CN109764962A - A kind of optimization method of grating monochromator - Google Patents
A kind of optimization method of grating monochromator Download PDFInfo
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- CN109764962A CN109764962A CN201910062914.3A CN201910062914A CN109764962A CN 109764962 A CN109764962 A CN 109764962A CN 201910062914 A CN201910062914 A CN 201910062914A CN 109764962 A CN109764962 A CN 109764962A
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Abstract
The present invention relates to a kind of optimization methods of grating monochromator comprising following steps: step S0, provides a light source, a preceding focus mirror, a plane mirror and a varied line-space grating；Step S1, the light for issuing the light source is incident to the plane mirror after preceding focus mirror convergence, then reflexes to the varied line-space grating by the plane mirror, and the diffraction light of generation is converged to a focus point finally by the varied line-space grating；Step S2 adjusts the focal length of the preceding focus mirror using the focus of the preceding focus mirror as an imaginary light source, so that the distance between the imaginary light source and the varied line-space grating are equal to the distance between the focus point and the varied line-space grating；Step S3 calculates the focusing factor of the varied line-space grating according to the focused condition of grating equation and the varied line-space grating.The present invention is become using varied line-space grating still can choose different Focusing constants comprising angle grating monochromator, to realize flexible operating mode.
Description
Technical field
The present invention relates to a kind of optimization methods of grating monochromator.
Background technique
The large scientific facilities such as Synchrotron Radiation and X-ray free-electron laser device are answered in basic scientific research and industry
It is widely used with equal fields.It is typically necessary using X-ray caused by this large scientific facilities and is focused, is monochromatic
Scientific experiment could be used for after the processing such as change, the main function of monochromator to be exactly the polychromatic light monochromatization for generating light source, is generated
Monochromatic light needed for scientific experiment.In Soft X-Ray Region, generally use grating as dispersion element, it is this using grating as color
The monochromator for dissipating element is known as grating monochromator.
As shown in Figure 1, the angle of incident light and 1 ' normal of grating is incidence angle, diffraction light and light in grating monochromator
The angle of 1 ' normal of grid is the angle of diffraction.If the incidence angle of grating 1 ' is α, angle of diffraction β, the wavelength of incident light is λ, grating 1 '
Line density is N, then the equation of grating 1 ' can indicate are as follows:
Sin α-sin β=Nm λ
Wherein, m indicates diffraction time.
Based on the above principles, grating may be defined as comprising angle:The Focusing constant of grating may be defined as:
Cff=cos β/cos α.According to the variation comprising angle of grating when work, grating monochromator can be divided into two classes: fixation includes
Angle grating monochromator and change include angle grating monochromator.As its name suggests, fixed includes angle grating monochromator its light at work
Grid immobilize comprising angle, are steady state value；And become that its grating can occur comprising angle at work comprising angle grating monochromator
Variation, is no longer steady state value.
The advantages of change includes angle grating monochromator is that it can cover very wide wave-length coverage, and can pass through change
Focusing constant CffTo realize flexible operating mode, such as high energy resolution mode or higher harmonics suppression mode etc..Based on these
Advantage, this grating monochromator are widely used on global synchrotron radiation and free-electron laser device.
As shown in Fig. 2, it includes: plane mirror 2 and grating 3 that traditional change, which includes angle grating monochromator, wherein light source issues
Light need to be incident in parallel on plane mirror 2 after preceding focus mirror 1 collimates, light beam is changed by the rotation of plane mirror 2 and is existed
Incidence angle on grating 3, the diffraction light needed by the rotation selection of grating 3；But since grating 3 does not have focusing function
Can, therefore this grating monochromator is needed to increase one side postposition focus lamp 4 after grating and is focused to the monochromatic light after dispersion.
However, this can introduce additional aberration, to reduce the energy resolution of grating monochromator.
With the development of grating preparation process, the appearance of varied line-space grating changes this above-mentioned situation.Varied line-space grating
Have the function of aberration correction, self-focusing may be implemented, therefore can be omitted postposition focus lamp using the monochromator of varied line-space grating,
And also no longer need light beam incident in parallel, which simplifies the structures of grating monochromator, improve the performance of grating monochromator.
When being optimized to this monochromator based on varied line-space grating, it is necessary first under a fixed reference wavelength
Select a suitable Focusing constant Cff(Focusing constant CffSelected according to monochromator performance to be achieved, maximum value by
It is limited to grating length, the factors such as monochromator impact conditions), the modified line of varied line-space grating is then calculated away from coefficient b2、b3、b4Deng,
Thus it can determine the parameter of varied line-space grating, to realize the optimization to monochromator.However, the modified line of varied line-space grating at this time
Away from coefficient b2With optimization when select reference wavelength, Focusing constant CffAnd the object image distance of varied line-space grating has relationship, because
This, cannot arbitrarily change after these parameters determine, in other words, cannot when being worked using the monochromator of varied line-space grating
Any change Focusing constant Cff, can only there is unique Focusing constant C under a certain wavelengthff, this means that this grating is monochromatic
Device or else can flexible choice operating mode.
