1. Bunch Profiling with a Rotating Mask
Mitchell Miller with Dr. Alan Fisher

2. Synchrotron Light Acceleration of charged particles = radiation
As V  C the radiation becomes focused
Using a strong B field forces electrons to orbit
Synchrotrons are a large ring of uniform B
Beams generated are used for nearly infinite applications

3. LHC LHC is a proton collider, not synchrotron
Greater mass = less synchrotron radiation
Collisions require careful beam alignment
Order of microns compared to kilometers in circumference
Previous bunch measurement techniques involved:
High speed camera
Long time
Frequent replacement from radiation damage

4. Solution: Rotating Mask
Wheel with four groups of three slots
Each group has slot at 0°,45°, and 90°
Slots provide line integration points
PMT will detect light that passes through slot
In one ring turn slot has shifted slightly providing a new point with every ring turn
Combining every point will give a Gaussian profile
Each bunch will have a unique profile

5. Slot Positions

6. Profile Creation Each bunch provides a peak
Peaks are chosen using software that indexes each bunch
Output from motor is recorded, giving position of wheel
One bunch measured for this experiment
“Timing Bunch”

7. Profile Results

8. Fitting to Obtain Beam Size
Beam sigma = µm
Expect sigma = µm

9. Error Diffraction effects Precise focus PMT charging effects
Sampling and data access

10. Conclusion Benefits Drawbacks Deployment at LHC Fast
Radiation resistant
Simple
Drawbacks
Error from diffraction (possibly from sampling rate)
Deployment at LHC

11. Thank You
Questions