Laser beam diagnostics : BEAMDIAG program. Stéphan Del Burgo CERN PS/LP 30 January 1998 DBS 01/98-101

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

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

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

How does it work ? DBS 01/ 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.

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 : DBS 01/ Display Data Acquisition ( TIFF file ) Conversion into an Intensity Matrix Calculations and Analysis 1 loop : ~15 s

Calculations and Analysis : –The projections from the beam to the screen and the camera are compensated ( X scale = Y scale ). –Matrix conversion and normalization : DBS 01/ RGB LUT TIFF Matrix Intensity Matrix Video picture : 2 frames Level Pixels 100 Histogram Normalization

Analysis - video matrix, contours, barycentre, profiles DBS 01/98-108

Analysis - normalized matrix, maximum, integrated profiles DBS 01/98-109

Analysis - normalized, barycentre, personal, length DBS 01/98-110

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

Analysis - normalized, barycentre, gaussian fit, real beam DBS 01/98-112

Analysis - normalized, 3-D DBS 01/98-113

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