Coherent Synchrotron Radiation in the ANKA Storage Ring Marcel Schuh On behalf of the ANKA THz-Group Laboratory for Applications of Synchrotron Radiation (LAS) / Institute of Synchrotron Radiation (ISS) KIT University of the State Baden-Wuerttemberg and National Laboratory of the Helmholtz Association marcel.schuh@kit.edu www.kit.edu
Outline ANKA storage ring Operating with a low-alpha optics Studies of / with CSR Bursting patterns & micro bunching instability Influence of geometric impedance Influence of long range wake fields Next steps Summary 2
ANKA Storage Ring Key parameters: β and D*10 [m] Circumference: 110.4 Meter RF-frequency: 500 MHz Revolution time: 368 ns Harmonic number: 184 Lattice: double DBA 30 horizontal β Dispersion*10 vertical β 25 20 15 10 5 0 0 5 10 15 20 25 s [m] Normal operation mode: Beam energy: 2.5 GeV Multi bunch mode: up to 200 ma Bunch length: > 30 ps 3
Ports Used for Accelerator Studies THz port planned courtesy E. Bründermann IR2 beamline in commissioning IR1 beamline Optical light diagnostics port 4
Low-αc Optics at ANKA and D*10 [m] 40 30 20 Dedicated low-αc optics with negative dispersion in the long and short straight sections for flexible bunch length tuning following the pioneering work of e.g. BESSY II At ANKA: Observed momentum compaction factor range as extrapolated from Qs measurements: from 7.2 10-3 to 1.4 10-4 α c = 1 L horizontal Dispersion*10 vertical ds D(s) ρ(s) s / mm 15 10 c scan at 0.8 GeV c scan at 1.0 GeV c scan at 1.3 GeV c scan at 1.6 GeV c scan at 1.8 GeV from fit with V RF =0.6 MV from fit with V RF =1.2 MV E 3/2 10 0 5-10 0 5 10 15 20 25 s [m] 0 1000 2000 working point E beam / MeV 5
Operation in the Low-αc Mode Energy ramp (reguar optics) fill various pattern at 0.5 GeV Low-αc squeeze change quadrupoles & sextupoles orbit correction between steps f RF / khz 1 0.5 RF frequency adjustment Beam energy: E BdL contribution from correctors 0-0.5 depends on αc solution: correct simultaneously orbit and frf -1 0 0.002 0.004 0.006 0.008 c p p = 1 α c (f RF f c RF ) f RF 6
THz Detector System Hot Electron Bolometer (HEB) detector Based on: SC niobium nitride Response time < 160 ps Spectral range 150 GHz - 3 THz High temporal resolution of HEB allows to study signals from individual bunches in multiand single bunch environment. Joint development of IMS (KIT) & DLR (Berlin) courtesy V. Judin 7
THz Bunch Signals in Time Domain Observe one bunch in its natural environment over many turns Saturation Bursts of of the radiation generating in multi instability turn and measurements subsequent radiation damping leads to a sawtooth-like pattern as a function of time V. Judin 8 6 Vitali Judin Longitudinal Diagnostics at ANKA
Current and Bursting Spectrum Spectrogram for a decaying current (fs = 9 khz ) HEB Signal [a.u.] 1 0.8 0.6 0.4 0.2 Measurement Graph Spectrogram 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Turn coh. power [a.u.] HEB Signal [a.u.] itali Judin 10 5 0.5 10 4 0.4 0.3 0.2 0.1 0-0.1-0.2 Graph Simulation Span: 1357.86 khz Resolution: 331.51 Hz 1. Peak at: 0.663 khz 2. Peak at: 0.995 khz Frequency [khz] -0.3 0 50 100 150 200 250 300 350 400 Hot Electron Bolometer at ANKA N = 5 10 8 N = 6 10 8 N = 8 10 8 N = 13 10 8 Graph 140 145 150 155 160 Time 165 [ns] synchrotron periods M. Klein V. Judin 9
