Time-domain experiments in diamond anvil cells

Transcription

1 Time-domain experiments in diamond anvil cells NSLS-II Alexander Goncharov Geophysical Laboratory, Carnegie Institution of Washington Challenges: Materials characterization under extreme conditions of high P T strain rate New materials synthesis under extremes including non equilibrium conditions New pulsed laser and X ray techniques: Pulsed laser heating Ultrafast laser pump probe techniques Combined Xray synchrotron pulsed laser experiments Laser driven shock compression in the DAC Reaction Product (arb. units) Induction Reaction Probe Delay Time (ns) Themes: Metals thermal EOS and melting: Pt Simple diatomics molecular dissociation: H 2, D 2, N 2, O 2 Minerals: MgO Noble metals thermal conductivity: Ar

2 Acknowledgements D. A. Dalton V. V. Struzhkin M. Somayazulu R. J. Hemley S. R. McWilliams M. Mahmood Geophysical Laboratory Howard University Support NSF DOE BES (EFree) DOE NNSA (CDAC) DCO ARO CIW Carnegie Washington DC campus M. R. Armstrong J. C. Crowhurst V. Prakapenka I. Kantor M. Rivers LLNL GSECARS, APS, ANL

3 Scientific challenges: bridge the gap between static and dynamic experiments in P T strain rate conditions reached & probed Phase diagram of hydrogen Temperature (K) Hydrogen Jupiter isentrope Hugoniot Molecular fluid Quantum Monte Carlo Melt line Orientationally disordered solid Orientationally ordered solids Reverberating shock Theory Pressure (GPa) Hugoniot precompressed Proposed shock in DAC (sketch) Proposed pulsed heating (sketch) Dissociation Atomic fluid? Melt line DAC limit Fluid? Gap Extreme P T conditions are relevant for: warm dense matter new materials synthesis fast chemical reactivity materials strength melting curves planetary interior Here we propose to combine static and dynamic experiments in the DAC by performing pulsed laser heating laser driven shock in the DAC

4 Melting phenomena and properties of fluids at high P T condition Shock & static experiments disagree by 1000 s K Dramatic decline of melting line?! Diagnostics of melting is scarce Problems with static methods Instabilities (e.g., diffusion) chemical reaction indirect criteria and lack of positive observations New techniques are needed to enable accurate measurements of melting phenomena improved laser heating techniques: Time resolved X ray & optical techniques : diffuse peak in XRD XAS spectroscopy elastic, optical, and vibrational properties Guillaume et al., 2011

5 Pulsed versus continuous laser heating in the DAC Pulsed laser heating: experiment Finite element calculations, maps Continuous Heating Intensity (arb. units) Planck Fit, T=10570±190 K Measurements Axial Distance (10-6 m) Wavelength (nm) Temperature histories (FE calculations) Continuous heating after turning on power Pulsed heating Radial distance (10-6 m) Pulsed Heating Temperature (K) Power (W) Power ramp Time (10-6 s) Temperature (K) Power (W) Time (10-6 s) Axial Distance (10-6 m) Radial Distance (10-6 m) Measurements are very challenging (small volume, strong thermal radiation) Uniform in space and time heating in the DAC require longer pulses

6 Coupler Time domain experiments in laser heated DAC: thermal radiation & chemical reactivity suppression Timing for pulsed heat + pulsed Raman operation: Measurement T map: FE calculations Temperature Map Temperature (K) T coupler T center Laser Pulse Intensity (arb. units) Axial Distance ( s) Radial Distance ( s) Time ( s) Pulsed heating (ns and s): we discriminate spatially and temporally (by measuring ~5 10 s after the arrival of the heating pulse). A. F. Goncharov & J. Crowhurst (2005); Goncharov et al., 2008; Goncharov et al., 2010

