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Task 10.5 - High Precision SC Cavity Alignment/Diagnostics/BPM with HOM Measurements

Task 10.5 - High Precision SC Cavity Alignment/Diagnostics/BPM with HOM Measurements. Nicoleta Baboi, Ursula van Rienen Roger M. Jones DESY, Univ. of Rostock, Univ. of Manchester/ Cockcroft Inst. Participating institutes/staffing

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Task 10.5 - High Precision SC Cavity Alignment/Diagnostics/BPM with HOM Measurements

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  1. Task 10.5 -High Precision SC Cavity Alignment/Diagnostics/BPM with HOM Measurements Nicoleta Baboi, Ursula van Rienen Roger M. Jones DESY, Univ. of Rostock, Univ. of Manchester/ Cockcroft Inst.

  2. Participating institutes/staffing HOM diagnostic measurement method and results achieved to date Breakdown of each sub-task Milestones/goals Finances/budget profile Summary Task 10.5 -Overview

  3. Task 10.5 HOM Diagnostics in SC Accelerator Cavities -Staff • Sub-task leaders: Nicoleta Baboi (DESY), Ursula van Rienen (Univ. Rostock), Roger M. Jones (CI/Univ. Manchester). • PDRAs: Hans-Walter Glock (Univ. Rostock), Ian Shinton (CI/Univ. of Manchester), TBA (DESY) • Ph.Ds: Nawin Juntong (CI/Univ. Manchester), Chris Glasman (CI/Univ. Manchester) H-W Glock, Univ. of Rostock, PDRA U. Van Rienen, Univ. of Rostock N. Baboi, DESY C. Glasman, CI/Univ. of Manchester Ph.d student (PT on FP7) N. Juntong, CI/Univ. of Manchester Ph.d student (PT on FP7) I. Shinton, CI/Univ. of Manchester PDRA

  4. Task 10.5 HOMs in SC Accelerator Cavities • HOM based monitors can radically contribute to the improvement of the beam quality in existing accelerator facilities FLASH at DESY and ERLP at Daresbury Laboratory, as well as the stretched wire test HOM characterisation facility at the Cockcroft Institute, CMTF at DESY, and further facilities using superconducting cavities such as the future XFEL, ILC and 4GLS. • The existing international work with SLAC and FNAL, USA, and KEK, Japan is expected to continue as it has important implications on maintaining beam quality in the development of the 16,000 or more main linac accelerating cavities for the ILC. • Participating institutes: -         DESY, Germany -         Cockcroft Institute, UK -         Dept. of Physics and Astronomy, University of Manchester, UK -         Institute of General Electrical Engineering, University of Rostock,Germany -        ASTeC, Daresbury Laboratory, UK

  5. Task 10.5 Response of HOM modes to beam

  6. bunch compressors bypass line gun undulators FEL beam collimator section dump 5 accelerating modules with 8 cavities each • 1.3GHz SC, typically 450-700MeV, 1 nC charge for FLASH/XFEL • HOMs generated in accelerating cavities must be damped. • These HOMs may also be monitored to obtain beam/cavity info • Forty cavities exist at FLASH. • Couplers/cables already exist. • Electronics installed to monitor HOMs (wideband and narrowband response).

  7. Task 10.5 Analysis of Narrowband Signals – Beam Position • Resolution of position measurement. • Predict the position at cavity 5 from the measurements at cavities 4 and 6. • Compare with the measured value. • X resolution • 9 microns • Y resolution • 4 microns

  8. Task 10.5 HOM-BPMs • Calibration based on SVD • Resolution achieved: • ~5/10m rms (Y/X) single bunch, limited by LO • Issues: • improve resolution • multi-bunch: • individual bunches measurable with lower resolution (frep ≤ 1MHz at FLASH) • speed issues • suitability of various HOMs • alternative electronics • electronics for 3.9GHz cavities needed

  9. Task 10.5 HOM Diagnostics in SC Accelerator Cavities –Task Breakdown

  10. Task 10.5 HOM Diagnostics -Task Breakdown • 10.5.1 HOM based Beam Position Monitors (HOMBPM) • Initial electronics have been developed for single bunch and installed at FLASH allowing the beam to be centered precisely. • Method needs to be verified with additional modes • Multi-bunch issues need to be understood. • The 3.9 GHz bunch shaping cavities being installed in FLASH and XFEL can readily dilute the beam emittance –important to instrument with electronics modules to diagnose the beam position and improve emittance. • Characterisation of HOMBPMs after DESY installation in summer 2009. • 10.5.2 HOM Cavity Diagnostics and ALICE/ERLP (HOMCD) • HOM spectrum allows one to ascertain the cavity alignment and cell geometry. Will investigate: • Mechanical deviations of individual cells from the ideal geometry, • Cell-to-cell misalignment, • Deformation of fields by couplers. I. Shinton, CI/Univ. Manchester PDRA at FLASH (DESY) HOM shift C. Glasman, CI/Univ. Manchester Ph.D. student at FLASH (DESY) HOM Shift

