Wake field monitors conception, installation and measurements in the CTF3 TBM and TBTS Reidar Lunde Lillestøl The University of Oslo / CERN 28. January 2015 1/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Outline 1 INTRODUCTION / MOTIVATION WFMs in CLIC Available modes in the CLIC structure 2 THE CLIC TEST FACILITY 3 The CTF3 and CLEX The Two-Beam Module (TBM) WFM signal connections in the CTF3 WFM scan experimental setup in the TBM 3 MEASUREMENTS Two-Beam Test Stand (TBTS) measurements First Two-Beam Module (TBM) measurements The PSI electro-optical front-end 4 SUMMARY 2/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Introduction / Motivation • In order to achieve the necessary luminosity for CLIC, we need to preserve a small main beam emittance. L ∝ ( ǫ x ǫ y ) − 1 (Picture is monopole 2 wakefield, not dipole) • One cause for emittance blow-up can be transverse wakes in the accelerating structures, which can kick the beam. • Dipole wakefields depend on the beam offset from the axis, so we need to minimize the beam offset in the structures. • Wakefield monitors (WFMs) finds the beam position based on these wakes. Then, alignment of the accelerating structures can be done, and this is foreseen after 1-to-1 steering and DFS. • For CLIC, the specification is an alignment of the accelerating structures of 5 µ m. 3/30
Introduction / Motivation CTF3 Measurements Summary / Outlook WFM Test stand (see earlier talk this session) WFM ACS Beam pipe with bellows Hexa- Base + pod active optical table N. Galindo 4/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Wakefield monitors in CLIC • TD24 accelerating structures: 24 normal cells and 2 matching cells • 4 damping slots for each cell • 4 bent waveguides with rf absorbers make up the wakefield monitors. • In CTF3, the bent waveguides are currently installed on the 2nd cell, not the middle one • 2 coaxial rf pickups are installed on different sides of each bent waveguide. One measures TM-like modes, and the other measures TE-like modes. • In CTF3, the signals picked up are measured using log detectors. 5/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Available modes, found with GdfidL TM-like modes Slightly different now (2nd cell) TE-like modes F. Peauger 6/30
Introduction / Motivation CTF3 Measurements Summary / Outlook 18 GHz TM dipole mode – electric field map F. Peauger 7/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Outline 1 INTRODUCTION / MOTIVATION WFMs in CLIC Available modes in the CLIC structure 2 THE CLIC TEST FACILITY 3 The CTF3 and CLEX The Two-Beam Module (TBM) WFM signal connections in the CTF3 WFM scan experimental setup in the TBM 3 MEASUREMENTS Two-Beam Test Stand (TBTS) measurements First Two-Beam Module (TBM) measurements The PSI electro-optical front-end 4 SUMMARY 8/30
Introduction / Motivation CTF3 Measurements Summary / Outlook The CLIC Test Facility 3 (CTF3) 1-4 × 1-2 × TBM 9/30
Introduction / Motivation CTF3 Measurements Summary / Outlook The Two Beam Test Stand • In operation since 2008 • Many results on • two-beam acceleration, • rf breakdowns, • rf breakdown kicks, • PETS recirculation, • on/off mechanism, • CLIC instrumentation, • octupole component of fundamental frequency mode • and recently also WFMs 10/30
Introduction / Motivation CTF3 Measurements Summary / Outlook The remaking of CLEX 11/30
Introduction / Motivation CTF3 Measurements Summary / Outlook The Two-Beam Module in CTF3 Drive beam Probe beam • 2 PETS • 4 Accelerating structures (2 superstructures) • 2 Quadrupoles • 2 WFMs • 2 Stripline BPMs • 4 × 2 × 2 = 16 WFM signals 12/30
Introduction / Motivation CTF3 Measurements Summary / Outlook WFM signal connections in CTF3 13/30
