1 / 31

AMO Instrumentation: Review, Status, and Design for Multiphoton X-ray Processes

This presentation from July 2007 by John Bozek provides an overview of the scientific goals, status, and current designs of the AMO instrumentation. It covers multiphoton and high-field x-ray processes in atoms, molecules, and clusters, as well as temporal evolution and imaging of small systems. The presentation also discusses the effects of cost reductions and descoping on the instrument's capabilities.

finnd
Download Presentation

AMO Instrumentation: Review, Status, and Design for Multiphoton X-ray Processes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. AMO InstrumentationLehman Review Presentation, July 2007John 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, 131108, 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

  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 16 313 (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

More Related