Jakob Andreasson - Academia.edu (original) (raw)

Papers by Jakob Andreasson

Damage to VUV, EUV, and X-ray Optics IV; and EUV and X-ray Optics: Synergy between Laboratory and Space III, 2013

A super-polished substrate with an off-axis parabola figure was coated with a Sc/B 4 C/Cr multila... more A super-polished substrate with an off-axis parabola figure was coated with a Sc/B 4 C/Cr multilayer. This optic was used to focus pulses of 4.3 nm photons from the Free-electron LASer in Hamburg (FLASH) at normal incidence. Beam imprints were made in poly(methyl methacrylate) to align the optic and to measure the beam profile at the focal plane. The intense interaction resulted in imprints with raised perimeters, surrounded by ablated material extending out several micrometres. These features interfere with the beam profile measurement. The effect of a post-exposure development step on the beam imprints was investigated.

Conference on Lasers and Electro-Optics 2010, 2010

... to 100,000 atoms of xenon, argon, hydrogen, methane, and mixed species of xenon-methane. ... ... more ... to 100,000 atoms of xenon, argon, hydrogen, methane, and mixed species of xenon-methane. ... These properties will affect the evolution of explosions and are responsible for expected differences ... details about the FEL parameters can be found in [4]. The cluster source consists ...

Nature Communications, 2015

There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. ... more There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. Ultra-fast coherent diffractive imaging with X-ray free-electron lasers can probe structures at the relevant length scales and may reach sub-nanometer resolution on micron-sized living cells. Here we show that we can introduce a beam of aerosolised cyanobacteria into the focus of the Linac Coherent Light Source and record diffraction patterns from individual living cells at very low noise levels and at high hit ratios. We obtain two-dimensional projection images directly from the diffraction patterns, and present the results as synthetic X-ray Nomarski images calculated from the complex-valued reconstructions. We further demonstrate that it is possible to record diffraction data to nanometer resolution on live cells with X-ray lasers. Extension to sub-nanometer resolution is within reach, although improvements in pulse parameters and X-ray area detectors will be necessary to unlock this potential.

Proceedings of SPIE - The International Society for Optical Engineering, 2011

Powerful free electron lasers (FELs) operating in the soft X-ray regime are offering new possibil... more Powerful free electron lasers (FELs) operating in the soft X-ray regime are offering new possibilities for creating and probing materials under extreme conditions. We describe here simulations to model the interaction of a focused FEL pulse with metallic solids (niobium, vanadium, and their deuterides) at 13.5 nm wavelength (92 eV) with peak intensities between 10 15 to 10 18 W/cm 2 and a fixed pulse length of 15 femtoseconds (full width at half maximum). The interaction of the pulse with the metallic solids was modeled with a non-local thermodynamic equilibrium code that included radiation transfer. The calculations also made use of a self-similar isothermal fluid model for plasma expansion into vacuum. We find that the time-evolution of the simulated critical charge density in the sample results in a critical depth that approaches the observed crater depths in an earlier experiment performed at the FLASH free electron laser in Hamburg. The results show saturation in the ablation process at intensities exceeding 10 16 W/cm 2 . Furthermore, protons and deuterons with kinetic energies of several keV have been measured, and these concur with predictions from the plasma expansion model. The results indicate that the temperature of the plasma reached almost 5 million K after the pulse has passed.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

Understanding the ultrafast dynamics of matter under extreme conditions is relevant for structura... more Understanding the ultrafast dynamics of matter under extreme conditions is relevant for structural studies and plasma physics with X-ray lasers. We used the pulses from free-electron lasers (FLASH in Hamburg and LCLS in Stanford) to trigger X-ray induced explosions in atomic atoms (Xe) and molecular clusters (CH 4 and CD 4 ). The explosion dynamics depends on cluster size and the intensity of the X-ray pulse, and a transition from Coulomb explosion to hydrodynamic expansion is expected with increasing size and increasing pulse intensity. In methane clusters experiments at FLASH, the time-of-flight spectrometry shows the appearance of molecular adducts which are the result of molecular recombination between ions and molecules. The recombination depends on the cluster size and the expansion mechanism and becomes significant in larger clusters. In Xenon cluster experiments at the LCLS, measurements of the ion charge states in clusters suggest a formation of Xe nanoplasma which expands hydrodynamically. The dominance of low charge states of Xe is due to three-body recombination processes involving electron and Xe ions, and it depends on the X-ray intensity and nanoplasma formation.

