XFEL Undulator Efforts at DESY and Thoughts on LCLS-II

H.-D. NuhnJune 30, 2010

• XFEL Undulator– Undulator Magnet Development– Magnet Measurement Facility– Conceptual Design Review of Undulator Segments for Pre-Series Prototype

for SASE1-3– Production of circularly polarized radiation at SASE3

• 2 Talks– Experience with Commissioning of the LCLS Undulator System– Plans for LCLS-II

• FLASH control room• PETRA III / HERA III

2-week visit at XFEL June 7 – 18, 2010

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• XFEL Undulators (J. Pflueger)

• XFEL Undulator Alignment Concept

• XFEL Phase Shifters

• XFEL Earth Field Compensation

• XFEL Undulator Controls (S. Karabekyan)

• Production of Circular Polarization (M.Yurkov)

Overview

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Joachim Pflueger

XFEL Energy Change 17.2 GeV to 14 GeV Requires Change in Undulator Design

LCLS-I fixed gap undulators• MMF

– Install tuning benches in same orientation to Earth field as in the UH. Use mu-metal wrapper to suppress field differences.

• Undulator Hall– Undulators with mu-metal wrappers

and oriented tuning have sufficient Earth field compensation. No further protection needed.

The method can not easily be applied to variable gap undulators

Earth Field Compensation

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XFEL variable gap undulators• Tuning Lab

– Eliminate Earth field with 3 orthogonal Helmholtz coils mounted to the room edges.

• XFEL Tunnel– Eliminate Earth field with 3

orthogonal Helmholtz coils per segment mounted to the tunnel walls and floor.

• Vacuum chamber and RF cavity BPMs fixed to floor• Quadrupoles with (x, y) remote adjustability• Undulator segments with (y, jaw) remote adjustability

1.Align 175-m long vacuum chamber roughly to a straight line with conventional alignment methods

2.Align RF cavity BPMS to same straight line as vacuum chamber with conventional alignment methods

3.Straighten electron beam orbit using BBA by remotely adjusting quadrupole positions

4.Center undulators with beam based K measurements (find smallest K value for mid-plane position.

5.Adjust gap heights of all undulators with beam based K measurements.6.(Optional) Vertically center vacuum chamber inside undulator gap using

local adjustments.

XFEL Alignment Concept

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XFEL Phase Shifters

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NIM A 605 (2009) 399-408

XFEL Phase Shifters

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NIM A 605 (2009) 399-408

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• XFEL is planning to use one type of planar, variable gap undulator for the SASE 1, 2, and 3 lines.

• Ideas of adding helical or Apple-type undulators are being discussed but no designs or detailed plans exist, yet.

• Tuning by adjusting pole positions appears to be advantages for variable gap devices and should be considered for LCLS-II.

• Undulator Line Alignment Concept for XFEL is less flexible than for LCLS-I and depends quite heavily on K-Mono (or K-Spectrometer) measurements.

• Permanent magnet XFEL Phase Shifters are complex and do not appear to provide benefits over 4-EM dipole chicanes.

• XFEL Earth Field Compensation using 3 orthogonal Helmholtz coils might be need for LCLS-II variable gap undulators.

• XFEL Undulator Controls appear to be based on localized control system.• XFEL is working on ideas for polarization control, similar to what we are considering

for LCLS-II• Problem of removing unpolarized component is being addressed. 2nd harmonic

solution is presently preferred. Beam deflection while preserving micro-bunching is being studies.

Summary

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End of Presentation