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Energy Spread Measurement in the TESLA Extraction Line

Energy Spread Measurement in the TESLA Extraction Line. Nick Walker - DESY. Introduction. Question: can we accurately measure the energy spread (RMS) or energy distribution of the beam using a profile monitor in the current TDR extraction line First ‘peek’ at problem

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Energy Spread Measurement in the TESLA Extraction Line

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  1. Energy Spread Measurement in the TESLA Extraction Line Nick Walker - DESY

  2. Introduction • Question: can we accurately measure the energy spread (RMS) or energy distribution of the beam using a profile monitor in the current TDR extraction line • First ‘peek’ at problem • What do we really need for the physics?

  3. Extraction Line Concept strong final doublet electrostatic separator thin-bladed septum strong dipoles strong chromaticity of FD in conjunction with large disrupted emittance and energy spread will cause us problems

  4. ‘best’ (?) location linear dispersion Extraction Line Optics

  5. strong dipole magnet Ø120 mm Extraction Line Apertures

  6. Angles at IP Energy Distribution What do we want to measure? red: E<140 GeV disrupted beam for a design head-on collision

  7. projection ~65% of beam ~35% of beam has y<-5mm What we see at QED2

  8. What we see at QED2 Vertical Distribution Integrated ~4 orders of magnitude in signal -42mm = 1%

  9. linear dispersion Estimating Energy Distribution First we need the dispersion relation(from simulation) Use fit to map y measurementsto energy blue: reconstructed red: actual

  10. 248-250 GeV Estimating Energy Distribution misleading: really only a relative measurement (will need precision spectrometer to locate edge) Actual Measured Error Emean 241.529 241.525 210-5 ERMS 13.87 13.09 310-3 Emittance of disrupted beam will cause significant error if we need to get accurate measurements around energy peak (i.e. 250 GeV) AND that’s not all…

  11. Simulation representsBest Possible Case • realistic beams (not design collisions) • error in calibration curve for y-energy • how to do this (non-linearity a problem?) • Is simulation good enough? • effects of magnet misalignments and • beam jitter: • within bunch train (fast feedback) • train to train (5Hz) • How to measure? • laser wire (scan range?) • mechanical wire (survivability?) • What do we really need to measure?

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