Proceedings of SPIE - The International Society for Optical Engineering, 2009

The beam of the Free-Electron Laser in Hamburg (FLASH) was focused by a grazing incidence ellipti... more The beam of the Free-Electron Laser in Hamburg (FLASH) was focused by a grazing incidence elliptical mirror (32.5 nm and 13.5 nm) and an off-axis parabolic mirror coated with a Si/Mo multilayer (13.5 nm) to 20-micron and 1-micron spot, respectively. The grazing incidence and normal incidence focusing of ~25-fs pulses with an energy of 10 PJ resulted in an irradiance of 10 13 W/cm 2 and 10 16 W/cm 2 , respectively, at the surface of various solids (:YAG, poly(methyl methacrylate) -PMMA, stainless steel, etc.). The optical emission of the plasmas produced under these conditions was registered by a grating (1200 lines/mm and/or 150 lines/mm) spectrometer MS257 (Oriel) equipped with iCCD head (iStar 720, Andor). Surprisingly, only lines belonging to the neutral atoms were observed at intensities around 10 13 W/cm 2 . No spectral lines of ions have been identified in UV-vis spectra emitted from the plasmas formed by the FLASH beam focused in a 20-micron spot. At intensities around 10 16 W/cm 2 , the OE spectra are again dominated by the atomic lines. However, a weak emission of Al + and Al 2+ was registered as well. The abundance ratio of Al/Al + should be at least 100. The plasma has an excitation temperature Downloaded from SPIE Digital Library on 12 Jan 2010 to 130.238.41.194. Terms of Use: http://spiedl.org/terms equivalent to 0.8 eV found by a computer simulation of the aluminum plasma OE spectrum. A broadband emission was also registered, both from the single-element plasmas (typical is for carbon; there were no spectral lines) and the scintillating slabs (on Ce:YAG crystal, both the luminescence bands and the line plasma emission were recorded by the spectrometer).

Damage To Vuv, Euv, and X-Ray Optics Iii, 2011

The recent commissioning of a X-ray free-electron laser triggered an extensive research in the ar... more The recent commissioning of a X-ray free-electron laser triggered an extensive research in the area of X-ray ablation of high-Z, high-density materials. Such compounds should be used to shorten an effective attenuation length for obtaining clean ablation imprints required for the focused beam analysis. Compounds of lead (Z=82) represent the materials of first choice. In this contribution, single-shot ablation thresholds

Optics Express, 2009

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: λ = 13.5 nm, pulse length ... more We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: λ = 13.5 nm, pulse length 15 fs, pulse energy 10-40 μJ, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled sixaxis gimbal. Beam imprints on poly(methyl methacrylate) -PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of 1μm. Observations were correlated with simulations of best focus to provide further relevant information.

Advances in X-ray Free-Electron Lasers: Radiation Schemes, X-ray Optics, and Instrumentation, 2011

... and Karol Nass“ and Dusko Odie“ and Emanuele Pedersoli“ and Christian Reich“ and Daniel Rolle... more ... and Karol Nass“ and Dusko Odie“ and Emanuele Pedersoli“ and Christian Reich“ and Daniel Rollesci“ and Benedikt Rudek“'“ and Artem Rudenko“'“ and Carlo Schmidt“'“ and Joachim Schulz“ and M. Marvin Seibert“ and Robert L. Shoeman“ and Raymond G. Sierra“ and Heike ...

Optics Express, 2012

We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to... more We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 s after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems.

Conference on Lasers and Electro-Optics 2010, 2010

JM Glownia1, J. Cryan1, O. Kornilov2, M. Hertlein2, O. Gessner2, A. Belkacem 2, R. Wilcox2, G. Hu... more JM Glownia1, J. Cryan1, O. Kornilov2, M. Hertlein2, O. Gessner2, A. Belkacem 2, R. Wilcox2, G. Huang2, J. White1, V. Petrovic1, C. Raman3, H. Merdji4, D. Ray5, J. Andreasson6, J. Hajdu6, J. Frisch1, W. White1, C. Bostedt1, PH Bucksbaum1, and R. Coffee1 1 Stanford ...

Nature Photonics, 2014

ABSTRACT We overcome two of the most daunting challenges in single-particle diffractive imaging: ... more ABSTRACT We overcome two of the most daunting challenges in single-particle diffractive imaging: collecting many high-quality diffraction patterns on a small amount of sample and separating components from mixed samples. We demonstrate this on carboxysomes, which are polyhedral cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min with the Linac Coherent Light Source running at 120 Hz. We separate different structures directly from the diffraction data and show that the size distribution is preserved during sample delivery. We automate phase retrieval and avoid reconstruction artefacts caused by missing modes. We attain the highest-resolution reconstructions on the smallest single biological objects imaged with an X-ray laser to date. These advances lay the foundations for accurate, high-throughput structure determination by flash-diffractive imaging and offer a means to study

Optics express, Jan 17, 2014

We use a Mach-Zehnder type autocorrelator to split and delay XUV pulses from the FLASH soft X-ray... more We use a Mach-Zehnder type autocorrelator to split and delay XUV pulses from the FLASH soft X-ray laser for triggering and subsequently probing the explosion of aerosolised sugar balls. FLASH was running at 182 eV photon energy with pulses of 70 fs duration. The delay between the pump-probe pulses was varied between zero and 5 ps, and the pulses were focused to reach peak intensities above 10¹⁶W/cm² with an off-axis parabola. The direct pulse triggered the explosion of single aerosolised sucrose nano-particles, while the delayed pulse probed the exploding structure. The ejected ions were measured by ion time of flight spectrometry, and the particle sizes were measured by coherent diffractive imaging. The results show that sucrose particles of 560-1000 nm diameter retain their size for about 500 fs following the first exposure. Significant sample expansion happens between 500 fs and 1 ps. We present simulations to support these observations.

