain nearly diffraction limit high resolving power.

2. above-mentioned second kind of no lens Fourier transform X ray holographic microscope that device is used, though lower to the resolution requirement of recording medium, require very high to the fresnel's zone plate that produces with reference to point source.Because the spatial frequency of the peripheral endless belt of fresnel's zone plate will determine the resolution of X ray lensless Fourier transform hologram.And the making of high-resolution fresnel's zone plate is faced with the problem of high-resolution recording medium equally.So the making of this holographic microscope is difficult to realize equally.

Summary of the invention:

The present invention is directed to existing shortcoming in the above-mentioned technology formerly, propose a kind of new pen recorder, promptly x-ray photoelectron amplifies the pen recorder of hologram.Be with the X ray hologram, be translated into photoelectronic hologram by an X ray photocathode, the acceleration amplifier section that utilizes electron microscope again amplifies the coherent light electronics of photocathode, receive with CCD then, note the electronic holographic interferogram of amplification, import computing machine again and be reconstructed, just obtain the micro-intensified image of object.

X-ray photoelectron hologram recorder of the present invention as shown in Figure 3.

Be equipped with x-ray source 1 for 13 li at vacuum chamber, locate to be equipped with a zone plate 2 at the 10000mm of distance x-ray source 1 (10 meters), first-order diffraction focus O place at zone plate 2, put a pin hole light hurdle 3, put a photocathode 8 on distance pin hole light hurdle 3 for the 700mm place, between pin hole light hurdle 3 and photocathode 8, apart from photocathode 8 is that testing sample 4 is put in 50 microns to 1 millimeter disposal, between photocathode 8 and receiver 11, be equipped with accelerating anode 9 successively and amplify electromagnetic lens 10 from photocathode 8 beginnings, the output of receiver 11 links to each other with computing machine 12.

Said zone plate 2 is to be used for heterogeneous X-ray is carried out chromatic dispersion, and a monochromator is formed on it and pin hole light hurdle 3, becomes homogeneous X-ray surely from the X ray of pin hole light hurdle 3 outgoing, incides on the testing sample 4.It is to be noted especially: testing sample 4 is a very important parameter to the distance of photocathode, and it directly has influence on imaging resolution and to electron beam source coherence's requirement, available following formulate: $\frac{{\mathrm{\λ}}^2}{\mathrm{\Δ\λ}}=\frac{0.186\mathrm{\λz}}{r_0^2}$ λ is the X ray wavelength in the formula, and Δ λ is the live width of X ray, r ₀For the minimum dimension that can differentiate in the testing sample 4 is called the radius of matter-element, Z is the distance of testing sample 4 to photocathode 9.General desirable 50 microns to 1 millimeter.

Said photocathode 8, be that the X ray that will be radiated at above it is converted to photoelectron, the material of photocathode 8 has three classes usually: (1) metal species, mainly contain gold, copper, magnesium, tantalum etc., its characteristic is the threshold power height, quantum efficiency is low, because most of incident optical energy converts heat energy to, the photocathode that high-repetition-rate is turned round needs cooling; Advantage is easy preparation, and long service life is low to the vacuum tightness requirement, is generally 10 ^-5～10 ^-8(2) metallic compound and alloy typically have LaB ₆, higher quantum efficiency is arranged, ultraviolet band there is higher sensitivity, require also low to vacuum tightness.(3) semiconductor photocathode.It mainly is the polybase antimonide material.As: Cs ₃Sb, CsK ₂Sb and GaAs etc.The quantum efficiency of semiconductor photocathode is the highest, can reach 2～8%; The threshold value merit is lower, can obtain higher current density.Unique shortcoming is that the life-span is short, has only tens hours.(referring to document: Chen Jianwen, Ou Yangbin, the king Zhijiang River, the light laser technical progress, 1992, the 3rd volume, 1-5).

Must from three class materials, make one's options according to the combination property of each side such as the threshold value merit of the wavelength of x-ray photon, required photocathode and quantum efficiency in actual the use.Select the metal of long service life to make photocathode among the present invention.

X ray hologram recorder of the present invention:

The X ray that sends from x-ray source 1, focus on and 3 filtering of pin hole light hurdle through zone plate 2 chromatic dispersion diffraction, become homogeneous X-ray surely, incide on the testing sample 4, the accurate homogeneous X-ray of the scattering of and translucent portion opaque to X ray is as the thing bundle in the testing sample 4; Another part accurate homogeneous X-ray of transparent part in testing sample 4 is with reference to bundle; Thing bundle and the overlapping interference of reference bundle form an interference field that covers the coaxial X ray holography of cypress.When this interference field affacts on the photocathode 9, just produce corresponding photoelectron interference field.After carrying out photoelectron conversion by photocathode, carried the photoelectron of testing sample 4 information, quicken through accelerating anode 9 again and electromagnetic lens 10 amplification imagings on the receiving plane of receiver 11.Receiver 11 adopts charge-coupled device (CCD) among the present invention.The output of receiver 11 is input to carries out data processing, reproduced image in the computing machine 12.The enlargement factor of amplifying electromagnetic lens 10 depends on the enlargement factor of electron microscope, can be from several thousand times to 1,000,000 times.So just greatly reduce requirement to the CCD resolution of receiver 11.