7 Time Resolved Raman Spectra of Hydrogen with double sided microsecond laser heating Raman spectra CW excitation 60 GPa Sample: H 2, Ir Coupler P = GPa before after Timing Laser heating Raman excitation 1800 K Intensity (relative units) 1500 K 1200 K 815 K Fluid Raman spectra Time domain experiment 445 K 300 K Raman shift (cm -1 ) Rapidly collected Raman spectra show modified intramolecular bonds above 40 GPa. Subramanian et al. PNAS, 2011 S. R. McWilliams

8 X-ray diffraction combined with pulsed laser heating Pulsed fiber laser 1 50 μs, 5 20 KHz Spectrograph & Intensified gated CCD detector 0.6 up to 50 khz Intensity, a.u. 0.3 Laser Thermal radiation Time, ms Pulse generator X ray Sector 13: GSECARS Diffraction Time resolved detector: Pilatus Goncharov, Struzhkin, Prakapenka, Kantor, Rivers, Dalton

9 Pulsed laser heating in the DAC: s timescales Pulse profile vs Thermal expansion & temperature histories Time-resolved X-ray diffraction Detection of melting 3000 T m Pt 38 GPa 55.5 Pt T (K) Unit Cell Volume FE calculated temperatures: surface center Unit Cell Volume (A 3 ) Intensity, a.u. 2 1 Reletive Intensity Pulse profile Time ( s) theta, degree GL: A. Goncharov, V. Struzhkin, A. Dalton; GSE CARS: V. Prakapenka, M. Rivers, I. Kantor

10 Optical Pump Probe System for Time Domain Thermoreflectance experiments use a double modulation approach DAC Pump + Probe Sample cavity Aluminum MgO Argon T ( 1 R) Q C Al Ad Al D. Dalton, A. Goncharov, W. P. Hsieh, D. Cahill

11 We are developing a new coherent Antistokes Raman and broad band spectroscopy systems Fianium Laser Wavelength: 1064 nm Rep Rate: Single Shot to MHz Energy: 2 μj, Pulse Width: <10 ps Peak Power: ~20 kw 1064, 532 nm mirrors ½ WP Heating Laser μsscale pulse Spectrometer with Gated Detector (300nm 780 nm) Short pass 532 nm notch 532 nm notch 10 x DAC 10 x KTP Doubling crystal Long pass Delay Stage Narrowband fundamental Broadband, chirped Source for CARS Polarizer Objective Photonic Crystal Fiber Objective Broadband mirrors D. A. Dalton, McWilliams

12 Broadband Optical Spectroscopy will enable single shot study of optical properties at the extreme environments attainable in the DAC. Supercontinuum Generation (SG) results in a very bright, white light source. lens nonlinear fiber lens The supercontinuum data was collected in a single shot manner at ~180 nj/pulse into the fiber Tungsten lamp (~3000 K) data collected at 10 3 longer accumulation time. D. A. Dalton & S. McWilliams

13 Time domain optical spectroscopy in the diamondanvil cell. Transient extreme conditions; diamond anvil cell combined with pulsed laser heating. heating laser insulator sample Oxygen, absorbance with P & T 25 GPa Heating pulse transmitted probe nm background super continuum probe Ultrafast absorption spectroscopy using super continuum optical probe. present probe: 400 to 850 nm T T T 60 GPa 45 GPa 25 GPa PCF fiber output 20 picosec. 7 GPa Goncharov, McWilliams, Dalton, Geophysical Lab

14 First Sweep of the Supercontinuum using a streak camera Wavelength (arb. units)

15 Coherent Anti Stokes Raman Spectroscopy (CARS) will be used for time resolved chemistry in the DAC Raman Effect Rayleigh Stokes Anti Stokes ω probe CARS ω 0 ω 0 ω 0 ω ω 0 + ω ω pump ω Stokes ω CARS ω molecule CARS has better conversion efficiency that Raman CARS can discriminate from fluorescense and thermal background CARS does have non resonant background Second harmonic Supercontinuum ω pump =ω probe ω Stokes ω CARS λ=532 nm λ= 532 nm 2 μm λ= ~ nm ω molecule =ω pump ω Stokes

