1. Impedance Measurement Techniques and Lessons from Light Sources
Victor Smaluk
NSLS-II

2. Wake Fields and Impedances
eeFACT
2016
Wake function: point charge (d–function) response
Wake potential: l(t) beam response
Impedance: frequency-domain transfer function
Daresbury, UK Oct 2016

3. Longitudinal Broad-band Impedance: What Can We Measure?
eeFACT
2016
Single-bunch effects
bunch lengthening;
energy spread growth (microwave instability)
coherent energy loss (heat load);
synchronous phase shift.
effective impedance
loss factor
(for Gaussian bunch)
Daresbury, UK Oct 2016

4. Longitudinal Impedance Models
eeFACT
2016
short bunch
k|| (V/pC)
3D simul
BBR
| Z||/n|eff (Ω)
3D simul
BBR
inductive
long bunch
k|| (V/pC)
3D simul
BBR
| Z||/n|eff (Ω)
3D simul
BBR
inductive
Daresbury, UK Oct 2016

5. Bunch Lengthening eeFACT 2016 Haissinski equation
J.Haissinski, Nuovo Cimento 18, 1 (1973)
PRSTAB (2015)
3-rd order equation for r.m.s. bunch length
Instrumentation:
streak camera
dissector tube
button-type BPM (indirect, bunch spectrum width)
B.Zotter, CERN SPS/81-14 (DI), 1981
Daresbury, UK Oct 2016

6. Coherent Energy Loss eeFACT 2016
Current-dependent synchronous phase shift
Instrumentation:
streak camera
dissector tube
RF system diagnostics
PRSTAB (2003)
Current-dependent dispersive orbit distortion
J.P.Koutchouk, CERN LEP- TH/89-2, 1989
Instrumentation:
beam position monitors
Daresbury, UK Oct 2016

7. Energy Spread – Microwave Instability
eeFACT
2016
measurement
PAC-2001 TPPH068
Instrumentation:
pin-hole X-ray camera
synchrotron light monitor
simulation
NAPAC-2016 TUPOB51
Software:
SPACE code
PRAB 19, (2016)
Vlasov-Fokker-Planck equation solver
Daresbury, UK Oct 2016

8. Beam-based Impedance Model
eeFACT
2016
PRSTAB (2015)
G0 is a form-factor for elliptical or rectangular cross-section
R. L. Gluckstern e.a., Phys. Rev. E 47, 656 (1993)
Daresbury, UK Oct 2016

9. Transverse Broad-band Impedance: What Can We Measure?
eeFACT
2016
Single-bunch effects
coherent betatron tune shift
chromatic head-tail damping
effective impedance
kick factor
(for Gaussian bunch)
always beta-weighted
Daresbury, UK Oct 2016

10. Transverse Impedance Models
eeFACT
2016
short bunch
kt (V/pCm)
3D simul
BBR
| Zt|eff (kΩ/m)
3D simul
BBR
inductive
long bunch
kt (V/pCm)
3D simul
BBR
| Zt|eff (kΩ/m)
3D simul
BBR
inductive
Daresbury, UK Oct 2016

11. Complex Frequency Shift
eeFACT
2016
Eigenvalue problem for head-tail modes:
(for Gaussian bunch)
Instrumentation:
beam position monitors
pinger
PRSTAB (2003)
Daresbury, UK Oct 2016

12. Beam-based Impedance Model
eeFACT
2016
PRSTAB (2015)
G1x,y is a form-factor for elliptical or rectangular cross-section
R. L. Gluckstern e.a., Phys. Rev. E 47, 656 (1993)
Daresbury, UK Oct 2016

13. Measurement of Local Impedance
eeFACT
2016
transverse kick by wake fields
Instrumentation:
beam position monitors
betatron phase shift
PAC-1995 Proc. pp
orbit bump method
DIPAC-1999 PT19;
NIM A 525 (2004) 433–438
VEPP-4M, 1998: Δy ~ 100μm EPAC-1998 THP09F
Diamond, 2014: Δy ~ 2μm PRSTAB 17, (2014)
Daresbury, UK Oct 2016

14. Measurement of Local Impedance
eeFACT
2016
Movable elements – variable impedance
Instrumentation:
beam position monitors
ELETTRA scraper – orbit distortion PRSTAB (2003)
NSLS-II scraper – tune shift, 2 bunch technique IBIC2016 TUCL02
Daresbury, UK Oct 2016

15. Transverse Narrow-band Impedance
eeFACT
2016
Multi-bunch instability
Instrumentation:
bunch-by-bunch feedback system
resistive-wall impedance
resonance modes
rising/damping time Diamond Light Source IPAC2016 TUPOR013
horizontal
vertical
Daresbury, UK Oct 2016

16. Transverse Narrow-band Impedance
eeFACT
2016
model impedance – Diamond Light Source IPAC2016 TUPOR013
Daresbury, UK Oct 2016

17. Summary eeFACT 2016 Daresbury, UK 24-27 Oct 2016 Impedance
Measurable effects
Instrumentation
longitudinal broad-band impedance
bunch lengthening
synchronous phase shift
dispersive orbit distortion
energy spread growth (microwave instability)
streak camera
dissector tube
RF system diagnostics
beam position monitors
pin-hole X-ray camera
synchrotron light monitor
transverse broad-band impedance
coherent betatron tune shift
chromatic head-tail damping
orbit distortion (bump method)
pinger
transverse narrow-band impedance
mode rising/damping times of transverse coupled-bunch instability
bunch-by-bunch feedback system
Daresbury, UK Oct 2016

18. Measurements vs Calculations
eeFACT
2016
Daresbury, UK Oct 2016

19. Thank you for your attention!
eeFACT
2016
Thank you for your attention!
Daresbury, UK Oct 2016