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Introduction
Cornell SLAC Pixel Array Detector (CSPAD) is an imaging X-ray detector made of silicon sensors (2x1) covering about 20x20cm² surface, as shown in the plot:
Pixel coordinates in 2x1 sensor chip are known with sub-micrometer precision. Construction of the detector allows significant freedom in relative positions of 2x1 sensors. To get precise pixel positions in the detector the 2x1 sensor coordinates needs to be calibrated. In this note we describe geometry of the CSPAD detector, optical and quad alignment procedure, parameters, and software providing access to precise geometry information.
2x1 Sensor Geometry
The 2x1 sensor geometry was tested with microscopic measurement. Two slides from Chris Kenney's presentation shows the pixel sizes:
The same slides in PDF format.
Important 2x1 features:
- Number of rows x columns = 185 x 388. (In DAQ notation of rows and columns is interchanged...)
- Most of pixels have size 109.92 x 109.92 um².
- Gap between two ASICS is covered by the two rows of elongated pixels with size 109.92 x 274.8 um².
- Two versions of sensors have different dimensions between corners, so it is reasonable to define pixel coordinates w.r.t. the sensor center.
Shield to sensor distance
Chart of CXI Camera1 provided by Serge Guillet on 2017-06-12.
Optical measurement
Optical measurement is conducted by Gabriel Blaj. Detector or its quad is installed on microscope table and 3-d coordinates of all 2x1 sensor corners are measured with precision about 8um (RMS) in x-y plane. All corners in the measurement are numerated in arbitrary order. It is expected that numeration order should be the same for different measurements. This procedure depends on CSPAD construction;
- For CSPAD with movable quads (i.e. for CXI) optical measurement is done separately for each quad. The numeration of corners is shown in the plot:
The same plots in PDF format: CSPAD quad metrology and CSPAD pixel layout in quads.
For each quad measurement is started from the point #1 which in assembled detector is closest to the beam. The 1-st point (x,y,z) coordinates are re-set to (0,0,0) in the beginning of measurements. At the end, it is checked that the 1-st point coordinates are reproduced within precision of measurement.
Note |
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The order of points in optical measurement does not coincide with numeration of 2x1 in DAQ, as shown in the plot (and in PDF file): |
- For CSPAD with fixed quad geometry (i.e. for XPP) optical measurement is done for entire detector. The numeration of corners in this case is shown in the file XPPMetrologyAnnotated.pdf and in the plot:
The 1-st corner of the 3-rd quad (x,y,z) coordinates are re-set to (0,0,0) in the beginning of measurements. At the end, it is checked that the 1-st point coordinates are reproduced within precision of measurement.
Corner coordinates are measured in micrometers (um) and are saved in the xlsx format table, also containing numeration of quads and points. Then, xlsx format table is converted to the text file format in order to use it in python script.
Example of tables for CXI:
Example of tables for XPP:
- Metrology in XLSX
- Metrology in TXT Python script converts this table to the table with standard numeration of points in quads:
- Metrology in standard TXT
Then, text table with "standard" numeration of points in quads is feed to the python script which provides quality check of optical measurement and evaluates the alignment parameters for quads. In the beginning, this script changes the numeration of points adopted in optical measurement to numeration of 2x1 used in DAQ. Further, all calibration parameters are associated with numeration of 2x1 sensors and quads in DAQ.
Quality Check Procedure
For quality check of optical measurement we calculate
S1 - 1st short side length of 2x1
S2 - 2nd short side length of 2x1
L1 - 1st long side length of 2x1
L2 - 2nd long side length of 2x1
D1 - 1st diagonal of 2x1 between corners 1 and 3
D2 - 2nd diagonal of 2x1 between corners 2 and 4
dS and dL are the deviations of the 1st and 2nd corner along the short and long sides, respectively. The sign of all dS are chosen in order to provide correct sign for the tilt angle (the same direction for all 2x1 sensors).
<dS/L> - the tilt angle of 2x1 averaged over two sides in radians.
angle(deg) - the same angle in degrees.
dD = D1 - D2
d(dS) = dS1 - dS2
d(dL) = dL1 - dL2
dz3(um) - signed distance from 2x1 sensor plane and corner 3, where the 2x1 sensor plane contains the corner points p1, p2, and p4. This plane is defined by the vectors v21=p2-p1, v41=p4-p1, and their orthogonal vector
Code Block |
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vort = [v21 x v41].
