CCD Performance, Laser Measurements and Analysis

1
CCD Performance, Laser Measurements and Analysis

• Steve Malton, UCL
• Laserwire meeting, Oxford
• 10th Nov. 2004

2
Overview

• CCD performance
• Measurements from RHUL
• Laser profile
• Measurements from DESY
• Hut and Tunnel
• Laser spot scanning calibration
• Practicalities
• Analysis code upgrade

3
Camera

• Basler A601f-HDR
• CMOS camera
• Radiation hard
• 656 x 491 pixels
• 9.9 mm pixel size
• 2W heat output
• Cheaper
• Simple trigger connecter (RJ45)

• Compare A302f
• CCD
• 752 x 582 pixels
• 8.3 mm pixel size
• 5W heat output

4
CCD Resolution
Photodiode
Removable mirror
Focussing lens
Knife edge
CCD

• Lab setup at RHUL
• Measure voltage of photodiode as knife edge steps
  through beam
• Fit plot to Error function to deduce width of
  beam
• Fit CCD image for width of beam
• Minimise both spots to fix positions of CCD and
  knife edge
• Move focusing lens to change beam width at both
  points

5
CCD Resolution (cont.)

• CCD image fit
• 9.9mm pixel width
• 2 Gaussians O(1) Polynomial fit
• Second Gaussian is reflection from optics
• Require s1

s1
s2

• Knife Edge scan
• Error function fit
• Require s

6
CCD Resolution (cont.)

• Compare sCCD with sKE
• Two Gaussian fit
• Gradient 1.134
• Loses accuracy above 150mm
• One Gaussian fit
• Gradient 1.118
• Loses accuracy below 150mm

7
Laser Waist
Laser in
x
Final Focus lens
Alignment mirrors
CCD camera on tracking rail
y

• Setup on small breadboard at DESY for easy
  installation
• NdYAG laser, l 532nm
• Final focus lens LAP 125
• 125mm focal length
• Camera moved through waist
• Beam size measured at each point
• Data taken with Stewart Boogert and Thorsten Kamps

8
Laser Waist (cont.)

• Fit to
• Beam waist 35-40 microns
• M2 and sigma improve after beam transport to
  tunnel
• Errors large in tunnel due to ambient light
• Gaussian will
• not fit x-projection

9
Upgrades

• Reduce ambient light on camera
• Laser line filter 530 10nm
• Signal saturation
• Need to be able to modify signal intensity easily
• ND filter wheel 0.04 6 (?)

10
Laser Spot Scanning

• Mirror on piezo-electric stack
• Applied voltage 0-10V amplified to 0-100V
• Maximum tilt 5mrad
• Produces travel at IP of 600mm

y2
x2
x1
y1
11
Laser Spot Scanning (cont.)
y2/y1

• Placement of imaging lens doesnt seem to matter
• We need to track this spot
• Make measurements during next access visit to DESY

x2-x1
12
DAQ and Analysis - Current

• Visual C
• Fast 60Hz
• Current features
• Triggered
• Multi-camera
• Greyscale
• x,y projections display in ROOT

13
TTF Display

• TTF OTR cameras
• Basler A302
• Slow 1Hz
• LabView
• Some nice features
• Projection overlay
• History display
• Colour

14
DAQ Upgrades

• Colour map
• Replace greyscale with colour palette
• Overlay projections and analysis on image
• Background subtraction?

15
Summary

• CCD spot fit scales linearly with actual spot
  size
• Gradient 1.118 1.134
• Laser waist sy 35 - 40mm
• But beam quality is poor M2 7.5 11
• Spot travel can be tracked accurately
• DAQ software final upgrades
• Colour map and analysis overlay