  11. 10.5.2  HOM Cavity Diagnostics and ALICE/ERLP (HOMCD) contin. • This part of the project requires beam-based measurements at FLASH, DESY and ALICE and RF-based measurements using the wire test facility at CI. • 10.5.3 HOM Distributions and Geometrical Dependences (HOMDG) • Combining finite element and S-matrix cascading techniques allows the eigenmodes in multiple accelerating cells and cavities to efficiently modeled. The University of Rostock and the University of Manchester have developed a suite of codes. • Will apply these powerful computing methods in order to specify allowable tolerances on fabrication and alignment of the TESLA cells and cavities Ian Shinton’s Beam Time Shifts at FLASH (DESY) January 2007 (R.M. Jones, CI/Univ. of Manchester Faculty also participated) 7/1/07-13/1/07: Participated in HOM shifts September 2007 25/9/07-29/9/07: Attended as part of HOM shift groups of SLAC, FERMI and KEK – calibration data taken, HOM phase measurements taken across module 4, multibunch data taken January 2008 (Hans-Walter Glock, Univ. Rostock, also participated) 15/1/08-23/1/08: 5 shifts in total: remote access control of the machine achieved, 5 collaborative shifts in which calibration data was taken, Multibunch data taken, Phase measurements taken across module 5 for various offsets (beam moved in a circle) – broadband data. September 2008 (C. Glasman, CI/Univ. of Manchester Ph.D. student also participated) 21/9/08 – 29/9/08: 1: Collaborative shift, 3 HOM phase/position assigned shifts

  12. HOM-couplers (pick-ups) 10.5.1 HOMBPM Highlights • Purpose: on-line measuring device for 1. beam alignment on the axes of the 3.9GHz cavities (& 1.3 GHz cavities) in FLASH (&XFEL&ILC) 2. measurement of beam position at the cavity locations • Task: -develop, build, test electronics for 3.9 GHz cavities -interpret signals and integrate in control system -measure cavity alignment • HOM-couplers -one at each cavity end -enable monitoring the HOMs excited by beam

  13. 10.5.2 Stretched Wire Measurement of Modes in Crab Cavity Purpose-built set-up of wire measurement of modes in crab cavity Convert to impedance Measurement of S21 for various offsets • Dispersion curves reveal expected modal perturbation • Measure S21, convert to impedance, fit to Lorentzian, and hence determine: f, kloss Dispersion curves of wire displaced from centre of cavity See: 1. M.Sc. Thesis, N. Chanlek 2007 (Univ. Manchester) 2 IEEE Trans Nucl. Sc. , vol. 54,No 5, Oct 2007, Burt, Jones and Dexter

  14. Task 10.5.2 HOMCD –Future Development for ALICE/ERLP • Experience gained on FLASH measurements is invaluable. • HOMs in ALICE TESLA cavities will provide information on: • 1. Beam position (effectively a built-in BPM) • 2. Alignment of cells (and groups thereof). Schematic illustrating ALICE • Proposal for similar HOM diagnostic measurement on ALICE CI/Univ. of Manchester PDRA I. Shinton (left) and Ph.D. student N. Juntong (right; supported by the Thai Government) will participate in ALICE commissioning in Nov/Dec 2008

  15. Task 10.5.3 –Resonator inc. Couplers Input coupler HOM coupler CAD-plot: DESY HOM coupler • Resonator without couplers: N ~ 29,000 (2D) • N ~ 12·106 (3D) • Resonator with couplers: N ~ 15·106 (3D) •  N increases by ~ 500 • CSC: „Coupled S-Parameter Calculation“ allows for combination of 2D- and 3D-simulations K. Rothemund; H.-W. Glock; U. van Rienen. Eigenmode Calculation of Complex RF-Structures using S-Parameters. IEEE Transactions on Magnetics, Vol. 36, (2000): 1501-1503.

  16. Task 10.5.3 –CSC Resonator Chain Identical sections SHom1Hom2 /dB Weak dependence on position HOM1 HOM2 Variation of coupler position 1,000 frequency points 31 lengths resulting S-matrix: 16 x 16 intern 84 x 84, 1h 12min, Pentium III, 1 GHz

  17. Task 10.5 –Planning

  18. Task 10.5 –Milestones/Deliverables 1=prototype; R=report

  19. Task 10.5.1 –Finances

  20. Task 10.5.2 –Finances

  21. Task 10.5.3 –Finances

  22. Task 10.5 HOM Diagnostics -Finances

  23. Summary of Task 10.5 • HOM characterisation of cavity wake-fields and beam dynamics for ILC/XFEL. Globalised scattering technique provides a unique method to enable trapped modes in modules to be probed. • HOMs as BPM diagnostic for ILC/XFEL: FP7 proposal as part of DESY/Cockcroft/Univs Manchester & Rostock collaboration. Experimental and simulation/analytical aspects at FLASH/DESY. • 3.9 GHz bunch-shaping cavities due to be installed at FLASH will have a significantly larger wakefields (~ a3). Major part of program will be entail characterising these cavities –beam and cavity alignment

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