Introduction / Motivation CTF3 Measurements Summary / Outlook WFM scan experimental setup • Focus beam using quadrupole triplet • Use corrector(s) to steer beam • Read position on downstream screen (and with BPMs) 0 0 7 5 6 6 0 / / 0 0 0 0 4 0 5 5 1 0 5 0 0 0 0 6 4 0 5 0 0 0 0 0 0 5 9 6 7 7 9 1 1 6 6 6 6 3 3 0 8 6 5 2 4 0 2 7 7 0 0 5 5 5 0 0 8 8 8 7 7 7 7 5 5 5 5 0 J J 0 J 0 0 0 V 0 0 0 0 0 0 V 0 V S S 0 0 0 0 D J D D V V V C B M D C / C / C C M V / M D D D H H H F T P H T F P A A / T F P P H P P Q D D Q Q M B B M Q B B M D Q B . . B B D . . . . . A A . . . . . A . . A A . . . . . A A A A A . A A A A . A A A A A A C C C C A C C C C C C C C C C C C C C C C C 174 263 213 259 246 201 466 539 500 300 897 1142 1005 1764 860 403 500 500 602 488 7464 CAS.BPM0820 CAS.MTV0830 1339 1071 4383 1307 14/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Outline 1 INTRODUCTION / MOTIVATION WFMs in CLIC Available modes in the CLIC structure 2 THE CLIC TEST FACILITY 3 The CTF3 and CLEX The Two-Beam Module (TBM) WFM signal connections in the CTF3 WFM scan experimental setup in the TBM 3 MEASUREMENTS Two-Beam Test Stand (TBTS) measurements First Two-Beam Module (TBM) measurements The PSI electro-optical front-end 4 SUMMARY 15/30
Introduction / Motivation CTF3 Measurements Summary / Outlook TBTS measurements (i) Wakefield signals as a function of corrector current (Changing a single corrector) L. Navarro 16/30
Introduction / Motivation CTF3 Measurements Summary / Outlook TBTS measurements (ii) WF signals as a function of WF signals correlation beam position (Signals in ACS2 vs. (Originally position on signals in ACS1) downstream screen, adjusted L. Navarro to the ACS position) 17/30
Introduction / Motivation CTF3 Measurements Summary / Outlook TBTS measurements (iii) Beam position correlation (a misalignment was found in the horizontal plane) Right : Residuals of the vertical fit With scaling, the L. Navarro resolution can fulfil the CLIC requirements 18/30
Introduction / Motivation CTF3 Measurements Summary / Outlook First results in TBM: Delta signals at ∼ 18 GHz − 3 x 10 0.2 8 Beam Beam 6 0.15 LEFT LEFT 4 0.1 ∆ H signal ∆ V signal 2 0 0.05 − 2 0 − 4 − 0.05 − 6 2000 2200 2400 2600 2800 3000 1500 2000 2500 3000 Time [ps] Time [ps] 0.6 0.3 Beam Beam 0.5 0.25 TOP RIGHT TOP RIGHT 0.4 0.2 ∆ H signal ∆ V signal 0.3 0.15 0.2 0.1 0.1 0.05 0 0 − 0.1 − 0.05 2000 2200 2400 2600 2800 3000 2000 2200 2400 2600 2800 3000 Time [ps] Time [ps] 19/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Delta signals over sum signals, vs. position (all at ∼ 18 GHz) 3 0.7 0.65 2.5 0.6 2 0.55 ∆ H / Σ H ∆ H / Σ H 1.5 0.5 1 0.45 0.5 0.4 0 0.35 − 1.5 − 1 − 0.5 0 0.5 1 − 1 − 0.5 0 0.5 1 1.5 Beam position in X [mm] Beam position in Y [mm] 0.1 2.5 0.09 2 0.08 0.07 1.5 ∆ V / Σ V ∆ V / Σ V 0.06 1 0.05 0.04 0.5 0.03 0.02 0 − 1.5 − 1 − 0.5 0 0.5 1 1.5 − 1 − 0.5 0 0.5 1 1.5 Beam position in X [mm] Beam position in Y [mm] 20/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Single antenna signals ( ∼ 24 GHz) 0.01 0.06 0 0.05 Beam Beam − 0.01 FAR LEFT 0.04 FAR LEFT − 0.02 0.03 ’Left’ signals ’Up’ signals − 0.03 0.02 − 0.04 0.01 − 0.05 0 − 0.06 − 0.01 − 0.07 − 0.02 − 0.08 − 0.03 0 2000 4000 6000 8000 10000 2000 2200 2400 2600 2800 3000 Time [ps] Time [ps] 0.15 0.08 Beam Beam 0.06 TOP RIGHT TOP RIGHT 0.1 0.04 ’Left’ signals ’Up’ signals 0.05 0.02 0 0 − 0.02 − 0.05 − 0.04 2000 2200 2400 2600 2800 3000 2000 2200 2400 2600 2800 3000 Time [ps] Time [ps] 21/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Background issues ( ∼ 24 GHz) Possible peak detected as zero, because of the strange looking background signal! (Background somewhat different between datasets, so it is challenging to subtract) 22/30
Introduction / Motivation CTF3 Measurements Summary / Outlook Drive beam noise in WFM signals 2.5 1.6 1.4 Proper 2 ’Left’ antenna signal (treated) 1.2 WFM Drive ∆ H signal (treated) signal – 1 1.5 beam 0.8 in 1 0.6 TBM 0.4 0.5 0.2 0 0 0 200 400 600 800 1000 0 200 400 600 800 1000 Time [ns] Time [ns] Drive beam in Test Beam Line (timing wrong) 23/30
Introduction / Motivation CTF3 Measurements Summary / Outlook The PSI electro-optical front-end • New WFM front-end, based on an electro-optical approach • Radiation hardness well understood, can carry signals with negligible EM interference • Use of Electro-Optical Modulators, that via the applied electric fields change the phase delay of light paths in a LiNbO 3 crystal and enables QAM modulation M. Dehler • Possible testing in the TBM this year 24/30
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