1. Operation and Safety
ART Review
Harald Sinn

2. Mission (in principle) impossible!
How to stop this beam?
10 micron LCLS beam (AMO station) on B4C, 2009 Hau-Riege et al.
Mission (in principle) impossible!

3. How to stop unfocused XFEL beam?
Example: Front end to experimental hall for unfocused beam
Experiment Hall

4. Beam power absorber (< 300 W)
max. FEL beam
FEL beam
B4C, 8°
At 2-8 keV danger from XFEL full pulse trains could damage absorber (small beam)

5. Solution: Beam Modes Green: Machine modes
‘Mode 2’ is safe for diamond window at FXE, screen ….
‘Mode 3’ is safe for X-ray beam stops, apertures, slits, Si-mono…..

6. Implementation of beam modes

7. Problem: Beam Modes at a Multi-User Facility!
De-coupling of SASE1-SASE3 requires fresh bunch technique!

8. Other problem: Missteered Beam!
100 μrad

9. Other problem: Missteered Beam!
Static collimators work
only > 100 m (Mode 3)
100 μrad
2.2 mrad

10. Active protection: X-ray beam loss monitor
Can stop beam during pulse train (min 50 pulses)!
Photomultiplier + Szintillator WP17
Is one per beamline enough?

11. Ray Tracing SBP horizontal
Better: XBLMs (slits) after (before) each mirror

12. Components SASE1

13. Idea: Use diamond-coated B4C as scintillator
Slits as XBLMs
SRAs (white beam slits), prototype in our lab, works in horizontal and vertical geometry
Idea: Use diamond-coated B4C as scintillator

14. View from bottom

15. XBLMs PMT View from bottom HV + photo current measurement
Need 12 BLM pairs for all beamlines (9 extra hor. slits)

16. SRA-XBLM-slits
Pros (slit XBLMs versus only disk one a the end)
If it works, it will enable safe Mode4 operation
If electronics doesn’t work, still best possible protection in Mode3 (4-8° incidence angle B4C)
Protects downstream mirror
Defines intermediate focus
Could also work as coarse BPM
Cons
Many more slits required (budget: 6/2 SRA, required: min.15/2 slit units + 15 x electronics for horizontal operation)
(False) trips will affect coupled undulator
Requires additional (rack) space + infrastructure

17. Summary
Front-ends contain water-cooled B4C block with burn-through absorber
FEs and other absorbers, attenuators will have to be protected by beam modes (Mode 3)
X-ray beam loss monitors will be developed to protect beamline in Mode 4 operation (but which ones?).
Existing slit design could be modified to achieve that.
Requires some re-shuffling of resources

18. Supplementary slides for discussion

19. Watch dog functions
Problem: 2-d focusing in beam transport by CRL lens or soft mono

20. Damage Levels SASE1&2

21. Damage on grating structure (Gaudin et al. 2012)
Data from Flash

22. Operation Mode, Beam Mode

23. Bunch pattern table Discuss definition of charge modes Increase from
2 to 5 bits here
From XFEL Timing System Specification, Kay Rehlich et al.,