1 BROOKHAVEN SCIENCE ASSOCIATES National Synchrotron Light Source II Semi-permanent Setup at the NSLS for 0.1 meV Optics R&D Zhong

1 BROOKHAVEN SCIENCE ASSOCIATES

National Synchrotron Light Source II

Semi-permanent Setup at the NSLS for 0.1 meV Optics R&D

Zhong Zhong


Acknowledgement

Collaborators:

Lonny Berman, Yong Cai, John Hill, Xianrong Huang, Yuri Shvyd’ko, and Peter Siddons

Technical help:

Scott Coburn, Shu Cheung, Richard Greene, Anthony Lenhard, Zhijian Yin, and Hui Zhong

Expert advice:

Alfred Baron, Michael Hart, Steve Hulbert, Chi-Chang Kao, and Francesco Sette, and many others


Why Bother?

• A semi-permanent setup is attractive for serious experimentalists • 0.1 meV R&D will involve lots of trial-and-error … a local home base is preferred• Access may entice experts (such as Shvyd’ko, Alp, Baron) to come to BNL more often• A playground may entice local experts (Siddons, Berman, Kao to name a few) to roll up their sleeves, and play• Develops local expertise: one can only learn by doing, and making mistakes• Readily available x-ray is a NSLS-advantage, a luxury for APS, ESRF and Spring-8


The Approach

• 0th-order approximation: Repeat the Shvyd’ko experiment (0.7 meV target) • Get to the end results as soon as we can, then work backwards • Small crystals will be used• It may be advantageous to have a CCD detector to watch the beam from day-one. The detector helps in understanding what really goes on in the crystals• Study and refine: surface quality? Crystal d-spacing uniformity? Crystal strain/mounting? Temperature uniformity and stability? Role of dispersion compensation? … The list goes on, but the point is to get our hands dirty and start learning.

We hope to migrate/creep/leap: 0.7 meV -> 0.3 meV -> 0.1 meV


Feasibility

• Involves direct beam, flux should not be a problem.• The angles involved are large (a few to 100 micro-radians) -> Vibration should not be a problem. • The divergence Shvyd’ko used is 15 micro-radians. We can do that at the NSLS with 200-micron slit at 15 m. • 200 micron in-plane -> 4 mm footprint on C, W crystals (b=20), and 4/tan(1.5)=120 mm on D crystal (1.5 deg offcut). Thus small crystals are sufficient. • Temperature stability is important but we can start with ambient and see what other problems we have.


Haves and Have-notsWhat we have:• Access to X12A: NSLS R&D beamline on a bending magnet port• Control system, 111 channel cut monochromator• A CCD detector borrowed from X15A (10 micron pixel size, 30 x 40 mm2)

What we made: • Two asymmetric (88.5 deg) 008 D crystals• Two 220 CW crystals, with fancy 200-500 micron thin wafer… Enough to keep us going for a while

What we (eventually) need• Temperature controlled crystal environment• Scanning diagnostic aperture in beam• A dedicated high resolution detector


CW (Collimator and Wavelength Selector) Crystal

APS Design

C

W


NSLSII CW Channel-Cut Design

1

2-20

1

top-view

side-view

Quantity: 2, cut 1.5x1x2, polish top, cut channels, slice into 2 crystals

004

1.5

3/4

-2-20

200-500 microns

3/83/8

lap

1/8

400

040

26 d

eg

19 d

eg

Weak linkC

W

C W


CW Tilt and W Tweak

2 picomotors

220

1.7 deg

tth=41.4 deg, th=20.7

leaf spring, ½ mm thick

Newport tilt #39http://www.newport.com/store/genproduct.aspx?id=144557&lang=1033&Section=Graphics

9.1315 keV

Tweak

Tilt

Epoxy Ball-bearing

C

W


D Crystal (Dispersion Element)

APS Design


NSLSII D Crystal Design4

3/8

400400, 1.5 degrees offcut

004

1 top-view

side-view

end-view

3/8

1

1/8

Top surface polished

Quantity: 2, cut 4x2x3/8, polish top, slice into 2 crystals

040

004 lattice planes

1/4

T shape to minimize weight and maximize stiffness


Cutting from a 5-inch 004 boule4

3/8

400400, 1.5 degrees offcut

004

side-view 004 lattice planes

Radial cutting to minimize longitudinal d-spacing variation during crystal growth


Rough Cutting at the BNL Central Shop

Abrasive Water Jet


Alignment at the NSLS


Aligned


CW CrystalNSLSII CW Crystal

Before etching

After etching

Two blanks for future

0.4 mm

1 mm


Glued


Assembled in Beam

After etching

Two blanks for future

0.5 mm

1 mm

TiltTweak


C Crystal Rocking Curve

• Data is for 0.3x12 mm and 0.3x1 mm beams • Width (FWHM) is about 120 micro-radians, in agreement with expectations of 106 micro-radians• Monochromator energy was changed, and dE/E=dth/th was used to calibrate tilt motor

C

W


Beam Off CW

1 mm

Tuned

Detuned

By-passing W

Through W

Imperfections mostly due to coating on Be window

C

W

Image plate

50 micron resolution

Half-tuned

¼ -tuned

12-mm wide


Rocking Curves Through W

W Rocking curve

tuned

½ detuned

C rocking curve, through tuned W


W Transmissivity

• Experiment w/ 0.2x1 mm beam • Simulation assumes 0.35 mm thick W• Excellent qualitative agreement• Peak Transmissivity is about 40%, in agreement with simulation of about 45%. • Measurement is consistent with 80% W intrinsic transmissivity.


NSLSII D crystal Glued

RTV

Epoxy

Leveling pin, removed later

Spare


In Beam


Poor-person’s Temp. Stabilization

• Lights were turned off, and hutch door was closed overnight• Everything else stayed the same

Before

After

20 min. scan time


What Next?

• Further characterization of D crystal• Verify the angular acceptance by mis-aligning the CDW assembly.• Design and build a second set of CDW assembly• CDW will be scanned against the second set to determine the energy resolution.• Depending on the resolution achieved, 0.3 or 0.1 meV version will be designed and tested.


Two Legs


Summary

• NSLS bending magnet is suitable for 0.1 meV R&D.• CW Crystal performs as expected. Two such crystals in hand will be used for further development• Vibration control is appropriate (keeping it simple and stiff, minimize adjustments/weak links).• Free-standing thin-wafer concept provides good strain-relief for W crystal • Leaf-spring/weak-link mechanism provides fine adjustment


C Dumond Diagram


C Rocking Curve Simulation

111 pre-mono

220 intrinsic

Convolved


CW Dumond Diagram

Beam through W

< 5 micro-radians


Detector Sheilding


CW Tilt and W Tweak

Documents

1 BROOKHAVEN SCIENCE ASSOCIATES National Synchrotron Light Source II Semi-permanent Setup at the NSLS for 0.1 meV Optics R&D Zhong