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Scalar product with normalization defines the distance from point 3 to the 2x1 plane containing 3 other points:
Code Block |
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dz3 = (v31 * vort) / |vort|.
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Quality check parameters expected for perfect geometry:
S1=S2, L1=L2 - the 2x1 sides should have equal length and width,
D1=D2 - the 2x1 diagonals should be equal,
dS1 = dS2 ? (388/185)*dL1 = (388/185)*dL2 - tilt angle should provide consistent deviation for all corners,
dD=0, d(dS)=0, and d(dL)=0 - within precision of measurement.
dz3(um) = 0
Everything, excluding <dS/L> and angle(deg), are in micrometers.
Example of the table with quality check results:
Code Block |
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pair: S1 S2 dS1 dS2 L1 L2 dL1 dL2 <dS/L> angle(deg) D1 D2 dD d(dS) d(dL) dz3(um)
Quad 0
pair: 0 20891 20913 200 222 43539 43541 -102 -100 0.00485 0.27766 48298 48297 1 -22 -2 2.981
pair: 1 20910 20894 293 277 43540 43535 -127 -132 0.00655 0.37506 48302 48289 13 16 5 -23.986
pair: 2 20890 20906 99 83 43536 43536 42 42 0.00209 0.11976 48290 48293 -3 16 0 -3.034
pair: 3 20897 20895 131 133 43545 43543 65 63 0.00303 0.17369 48299 48297 2 -2 2 6.003
pair: 4 20911 20896 -30 -45 43549 43547 17 15 -0.00086 -0.04934 48303 48306 -3 15 2 -5.994
pair: 5 20901 20898 10 7 43540 43544 -8 -4 0.00020 0.01119 48296 48299 -3 3 -4 9.993
pair: 6 20904 20903 104 105 43536 43540 55 59 0.00240 0.13752 48302 48290 12 -1 -4 52.002
pair: 7 20901 20901 -7 -7 43545 43543 -3 -5 -0.00016 -0.00921 48299 48301 -2 0 2 14.001
Quad 1
pair: 0 20913 20914 -343 -342 43540 43550 165 175 -0.00787 -0.45066 48313 48303 10 -1 -10 -24.002
pair: 1 20898 20901 -145 -142 43548 43551 62 65 -0.00330 -0.18880 48300 48309 -9 -3 -3 -23.005
pair: 2 20895 20903 -151 -159 43535 43532 -74 -77 -0.00356 -0.20400 48289 48291 -2 8 3 -17.995
pair: 3 20872 20909 -235 -272 43341 43354 -37 -24 -0.00585 -0.33507 48201 48036 165 37 -13 -13.010
pair: 4 20940 20904 -455 -491 43527 43554 214 241 -0.01086 -0.62242 48309 48309 0 36 -27 1.101
pair: 5 20910 20903 -302 -309 43546 43546 145 145 -0.00702 -0.40196 48304 48307 -3 7 0 6.016
pair: 6 20901 20919 -421 -439 43529 43539 -213 -203 -0.00988 -0.56593 48296 48298 -2 18 -10 -8.026
pair: 7 20907 20907 -452 -452 43548 43539 -201 -210 -0.01038 -0.59475 48315 48294 21 |
Optical measurement
Optical measurement is maintained by Chris Kenney. Detector or its quad is installed on microscope table and 3-d coordinates of all 2x1 sensor corners are measured with precision about 8um (RMS) in x-y plane. All corners in the measurement are numerated in arbitrary order. It is expected that numeration order should be the same for different measurements. This procedure depends on CSPAD construction;
- For CSPAD with moving quads (i.e. for CXI) optical measurement is done separately for each quad. The numeration of corners is shown in the plot:
For each quad measurement is started from the point #1 which in assembled detector is closest to the beam. The 1-st point (x,y,z) coordinates are re-set to (0,0,0) in the beginning of measurements. At the end, it is checked that the 1-st point coordinates are reproduced within precision of measurement. - For CSPAD with fixed quad geometry (i.e. for XPP) optical measurement is done for entire detector. The numeration of corners in this case is shown in the plot:
The 1-st corner of the 3-rd quad (x,y,z) coordinates are re-set to (0,0,0) in the beginning of measurements. At the end, it is checked that the 1-st point coordinates are reproduced within precision of measurement.
