1. Kicker specifications for Damping Rings
CLIC Beam dynamics meeting
Kicker specifications for Damping Rings
F. Antoniou, M. Barnes, J. Borbourgh, T. Fowler, Y. Papaphilippou
February 4th, 2009

2. Design optimisation for CDR (2010) M. Korostelev, PhD thesis, 2006
Outline
CLIC damping rings (DR) layout and parameters
DR injection and extraction optics
DR septa and kicker parameters
Pre-damping rings (PDR) parameters
Kicker considerations for PDR
Summary
CLIC parameter note 2005
CLIC parameter note 2008
Design optimisation for CDR (2010)
M. Korostelev, PhD thesis, 2006
04/02/09 YP

3. CLIC damping ring layout
04/02/09
M. Korostelev, PhD thesis, EPFL 2006

4. DR bunch structure and timing
CLIC DR timing parameters
Old
(2005)
New
(2008)
Repetition rate [Hz]
150 50
Number of bunches
110
312
Number of trains 4 1
Bunch spacing [ns]
0.533
0.500
Revolution Time [μs]
1.2
>1.2
Machine pulse [ms]
6.67 20
H/V/L damping times [ms]
2.8/2.8/1.4
1.5/1.5/0.76
Reduction of repetition rate from 150 to 50Hz leaves enough time for the emittances to reach their equilibrium
Bunch spacing increased almost to same level as for the interleaved train scheme
Interleaved train scheme abandoned
Extraction kicker rise time relaxed
Injection and extraction process simplified
312 bunches with 0.5ns spacing, fill 13% of the rings 4

5. Kicker and septa optics
The angular deflection at the septum is
The angular deflection of the kicker is defined as
Large beta functions and π/2 phase advance are necessary for minimizing the kicks and small position at the septa
The injected beam position at the septum should be
Typically, injection and extraction
region is dispersion free
For lepton rings
The thickness of the septum
cannot be smaller than 3mm
The input emittance can reduce
the kick requirements

6. DR injection/extraction optics
Injection and extraction system placed at the same area, upstream of the super-conducting wigglers
Kickers placed at maximum beta functions for minimum deflection angle
Septa and kickers share the same cell
Additional cells to be added in order to increase available space for elements and protection system
Phase advance between injection (extraction) septa and kickers of around π/2
M. Korostelev, PhD thesis, EPFL 2006
04/02/09 YP

7. DR Septa parameters
DR septa parameters
SEP-1
SEP-2
Effective length [m]
0.4
0.5
Bending angle [mrad] 13 42
Field integral [T.m]
0.11
0.34
Blade thickness [mm] 5
Same parameters for injection/extraction elements due to optics mirror symmetry
Septum parameters are scaled from NLC damping rings
Two DC modules with blade thickness of 5 and 13mm
Effective length can be increased to 2m if additional cells are added
Larger septa blade thicknesses and smaller peak field
04/02/09 YP

8. Kicker stability
Kicker jitter is translated in a beam jitter in the IP.
Typically a tolerance of σjit ≤0.1σx is needed
Translated in a relative deflection stability requirement as
For higher positions at the septum (larger injected emittances or lower beta functions) the stability tolerance becomes tighter
The tolerance remains typically to the order of 10-4
A similar tolerance can be established for the kicker roll

9. DR Kicker parameters Rise and fall time significantly increased
Effective length can be increased to 2m
Smaller peak field
Kicker stability refers to field uniformity and pulse-to-pulse stability
Tolerance of 0.1σx beam centroid jitter
DR kicker parameters
Old
New
Rise and fall time [ns] 25
1000
Flat top [ns]
142
~160
Repetition rate [Hz]
150 50
Effective length [m]
0.4
0.4-2
Aperture [mm] 20
Kick [mrad]
2.45 3
Field [Gauss]
500
<610
Kicker stability
inj
ext
Second kicker in transfer phase advance of π for jitter compensation (as in NLC/ATF)
Achieved 2.8x10-4 at ATF for shorter rise/fall times and flat top (all of 60ns)
Third kicker, delay line and RF deflector are removed
Contribution to beam impedance should be addressed (budget of a few MΩ/m in transverse and a few Ω in longitudinal) –external circuit may be important

10. PDR working parameters
F. Antoniou
Parameter [unit]
Value
beam energy [GeV]
circumference [m]
bunch population [E+09]
bunch spacing [ns]
bunches per train
rms bunch length [mm]
rms momentum spread [%]
hor. Emittance w/o IBS [nm]
no. of arc bends
arc-dipole field [T]
length of arc dipole [m]
number of wigglers
wiggler field [T]
length of wiggler [m]
wiggler period [cm]
mom. compaction [10-5]
RF frequency [GHz]
energy loss/turn [MeV]
RF voltage [MV]
h/v/l damping times [ms]
Revolution time [ns]
Repetition rate [Hz]
2.424
260.1
4.5
0.5
312
0.2
0.3
13000 30
1.7 1 20 2
4.7
1.54 16
2.7/2.7/1.35
870 50
312 bunches with 0.5ns spacing, fill 18% of the pre-damping rings
Designed for large momentum acceptance and fast damping
Large RF voltage, small momentum compaction factor
Injected Parameters e- e+
Bunch population [109]
4.4
6.4
Bunch length [mm] 1 5
Energy Spread [%]
0.1
2.7
Hor.,Ver Norm. emittance [nm]
100 x 103
9.3 x 106
PDR Extracted specs
Value
Bunch length [mm] 10
Energy Spread [%]
0.5
Hor. Norm. emittance [nm]
63000
Ver. Norm. emittance [nm]
1500 10

11. PDR injection/extraction optics
Kickers
Septa
PDR kicker parameters
Value
Rise and fall time [ns]
700
Flat top [ns]
~160
Repetition rate [Hz] 50
Effective length [m] ~2
Aperture [mm]
~55
Kick [mrad] ~3
Field [Gauss]
~150
Kicker stability
inj
ext
Injection and extraction system placed at symmetric points of the matching area, upstream of the super-conducting wigglers
Kickers placed at maximum beta functions with available space of around 2m
Phase advance between septa and kickers of around π/2
Kicker stability at extraction quite challenging for positrons
04/02/09 YP

12. Summary PDR and DR injection and extraction systems
Extraction process simplified (1 train)
Main issues the kicker stability for both DR and PDR
Design should target for low impedance
04/02/09 YP