Summary of the invention
In order to solve the above-mentioned problems of the prior art, the present invention is intended to provide a kind of optimization side of grating monochromator
Method, so that the change based on varied line-space grating being capable of flexible choice operating mode comprising angle grating monochromator.
A kind of optimization method of grating monochromator of the present invention comprising following steps:
Step S0 provides a light source, a preceding focus mirror, a plane mirror and a varied line-space grating；
Step S1, the light for issuing the light source are incident to the plane mirror after preceding focus mirror convergence,
The varied line-space grating is reflexed to by the plane mirror again, converges to the diffraction light of generation finally by the varied line-space grating
One focus point；
Step S2 adjusts the focal length of the preceding focus mirror using the focus of the preceding focus mirror as an imaginary light source, with
Make the distance between the imaginary light source and the varied line-space grating be equal between the focus point and the varied line-space grating away from
From；
Step S3 calculates the varied line-space grating according to the focused condition of a grating equation and the varied line-space grating
Focusing factor.
Further, the step S3 includes:
The focused condition of the varied line-space grating are as follows:
Wherein, α indicates the incidence angle of the varied line-space grating, and β indicates the angle of diffraction of the varied line-space grating, r1Indicate institute
State the object distance of varied line-space grating, r2For the image distance of the varied line-space grating, R is the radius of curvature of the varied line-space grating, b2It indicates
The focusing factor of the varied line-space grating, λ indicate that the wavelength for the light that the light source issues, m indicate diffraction time, d0Indicate institute
State the line-spacing at varied line-space grating center；
Work as F20When=0, meet focused condition, in the case where R → ∞,
Wherein, α*Indicate grazing angle, β*Indicate the complementary angle of the angle of diffraction；
When the distance between the imaginary light source and the varied line-space grating are equal to the focus point and the varied line-space grating
The distance between when, r1=-r2, then:
By grating equation sin α-sin β=m λ/d0Substitution formula (3), obtains the focusing factor of the varied line-space grating
b2:
Due to use above-mentioned technical solution, by the present invention in that the object distance of varied line-space grating be virtual object away from, and
Virtual object away from distance be equal to varied line-space grating image distance so that the focusing factor of varied line-space grating can be approximated to be one only
With grating image away from related constant, and it is no longer related with Focusing constant, it does not need to carry out under a certain fixed reference wavelength excellent yet
Change.Becoming using varied line-space grating as a result, still can choose different Focusing constants comprising angle grating monochromator,
To realize flexible operating mode.
Detailed description of the invention
Fig. 1 is the light path schematic diagram of grating；
Fig. 2 is the light path schematic diagram that traditional change includes angle grating monochromator；
Fig. 3 is to be illustrated using a kind of change of optimization method of grating monochromator of the present invention comprising the optical path of angle grating monochromator
Figure.
Specific embodiment
With reference to the accompanying drawing, presently preferred embodiments of the present invention is provided, and is described in detail.
As shown in figure 3, of the invention, i.e., a kind of optimization method of grating monochromator, comprising the following steps:
Step S0 provides light source 10, preceding focus mirror 20, plane mirror 30 and varied line-space grating 40；
Step S1, the light for issuing light source 10 are incident to plane mirror 30 after the convergence of preceding focus mirror 20, then by putting down
Face mirror 30 reflexes to varied line-space grating 40, and the diffraction light of generation is converged to focus point P finally by varied line-space grating 40；
Step S2 adjusts the focal length of preceding focus mirror 20, so that empty using the focus of preposition focus lamp 20 as imaginary light source 50
The distance between light source 50 and varied line-space grating 40 are equal to the distance between focus point P and varied line-space grating 40；
Step S3 calculates the focusing factor of varied line-space grating 40 according to the focused condition of grating equation and varied line-space grating.
