1. Update of the vacuum system of the European X-ray free electron laser XFEL
Sven Lederer (MVS) Lutz Lilje (MVS) Torsten Wohlenberg (MVS)
DESY, HAMBURG
OLAV III July 11-14, 2011 Oak Ridge, Tennessee
How to edit the title slide
Upper area: Title of your talk, max. 2 rows of the defined size (55 pt)
Lower area (subtitle): Conference/meeting/workshop, location, date, your name and affiliation, max. 4 rows of the defined size (32 pt)
Change the partner logos or add others in the last row.

2. Outline Outline Introduction
Vacuum- & RF-requirements for the warm vacuum system
Warm vacuum section & components
Gun Injector
Bunch compressors (BC1, BC2)
Collimator
Beam distribution
Undulator chamber & Intersection
Exit-window for the main dumps
Summary and Outlook
Before you start editing the slides of your talk change to the Master Slide view: Menu button “View”, Master, Slide Master:
Edit the following 2 items in the 1st slide: 1) 1st row in the violet header: Delete the existent text and write the title of your talk into this text field 2) The 2 rows in the footer area: Delete the text and write the information regarding your talk (same as on the Title Slide) into this text field.
If you want to use more partner logos position them left beside the DESY logo in the footer area Close Master View
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

3. Introduction
European X-ray free electron laser (XFEL) is a light source of the 4th generation. Comparable with LCLS in California and SACLA in Japan Spring-8
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

4. Introduction Location of the European XFEL:
The 3.4-km-long X-ray laser will begin on the DESY site in Hamburg-Bahrenfeld and run mostly underground to the research site, south of the town of Schenefeld (Schleswig-Holstein).
DOP, FHH, Landesbetrieb Geoinf. und Vermessung, LGV //DOP, (c) LVermA S-H 2007, S
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

5. Introduction Research examples:
Deciphering the structure of biomolecules:
Exploring the nanoworld in 3D:
Filming chemical reactions:
Observing small objects in strong fields:
Investigating extreme states of matter:
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

6. XFEL- vacuum sections:
Introduction
XFEL- vacuum sections:
5 m Undulator
Warm vacuum system at room temperature
Cold vacuum system superconducting linear accelerator in TESLA-technologie
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

7. Vacuum and RF requirements for the warm vacuum system
Goal: Avoid effects that causes of significant beam losses or beam quality deterioration
Pressure requirements
beam loss from scattering on residual gas PCO=10-7m bar (Ptot=5·10-7 mbar), calculation 10 e- from each bunch negligible! Bremsstrahlung is small, mirrors!
Emittance growth negligible as well
Fast ion instability: ionized molecules interact with bunches along train, initial small offset is exponentially amplified along bunch train; for XFEL bunch distance of 200 ns only ion masses beyond M≈100 can be captured → no thread independent of pressure
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

8. Vacuum and RF requirements for the warm vacuum system
Caused by the short elctron bunch length, wake fields are a critical issue to the performance of the machine.To minimize the deterioration of the beam quality for each vacuum section requirements on…
rms surface roughfness
Oxide layer
Relative permeability
Maximal step at flange connections
Maximal gap in longitudinal direction
RF-shielding of bellows, valves and pump ports
are specified in the „High level specifications for aligment and surface
properties of vacuum components“
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

9. Vacuum and RF requirements for the warm vacuum system
High Level Specifications for Alignment and Surface Properties of Vacuum Components, Available at EDMS D
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

10. Warm vacuum section & components
Gun & Injector :
RF-gun copy of the prototype RF- gun”4” 1.5 cell L-band normal conducting Cu cavity. Tuning to the resonance frequency is done by controlling the cooling water temperature of 14 separated cooling channels
Average pressure in the gun section p <1∗ 10 −10 mbar due to the photocathode & the accelerating module (high density of pumps 10 SIPs & 5 TSPs)
RF-gun has to be particle free cleaned to ensure operation with high accelerating gradients and long RF-pulses
High density of diagnostic components
RF-gun, coupler solenoids & photocathode load-lock-system
RF-gun 4
Double diagnostic cross
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

11. Warm vacuum section & components
Bunch compressors (BC1, BC2)
Bunch compressors section particle free cleaned due to the accelerating modules
Average pressure in the bunch compressor section: 1.8∗ 10 −8 mbar
Pressure stage on both ends of each section to reduce the pressure in a short distance 1.5 m over two orders of magnitude due to the transitions to the cold vacuum
Fast shutter
Chicane 21m long
TDS
Pump vessel
4 TSPs
Gate valve
TSP
𝑒 −
Slotted beam pipe
300l/s SIPs
Gate valve
Pressure stage 1.5m long, pressure reduction from 10 −8 mbar to 10 −10 mbar
Inside of the pump vessel of the pressure stage
Pressure profil along BC1
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

