X-Ray Imaging (0.1 arcsec at 6.7 keV) and HXR Polarimetry (10 – 50 keV)
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X-Ray Imaging (0.1 arcsec at 6.7 keV) and HXR Polarimetry (10 – 50 keV) Brian Dennis NASA/GSFC
description
X-Ray Imaging (0.1 arcsec at 6.7 keV) and HXR Polarimetry (10 – 50 keV). Brian Dennis NASA/GSFC. Focusing X-rays. Zone Plate Phase Zone Plate Phase Fresnel Lens e < 10.1% e < 40.4% e< 100%. G.K.Skinner. Phase Fresnel Lens. - PowerPoint PPT Presentation
Transcript of X-Ray Imaging (0.1 arcsec at 6.7 keV) and HXR Polarimetry (10 – 50 keV)
X-Ray Imaging (0.1 arcsec at 6.7 keV)
andHXR Polarimetry
(10 – 50 keV)
Brian DennisNASA/GSFC
G.K.Skinner
Zone Plate Phase Zone Plate Phase Fresnel Lens
10.1% 40.4% 100%
Focusing X-rays
Phase Fresnel Lens
Focal length is a function of photon energy
DEM = 0.36 1049 (T/2keV)-0.72 cm-3 keV-1
Fe abundance = 2.0 x photosphericCa – 4.7 x photosphericS – 0.4 x coronalSi – 0.2 x coronal
1 2 4 6 8
GOES M2.8 Flare
Phase Fresnel Lens – a possible design concept
50-100 m boomor
formation flying
CCD array(s)eg 100 mm
Fresnel lens(es)or PZPs eg 1-2 cm dia
CCD arrayeg 100 mm
Fresnel lensor PZPs eg 1-2 cm dia
Angular resolution ~ 0.1 arc secField of view ~ few arc minsEffective area ~ 1 cm2 (in a line)
Hard X-ray Imaging Polarimetry• Energy range ~2 – ~50 keV
– Complements Compton scattering polarimetry >50 keV
• Photoelectron track imaging– Time Projection Chamber (TPC)
• Goddard development– Gas Electron Multiplier (GEM) with strip readout– 70%/30% mixture of argon and dimethyl ether (DME)– 2-D positional information – strip number & time– Modulation collimators for Fourier-transform imaging– Leverage off GEMS SMEX for astrophysics
• Italians developing direct 2-D capability– Focusing optics for direct imaging polarimetry
Time Projection ChamberPolarimeter
Effective Area vs. Energy
Time Projection Chamber
Imaging Polarimeter Concept
100 cm
Bi-g
rid
R
MC
Fill
/p
um
p
Drift electrode
10 cm
30 cm
GEM
Readout anodeX-r
ay
win
do
w
Inci
de
nt
X-r
ays
100 cm
Bi-g
rid
R
MC
Fill
/p
um
p
Drift electrode
10 cm
30 cm
GEM
Readout anodeX-r
ay
win
do
w
Inci
de
nt
X-r
ays
The End
Lens Parametersto focus 6.7 keV X-rays
Lens material Silicon
Focal length 90 m
Aperture diameter 2 cm
Finest pitch 1.7 μm
Profile height 8.4 μm
Base thickness <5 μm
X-ray Imaging RequirementsUnits Notes
Lens – detector requirements
Lens –detector separation 80-100 m
Pixel size for 0.1” resolution 25 microns X-ray CCD array or X-ray pixel detector
Field of view 3 arc min Assumes 10 cm detector to cover a typical active region - could be larger.
Station keeping requirements
Control - transverse 2 cm Requirement is to keep image on detector – could move detector or lens independently.
Control – axial 25 cm Not critical; 25 cm is equivalent to 20 eV energy shift
Knowledge - transverse <0.1 arc sec Alignment of line joining lens and detector must be known relative to the Sun direction to an accuracy better than the desired resolution, equivalent to 25 microns at 100 m
Knowledge – axial 10 cm Not critical
Attitude requirement 10 arc min Tilt and tip of lens and detector are not critical
