1. New Science Opportunities with X-ray Free Electron Lasers (FEL)
What are X-ray FELs
Current UK position
Science with X-ray FELs
Developing a national capability
Jon Marangos
Imperial College Physics Department

2. X-ray FEL Using Coherent High Brightness X-rays From
SASE (Self Amplified Spontaneous Emission)
Undulator
Input
Low emittance,
relativisitic electron bunch
5 – 15 GeV
E/E < 10-3
Output
High brightness,
short pulse of coherent
soft to hard X-rays
Pulses < 10 fs
Narrow spectral bandwidth
Wide tuning range with multi-keV photons for structural methods (e.g. XAS, IXS, X-ray diffraction)
Exceptional available brightness
High peak flux on target 2
High Photon Number
Short pulses
Unmatched brilliance
Nine orders of
magnitude

3. X-ray SASE Free Electron Lasers
LCLS
Euro XFEL
Hard X-ray projects
SLS FEL
KOREA
LINAC COHERENT LIGHT SOURCE
LCLS
2009
2017
2012
European XFEL Facility
SACLA
SPring-8 Compact SASE Source

4. New High Repetition Rate Superconducting Machines Will Be Even More Transformative
XFEL in Hamburg: A High Rep Rate SASE Machine
~ 10,000 shots per second
LCLS II
Existing 120 Hz machine to 20 keV
+ High rep-rate (100 kHz to 1 MHz) 250 eV – 5 keV machine
JPM & RW led UK NLS project with a CDR published in June 2010.
Passed peer review and remains one of the UK’s highest priority large capital scientific projects awaiting funding approval.
Ongoing discussion on UK FEL strategy

5. The Current UK Landscape
The current UK XFEL community is small but very effective – 20 PIs, and ~80 active researchers based at 12 different institutions.
They have been using the facilities at LCLS, FLASH, SACLA, and FERMI to investigate:
protein structural dynamics
nanocrystal protein structures
matter at extreme conditions (solids and plasmas)
fast modifications to metals
time resolution of prototypical photo-chemical reactions ultrafast electron dynamics in molecules

6. Current UK position
STFC: The UK has committed to becoming a full member of the European XFEL facility (now under construction near Hamburg, Germany). A review has been undertaken that will provide the framework for making decisions on any further FEL commitments that the UK may make.
UK is part of the Helmholtz International Beamline for Extreme Fields (HIBEF) and the Serial Femtosecond Crystallography (SFX) beamline consortia at XFEL.EU.
UK’s contribution to HIBEF is the DiPOLE laser, funded by STFC and EPSRC at ~£4M each, with its operation costs yet to be confirmed.
UK will contribute £5.6M  to the SFX beamline, through BBSRC, MRC and the Wellcome Trust.

7. In was recognised that STFC needs to develop a coherent strategy for facility provision – including FELs
Set up a review panel that:
identified key science challenges that would benefit from access to a FEL facility
considered the ability of existing and near-future FEL facilities to address these science challenges.
proposed a 7 year strategy for FEL access, UK FEL facility provision, community development, and underpinning technology/skills.
Proposed a 15 – 20 year vision for UK FEL science
Courtesy of Malcolm McMahon

8. A UK FEL Strategy: UK FEL Forum Position
Doing nothing is not an option.
Support and grow the FEL science community so that UK can be competitive across broad areas of science
Invest in current and near-future facilities internationally
Attract new researchers via studentships, travel grants, fellowship calls, and a cross-RC CDT
Targeted project funding from the relevant RCs for travel, equipment and postdocs
Re-engaging communities associated with previous proposals for UK FEL facilities.

9. A UK FEL Strategy: UK FEL Forum Position
Meeting the UK’s long term needs may require constructing an X-ray FEL facility in the UK
Even if the UK maximises its opportunities for access elsewhere, the UK’s demand may exceed this level in <10 years
In the long term, the UK’s capacity requirements may be best served by constructing a UK-XFEL facility
To address the majority of key science challenges, a UK facility would need to deliver hard X-rays.
Ideally it would have a high (MHz) repetition rate. However, this is likely to be costly as a national facility. A compromise specification may need to be defined to fit UK science.

10. Frontiers In Science for the Mid-21st Century Include
Understanding the structural dynamics of physical, chemical and biochemical processes at the atomic scale: Making molecular movies
Controlling quantum scale processes in matter: Directing electronic dynamics, information and energy flow
Sub-nanometre scale imaging of arbitrary objects in their native state: Capturing the structure of an individual living cell or nanostructure

11. X-ray FELs are uniquely suited
The science calls for:
ULTRAFAST
HIGH BRIGHTNESS
HIGH REP-RATE
X-RAY
photon sources.
X-ray FELs are uniquely suited

12. Current X-ray FEL Science Highlights
Structural dynamics
Matter at extreme conditions
Nanostructure imaging
Serial nano-crystallography

13. Incisive structural probes such as time resolved X-ray spectroscopy and diffraction are key to this science
UV/IR/THz pump (including optimally shaped control pulses)
Ultrafast X-ray probes e.g. XAS, XPS,RIXS, XRD to give instantaneous structure during chemical reactions and condensed matter changes
Capture time evolution: Structure Electronic states Spin states

14. Time Resolving Chemical Reactions
Catalysis and chemistry in solution phase:
“Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)5 in solution”
Nature 520, 78 (2015)
“Tracking excited-state charge and spin dynamics in iron coordination complexes”
Nature 509, 345 (2014)
Time resolving surface catalysis Science 347,978 (2015)
Fundamental events in chemistry:
“Ultrafast X-ray Auger probing of photoexcited
molecular dynamics” Nature Comm., 10, 1038
(2014)
“X-ray induced ultrafast isomerization acetylene - vinyldiene” Nature Comm. , 6, 8199 (2015)