Corner coordinates are measured in micrometers (um) and are saved in the xlsx format table, also containing numeration of quads and points. Then, xlsx format table is converted to the text format in order to feed the python script for quality check and getting calibration parameters for 2x1 center coordinates and tilt angles.
Example of tables for CXI:
Example of tables for XPP:
QC procedure
For quality chech we calculate
S1 - 1st short side length of 2x1
S2 - 2nd short side length of 2x1
L1 - 1st long side length of 2x1
L2 - 2nd long side length of 2x1
D1 - 1st diagonal of 2x1 between corners 1 and 3
D2 - 2nd diagonal of 2x1 between corners 2 and 4
dS and dL are the deviations of the 1st and 2nd corner along the short and long sides, respectively. The sign of all dS are chosen in order to provide correct sign for the tilt angle (the same direction for all 2x1 sensors).
<dS/L> - the tilt angle of 2x1 averaged over two sides in radians.
angle(deg) - the same angle in degrees.
dD = D1 - D2
d(dS) = dS1 - dS2
d(dL) = dL1 - dL2
Quality check parameters for the perfect measurement:
S1=S2, L1=L2 - the 2x1 sides should have equal length and width,
D1=D2 - the 2x1 diagonals should be equal,
dS1 = dS2 = 2*dL1 =2*dL2 - tilt angle should provide consistent deviation for all corners,
dD=0, d(dS)=0, and d(dL)=0 - within precision of measurement.
Everything, excluding <dS/L> and angle(deg), are in micrometers.
Example of the table:
Code Block |
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pair: S1 S2 dS1 dS2 L1 L2 dL1 dL2 <dS/L> angle(deg) D1 D2 dD d(dS) d(dL) Quad 0 pair: 0 20891 20913 200 222 43539 43541 -102 -100 0.00485 0.27766 48298 48297 1 -22 -2 pair: 1 20910 20894 293 277 43540 43535 -127 -132 0.00655 0.37506 48302 48289 13 16 5 pair: 2 20890 20906 99 83 43536 43536 42 42 0.00209 0.11976 48290 48293 -3 16 0 pair: 3 20897 20895 131 133 43545 43543 65 63 0.00303 0.17369 48299 48297 2 -2 2 pair: 4 20911 20896 -30 -45 43549 43547 17 15 -0.00086 -0.04934 48303 48306 -3 15 2 pair: 5 20901 20898 10 7 43540 43544 -8 -4 0.00020 0.01119 48296 48299 -3 3 -4 pair: 6 20904 20903 104 105 43536 43540 55 59 0.00240 0.13752 48302 48290 12 -1 -4 pair: 7 20901 20901 -7 -7 43545 43543 -3 -5 -0.00016 -0.00921 48299 48301 -2 0 2 Quad 1 pair: 0 20913 20914 -343 -342 43540 43550 165 175 -0.00787 -0.45066 48313 48303 10 -1 -10 pair: 1 20898 20901 -145 -142 43548 43551 62 65 -0.00330 -0.18880 48300 48309 -9 -3 -3 pair: 2 20895 20903 -151 -159 43535 43532 -74 -77 -0.00356 -0.20400 48289 48291 -2 8 3 pair: 3 20872 20909 -35 -72 43541 43554 -37 -24 -0.00123 -0.07039 48294 48303 -9 37 -13 pair: 4 20940 20904 -455 -491 43527 43554 214 241 -0.01086 -0.62242 48309 48309 0 36 -27 pair: 5 20910 20903 -302 -309 43546 43546 145 145 -0.00702 -0.40196 48304 48307 -3 7 0 pair: 6 20901 20919 -421 -439 43529 43539 -213 -203 -0.00988 -0.56593 48296 48298 -2 18 -10 pair: 7 20907 20907 -452 -452 43548 43539 -201 -210 -0.01038 -0.59475 48315 48294 21 0 9 Quad 2 pair: 0 20914 20914 -25 -25 43536 43540 10 14 -0.00057 -0.03290 48300 48300 0 09 -4-8.982 Quad 2 pair: 10 2090120914 2089720914 -25 7 -25 3 43536 43540 43546 43536 10 -1 14 -110.00057 -0.0001103290 48300 48300 0.00658 48293 483000 -74 -11.013 pair: 1 4 20901 20897 10 pair: 2 20899 7 20903 -256 3 -260 43546 43533 43536 43539 -1271 -12111 -0.0059300011 -0.3395400658 48293 4829448300 -17 4 -610 4.036 pair: 32 2091220899 2090420903 -210256 -202260 4354043533 4354743539 -106127 -99121 -0.0047300593 -0.2710633954 4830048293 