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

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 24-27 Oct 2016

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 24-27 Oct 2016

Longitudinal Impedance Models eeFACT 2016 short bunch k|| (V/pC) 3D simul. 164 BBR 157 | Z||/n|eff (Ω) 3D simul. 0.41 BBR 0.38 inductive 0.50 long bunch k|| (V/pC) 3D simul. 4.4 BBR 6.5 | Z||/n|eff (Ω) 3D simul. 0.47 BBR 0.48 inductive 0.50 Daresbury, UK 24-27 Oct 2016

Bunch Lengthening eeFACT 2016 Haissinski equation J.Haissinski, Nuovo Cimento 18, 1 (1973) PRSTAB 18 064401 (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 24-27 Oct 2016

Coherent Energy Loss eeFACT 2016 Current-dependent synchronous phase shift Instrumentation: streak camera dissector tube RF system diagnostics PRSTAB 6 030703 (2003) Current-dependent dispersive orbit distortion J.P.Koutchouk, CERN LEP- TH/89-2, 1989 Instrumentation: beam position monitors Daresbury, UK 24-27 Oct 2016

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, 024401 (2016) Vlasov-Fokker-Planck equation solver Daresbury, UK 24-27 Oct 2016

Beam-based Impedance Model eeFACT 2016 PRSTAB 18 064401 (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 24-27 Oct 2016

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 24-27 Oct 2016

Transverse Impedance Models eeFACT 2016 short bunch kt (V/pCm) 3D simul. 5672 BBR 5094 | Zt|eff (kΩ/m) 3D simul. 202 BBR 181 inductive 230 long bunch kt (V/pCm) 3D simul. 2167 BBR 2128 | Zt|eff (kΩ/m) 3D simul. 233 BBR 229 inductive 230 Daresbury, UK 24-27 Oct 2016

Complex Frequency Shift eeFACT 2016 Eigenvalue problem for head-tail modes: (for Gaussian bunch) Instrumentation: beam position monitors pinger PRSTAB 6 030703 (2003) Daresbury, UK 24-27 Oct 2016

Beam-based Impedance Model eeFACT 2016 PRSTAB 18 064401 (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 24-27 Oct 2016

Measurement of Local Impedance eeFACT 2016 transverse kick by wake fields Instrumentation: beam position monitors betatron phase shift PAC-1995 Proc. pp 570-572 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, 074402 (2014) Daresbury, UK 24-27 Oct 2016

Measurement of Local Impedance eeFACT 2016 Movable elements – variable impedance Instrumentation: beam position monitors ELETTRA scraper – orbit distortion PRSTAB 6 030703 (2003) NSLS-II scraper – tune shift, 2 bunch technique IBIC2016 TUCL02 Daresbury, UK 24-27 Oct 2016

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 24-27 Oct 2016

Transverse Narrow-band Impedance eeFACT 2016 model impedance – Diamond Light Source IPAC2016 TUPOR013 Daresbury, UK 24-27 Oct 2016

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 24-27 Oct 2016

Measurements vs Calculations eeFACT 2016 Daresbury, UK 24-27 Oct 2016

Thank you for your attention! eeFACT 2016 Thank you for your attention! Daresbury, UK 24-27 Oct 2016