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Vibrations effect on 1nm focussingPowerPoint Presentation

Vibrations effect on 1nm focussing

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## PowerPoint Slideshow about 'Vibrations effect on 1nm focussing' - lucille

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Presentation Transcript

Outline

- Background and important optics metrics
- Simple optics layout
- How we see the source; some stability reqs

- More complex layout (Waveguide)
- Can we position with 1nm beam sufficient accuracy?

Towards 1nm X-ray Optics

Figure courtesy of C. Jacobsen

- Future
- It can be done: There is no physical reason we cannot get to 1nm
- However, it will take resources and a targeted effort.

Basic Issues

- Metrics
- Numerical Aperture and resolution
- Depth of field
- Aperture
- Efficiency
- Chromaticity
- Modulation Transfer Function

Resolution of 1nm at l=1A requires NA < 0.1

If resolution is 1nm

=> then DOF =27nm

Simplest configuration

Mono deleted for clarity

Order of magnitudes for stability

~ 10 microns(v) x 40 microns (h)

Slit down in the horizontal to get 10 by 10.

Demagnify by 104 to get 1nm.

For a source to lens of 50m, this implies 5mm focal length.

If you include details, we expect focal lengths of between 1 to 5mm

(We would really like to get out to 100mm, but this is probably too tough, Aperture)

Main point: Easy to integrate lens and sample stage monolithically.

Stability of e-beam is crucial for effective source size

- Position of electron beam translates directly into stability of image.
- Typical tolerance is 10% if e-beam size; 0.3microns?.
- Angular stability?

L

Angular uncertainty ~ (0.3 microns/ 3 meter) ~ 1e-7 radians

How the stability comes in

A: Size

If sigma stability is 10%, then stability adds negligibly to size

B: Intensity

If you are measuring fluorescence intensity, and we assume a gaussian profile

And we want to keep signal intensities within 1%:

1% criterion

5% criterian

Off-axis Abberrations

Using zone plate as a guide: will have to revisit this in optics R&D

Aberration angular field of view , , is given by

Using N=1e5, F=0.1, =0.1nm

1e-3 radians which is much bigger than everything else so not a problem.

Main advantages of waveguide geometry

- More stable, but more optics so more loss.( 4.7% experimental state of the art, but not optimal)
- Wave guide provides new source size (50nm)
- Allows better working distances
- All fluctuations in position,angle translate to intensity fluctuations
- Attempt to do normalization, not invented yet for small WD.

Can we position with 1nm accuracy?

It is difficult, but possible.

Worry about materials, and temperature control.

- Time scale : 1second /scan.
- If normalization invented then stability to 1 second ok
- If not ~2 hour full scan stability.

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