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Table of Contents

2x1 Sensor Geometry

Pixels size
Image RemovedImage Removed

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:
    Image RemovedImage RemovedImage Removed
    Image Removed

The same plots in PDF format: CSPAD quad metrologyCXI pixel layout

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:
    Image Removed
    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:

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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:
Image Added
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:
Image Added Image Added
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.

                         Image Added

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:
    Image Added Image Added Image Added
    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

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):
Image Added

  • 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:
    Image Added
    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:

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
      vort = [v21 x v41].

Scalar product with normalization defines the distance from point 3 to the 2x1 plane containing 3 other points:

Code Block
      dz3 = (v31 * vort) / |vort|.

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
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
Code Block

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      -365      63 -5   -0.0001600303    -0.0092117369   48299   4830148297       -2      -2 0      2    2

Quad  16.003
pair: 4 0  20911 20913  20896 20914    -34330     -34245     4354043549   43547 43550     17 165     17515   -0.0078700086   -0.4506604934   4831348303   4830348306      -3 10     15 -1     -10 2     -5.994
pair: 15   20901   20898   20901   10  -145     -1427     4354843540   43544 43551     -8 62     -4 65   -0.0033000020    -0.1888001119   4830048296   4830948299      -93       -3      -34      9.993
pair: 26   2089520904   20903    -151 104   -159  105     43536   4353543540   43532   55  -74    59 -77   -0.0035600240    -0.2040013752   48302   4828948290   48291   12   -2   -1    8  -4     352.002
pair: 37   2087220901   2090920901      -357      -727     43545 43541  43543 43554     -373      -245   -0.0012300016   -0.0703900921   4829448299   4830348301      -92       0       2  37   14.001

Quad  -131
pair: 40   2094020913   2090420914    -455343    -491342     4352743540   4355443550     214165     241175   -0.0108600787   -0.6224245066   48313   4830948303   48309   10    0  -1    36 -10    -2724.002
pair: 51   2091020898   2090320901    -302145    -309142     43548  43546 43551  43546    62 145     14565   -0.0070200330   -0.4019618880   4830448300   4830748309      -39      -3   7   -3    0-23.005
pair: 62   2090120895   2091920903    -421151    -439159     4352943535   4353943532     -21374     -20377   -0.0098800356   -0.5659320400   4829648289   4829848291      -2      18 8    -10   3    -17.995
pair: 73   2090720872   2090720909    -452235    -452272     4354843341   43354 43539    -20137     -21024   -0.0103800585   -0.5947533507   4831548201   4829448036     165 21     37  0   -13    9

Quad  2
-13.010
pair: 04   2091420940   20914 20904    -25 455    -25491     4353643527   4354043554     214 10      14241   -0.0005701086   -0.0329062242   4830048309   4830048309       0      36 0      -4
pair: 1-27    20901   208971.101
pair: 5   20910   20903 7   -302    3-309     43546   4353643546     145 -1    145 -11    -0.0001100702    -0.0065840196   4829348304   4830048307      -73       7 4      100      6.016
pair: 26   2089920901   2090320919    -256421    -260439     4353343529   43539    -127213    -121203   -0.0059300988   -0.3395456593   4829348296   4829448298      -12      18   4  -10     -68.026
pair: 37   2091220907   2090420907    -210452    -202452     4354043548   4354743539    -106 201    -99210   -0.0047301038   -0.2710659475   48315   48294   48300   4830621      -6 0     -8  9    -7 -8.982

Quad  2
pair: 0 4  20914 20910  20914 20903    -54325     -55025     43536  43535 43540  43536    10 261     26214   -0.0125500057   -0.7192303290   4829848300   4829948300       -10       70      -1
pair:4 5   20904 -11.013
pair: 1  20905 20901   -24120897    -240   7  43538   43544  3   111  43546   11743536   -0.00552   -0.316471    48298 -11  48301  0.00011    -30.00658   48293   -148300      -6
pair:7 6   20903   209024      2110      22 4.036
pair: 2   20899 43539  20903 43543   -256    8-260     43533  12 43539   0.00049 -127   0.02829 -121  48298 -0.00593  48298 -0.33954   48293   048294      -1       -4
pair: 7   20902  -6 20903    -1.023
pair: 3 82  20912   20904 81   -210  43546  -202 43547    43540  35 43547    -106 36    -99   -0.0018700473    -0.1072327106   48300   48306      -6      -8 1     -7   -1

Quad  324.004
pair: 04   2090220910   20898 20903    -82543     -86550     4353643535   4354343536     261 30    262  37   -0.0019301255   -0.1105471923   48298 48289  48299 48302     -131       47      -7
pair: 1   20900   20904  0.004
pair: 5   20904   20905 79   -241   83 -240    43548 43538  43541 43544    -35 111    -42 117   -0.0018600552    -0.1065831647   48298   48301   48301   -3    0  -1    -4  -6     7-6.024
pair: 26   2091220903   2089420902     181 21    199  22   43536  43539 43535  43543    97   8   96   12    0.0043600049    0.2500502829   48298   48298 48289      0 9     -18 1      -4      18.999
pair: 7 3  20902  20912 20903  20905    82 119     12681     4353943546   4353843547      5735      5636    0.0028100187    0.1612110723   4829648300   4830148306      -56      -7 1      -1
pair: 4   20894   209129.995

Quad  3
pair: 0   20902   20898     -45482     -43686     43536  43534 43543  43545    30 212     22337   -0.0102200193   -0.5856011054   48289   48302   48303  -13 48296      4 7     -187      -111.994
pair: 51   2090620900   2091920904    -336  79  -323    83 43527    4353543548   43541  155   -35  163   -42    0.0075700186    -0.4336910658   4829548301   4829448301       0 1     -134       7    -817.993
pair: 62   2090220912   2090520894    -203 181   -206  199   43537  43536 43525  43535   -89   97 -101   -0.00470  96 -0.26916   482930.00436    0.25005   48298   48289    48287   9    6 -18      3 1     1210.011
pair: 3  7 20912  20900 20905  20897   119 -140    -137126     43539   4354443538     -68 57    -63  56 -0.00318   -0.1822500281    482980.16121   48296   48301    2  -5    -3  -7       1    -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 the offset_corr and marg_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

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

        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

...

References

16.000
pair: 4   20894   20912    -454    -436     43534   43545     212     223   -0.01022   -0.58560   48303   48296       7     -18     -11      2.023
pair: 5   20906   20919    -336    -323     43527   43535     155     163   -0.00757   -0.43369   48295   48294       1     -13      -8      5.993
pair: 6   20902   20905    -203    -206     43537   43525     -89    -101   -0.00470   -0.26916   48293   48287       6       3      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:
Image Added Image Added Image Added

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
/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

Detector data access software

 

References

...