Effects of DFS on Single-beam
Tuning
Ryan Bodenstein
Jochem Snuverink
CLIC Workshop 2016
Tuesday, January 19, 2016
1
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
2
2
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
cm-2s-1
2.4 * 1034
2.4 * 1034
Optimized lattice achieves similar luminosity
as local scheme
3
3
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:
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Tuning
Knobs – 1
Maximize
Luminosity
4
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Step by step…
1. Apply the first corrections to
the uncorrected beam
There are actually points
there, but on this plot
they barely show up.
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Maximize
Luminosity
Tuning
Knobs – 1
5
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Step by step…
1. Apply the first corrections to
the uncorrected beam
2. Correct the dispersion to
approach design values
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Maximize
Luminosity
Tuning
Knobs – 1
6
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Step by step…
1. Apply the first corrections to
the uncorrected beam
2. Correct the dispersion to
approach design values
3. Use the tuning knobs to
maximize luminosity
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Maximize
Luminosity
Tuning
Knobs – 1
7
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Step by step…
1. Apply the first corrections to
the uncorrected beam
2. Correct the dispersion to
approach design values
3. Use the tuning knobs to
maximize luminosity
4. Attempt to optimize
dispersion again
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Maximize
Luminosity
Tuning
Knobs – 1
8
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Step by step…
1. Apply the first corrections to
the uncorrected beam
2. Correct the dispersion to
approach design values
3. Use the tuning knobs to
maximize luminosity
4. Attempt to optimize
dispersion again
5. Maximize luminosity once
more
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Maximize
Luminosity
Tuning
Knobs – 1
9
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Looks good, what’s the problem?
Well, for starters we want more seeds reaching a higher luminosity.
10
What happens if we do it multiple times, using the previous outputs as inputs?
Not much. Things actually get worse with each iteration.
11
Don’t believe me? Check it out!
Iteration 1
Iteration 5
12
Don’t believe me? Check it out!
Iteration 1
Iteration 5
13
Looking at it another way...
Iteration 1
Iterations 1-5
14
Looking at it another way...
15
Looking at it another way...
16
Something needs to change...
1. The main goal is to
maximize luminosity
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Tuning
Knobs – 1
Maximize
Luminosity
17
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Something needs to change...
1. The main goal is to
maximize luminosity
2. It is also important for as
many seeds as possible to
reach a high luminosity
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Tuning
Knobs – 1
Maximize
Luminosity
18
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Something needs to change...
1. The main goal is to
maximize luminosity
2. It is also important for as
many seeds as possible to
reach a high luminosity
3. The second DFS tuning step
drops the majority of seeds
to a much lower luminosity
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Tuning
Knobs – 1
Maximize
Luminosity
19
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
Something needs to change...
1. The main goal is to
maximize luminosity
2. It is also important for as
many seeds as possible to
reach a high luminosity
3. The second DFS tuning step
drops the majority of seeds
to a much lower luminosity
4. Investigate skipping this step
1-2-1
Tuning
First step
applied to
uncorrected
beam
Dispersion
Free
Steering –
1
Bring
dispersion
to design
values
Tuning
Knobs – 1
Maximize
Luminosity
20
Dispersion
Free
Steering –
2
Bring
dispersion
back toward
design
Tuning
Knobs - 2
Final shot to
maximize
Luminosity
To start with the obvious…
This doesn’t seem like the right plan of action.
21
Let’s compare survival plots
22
Looking at a single iteration from each method
Original
Without DFS-2
23
Without DFS-2: The Good
Original
Without DFS-2
24
Without DFS-2: The Bad
Original
Without DFS-2
25
The Good and The Bad Together
26
The Good and The Bad Together
27
The Good and The Bad Together
28
Putting it all together
1. Current techniques do not
have enough seeds reaching
a high luminosity. Too many
seeds lose luminosity in the
2nd Knobs step.
29
Putting it all together
1. Current techniques do not
have enough seeds reaching
a high luminosity. Too many
seeds lose luminosity in the
2nd Knobs step.
2. Skipping the DFS-2 step
addresses the seed loss in
the 2nd Knob step, but too
many seeds only reach
moderate luminosities.
30
Putting it all together
1. Current techniques do not
have enough seeds reaching
a high luminosity. Too many
seeds lose luminosity in the
2nd Knobs step.
2. Skipping the DFS-2 step
addresses the seed loss in
the 2nd Knob step, but too
many seeds only reach
moderate luminosities.
3. Simply skipping DFS-2 is not
the solution in itself, but
other methods will be
investigated.
See Jochem’s talk next
31
CLIC Workshop 2016
Thanks!
32