Low Alpha Operation at Diamond Ian Martin R. Bartolini , G. Cinque, M. Frogley, A. Morgun, G. Rehm, C. Thomas, R. Walker XX European Synchrotron Light Source Workshop Helmholtz Zentrum Berlin 20th November 2012

Talk Outline Low Alpha Lattice Instability Threshold Studies Optics / Main parameters Instability Threshold Studies Mm-wave port, Schottky Barrier Diodes Measured spectrograms / bursting thresholds / comparison with theory Differences for positive / negative alpha operation Differences for single bunch / multi-bunch operation Low Alpha for Users Modes of operation / how we operate Machine performance / Beamline data Conclusions Low Alpha Lattice Optics / Main parameters Instability Threshold Studies Mm-wave port, Schottky Barrier Diodes Measured spectrograms / bursting thresholds / comparison with theory Differences for positive / negative alpha operation Differences for single bunch / multi-bunch operation Low Alpha for Users Modes of operation / how we operate Machine performance / Beamline data Conclusions Ian Martin ESLS XX, HZB, 20th Nov 2012

Lattice user low alpha Ian Martin ESLS XX, HZB, 20th Nov 2012

Lattice Parameter Standard User Lattice Low Alpha Lattice Emittance 2.7nm.rad 4.4nm.rad α1 1.7×10-4 -1×10-5 α2 (with/without sext.) 1.7×10-3 / 5.1×10-3 -2×10-5 / 0.005 α3 (with/without sext.) -1.4×10-4 / 0.051 0.004 / 0.008 Tune point (Qx / Qy) 27.205 / 12.360 29.390 / 8.284 Natural chromaticity (ξx0 / ξy0) -79 / -35 -66 / -43 σx / σy at IDs (0.2% coupling) 124μm / 2.9μm 94μm / 7.0μm Energy spread 9.62×10-4 Damping times (hor. / long.) 11.2ms / 5.6ms Natural bunch length (3MV) 10.0ps 2.4ps Synchrotron frequency (3MV) 2608Hz 629Hz Ian Martin ESLS XX, HZB, 20th Nov 2012

Talk Outline Low Alpha Lattice Instability Threshold Studies Optics / Main parameters Instability Threshold Studies Mm-wave port, Schottky Barrier Diodes Measured spectrograms / bursting thresholds / comparison with theory Differences for positive / negative alpha operation Differences for single bunch / multi-bunch operation Low Alpha for Users Modes of operation / how we operate Machine performance / Beamline data Conclusions Ian Martin ESLS XX, HZB, 20th Nov 2012

Schottky Barrier Diodes 60-90GHz SBD 60-90 GHz 220-300 GHz Sensitivity 28 V/W 1500 V/W Response Time <250 ps ~1 μs Measurement Bandwidth >4 GHz ~1 MHz Pre-amp input impedance 50 Ω 100 kΩ Pre-amp gain 60 dB 40 dB 220-300GHz SBD Ian Martin ESLS XX, HZB, 20th Nov 2012

mm-wave beam port Installed during Dec 2011 shutdown Increased power measured by SBD by factor ~3-4 Ian Martin ESLS XX, HZB, 20th Nov 2012

Positive Alpha (4 Bunches) α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 81.1µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 97.2µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 8.5µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 63.0µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 21.9µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 45.0µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 30.8µA α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 37.7µA Instability threshold Ian Martin ESLS XX, HZB, 20th Nov 2012

Instability Thresholds Free-space CSR theory: α1 > 0 Stupakov, Heifets, PRST-AB 5, 054402 (2002) Byrd et al., PRL 89, 224801 (2002) Ian Martin ESLS XX, HZB, 20th Nov 2012

Instability Thresholds Shielded CSR theory: α1 > 0 From VFP simulations: From free-space CSR theory: Bane, Cai, Stupakov, PRST-AB 13, 104402 (2010) Wuestefeld et al., IPAC 2010, p. 2504 (2010) Cai, IPAC 2011, p. 3774, (2011) Ries et al., IPAC 2012, p. 3030 (2012) Ian Martin ESLS XX, HZB, 20th Nov 2012

