The difficult points of kicker magnets. ◇ High Repetition rate (for power supply). •
Switching device ? ◇ Fast rise/fall time. • Ringing and reflection must be small.
Kicker Overview
T.Mimashi KEK
Requirements
Injection beam • 2820 bunches, 337nsec spacing
Deflection angle • Injection 0.5mrad • Extraction 4 µrad (Vertical) or 30µrad (Horizontal)
Recombination factor > 20? • => Bunch space less than 20nsec ? • => Total Length of DR 17km
Pulse to pulse reproducibility (extraction) • Less Than ±0.07%
The difficult points of kicker magnets
High Repetition rate (for power supply) • Switching device ?
Fast rise/fall time • Ringing and reflection must be small • Fast rise/slow fall => “kicker gap scheme” needs pre-damping ring if positron generated by luminosity generating electron beam
Injection kicker • Larger input beam size（need large kick）
Extraction kicker • Extremely good pulse-to-pulse reproducibility
To avoid beam jitter at the collision point (The fast intra-train feedback at TESLA can NOT compensate)
• preserve transverse emittance
Candidates of Kicker System for TESLA Damping Ring 1: Conventional Kicker System Ferrite Kicker , Strip Line Kicker,etc 2:RF deflectors A Fourier Series Kicker, CTF3-like, (Club Cavity) 3:New ideas Beam-beam kicker, A high intensity laser pulse kicker
Conventional Kicker System
Kicker magnet (G.Dugan, Jurgen Rummler et al) • • •
Ferrite kicker with resistive coating on ceramic tube Ferrite kicker with strips(DESY DRIS,PETRA,HERA Type) Strip Line Kicker (Budker INP, DESY,FNAL)
Pulsers (Switching device etc) (From J. Frisch talk) • • •
Requirements -> 5kV, 50A Peak Power : 250kW Average power in 1msec : 2.5kW Long Term: 25W
• •
Switching speed : nsec rise and fall time Settling < 7x10-4
Magnetic field B Length L Voltage on input V Half-aperture a Kicker strength S
Grishanov et al, TESLA note 96-11
Minimum pulse rise/fall time T
V=2000 v -> 8-10kV? L=0.5 m -> 3m (for 20nsec) a=25 mm -> 20mm ? S=2.67 G-m -> 80G-m ? T=3.33 ns Need 18 kickers -> 1 kicker ?
Candidates (From J. Frisch talk and comments from A.Krasnykh)
Snap/Step Diode - Power dissipation probably limits Avalanche Transistors MOSFETs Shock Lines (Ferromagnetic) • 95kV 380psec (Used for SLAC kicker)
Shock Lines (Others) • Ferroelectric 20kV 400psec • Diode loaded line 6V < 0.7psec • Vacuum Magnetic line
Hard Tube Switches -> Eimac Y-690 6kV, 30A, 1.5ns Driven by avalanche transustors (Not appropriate for high repetition rate)
R&D activities
Strip Line kicker (LEPP,FNAL,UIUC,DESY) • Install simple strip line kicker in the A0 photoinjector beam line (16 MeV electrons) to study timing/stability property (Information from G.Gollis’s talk in SLAC)
Strip Line kicker (KEK/DESY?) • Install simple strip line in the KEK ATF • Borrow pulser from DESY (F.Obier) ?
KEK/ATF
FNAL/A0
RF Deflectors
Crab cavity and kicker (Richard Helms, Cornel Univ.)
CTF3-like Inj/ext schemes (D.Alesini et al, Frascati)
Fourier Series Kicker ( George Gollin Univ. of Illinois Urbana-Champaign)
Crab Cavity and kicker magnet (Richard Helms, Cornel Univ.)
We can reduce the DR size without changing the kicker specs 17km -> 4-5km
Lines are recombined approximately 200m later
Crab Cavity in KEKB (Hosoyama et al KEK)
(Crab cavity will be installed in the KEKB Ring in Dec 2005 )
CTF3-like Inj/Ext Schemes (D.Alesini et al, Frascati)
E
H
CTF3-Like Injection
(D.Alesini et al, Frascati)
CTF3-Like Extraction
Some limit (D.Alesini et al, Frascati) ∆φ∗> 0.6mrad for Φ=12mrad
Increase ∆φ∗/φ •
2 frequencies
Use the combination of 2 or more frequencies
3 frequencies
Fourier Series Kicker
Kicker would be a series of N “rf cavities” oscillating at harmonics of the linac bunch frequency 1/(337 nsec)=2.97MHz Kick could be transverse or (longitudinal + Bend) George Gollin University of Illinois at Urbana-Champaign
Adjust each Amplitude
dpt/dt=0 at every-spaced Major zeroes in pt
George Gollin University of Illinois at Urbana-Champaign
a “Fourier series kicker” George Gollin University of Illinois at Urbana-Champaign kicker rf cavities
injection/extraction deflecting magnet
injection/extraction deflecting magnet
pT injection path
extraction path
RF deflectors are always “ON” (fast filling/draining is NOT an issue) Fourier series kicker is located in a bypass section (more about this on the next slide…) While damping, beam follows the dog bone-shaped path (solid line). During injection/extraction, deflectors route beam through bypass (straight) section. Bunches are kicked onto/off orbit by kicker.
Even though net Pt is zero there can be a small displacement. To compensate the displacement, civities in phase must be installed Symmetry: +3MHz,+6MHz ….. ,+6MHz,+3MHz
George Gollin University of Illinois at Urbana-Champaign
A novel scheme for a super fast kicker 1
Beam-Beam kicker(V.D.Shiltsev DESY) Use a high pulse current, low energy beam
Advantage
• No cancellation devices and Tiny ring impedance
Disadvantage • The injection BBK scheme need extremely high charge source
Issues • Stability requirements
Beam charge, Distance between two beams
• The effect of resistive vacuum chamber wake field is Negligible
Beam-beam kicker
3.3GeV
Injection
Extraction
(V.D.Shiltsev DESY)
Vertical
50Gsm
0.43Gm
Horizontal 50Gsm
Cross
Head On
Charge Source: • RF photo-injector Max Pbbk=16 [Gsm] • Q=300nC,σr =10mm
3Gm
Charge Source: • RF photo-injector(300nC) ->ferroelectric cathode gun(500-100nC)
Max Pbbk=2.2 [Gsm] • Q=300nC,σz =10cm
End
