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Table of Contents

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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 Removed
    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
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 1     -222      -2      2.981
pair: 41   2091120910   2089620894     -30293     -45277     4354943540   4354743535    -127   17 -132    0.00655 15   -0.0008637506   -0.0493448302   48289 48303   48306  13    -3  16    15   5    2-23.986
pair: 52   2090120890   2089820906      1099      83 7    43536 43540  43536 43544     42 -8      -442    0.0002000209    0.0111911976   4829648290   4829948293      -3      16 3      0     -43.034
pair: 63   2090420897   2090320895     104131     105133     4353643545   4354043543      5565      5963    0.0024000303    0.1375217369   48299 48302  48297 48290      122      -12      -4
pair: 72   20901   209016.003
pair: 4   20911   20896     -730      -745     4354543549   4354343547      -317      -515   -0.0001600086   -0.0092104934   4829948303   4830148306      -23      15  0     2  2

Quad   1-5.994
pair: 05   2091320901   2091420898    -343  10  -342     435407   43550  43540   16543544      -8   175   -4    0.0078700020    -0.4506601119   48296   48299    48313  -3 48303      103      -14      -109.993
pair: 16   2089820904   2090120903    -145 104   -142  105   43548  43536 43551  43540    62  55    65  59 -0.00330   -0.1888000240    0.13752   4830048302   4830948290      -912      -31      -34     52.002
pair: 27   20901  20895 20901  20903    -1517      -1597     4353543545   4353243543      -743      -775   -0.0035600016   -0.2040000921   4828948299   4829148301      -2       80       3
pair:2 3   20872   20909   14.001

Quad  1
pair: 0   20913   20914    -35343     -72342     4354143540   4355443550     -37165     -24175   -0.0012300787   -0.0703945066   4829448313   48303      -910      -1    37 -10    -1324.002
pair: 41   2094020898   2090420901    -455145    -491142     4352743548   4355443551      21462      24165   -0.0108600330   -0.6224218880   48300   48309   48309   -9    0  -3    36  -3    -2723.005
pair: 52   2091020895   20903    -302151    -309159     4354643535   4354643532     145-74     145-77   -0.0070200356   -0.4019620400   4830448289   4830748291      -32       78       0
pair:3 6   20901-17.995
pair: 3   20872   2091920909    -421235    -439272     43341 43529  43354 43539    -21337     -20324   -0.0098800585   -0.5659333507   48201   4829648036   48298  165    -2  37    18 -13    -1013.010
pair: 74   2090720940   2090720904    -452455    -452491     4354843527   4353943554     -201214    -210 241   -0.0103801086   -0.5947562242   48309  48315 48309  48294     0 21     36  0   -27    9

Quad  21.101
pair: 05   2091420910   20914 20903    -25302     -25309     4353643546   4354043546     145 10    145  14   -0.0005700702   -0.0329040196   4830048304   4830048307      -3 0      7 0      -4
pair:0 1   20901   208976.016
pair: 6   20901   20919 7   -421    3-439     4354643529   4353643539      -1213     -11203    -0.0001100988    -0.0065856593   4829348296   4830048298      -72      18    4 -10     10-8.026
pair: 27   2089920907   2090320907    -256452    -260452     4353343548   43539    -127201    -121210   -0.0059301038   -0.3395459475   4829348315   48294      21     -1  0     4  9     -68.982

Quad  2
pair: 30   20914 20912  20914 20904    -21025     -20225     43536   43540   43547   10 -106     -9914   -0.0047300057   -0.2710603290   48300   4830648300       0 -6      -80      -7
pair: 4   20910  -11.013
pair: 1  20903 20901   -54320897    -550   7  43535   43536  3   261  43546   26243536   -0.01255   -0.719231   48298  -11 48299   0.00011   -1 0.00658   48293   748300      -1
pair:7 5   20904   209054    -241  10  -240     435384.036
pair: 2   4354420899   20903  111  -256   117 -260  -0.00552   -0.3164743533   4829843539   48301  -127    -3121   -0.00593   -10.33954   48293   -6
pair:48294 6   20903  -1 20902      214      22-6     43539 -1.023
pair: 3  43543 20912   20904   8 -210    -202 12    0.0004943540   43547 0.02829   48298-106   48298  -99   -0.00473   -0.27106   48300   -148306      -4
pair:6 7   20902  -8 20903     -7 82    24.004
pair: 4 81  20910   4354620903   43547 -543    -550 35    43535  36 43536   0.00187  261  0.10723   48300262   48306-0.01255   -0.71923   48298   48299      -61       17      -1

Quad      30.004
pair: 05   2090220904   20898 20905    -82241     -86240     4353643538   4354343544     111 30    117  37   -0.0019300552   -0.1105431647   48298 48289  48301 48302     -133       4 -1      -6     -76.024
pair: 16   20903   2090020902   20904   21   79   22   83  43539   4354843543   43541    8 -35     -4212    0.0018600049    0.1065802829   4830148298   4830148298       0      -1      -4       78.999
pair: 27   2091220902   2089420903     181 82    199  81   43536  43546 43535  43547    97  35      9636    0.0043600187    0.2500510723   48300   48306   48298   48289-6       1 9     -181      9.995

Quad  13
pair: 30   2091220902   2090520898     119-82     126-86     4353943536   4353843543      5730      5637    -0.0028100193    -0.1612111054   4829648289   4830148302      -5-13       4      -7       1.994
pair: 41   20900 20894  20904 20912    -454 79   -436   83  43534   4354543548   43541  212   -35  223   -0.0102242    -0.5856000186   48303 0.10658  48296 48301   48301   7    0 -18     -11
pair:4 5   20906   209197    -336    -323 17.993
pair: 2   20912   20894 43527   43535 181    155 199    163 43536  -0.00757 43535  -0.43369   48295 97  48294    96   1 0.00436    -130.25005   48298   -8
pair: 648289     20902  9 20905    -20318    -206   1  43537   43525 10.011
pair: 3   20912 -89  20905  -101   -0.00470119    -0.26916 126  48293   4828743539   43538    6  57     3 56     12
pair: 70.00281    0.16121 20900  48296 20897  48301  -140    -1375     43539 -7  43544     -68 1    -63 16.000
pair: 4  -0.00318 20894  -0.18225 20912  48298  -454 48296   -436     43534   43545 2    212  -3   223   -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.

List 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.

offset_corr

For individual quad position alignment use file: offset_corr/<run-range>.data

Code Block

dXq0 dXq1 dXq2 dXq3
dYq0 dYq1 dYq2 dYq3
dZq0 dZq1 dZq2 dZq3

marg_gap_shift

For common gap and shift between quads correction use file marg_gap_shift/<run-range>.data

...

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