15. Time resolving phase changes in strongly correlated materials
Light control of quantum solids (THz pump – X-ray probe):
Field induced high temperature superconductivity?
Femtosecond dynamics of long range order: coupling of; lattice, spin, charge and orbitals

16. Matter at extreme conditions
Measuring highly transient states:
“Direct observation of melting in shock compressed bismuth with fs X-ray diffraction
PRL 115, (2015)
Probing laser generated warm dense matter:
“Ultra-bright X-ray laser scattering for dynamic
Warm dense matter physics” Nature Phot. 10, 1038 (2015)
Probing hot dense matter:
Nature Communications 6, 6397 (2015)
Phys. Rev. Lett. 114, (2015)
Nature Communications 5, 3313 (2014)
Phys. Rev. Lett. 109, (2012)
Phys. Rev. Lett. 109, (2012)
Nature 482, 59 (2012)

17. Imaging the dynamics of individual nanostructures
“Imaging transient melting of a single gold nanocrystal” PNAS 112, 7444 (2015)
“Ultrafast 3-D imaging of lattice dynamics individual gold nanocrystals” Science 341, 6141 (2013)
Nanoscopic imaging single biological organisms:
“3-D reconstruction of the giant mimivirus particle with X-ray FEL” PRL, 114, (2015)
“High throughput imaging of heterogeneous cell organelles with an X-ray FEL” Nature Phot. 8, 943 (2014)
“Imaging single cells in a stream of live cyanobacteria… “ Nature Comm. (2015)

18. “Diffract and Destroy” possible if pulse very short and very bright
Non-crystal samples destroyed before signal enough to image
“Diffract and Destroy” possible if pulse very short and very bright

19. “Diffract and Destroy” has been applied to protein
nanocrystals with 20fs X-ray pulses first demonstrated 2011
Kuptiz et al, Nature 513, 261 (2014)

20. Serial nanocrystallography is a promising development in structural biology

21. Applications to medicine
TbCatB protein of the Trypanosoma brucei protozoan – critical agent in sleeping sickness
Applications to neuroscience
“Architecture of the synaptotagnmin-
SNARE machinery for neuronal exocytosis”
Nature 525, 62 (2015)

22. What do we need if we build a national facility to do this science?
Broad photon tuning capability: photons from 100 eV to > 10 keV
Versatile configuration: Synchronised laser sources, X-ray double pulse, seeded
High peak brightness: >1012 photons pulse for “diffract and destroy” of single molecules
High repetition rate: ARPES, RIXS etc. demand low intensity on target so need to have many pulses for SNR

23. What will we need to do to enable this?
Develop a fully coordinated FEL R&D programme, building upon existing expertise in the following areas:
accelerators;
detectors;
lasers and auxiliary light sources;
diagnostics;
sample environment and target delivery;
simulation, control, data acquisition, data analysis, and storage.

24. To build a uniquely capable facility
Need to overcome existing limits on pulse synchronization, coherence and pulse shape
Can we develop a high rep-rate hard X-ray machine cost effectively?
e.g. taking lessons from compact FEL projects like SACLA and Swiss FEL and adopting new technologies like super-conducting undulators

25. SASE: Wavelength Fluctuation and Temporal Jitter
Temporal (+/- 100 fs) jitter inhibits:
Synchronisation with external sources
High temporal resolution measurements
Quantitative non-linear interaction studies
Wavelength fluctuation inhibits:
X-ray spectroscopy
Inelastic scattering
- Chemically sensitive CDI
Ultrafast structural dynamic measurements at the femtosecond timescale
need to overcome these limitations

26. Atomic Inversion Laser
Rohringer, N. et al. Nature 481, 488–491 (2012).
Results in a fixed wavelength but hard to do……..

27. Injection Seeding courtesy of Fulvio Parmigiani
Not viable for hard X-rays…..

28. Self Seeding: Eliminates Wavelength Jitter
courtesy of Jerry Hastings
Promising and fixes wavelength jitter, but not temporal jitter…….

29. Time Stamping Courtesy of Ryan Coffee X-ray gated reflectivity
Using chirped pulse for single shot timing measurement – Sub 20fs resolution demonstrated
Combined with self seeding this might just do, but still need higher rep-rate to overcome
fluctuations (in self seeding spectral fluctuations transferred to intensity fluctuation)….

30. X-ray FEL Measurement of Few Femtosecond Electron Dynamics
LCLS
LCLS with “low bunch charge” operation ~ 3 fs X-ray pulses are generated
with ~ 1011 photons/pulse
Several options are currently used at LCLS for few-fs resolved pump - probe
X-ray Split and delay
Two-pulse generation at single frequency
Two-pulse / two-colour generation
XFEL
SACLA

31. Two bunch mode XTCAV After undulator Slot 1 Electron current
time
Bunch 1
Bunch 2
Slot 1
Slot 2
X-ray power
After undulator
Electron current τ
From Marinelli et al Nature Communications (2015)

32. What do we need if we build a national facility to do future science?
Laser-e-beam modulation: Slicing and seeding schemes to get ~ 1 fs level laser-X-ray synchronization – structural dynamics
Attosecond pulses: Push the limits on pulse duration in two-pulse mode towards 100 as – electron dynamics
Multi-colour operation: Synchronised X-ray pulses of very different and tuneable photon energy would be revolutionary – multi-dimensional spectroscopy for structural and electron dynamics
Synchronised e-beam: Relativistic electron beam + XFEL pulse experiments would be a unique capability- radiobiology and structural dynamics

33. Thank you for your attention