Negative Alpha (1 Bunch) α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 8.3µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 60.7µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 49.3µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 55.5µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 40.8µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 18.4µA α1 = -1×10-5 VRF = 3.4MV fs0 = 675Hz Ibunch = 33.0µA Bursting threshold Instability threshold Ian Martin ESLS XX, HZB, 20th Nov 2012

Instability Thresholds Instability threshold data Free-space CSR theory: α1 < 0 Stupakov, Heifets, PRST-AB 5, 054402 (2002) Byrd et al., PRL 89, 224801 (2002) Ian Martin ESLS XX, HZB, 20th Nov 2012

Instability Thresholds Bursting threshold data Free-space CSR theory: α1 < 0 Stupakov, Heifets, PRST-AB 5, 054402 (2002) Byrd et al., PRL 89, 224801 (2002) Ian Martin ESLS XX, HZB, 20th Nov 2012

Comparison Single/Multibunch α1 = -4.5x10-6 VRF = 3.4MV fs = 450Hz 1 bunch α1 = -4.5x10-6 VRF = 3.4MV fs = 450Hz 400 bunches Ian Martin ESLS XX, HZB, 20th Nov 2012

Comparison Single/Multibunch α1 = -4.5x10-6 VRF = 3.4MV fs = 450Hz 1 bunch α1 = -4.5x10-6 VRF = 3.4MV fs = 450Hz 400 bunches Ian Martin ESLS XX, HZB, 20th Nov 2012

Talk Outline Low Alpha Lattice Instability Threshold Studies Optics / Main parameters Instability Threshold Studies Mm-wave port, Schottky Barrier Diodes Measured spectrograms / bursting thresholds / comparison with theory Differences for positive / negative alpha operation Differences for single bunch / multi-bunch operation Low Alpha for Users Modes of operation / how we operate Machine performance / Beamline data Conclusions Ian Martin ESLS XX, HZB, 20th Nov 2012

User Requirements NANOSCIENCE (I06) for short pulses 2 helical undulators Use single bunch for time-resolved science Preference for higher bunch charge over shortest absolute pulse duration (no benefit for reducing alpha) Request stable beam (higher alpha for transverse stability and below bursting threshold) MIRIAM (B22) for THz emission Requirements depends on particular users and region of spectrum required Can make use of beam in short pulse mode, but some experiments require CSR emission up to 100cm-1 => need to operate above bursting threshold Ian Martin ESLS XX, HZB, 20th Nov 2012

Lattice Parameters Short Pulse Mode THz Mode α1 -1×10-5 -4.5×10-6 Number of bunches 400 + 1 200 Bunch current 50 µA (93 pC) Emittance coupling ratio 0.3% 1% Lifetime ~20h Injection efficiency (IDs open) 30-40% 15-20% VRF 3.4MV Micro-bunching instability threshold (SB) ~30-35 µA ~15 µA Bursting threshold (SB) ~55-60 µA ~25-30 µA Ian Martin ESLS XX, HZB, 20th Nov 2012

Why negative alpha? Negative alpha operation benefits both short pulse and THz users: Bunch lengthening with current reduced ‘Sharper’ longitudinal profile Measured instability thresholds similar α1 = -1x10-5 VRF = 1.5MV Ibunch = 25µA α1 = +1x10-5 VRF = 1.5MV Ibunch = 25µA α1 = +1x10-5 / 1.5MV α1 = -1x10-5 / 1.5MV Ian Martin ESLS XX, HZB, 20th Nov 2012

Bunch Length Target bunch current same for both modes Ian Martin ESLS XX, HZB, 20th Nov 2012

Short Pulse Mode 19/07/2012 20/07/2012 Requested beam fill Ian Martin ESLS XX, HZB, 20th Nov 2012

