Possible spectrometers

• Bent Bragg (after P. Siddons-NSLS)

• Mosaic crystal

• Bent Laue– Zhong Zhong-NSLS

• X-ray Grating– P. Heimann-ALS, S. Hulbert-NSLS

2 mm

Si (422)

surface normal

R=3.9 m

76 mm

Strip detector(200 strips)

Bent Bragg Spectrometer

Cu foil

SPPS Cu near edge - Si (422) dispersive analyzerSPPS Cu near edge - Si (422) dispersive analyzer

Cu near edge structure (for reference)Cu near edge structure (for reference)

2 mm

Si (422)

surface normal

R=3.9 m

76 mm

Strip detector(200 strips)

Bent Bragg Spectrometer

cotE

E

02.0E

E0195.0

Adjust crystal asymmetry so that the Si (422) reflection width is Δθ/200 Corresponding to 200 resolution elements

radSi 100)422(

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 100 200 300 400 500 600

Series1

Asymmetric Si (422) FWHM: 100 microrad 8000eV

Angle (microradians)

100 microrad

Ref

lect

ivit

y

For reference θB=45;E=7908 eVΔE/E = 1 x 10-4

0.00E+00

1.00E+12

2.00E+12

3.00E+12

4.00E+12

5.00E+12

6.00E+12

7.75 7.8 7.85 7.9 7.95 8 8.05 8.1 8.15 8.2

Series1

Series2

Series3

On axis

+0.5 mm

+1.0 mm

Photon energy (keV)

Und-pinhole distance 200 m Pinhole 2.0 x 0.02 mm2

Bent Bragg to do list

• Simulation considering position dependent spectrum

• Role of jitter

• Test K sensitivity with simulated data (including noise)

2 x Mosaic spread2ω

180-2θ

Mosaic crystal spectrometer

cotE

E

For PG (002) Δθ=0.3 deg

02.0E

E

How far away is the detector?

Divide the angular spread into 100 elements,

2Δθ / 100 = 1.0x10-4

For a 2 mm beam 20m

Andreas Freund, Anneli Munkholm, Sean Brennan,SPIE, 2856,68 (1996)

10 keV

24 keV

Mosaic crystal to do list

• Crystal uniformity ?

• Ultimate resolution ?

• Experimental geometry (20 m crystal to detector distance)

Grating spectrometer

Phil Heimann

RSI, 76, 063102 (2005)