1. AMO Instrumentation Lehman Review Presentation, July 2007 John Bozek, LCLS
Scientific goals of the instrument
Status before the CR
Effects of the CR & other descoping
Current designs
Looking forward
AMO Team Leaders:
Louis DiMauro (OSU)
Nora Berrah (WMU)

2. Scientific Goals of the AMO instrumentation
Investigate multiphoton and high-field x-ray processes in atoms, molecules and clusters
Multi-photon ionization/excitation in atoms/molecules/clusters are well known in optical and recently EUV regime – little known about multi-photon inner-shell processes
Accessible intensity on verge of high-field regime where field of light interacts with electrons in the sample
Study time-resolved phenomena in atoms, molecules and clusters using ultrafast x-rays
Inner-shell side band experiments using LCLS and laser photons
Photoionization of aligned molecules
Temporal evolution of state-prepared systems

3. Scientific Goals – Multiphoton Ionization

4. Scientific Goals – Multiphoton Ionization

5. Scientific Goals – Field Ionization
Multiphoton ionization
Tunneling ionization
Above-threshold-ionization (ATI)
And subsequent high harmonic generation (HHG)
Keldysh parameter:

6. Scientific Goals - Sidebands
Two photons of different energy in interaction region at same time can result in multiphoton ionization (i.e. FLASH FEL & laser)
Phenomenon provides a means to measure temporal overlap of two pulses – i.e. providing measure of temporal overlap between LCLS & laser
Measured relative jitter between two beams of 250fs using Xe 5p photoionization
P. Radcliffe et al, APL, 90, , 2007.

7. Scientific Goals – Temporal Evolution
Femtosecond time scale of LCLS pulse allows us to follow evolution of chemical reactions, but not fast enough for electron dynamics (requires <1fs).

8. Scientific Goals – Imaging Small System
Motivated by strong desire to image free clusters
Recent results from T. Moeller’s group at FLASH
Large RG clusters
Sometimes see twins
sometimes two in beam

9. Proposed AMO High Field Instrument Concept

10. Review of Concept…Dec 08, 2006
Reviewers: Phil Heimann (ALS, LBNL), Gunther Haller (SLAC), Donghui Lu (SSRL, SLAC)
Review Findings: “The committee found the science & technical requirements well-undestood…recommend that the experimental team move forward to preparing a baseline design…”
20 individual comments addressing different areas of the instrumentation which will be addressed in the PDR

11. Instrument Concept as presented:
Along with particle imaging, laser and controls

12. Conceptual Instrument designs
Gas jet (from below)
Five electron TOF spectro’s
1of 3 ion spectrometers
X-ray emission spectrometers

13. Layout of instrument into hutch 2

14. Changes since SCR & previous Lehman review
Continuing resolution – reduction of funds available in FY07 & FY08 with bifurcation of project completion into 4a and 4b
Delayed focusing optics, x-ray emission spectrometers, ion imaging spectrometers
Descoped Particle Imaging end-station and high-power amplifier for laser system to cover cost of timing fibre
Advanced design towards a Preliminary Design Review

15. Schematic of Instrument at 4a
4A instrument has capability of measuring ions and electrons from gaseous targets together with diagnostics

16. Schematic of Instrument at 4b
Add remaining capabilities for 4b

17. CR impacts on AMO Scientific Capabilities
Retained most of core capabilities in 4a instrument
Gas jet source for low density atomic – cluster targets
Electron & ion spectrometers to monitor photoionization processes
2-3mJ laser to provide pulsed ionization capabilities for off-line testing/debugging etc
Diagnostics to monitor pulse wavelength, bandwidth, temporal overlap with laser, size and position
Primary limitation – lack of focusing optics will preclude high-field studies initially

18. AMO Instrument Design - Overview
Mechanical Design Team – Nadine Kurita (LUSI Lead Engineer), Jean Charles Castagna, Michael Kosovsky, Jim Defever

19. AMO Instrument Design – beam rate shutter
LCLS rate 120Hz
Some detectors/exp. Schemes may want lower rate or even single shot

20. AMO Instrument Design – focusing optics
Peak intensity depends on size of beam focus – accessible physics depends on intensity
Focus
W/cm2
1mm
7×1012
100μm
7×1014
10 μm
7×1016
1 μm
7×1018
100nm
7×1020

21. AMO Instrument Design – electron spec’s
Based on a successful time-of-flight (TOF) design from D. Lindle’s (UNLV) group
Five spectrometers arrayed around interaction region to measure dipole & non-dipole angular distributions

22. AMO Instrument Design – diff. pumping
Isolate chamber from optics & diagnostics
Use of rare gases requires turbo pumps
Conflicting requirements of pumping & access

23. AMO Instrument Design – gas jet
120Hz LCLS rate suggests pulsed valve
Good experience with Proch & Tickl piezo actuated valve
3 axes motion, pulse duration & sync control

24. AMO Instrument Design – ion spectrometers
One of three spectrometers – simple ion TOF, velocity map imaging & ColTRIMS momentum imaging
Ion TOF will measure charge state & probe multiple ionization
Velocity map imaging maps ion velocity onto concentric rings on detector – provides quick look at ion momenta
ColTRIMS is the ultimate AMO detection (especially when combined with coincident electron detection
Suffers many limitations due to detector

25. AMO Instrument Design – magnetic shielding
Detection of charged particles requires nulling of magnetic field
Two schemes – high permeability shielding (mu-metal) – OR – Helmholtz coils
Shielding is passive but careful design required to ensure adequate attenuation, particularly junctions
Helmholtz coils are dynamically tunable but possible to set them wrong
Pursuing shielding option since high KE electron from inner-shell photoionization not very sensitive

26. AMO Diagnostics – magnetic bottle spectrometer
Primary diagnostic – provides wavelength, bandwidth, temporal overlap with laser
High collection efficiency – up to 2π angle
P. Kruit & F.H. Read, J. Phys. E (1983).

27. AMO Diagnostics – differential pumping
Transparent AMO sample allows diagnostics AFTER experiment
Want to decouple high-field end-station from diagnostics – may want to use each independently
Differential pumping optically aligned to axis of diagnostics chamber, then whole chamber aligned to beam axis

28. AMO Diagnostics – beam screens
Simple diagnostic of beam position/size
Two YAG screens positioned ~1m apart monitored simultaneously
Requires 500nm YAG coating on 200nm SiN membrane for ~50% transmission

29. AMO Diagnostics – total energy monitor
Pulse power will vary dramatically shot-to-shot
XTOD is providing gas detector in FEE to measure pulse energy
Simultaneous measurement in diagnostics will highlight any significant losses in transport of pulse through 5 optics and multiple differential pumping stages

30. AMO Diagnostics - interconnectivity
High-field physics chamber and diagnostics chamber connected by bellows – make sure not to overextend
Significant difference in position depending on optics in/out – 30mrad deflection

31. AMO Instrument – looking forward
Complete Preliminary Design Review – Aug 07
Finish detailing high field physics chamber, diagnostics
Advance design of Particle Imaging
Make decisions on emission spectrometers
Carry design to completion – Nov 07
Build/buy and assemble – Jul 08
Testing with laser – Nov 08
Ready for first light – Jan 09