MIRIAM (B22) Spectrum Courtesy G. Cinque 03/10/2012 04/10/2012 05/10/2012 Courtesy G. Cinque Ian Martin ESLS XX, HZB, 20th Nov 2012

THz Mode 03/10/2012 04/10/2012 05/10/2012 Beam trip Data acquisition paused Mirror adjusted Ian Martin ESLS XX, HZB, 20th Nov 2012

Talk Outline Low Alpha Lattices Instability Threshold Studies Optics / Main parameters Instability Threshold Studies Mm-wave port, Schottky Barrier Diodes Measured spectrograms / bursting thresholds / comparison with theory Differences for positive / negative alpha operation Differences for single bunch / multi-bunch operation Low Alpha for Users Modes of operation / how we operate Machine performance / Beamline data Conclusions Ian Martin ESLS XX, HZB, 20th Nov 2012

Conclusions User operations: Main issues now well understood Two lattices tailored to suit needs of individual beamlines Reliable, ‘stable’ operation demonstrated for last couple of years Top-up and FOFB big help in delivering this Physics studies: Strikingly different behaviour for positive / negative alpha (more investigations needed) Earlier onset of instabilities in multi-bunch; bunches do not need to be adjacent in order to have measurable influence on neighbours Still much to do: Need better understanding of how different types of wakefield influence bunch Develop an effective model that reproduces measured behaviour Ian Martin ESLS XX, HZB, 20th Nov 2012

Ian Martin ESLS XX, HZB, 20th Nov 2012

No instabilities visible on either detector at higher frequencies 60-90GHz detector 220-300GHz detector No instabilities visible on either detector at higher frequencies (VRF = 3.4MV, α1 = -1×10-5) Ian Martin ESLS XX, HZB, 20th Nov 2012

α1=-0.3x10-5 / VRF=1.5MV α1=-0.3x10-5 / VRF=2.2MV α1=-0.3x10-5 / VRF=3.4MV α1=-0.3x10-5 / VRF=4.0MV

α1=-0.6x10-5 / VRF=1.5MV α1=-0.6x10-5 / VRF=2.2MV α1=-0.6x10-5 / VRF=3.4MV α1=-0.6x10-5 / VRF=4.0MV

α1=-1.0x10-5 / VRF=1.5MV α1=-1.0x10-5 / VRF=2.2MV α1=-1.0x10-5 / VRF=3.4MV α1=-1.0x10-5 / VRF=4.0MV

α1=-1.4x10-5 / VRF=1.5MV α1=-1.4x10-5 / VRF=2.2MV α1=-1.4x10-5 / VRF=3.4MV α1=-1.4x10-5 / VRF=4.0MV

α1= 0.3x10-5 / VRF=1.5MV α1= 0.3x10-5 / VRF=2.2MV α1= 0.3x10-5 / VRF=3.4MV α1= 0.3x10-5 / VRF=4.0MV

α1= 0.6x10-5 / VRF=1.5MV α1= 0.6x10-5 / VRF=2.2MV α1= 0.6x10-5 / VRF=3.4MV α1= 0.6x10-5 / VRF=4.0MV

α1= 1.0x10-5 / VRF=1.5MV α1= 1.0x10-5 / VRF=2.2MV α1= 1.0x10-5 / VRF=3.4MV α1= 1.0x10-5 / VRF=4.0MV

α1= 1.4x10-5 / VRF=1.5MV α1= 1.4x10-5 / VRF=2.2MV α1= 1.4x10-5 / VRF=3.4MV α1= 1.4x10-5 / VRF=4.0MV

Talk Outline α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Gap = 0 α1 = +1×10-5 α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Gap = 0 α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Gap = 1 α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Gap = 9 α1 = +1×10-5 VRF = 3.4MV fs0 = 675Hz Gap = 4 Ian Martin ESLS XX, HZB, 20th Nov 2012

(VRF = 3.4MV, α1 = -1×10-5) quadratic linear Ian Martin ESLS XX, HZB, 20th Nov 2012