4830648294 -61 4 -8 6 -71.023 pair: 43 2091020912 2090320904 -543210 -550202 4353543540 4353643547 -106 261 -99 262 -0.0125500473 -0.71923.27106 48300 48306 48298 48299-6 -18 -7 -124.004 pair: 54 2090420910 2090520903 -241543 -240550 4353843535 4354443536 111261 117262 -0.0055201255 -0.3164771923 48298 4830148299 -31 -17 -6 pair:1 6 20903 209020.004 pair: 5 20904 2120905 22-241 -240 43539 43543 43538 43544 8 111 12 117 -0.0004900552 -0.0282931647 48298 4829848301 -3 0 -1 -46 -6.024 pair: 76 2090220903 2090320902 21 82 22 81 43539 43546 43543 43547 358 3612 0.0018700049 0.1072302829 4830048298 4830648298 -6 0 -1 -4 -1 Quad 38.999 pair: 07 20902 2089820903 -82 -86 81 43546 43536 43547 43543 35 30 36 37 -0.0019300187 -0.1105410723 4828948300 4830248306 -136 41 -71 9.995 Quad 3 pair: 0 120902 2090020898 20904 -82 79 -86 8343536 43543 43548 43541 30 -35 37 -420.00193 -0.0018611054 48289 0.10658 48302 48301 48301-13 04 -47 71.994 pair: 1 2 20900 2091220904 20894 79 181 83 199 43548 43536 43541 43535 -35 97 -42 960.00186 0.0043610658 48301 0.25005 48301 48298 48289 0 9 -4 -18 7 1-17.993 pair: 32 20912 2090520894 119181 126199 4353943536 4353843535 5797 5696 0.0028100436 0.1612125005 48298 48289 48296 48301 9 -518 1 10.011 pair: 3 -7 20912 20905 1 pair: 4 119 20894 20912 126 -454 43539 -436 43538 43534 57 43545 21256 0.00281 223 -0.0102216121 48296 -0.58560 48301 48303 48296 -5 -7 -18 1 -1116.000 pair: 54 2090620894 2091920912 -336454 -323436 4352743534 4353543545 155212 163223 -0.0075701022 -0.4336958560 48303 48296 48295 48294 7 1 -18 -1311 -82.023 pair: 65 2090220906 2090520919 -203336 -206323 43527 43537 43535 43525 155 -89 -101163 -0.0047000757 -0.2691643369 48295 4829348294 48287 1 6 -13 3-8 125.993 pair: 76 2090020902 2089720905 -140203 -137206 4353943537 4354443525 -68 89 -63101 -0.0031800470 -0.1822526916 4829848293 4829648287 26 -3 -5 |
This quality check works well to catch significant typos in input table. In case of obvious typos input table can be corrected. When the quality check is passed successfully the alignment parameters are saved in deployed under the calib
directory as explained below.
Alignment parameters
The official place for CSPad alignment parameters is
/reg/d/psdm/<INSTRUMENT>/<experiment>/calib/CsPad::Calib<VERSION>/<CSPad-name>/<type>/<run-range>.data
The file name consists of the run range followed by the .data
, for example, 0-end.data
, 11-end.data
, 47-52.data
, etc.
Description of types
All CSPAD geometry alignment parameters are split for 9 types:
center
- x, y, z center position of each 2x1 for all quadrants. Comes from optical measurement.center_corr
- additional manual correction to the center parameter. Can be applied if the optical measurement has (non-)obvious problems.marg_gap_shift
- margins, gaps, and shifts between quads, as explained below. Comes from image-based tuning.offset
- x, y, z coordinates for 4 quads. Fairly-reasonable assigned before tuning of theoffset_corr
andmarg_gap_shift
parameters.offset_corr
- additional correction to the offset. Comes from image-based tuning.quad_rotation
- 4 quad rotation in n*90 degree. Comes from basic geometry.quad_tilt
- 4 quad tilt in fractional degree. Has never been used. In latest optical measurement is accounted through the global 2x1 coordinate measurement in the detector.rotation
- 8 2x1-rotation angle for 4 quads in n*90 degree. Comes from basic geometry.tilt
- 8 2x1-tilt angle for 4 quads in fractional degree. Comes from optical measurement.