Bunch Lengthening for Different αc-settings RMS bunch length / ps 10 20 10 2 1 10-2 for low currents σ z = σ z,0 N. Hiller et al.: DPG Spring Meeting 2012 f s = 30.8 khz f s = 18.6 khz f s = 15.1 khz f s = 9.3 khz f s = 8.4 khz f s = 6.6 khz f s = 5.6 khz Previous bursting data (multi-bunch) -1 10 1 for high currents σ z I 3 7 bunch beam current / ma
Electro Optical Bunch Length Measurement Int. Spectral decoding (single shot) t EO-crystal λ/2 laser(long chirped pulse) electron bunch Pol. λ/4 Crossed pol. Spectrometer Phase sensitive detection of THz radiation with electro-optical femto-second sampling E t Installation at ANKA Spring 2012 N. Hiller et al.: IPAC11, TUPC086 A. Plech et al.: PAC 2009, TU5RFP026 11
Impedance & CSR Power The total power radiated by a bunch of N particles is described by P total = NP incoh (1 + Nf λ ) change in form factor fλ is seen on the emitted THz power 4.20 Signal [V] 4.10 4.00 3.90 scraper in N. Hiller Controlled change of the impendance by an asymmetric vertical scraper 3.80 scraper out clear influence on emitted CSR 3.70 6.80 6.70 6.60 Current [ma] 6.50 V. Judin 6.40 12
Scraper Effects courtesy A.-S. Mueller Geometrical impedance plays an important role for CSR! 13
Microwave Wake at ANKA Low cost Low Noise Block (LNB) device used as detector ( 11 GHz) Signal shows spikes corresponding to ring structure Envelope (a.u.) 3 2.5 2 1.5 inj. line IR1 IR2 rf cavity stripline 1 0.5 0 0 50 100 150 200 250 300 350 V. Judin (KIT), F. Caspars (CERN) Time (ns) 14
Single & Multi-Bunch Effects Fast THz detector (HEB) allows to study signals from individual bunches in a multi-bunch environment >10% >10% -./&012#34&*&5!"%#!"%!"#$%&'()%&*+',-&*,.)&#,(/%!+-!"#$%&'()%&%(/%,-&*,.)&#,(/%!+-!"$#!"$!"!# I 2 bunch 6 7!!!"!#!"$!"$#!"%!"%#!"&!"&#!"#$%&$"''(#)&*&+, THz emission depends on filling pattern 220 200 180 160 140 120 100 80 60 40 20 0-0.1-0.08-0.06-0.04-0.02 0 0.02 0.04 0.06 0.08 0.1 difference to global fit [V] V. Judin 15 Karlsruhe, 9.11.2011 A.-S. Müller - Coherent THz Radiation in Electron Storage Rings Institute for Synchrotron Radiation Lab. for the Appl. of Synchrotron Radiation
Next steps New HEB + fast readout electronics, developed by KIT, allows continuous bunch by bunch and turn by turn measurements in order to study bursting dynamics. 16
FLUTE: A Test Experiment FLUTE Allow small scale tests of THz generation, compression, radiation transport and instrumentation,... Outline: Photo injector (CTF Type) S band normal conducting linac Chicane compressor THz beamline Use existing bunker Parameters Output Energy < 50 MeV Bunch charge 3 nc Rep. Rate 10-100 Hz Used bandwith 0.05-5 THz 17
Summary Low Alpha operation for different energies and machine settings (fill pattern, RF) on a regular basis CSR emission is influenced by the beam current, fill pattern and geometrical impedance Ongoing projects to study bursting dynamics, bunch deformations, and micro bunching with novel high resolution detector systems 18
Thank you for your attention! Acknowledgments: KIT ISS / LAS, Karlsruhe, Germany: V. Judin, N. Hiller, A. Hofmann, B. Kehrer, M. Klein, S. Marsching, S. Naknaimueang, M. Nasse, N.J. Smale, E. Huttel, A.-S. Müller, M. Schwarz, C. Meuter, M. Steichert KIT IMS, Karlsruhe, Germany: P. Probst, S. Wuensch, M. Siegel KIT IPE, Karlsruhe, Germany: M. Caselle, I. Bauer, A. Menshikov, M. Schleicher, B. Osswald, S. Chilingaryan, M. Weber DLR, Berlin, Germany: A. Semenov, H.-W. Hübers SLS, Villingen, Switzerland: P. Peier, V. Schlott CERN, Geneva, Switzerland: F. Caspers 19