1. Exploring the limits of hybrid pixel detectors with MÖNCH
R.Dinapoli*,1,A.Bergamaschi1,M.Brückner1,S.Cartier1,2,D.Greiffenberg1,J.Jungmann-Smith1,D.Mezza1,A.Mozzanica1,M.Ramilli1,B.Schmitt1,X.Shi1,G.Tinti1
1-Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
2-Institut for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland
* Corresponding author;
High resolution using charge sharing
MOTIVATION: Understand the limits of hybrid pixel detectors (pitch,energy & position resolution…) for possible applications in:
The working principle
Hi-res X-ray imaging, spectrometers, X-ray tomography, low energy X-ray detection, resonant and nonresonant inelastic X-ray scattering
Radiation conversion
Charge collection after drift and diffusion
Low resolution
analog image
High resolution
digital image
If the photon flux is low enough with respect to the frame rate, impinging photons can be “singled out”. In this case the analog information delivered by all pixels sharing the charge generated by the impinging photon can be interpolated to get a resolution that is much better than the pixel pitch.
WHY CHARGE INTEGRATION?
Higher incoming photon flux (both XFELS and synchrotrons)
Charge sharing can improve resolution (“low flux” )
Energy information (“low flux” ) and lower energies (~keV) accessible
Challenges: sensitive to leakage current, bump-bonding at fine pitch, complex calibration, huge data throughput/amount
Interpolation at work with Gotthard
Charge integrating hybrid pixel detector with 25 x 25 μm² pixel size
Gotthard is a strip detector (20 μm pitch)
The sample (kidney stone) is scanned in front of the strips
A 2 μm slit defines the vertical opening
12 keV beam
20 μm
pitch
0.5 μm
bins
MÖNCH 0.3 prototype
MÖNCH0.3 readout chip (1x1cm2) bump bonded to 4 small sensors (4x4mm2)
NO INTERPOLATION
WITH INTERPOLATION *
MÖNCH with a nanoscope
Magnification: ~80x
Siemens star images
Sample under test: gold bookmark
*CDS: correlated double sampling
Y pixel #
Counts
Mönch
(25μm pixel, with 5x image stitching and charge interpolation, not cooled)
Targeting Hi-res low flux applications
400x400 pixels of 25x25μm²
Selectable preamp gain (lowG, highG)
Selectable CDS* gain (1-2-4)
High testability (e.g. CDS* can be bypassed)
Preliminary results very similar to MÖNCH0.2
~3 μm (x80)
X pixel #
Direct X-ray tube beam
Single photon image
Photonic Science CCD
(4μm pixel, with 2x image stitching, cooled)
Performance summary
~3 μm (x80)
Pixel pitch [μm] 25
World smallest pitch for hybrid pixel detectors!
Bump-bonding yield (on 4x4mm2)
99.99%
Stampanoni et al.,Physical Rev. B 81,140105(R)(2010)
CHIP
SETTINGS
NOISE (e-rms)
World lowest noise for hybrid pixel detectors!
MÖNCH spectral performance
Preamp HighGain,CDS Gain=4
Preamp LowGain,CDS Gain=4
Preamp LowGain,CDS Gain=1 31 50
214
Hybrid pixel detectors become competitive with monolitic active pixel detectors and CCDs
Monochromatic beam at 20 keV
The fluorescence lines come from the detector itself
No spectral information from single pixel with no cuts
Clusterization increases the noise
Monochromatic beam at 20 keV
The fluorescence lines come from the detector itself
No spectral information from single pixel with no cuts
Clusterization increases the noise
Main beam 20 keV
Si escape
18.2 keV In
3.3 keV Ti
(4.5 keV) Cu
(8.0 keV) Au
9.7 keV
Rb?
(13.3 keV) Ni
7.4 keV Br
(11.9 keV)
Spectral keV [ev,FWHM]
<450
Spatial resolution with interp. [μm] ~2
Compton Edge
1.45 keV
Single chip with 800x1200 pixels (1Mpixel)
Module with 4x3 cm2 and 2Mpixel
8 kHz frame rate
Low energy (~400eV ) detection development
High dynamic range version
(implementing dynamic gain switching)
Future
work