Versions Compared

Old Version 17

changes.mady.by.user Mikhail Dubrovin

Saved on

compared with

New Version Current

changes.mady.by.user Mikhail Dubrovin

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

Include Page
PageMenuBegin
PageMenuBegin
Table of Contents

...

Include Page
PageMenuEnd
PageMenuEnd

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     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:
    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:

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      -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 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

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

...