12. Warm vacuum section & components
Bunch compressors (BC1, BC2)
Girder concept: ( 8 girder in BC1& 12 girder in BC2)
The beamline components of the girders will be assembly particle free in a clean room
The connection of the girders in the tunnel will be done under local clean rooms
Vertical bunch compressor chicane (design by BINP)
brazing solution with Cu & stainless steel and flat seal flanges
BC1 chicane
Example for a BC1 girder
Cross sections of the vacuum chamber
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

13. Warm vacuum section & components
Collimator:
Collimator concept: Vacuum vessel with a vertical movable collimator inside
Collimator itself will made in „sandwich“ technology: copper(in the front)/titanium (on the back)
Manipulator for shifting
Collimator with different holes diamter
Vacuum vessel
Colimator with vacuum vessel(design by BINP)
Cooling tube
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

14. Warm vacuum section & components
Beam distribution
Standard inner beam pipe diameter 40.5 mm
Beam pipe material: Copper Cu-HCP (CW021A) tube or copper coated stainless steel (1.4435) tube
Standard flange CFX50 (modified CF50 conflat flange)
Particle cleanliness is in general not required (some exceptions)
Required average pressure is 2∗ 10 −8 mbar (some exceptions)
Simulated pressure profile along a standard transport line of 11 elements with 6.3 m distance between the SIPs (blue); same simulation but assuming malfunction of one SIP represented by red curve.
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

15. Warm vacuum section & components
Beam distribution: Some Details
RF-noses with 0.2mm gap
Flange 1
Flange 2
Conflat sealing
Beam axis 𝑒 −
Standard CFX50 flange connection
Alignment tool for standard flange connections
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

16. Warm vacuum section & components
Beam distribution: Inline sputter ion pump
Inline vacuum pump wich are directly mounted into the
beam line without T-piece
Symmetric arrangment of the magnets around the beam
Tube
No effect on the beam e.g. kick on the beam !
Integrated RF shielding
Pumping speed measured corresponding to DIN 28429
Rough pump connection
HV feedthrough
Space for magnets
Magnetic shielding (iron)
Copper tube with pumping slits
Vacuum
CFX50 flange
Magnetic stray field measurement
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

17. Warm vacuum section & components
Undulator chamber & Intersection
Extruded aluminium profile with high tolerance for wall thickness & straightness
A good survey and alignment concept are essential due to the small aperture of the beam pipe!
Small aperture for the undulator chamber: VERTICAL 8.8 mm HORIZONTAL 15.0 mm
Very high surface quality needed to minimize the wake fields losses
Material with a high electrical conductivity
Low surface roughness rms < 300 nm rms in beam direction (longitudinally)
Thin oxide layer ≤ 5 nm
Water cooling
Two wire corrector (inner channels)
Friction welding flanges transition SS/Al
Cross section of the 5.5 m long Undulator chamber
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

18. Warm vacuum section & components
Undulator chamber & Intersection
The calculation of the vacuum chamber deforming due to its vacuum pressure:
Requirement for the deforming: < 0.05 mm
Chamber dimensions: height 9.6 mm wall thickness 0.4 mm (like sFLASH chamber)
FEM analysis result: deforming 3.7·10-4 mm on each side → in line
3.7·10-4 mm
M. Rüter
M. Rüter
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

19. Warm vacuum section & components
Undulator chamber & Intersection
The calculation of the vacuum chamber deflection due to its dead weight:
Requirement for the deflection: < 0.05 mm
The distance of two chamber holder : 550 mm
FEM analysis result: mm → in line
M. Rüter
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

20. Warm vacuum section & components
Undulator chamber & Intersection
Support system for the Undulator vauum chamber
Undulator vacuum chamber fixation and aligment
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

21. Warm vacuum section & components
Undulator chamber & Intersection
Detail of the alignment system
Proof of principle of this alignment concept was
done at sFlash, and PETRAIII where the
undulator gap could be closed to design value:
sFlash 9 mm & PETRAIII 12.5 mm
PETRAIII
Horizontal adjustment
Vertical adjustment
Angular adjustment
Undulator vacuum chamber
sFLASH
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

22. Warm vacuum section & components
Undulator chamber & intersection
Surface roughness:
Roughness: nearly 200 nm r.m.s. for untreated vacuum chamber
Minimize the surface roughness with AFM (abrasive flow machinig) treatment by a factor of three
AFM
Extruded Profile roughness 100nm r.m.s.
Roughness 27nm r.m.s.
Mirrow like finish
Surface of the aluminium before and after the AFM (abrasive flow machining)
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

