Laser beam diagnostics : BEAMDIAG program.

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Laser beam diagnostics BEAMDIAG program.

• Stéphan Del Burgo
• CERN PS/LP
• 30 January 1998

DBS 01/98-101
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Laser beam diagnostics BEAMDIAG program.

• What is it for and where is it used ?
• How does it work ?
• The analysis with the main functions
  
  barycentre, contours, profiles,
  widths, fits, 3-D
• Conclusion - Next developments.

DBS 01/98-102
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• What is it for ?
• For laser beam diagnostics and analysis.
• To improve laser adjustments and beam geometry.
• For every kind of beams that a video camera can
  see with or without a screen.
• Where is it used ?
• In the CTF Laser room.
• In the photocathodes laboratory.
• In the new laser laboratory.

DBS 01/98-103
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• How does it work ?

Depending on the wavelength, a video camera looks
at a screen or directly at the beam. The video
camera is triggered. The pulse ( a few ns or ps )
is seen only during one frame ( two interlaced
frames usually ! ).
DBS 01/98-104
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• How does it work ?

The data are acquired by a frame grabber in the
PC. The frame grabber subtracts the noise from
the picture. The frame grabber output is a TIFF
file matrix in the PC. Each line of the matrix
corresponds to one line of one frame, one line of
the CCD matrix out of two. All these
developments have been done by Eric CHEVALLAY.
DBS 01/98-105
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• How does it work ?
• My work begins here with the calculations on the
  matrix.
• The size of the matrix can be very large ( e.g.
  512x256 ). The calculations are made with Matlab,
  Matlab 5 for the last version.
• The program is called BEAMDIAG ( or BEAMCTF ).
• This program contains around 80 files .
• The main loop is

Data Acquisition ( TIFF file )
Conversion into an Intensity Matrix
1 loop 15 s
Calculations and Analysis
Display
DBS 01/98-106
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• Calculations and Analysis
• The projections from the beam to the screen and
  the camera are compensated ( X scale Y scale ).
• Matrix conversion and normalization

R
G
B
LUT
0
0
0
0
11
16
35
5
1
0.1
0
0
3
125
78
11
2
0.2
0
0
204
204
12
16
...
...
...
...
202
251
121
11
254
1
1
0.9
TIFF Matrix
255
1
1
1
Video picture 2 frames
Pixels
Pixels
0.2
0.3
0.33
0.1
100
100
Histogram
Histogram
0.05
0.5
0.6
0.2
Normalization
0.9
0.9
0.23
0.3
0.7
0.95
0.42
0.2
DBS 01/98-107
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0
0
1
Level
Level
Intensity Matrix
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• Analysis - video matrix, contours, barycentre,
  profiles

DBS 01/98-108
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• Analysis - normalized matrix, maximum, integrated
  profiles

DBS 01/98-109
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• Analysis - normalized, barycentre, personal,
  length

DBS 01/98-110
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• Analysis - normalized, barycentre, gaussian fit

DBS 01/98-111
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• Analysis - normalized, barycentre, gaussian fit,
  real beam

DBS 01/98-112
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• Analysis - normalized, 3-D

DBS 01/98-113
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• Conclusion - Next developments.
• Last version of the laser beam analysis program
  with Matlab 5. User friendly.
• Adaptation from Windows 3.1 to Windows 95, and
  finally from Matlab 4 to Matlab 5 ? It runs
  better ( display speed, printing, saving,... ).
• Still a little bit slow.
• Good results for the analysis ( widths, fits, ).
  Reliable if correct calibration !
• Possible to add other specific functions
• different fits
• remote control for the aperture
• Next version with VME technology...

DBS 01/98-114