Post on 20-Dec-2015
transcript
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
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)
How far away is the detector?
Divide the angular spread into 100 elements,
2Δθ / 100 = 1.0x10-4
For a 2 mm beam 20m
Mosaic crystal to do list
• Crystal uniformity ?
• Ultimate resolution ?
• Experimental geometry (20 m crystal to detector distance)