16 Broadband Coherent Anti Stokes Raman Spectroscopy (CARS) is planned to perform single shot study of optical properties at the extreme environments attainable in the DAC: first tests at CIW CARS spectra with supercontinuum at CIW CARS spectra with supercontinuum Fianium Laser Wavelength: 1064 nm Rep Rate: Single Shot to MHz Energy: 2 μj, Pulse Width: <10 ps Peak Power: ~20 kw 1064, 532 nm mirrors ½ WP Methanol 0.5 GPa Heating Laser μsscale pulse Spectrometer with Gated Detector (300nm 780 nm) Short pass 532 nm notch 532 nm notch 10 x DAC 10 x KTP Doubling crystal Long pass Delay Stage Narrowband fundamental Broadband, chirped Source for CARS Polarizer Objective Photonic Crystal Fiber Objective Broadband mirrors Intensity (arb. units) CARS, 532 nm Raman, 457 nm Dalton, McWilliams, & Goncharov Raman Shift (cm-1)

17 Broadband Coherent Anti Stokes Raman Spectroscopy (CARS) is planned to perform single shot study of optical properties at the extreme environments attainable in the DAC: first tests at CIW CARS spectra with supercontinuum at CIW Heating Laser μsscale pulse Spectrometer with Gated Detector (300nm 780 nm) Fianium Laser Wavelength: 1064 nm Rep Rate: Single Shot to MHz Energy: 2 μj, Pulse Width: <10 ps Peak Power: ~20 kw Short pass 532 nm notch 532 nm notch 10 x DAC 10 x KTP Doubling crystal Long pass Delay Stage Narrowband fundamental Broadband, chirped Source for CARS 1064, 532 nm mirrors ½ WP Polarizer Objective Photonic Crystal Fiber Objective Broadband mirrors Raman Intensity (arb. units) CARS spectra with supercontinuum Nitrogen 22 GPa CARS, 2 s 488 nm Raman, 1 s Dalton, McWilliams, & Goncharov Raman Shift (cm-1)

18 Laser driven shock compression in the DAC: samples are dynamically compressed in the DAC Schematic Ultrafast interferometry diagnostics Shocked sample Moving Al surface Diamond Pump Shock front Precompressed sample Shocked Al Al Precompression in 100 GPa range is possible Preheating and precooling if needed Ultrafast experiments can be small scale: Table top system, unlike currently better known technique of laser shocks which involves large laser facilities (such as NIF) Armstrong and Crowhurst, LLNL

19 Observation of Off Hugoniot Shocked States with Ultrafast Time Resolution: Probing High pressure, Low temperature States Phase diagram of hydrogen Example of data for Ar Bonev et al., (2010) Armstrong et al., in press Laser shocks in the DAC can generate and detect 10s GPa shock waves (and low pressure acoustic waves) in materials under precompression of 10s GPa

20 First shots on deuterium Phase shift per 5 ps Delay (ps) Shock and particle velocities of ~12 13 km/s and ~1 km/s for precompression ranging up to 36 GPa, giving a shock pressure ~10 GPa. Possible phase transition over the duration of the probe window M. Armstrong. J. Crowhurst, LLNL

21 Outlook: the field is mature We are looking for new opportunities which will be given by new generation synchrotron sources Pulsed laser techniques have a great abilities to: access unavailable previously extreme P T conditions overcome problems of containing and probing chemically reactive and mobile materials study vibrational, optical, elastic, transport properties under extreme conditions The full potential of these techniques will be reached with further development of ultrafast (ps to fs) pump probe & single shot techniques coupled to pulsed laser heating and laser shocks in the DAC. perform experiments in a time domain to access the time scale and dynamics of phase transitions & chemical reactions We are looking forward for developing new combined X ray optical techniques at synchrotron beamlines (e.g., ERL, Petra III, XFEL, NSLS II)

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