1. Effects of DFS on Single-beam Tuning
Ryan Bodenstein
Jochem Snuverink
CLIC Workshop 2016
Tuesday, January 19, 2016

2. Before we start… Two separate sections for chromaticity correction
Lattice by Hector Garcia, see e.g. his talk at CLIC WS 2014
Relatively simple system for design and analysis

3. Traditional Final Focus
Parameter
Unit
Traditional
“Optimized”
Local
Length m
1460
450
Total Luminosity
cm-2s-1
7.5 * 1034
7.8 * 1034
Peak (1%) Luminosity
2.4 * 1034
Optimized lattice achieves similar luminosity as local scheme

4. So, what are we tuning?
Looking at the traditional final focus system, with 3 TeV collision energy.
Simulations using PLACET and GUINEA-PIG
Single-beam tuning:
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

5. Step by step… Apply the first corrections to the uncorrected beam
There are actually points there, but on this plot they barely show up.
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

6. Step by step… Apply the first corrections to the uncorrected beam
Correct the dispersion to approach design values
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

7. Step by step… Apply the first corrections to the uncorrected beam
Correct the dispersion to approach design values
Use the tuning knobs to maximize luminosity
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

8. Step by step… Apply the first corrections to the uncorrected beam
Correct the dispersion to approach design values
Use the tuning knobs to maximize luminosity
Attempt to optimize dispersion again
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

9. Step by step… Apply the first corrections to the uncorrected beam
Correct the dispersion to approach design values
Use the tuning knobs to maximize luminosity
Attempt to optimize dispersion again
Maximize luminosity once more
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

10. Looks good, what’s the problem?
Well, for starters we want more seeds reaching a higher luminosity.

11. Not much. Things actually get worse with each iteration.
What happens if we do it multiple times, using the previous outputs as inputs?
Not much. Things actually get worse with each iteration.

12. Don’t believe me? Check it out!
Iteration 1
Iteration 5

13. Don’t believe me? Check it out!
Iteration 1
Iteration 5

14. Looking at it another way...
Iteration 1
Iterations 1-5

15. Looking at it another way...

16. Looking at it another way...

17. Something needs to change...
The main goal is to maximize luminosity
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

18. Something needs to change...
The main goal is to maximize luminosity
It is also important for as many seeds as possible to reach a high luminosity
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

19. Something needs to change...
The main goal is to maximize luminosity
It is also important for as many seeds as possible to reach a high luminosity
The second DFS tuning step drops the majority of seeds to a much lower luminosity
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

20. Something needs to change...
The main goal is to maximize luminosity
It is also important for as many seeds as possible to reach a high luminosity
The second DFS tuning step drops the majority of seeds to a much lower luminosity
Investigate skipping this step
First step applied to uncorrected beam
1-2-1 Tuning
Bring dispersion to design values
Dispersion Free Steering – 1
Maximize Luminosity
Tuning Knobs – 1
Bring dispersion back toward design
Dispersion Free Steering – 2
Final shot to maximize Luminosity
Tuning Knobs - 2

21. To start with the obvious…
This doesn’t seem like the right plan of action.

22. Let’s compare survival plots

23. Looking at a single iteration from each method
Original
Without DFS-2

24. Without DFS-2: The Good
Original
Without DFS-2

25. Without DFS-2: The Bad
Original
Without DFS-2

26. The Good and The Bad Together

27. The Good and The Bad Together

28. The Good and The Bad Together

29. Putting it all together
Current techniques do not have enough seeds reaching a high luminosity. Too many seeds lose luminosity in the 2nd Knobs step.

30. Putting it all together
Current techniques do not have enough seeds reaching a high luminosity. Too many seeds lose luminosity in the 2nd Knobs step.
Skipping the DFS-2 step addresses the seed loss in the 2nd Knob step, but too many seeds only reach moderate luminosities.

31. Putting it all together
Current techniques do not have enough seeds reaching a high luminosity. Too many seeds lose luminosity in the 2nd Knobs step.
Skipping the DFS-2 step addresses the seed loss in the 2nd Knob step, but too many seeds only reach moderate luminosities.
Simply skipping DFS-2 is not the solution in itself, but other methods will be investigated.
See Jochem’s talk next

32. CLIC Workshop 2016 Thanks!