Specifically, for varied line-space grating 40, line-spacing be can be expressed as:
D (w)=d0(1+b2w+b3w2+b4w3+…)
Wherein, d0Indicate that the line-spacing (given value) at 40 center of varied line-space grating, w indicate 40 dispersion direction of varied line-space grating
Coordinate, b2、b3、b4Indicate the modified line of varied line-space grating 40 away from coefficient (here, the influence of higher order aberratons is negligible)；
The focused condition of varied line-space grating 40 is as follows:
Wherein, α indicates the incidence angle of varied line-space grating 40, and β indicates the angle of diffraction of varied line-space grating 40, r1Indicate modified line away from
The object distance of grating 40, r2For the image distance of varied line-space grating 40, R is the radius of curvature of varied line-space grating 40, and λ indicates that light source 10 issues
Light wavelength, m indicate diffraction time；
Work as F20When=0, meet focused condition, for plane grating (R → ∞),
Wherein, α*Indicate grazing angle, β*Indicate the complementary angle of the angle of diffraction；
When the distance between imaginary light source 50 and varied line-space grating 40 are equal to the distance between focus point P and varied line-space grating 40
When, r1=-r2, at this time:
Due to the grazing angle α in actual grating monochromator*With the complementary angle β of the angle of diffraction*All very littles, therefore above-mentioned derived
It is used in journeyApproximation.
By grating equation sin α-sin β=m λ/d0Above formula is substituted into, the focusing factor b of varied line-space grating 40 can be obtained2:
It can thus be seen that when the object distance of varied line-space grating 40 is virtual object away from and virtual object is away from-r1Distance be equal to modified line away from
The image distance r of grating 402When, the focusing factor b of varied line-space grating 402It can be approximated to be one only and grating image be away from related constant,
No longer with Focusing constant CffIt is related, it does not need to optimize under a certain fixed reference wavelength yet.Therefore, in optimization of the invention
Under method, the Focusing constant C that can selectffRange only limited by grating length and monochromator impact conditions, with other factors
It is unrelated.In addition, in the present invention, plane mirror includes angle grating monochromator phase with the operating mode of varied line-space grating and common become
Together, that is, by plane mirror rotation change grating include angle, pass through grating rotation realize energy scanning.
Above-described, only presently preferred embodiments of the present invention, the range being not intended to limit the invention, of the invention is upper
Stating embodiment can also make a variety of changes.Letter made by all claims applied according to the present invention and description
Single, equivalent changes and modifications, fall within the claims of the invention patent.The not detailed description of the present invention is normal
Advise technology contents.
Claims (2)
1. a kind of optimization method of grating monochromator, which is characterized in that the described method comprises the following steps:
Step S0 provides a light source, a preceding focus mirror, a plane mirror and a varied line-space grating；
Step S1, the light for issuing the light source are incident to the plane mirror after preceding focus mirror convergence, then by
The plane mirror reflexes to the varied line-space grating, and the diffraction light of generation is converged to one finally by the varied line-space grating and is gathered
Focus；
Step S2 adjusts the focal length of the preceding focus mirror using the focus of the preceding focus mirror as an imaginary light source, so that institute
The distance between imaginary light source and the varied line-space grating are stated equal to the distance between the focus point and the varied line-space grating；
Step S3 calculates the focusing of the varied line-space grating according to the focused condition of a grating equation and the varied line-space grating
Coefficient.
2. the optimization method of grating monochromator according to claim 1, which is characterized in that the step S3 includes:
The focused condition of the varied line-space grating are as follows:
Wherein, α indicates the incidence angle of the varied line-space grating, and β indicates the angle of diffraction of the varied line-space grating, r1Indicate the change
The object distance of line-spacing grating, r2For the image distance of the varied line-space grating, R is the radius of curvature of the varied line-space grating, b2Described in expression
The focusing factor of varied line-space grating, λ indicate that the wavelength for the light that the light source issues, m indicate diffraction time, d0Indicate the change
The line-spacing of line-spacing raster center；
Work as F20When=0, meet focused condition, in the case where R → ∞,
Wherein, α*Indicate grazing angle, β*Indicate the complementary angle of the angle of diffraction；
When the distance between the imaginary light source and the varied line-space grating are equal between the focus point and the varied line-space grating
Apart from when, r1=-r2, then:
By grating equation sin α-sin β=m λ/d0Substitution formula (3) obtains the focusing factor b of the varied line-space grating2:
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| US4492466A (en) * | 1982-06-28 | 1985-01-08 | At&T Bell Laboratories | Cylindrical grating monochromator for synchrotron radiation |
| US4991934A (en) * | 1989-08-10 | 1991-02-12 | Hettrick Michael C | Varied space diffraction grating and in-focus monochromator |
| CN1117997C (en) * | 1997-03-14 | 2003-08-13 | 中国科学院长春光学精密机械研究所 | Concave raster monochromator for eliminating astigmatism and incident light |
| CN105300518B (en) * | 2015-11-18 | 2017-10-20 | 中国工程物理研究院激光聚变研究中心 | The method for realizing length scanning comprising angle plane grating monochromator more than glancing incidence |
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