All coordinates are defined in size of pixel, which is 109.92 x 109.92um (and 274.80 x 109.92um for two rows between two of 2x1 ASICs.) The quadrant size is pre-defined as 850x850. The margins, shifts and gaps are defined for these quads. The offset
and offset_corr
are defined for low-left angle of the rotated by n*90 degree quad. Size of entire CSPad image does not matter for this alignment.
center
The tail of the path: center/<run-range>.data
...
center_corr
The tail of the path: center_corr/<run-range>.data
...
offset
The tail of the path: offset/<run-range>.data
...
offset_corr
The tail of the path: offset_corr/<run-range>.data
...
offset_corr
The tail of the path: offset_corr/<run-range>.data
Code Block |
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dXq0 dXq1 dXq2 dXq3
dYq0 dYq1 dYq2 dYq3
dZq0 dZq1 dZq2 dZq3
|
marg_gap_shift
The tail of the path: marg_gap_shift/<run-range>.data
Code Block |
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offset of 2x1s in quad (for tilt)
/ offset of quads in image (for tilt)
/ / gaps
/ / / shifts
/ / / /
X: 15 40 0 32
Y: 15 40 0 32
Z: 0 0 0 0
|
quad_rotation
The tail of the path: quad_rotation/<run-range>.data
...
quad_tilt
The tail of the path: quad_tilt/<run-range>.data
...
rotation
The tail of the path: rotation/<run-range>.data
...
tilt
The tail of the path: tilt/<run-range>.data
12 2.981
pair: 7 20900 20897 -140 -137 43539 43544 -68 -63 -0.00318 -0.18225 48298 48296 2 -3 -5 29.997
|
This quality check works well to catch significant typos in input table. In case of obvious typos input table can be corrected. When the quality check is passed successfully the alignment parameters are saved and deployed under the calib
.
Detector geometry model
Since 2014 we support universal detector geometry software which is documented in the Detector Geometry page and in CSPAD-geometry-parameters.pdf.
Alignment parameters from optical measurement
From optical measurement we extract coordinates of the center of each 2x1 sensor and its tilt angle.
The center coordinates are evaluated as an averaged over 4 corners measurements for each axis.
The tilt
parameters are used along with rotation
to completely define orientation of 2x1 in quad (for CXI) or in detector (for XPP).
Alignment of quads in the detector
For CSPad with fixed quad geometry (like in XPP) optical measurement of entire detector (should) produces complete information for geometry alignment.
For CSPad with moveable quads (like in CXI) quads relative position needs to be adjusted through the alignment parameters for quads. It is usually done using typical images with diffraction rings, wires or other shading objects:
Although few algorithms of automatic quad alignment were tried, we did not find good generic way for automated quad tuning. Currently, the quad tuning parameters in marg_gap_shift
and offset_corr
are adjusted manually for runs with specific images.
Calibration store
The official space for CSPAD alignment parameters is
/reg/d/psdm/<INSTRUMENT>/<experiment>/calib/CsPad::Calib<VERSION>/<CSPad-name>/<type>/<run-range>.data
For example:
Code Block |
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/reg/d/psdm/CXI/cxi80410/calib/CsPad::CalibV1/CxiDs1.0:Cspad.0/geometry/1142-end.data
|
The file name consists of the run range followed by the .data
extension, for example, 0-end.data
, 11-end.data
, 47-52.data
, etc.
Calibration type
Detector geometry calibration information is located in a single file of type
geometry
- contains hierarchical description of all detector components; for example for CSPAD, sensors' location and rotation in the quads, quads - in the detector, detector - in the setup, etc.
Archive and History
Optical measurement and other alignment files can be found in
- /reg/g/psdm/detector/alignment/cspad/
- Geometry History
Detector data access software
References
- CSPAD Geometry and Alignment - Depricated - old version of this page
- Detector Geometry - confluence page
- CSPAD in DAQ - schematic description of CSPAD geometry available in DAQ.
- CSPAD quad metrology - slides for CXI type CSPAD quads
- CSPad pixel layout in quads - pdf file with numeration of ASICs in the CSPAD quads
- XPPMetrologyAnnotated.pdf - order of measurements of XPP camera.
- Geometry History - page with references to calibration files.
- Detector data access software - auto-generated documentation of the Detector package.
...