The major advantage that the present invention compares with technology formerly is: 1, owing to adopt photocathode 8 to replace PMMA recording medium in technology [1] the middle cover cypress in-line holographic device formerly, the resolution of system imaging improves greatly, can reach about 0.5nm; 2, adopt to amplify electromagnetic lens 10 among the present invention and directly amplifies, avoided technology [1] formerly to cover in the cypress in-line holographic device the processing procedure of repeatedly processing, amplify, processing hologram, more convenient operation, the culture noise of introducing is littler; 3, the signal that detects of CCD outputs to computing machine when carrying out digital reconstruction, can handle reproducing the result, eliminates " twin image " interference noise in the in-line holographic.Can realize " real-time monitored " to testing sample.

Description of drawings:

Fig. 1 is the structure light path synoptic diagram of the coaxial X ray holographic apparatus of technology [1] middle cover cypress formerly.

Fig. 2 is the structure light path synoptic diagram of no lens Fourier transform X ray holographic apparatus in the technology [2] formerly.

Fig. 3 is the recording device structure synoptic diagram of x-ray photoelectron hologram of the present invention.

Embodiment:

As above-mentioned x-ray photoelectron hologram recorder of the present invention structure shown in Figure 3.

The X ray that sends from the synchrotron radiation source as x-ray source 1 is by the chromatic dispersion and pinhole diaphragm 3 filtering of zone plate 2.According to the character that the focal length and the wavelength of zone plate 2 is inversely proportional to, the X ray chromatic dispersion of different wave length can be carried out filtering and is reduced light line degree with pinhole diaphragm 3 again, adjust the size on pin hole light hurdle 3, can obtain the accurate homogeneous X-ray bundle of required spatial coherence.The centre wavelength of zone plate 2 is 2.3nm, outermost ring width 0.465 μ m, and number of rings N=1506, the radius ρ=1.4mm of zone plate 2, one-level focal length are 566mm.Zone plate 2 is elected 10m as with the distance of x-ray source 1, the aperture d=8 μ m of pinhole diaphragm 3, and live width Δ λ=λ d/ ρ=0.013nm then, monochromaticity is λ/Δ λ=10 ³, temporal coherent length is L _c=λ ²/ Δ λ=0.407 μ m.Testing sample 4 is R=700mm apart from pinhole diaphragm 3, and then the coherent ranges at this place is b=R λ/d=201 μ m.This shows to have certain coherence, be fit to carry out holographic imaging through the X ray after the monochromatization.

After the accurate homogeneous X-ray bundle irradiation testing sample 4, form the coaxial X ray holographic interference of a lid cypress field.The X ray field irradiation of this interference produces photoelectron holographic interference field on photocathode 8.Photocathode 9 is to be made of metal tantalum.Testing sample 4 is cancer cell sections of small white mouse.Testing sample 4 is 500 microns apart from photocathode 8 apart from Z.The photoelectron that is penetrated by photocathode 8 contains the structural information of testing sample 4, is accelerated anode 9 and quickens and amplify electromagnetic lens 10 and carry out amplification imaging, so form a photoelectron holographic interference pattern that contains testing sample 4 structural informations on the receiver 11 of CCD.

Because the interference fringe spacing can be amplified by amplifying electromagnetic lens 10, therefore greatly reduces the requirement to receiver 11 resolution.Adopt the receiver 11 of CCD to write down and change, can directly reappear at computing machine 13 enterprising line number words through A/D.Obtain the structural images of testing sample 4.

Photocathode photoelectron amplifying X-ray holographic apparatus of the present invention, can realize observing real-time the three-dimensional hyperfine structure of the biological sample under the state of nature, resolution can reach diffraction limit, be applied in the observational study of modern medical service diagnosis and biologically active cell, have accuracy, authenticity and promptness.

Claims (1)

1. the pen recorder of an x-ray photoelectron hologram, comprise: be seated in the x-ray source (1) in the vacuum chamber (13), in vacuum chamber (13), be equipped with zone plate (2) apart from (1) 10 meter of x-ray source, first-order diffraction focus (O) at zone plate (2) is located, be equipped with a pinhole diaphragm (3), there is output to be connected on the outer computing machine (12) of vacuum chamber (13), it is characterized in that in vacuum chamber (13), being equipped with photocathode (8) apart from 700mm place, pin hole light hurdle (3); Testing sample (4) is seated between pin hole light hurdle (3) and the photocathode (8) apart from (8) 50 microns to 1 millimeter place of photocathode; Between photocathode (8) and receiver (11), be equipped with and amplify electromagnetic lens (10).

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