23. Warm vacuum section & components
Undulator chamber & Intersection
Oxide layer
Oxide layer: nearly 10(Al-Oxid)+13(Al-Silikat) nm for untreated vacuum chamber
Chemical cleaning:
Aluminiumoxid 10nm
3,5nm Oxidlayer
Aluminiumsilikat 13nm
Oxide layer on the AFM polishing Aluminium before and after the chemical cleaning
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

24. Warm vacuum section & components
Undulator chamber & Intersection
Wakefield`s calculations: That a roughness off 300 nm r.m.s. and an oxide layer of 5 nm are acceptable. (Martin Dohlus, Igor Zagorodnov (MPY))
Al or Cu coating inside is essential if the material choice is stainless steel ! With the exception of the Cavity-BPM !
RF-shielding of flanges, bellows and pump ports are essential.
A good survey and alignment concept are essential due to the small aperture of the beam pipe!
Pressure profile along 10 undulator segments where 1 SIP malfunctions (red), and normal operation for comparison (blue).
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

25. Warm vacuum section & components
Undulator chamber & Intersection
Intersection details
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

26. Warm vacuum section & components
Undulator chamber & Intersection
Absorber details
For the spontaneous radiation of the SASE Undulators
top view –large shadow angle horizontal taper from 15mm to 9 mm
side view –small shadow angle, vertical from 8.8 mm to 8 mm
front view
Transition from elliptical beam pipe (v mm x h. 15 mm) to the round beam pipe 10 mm.
The calculation of photo desorption through the tapered absorber done by Ulrich Hahn (HASYLAB) and Horst Schulte-Schrepping (HASYLAB).
→ Result: the power lost at the last absorber is 51 W at 17.5 GeV and 30k bunches
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

27. Warm vacuum section & components
Undulator chamber & Intersection
Pump cross details:
6 Pump slits: 2.6 mm wide, 30 mm long
Roughness of the beam pipe ≤ 300 nm r.ms.
Beam tube inside coated with Cu or Al oxide layer ≤ 5 nm
As an example: Company Dockweiler: Ultron®
seamless tube 316l(1.4435) electro polish ≤ 162 r.m.s.
Picture taken from Company Dockweiler: Ultron® tube electro polish
Cross section of the pump cross
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

28. Warm vacuum section & components
Undulator chamber & Intersection
Flange connection:
UHV flange connection with UHV- RF-flat seal to reduce wakefields effects.
Four connection at each intersection
A very good and reliably RF- transition!
Flange connection are pinned to minimize the mismatch < 0.1 mm on the Undulator side & flange connection with male and female concept with small tolerance to minimize the mismatch on the cavity BPM side
Flange design for the link to the Undulator vacuum chamber
Flange design for the link to the cavity BPM (Female flange)
Elliptical RF-UHV-connection with a step in the aperture of 0.05 mm (vertical 8.85 mm, horizontal mm)
The transition from round to elliptical aperture placed at the UHV-flange
Round RF-UHV-connection with a step in the aperture of 0.05 mm (Ø mm)
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

29. Warm vacuum section & components
Undulator chamber & Intersection
Bellow details:
Needed for assembling the components
Needed for length compensation
Needed to provide decoupling of transversal forces into the BPM region
Longitudinal off-set ± 2 mm, 2 mm gab after installation
Lateral off-set ± 0.1 mm after installation
Simple bellow design from BINP
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

30. Warm vacuum section & components
Exit window for the main dumps
Separation of the machine vacuum and the absorber vacuum
Particle cleanness is not required
We need a reliable design concept
High reliably for the leak thightness
Dismounting is difficult due to the high radioactive activation
Copper
Titanium foil (0.5 mm) for leak thightness
Aluminium oxid ceramic (𝐴𝑙 2 𝑂 3 ) for beam diagnostic
Graphite
Water cooling
Exit window in braze technology , diameter 200 mm
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

31. Several requirements to be fulfilled
Summary & Outlook
Several requirements to be fulfilled
Baseline pressure not too ambitious in the warm sections of the XFEL, but:
Particle cleanliness required in the cold part and warm parts adjacent to the cold linac
High beam quality requires several solutions
Surface quality in chambers with small diameter (undulators)
Alignment
Steps between flanges
Etc.
Project is progressing well!
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg

32. Thank you for your attention!
OLAV III July 11-14, 2011 Oak Ridge, Tennessee Update of the vacuum system of the European X-ray free electron laser
Torsten Wohlenberg MVS DESY, Hamburg