Physical Review Letters, 2010

Intense and ultrashort x-ray pulses from free-electron lasers open up the possibility for near-at... more Intense and ultrashort x-ray pulses from free-electron lasers open up the possibility for near-atomic resolution imaging without the need for crystallization. Such experiments require high photon fluences and pulses shorter than the time to destroy the sample. We describe results with a new femtosecond pump-probe diffraction technique employing coherent 0.1 keV x rays from the FLASH soft x-ray free-electron laser. We show that the lifetime of a nanostructured sample can be extended to several picoseconds by a tamper layer to dampen and quench the sample explosion, making <1 nm resolution imaging feasible.

Physical Review Letters, 2010

Physical Review Letters, 2010

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have create... more By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

Physical Review Letters, 2012

Explosions of large Xe clusters (<N> ~ 11,000) irradiated by femtos... more Explosions of large Xe clusters (<N> ~ 11,000) irradiated by femtosecond pulses of 850 eV x-ray photons focused to an intensity of up to 10(17) W/cm(2) from the Linac Coherent Light Source were investigated experimentally. Measurements of ion charge-state distributions and energy spectra exhibit strong evidence for the formation of a Xe nanoplasma in the intense x-ray pulse. This x-ray produced Xe nanoplasma is accompanied by a three-body recombination and hydrodynamic expansion. These experimental results appear to be consistent with a model in which a spherically exploding nanoplasma is formed inside the Xe cluster and where the plasma temperature is determined by photoionization heating.

Physical Review E, 2011

Studies of materials under extreme conditions have relevance to a broad area of research, includi... more Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10 17 W/cm 2 were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10 16 W/cm 2 . This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Damage to VUV, EUV, and X-ray Optics IV; and EUV and X-ray Optics: Synergy between Laboratory and Space III, 2013

A super-polished substrate with an off-axis parabola figure was coated with a Sc/B 4 C/Cr multila... more A super-polished substrate with an off-axis parabola figure was coated with a Sc/B 4 C/Cr multilayer. This optic was used to focus pulses of 4.3 nm photons from the Free-electron LASer in Hamburg (FLASH) at normal incidence. Beam imprints were made in poly(methyl methacrylate) to align the optic and to measure the beam profile at the focal plane. The intense interaction resulted in imprints with raised perimeters, surrounded by ablated material extending out several micrometres. These features interfere with the beam profile measurement. The effect of a post-exposure development step on the beam imprints was investigated.

Conference on Lasers and Electro-Optics 2010, 2010

... to 100,000 atoms of xenon, argon, hydrogen, methane, and mixed species of xenon-methane. ... ... more ... to 100,000 atoms of xenon, argon, hydrogen, methane, and mixed species of xenon-methane. ... These properties will affect the evolution of explosions and are responsible for expected differences ... details about the FEL parameters can be found in [4]. The cluster source consists ...

Nature Communications, 2015

There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. ... more There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. Ultra-fast coherent diffractive imaging with X-ray free-electron lasers can probe structures at the relevant length scales and may reach sub-nanometer resolution on micron-sized living cells. Here we show that we can introduce a beam of aerosolised cyanobacteria into the focus of the Linac Coherent Light Source and record diffraction patterns from individual living cells at very low noise levels and at high hit ratios. We obtain two-dimensional projection images directly from the diffraction patterns, and present the results as synthetic X-ray Nomarski images calculated from the complex-valued reconstructions. We further demonstrate that it is possible to record diffraction data to nanometer resolution on live cells with X-ray lasers. Extension to sub-nanometer resolution is within reach, although improvements in pulse parameters and X-ray area detectors will be necessary to unlock this potential.

Proceedings of SPIE - The International Society for Optical Engineering, 2011

Powerful free electron lasers (FELs) operating in the soft X-ray regime are offering new possibil... more Powerful free electron lasers (FELs) operating in the soft X-ray regime are offering new possibilities for creating and probing materials under extreme conditions. We describe here simulations to model the interaction of a focused FEL pulse with metallic solids (niobium, vanadium, and their deuterides) at 13.5 nm wavelength (92 eV) with peak intensities between 10 15 to 10 18 W/cm 2 and a fixed pulse length of 15 femtoseconds (full width at half maximum). The interaction of the pulse with the metallic solids was modeled with a non-local thermodynamic equilibrium code that included radiation transfer. The calculations also made use of a self-similar isothermal fluid model for plasma expansion into vacuum. We find that the time-evolution of the simulated critical charge density in the sample results in a critical depth that approaches the observed crater depths in an earlier experiment performed at the FLASH free electron laser in Hamburg. The results show saturation in the ablation process at intensities exceeding 10 16 W/cm 2 . Furthermore, protons and deuterons with kinetic energies of several keV have been measured, and these concur with predictions from the plasma expansion model. The results indicate that the temperature of the plasma reached almost 5 million K after the pulse has passed.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

Understanding the ultrafast dynamics of matter under extreme conditions is relevant for structura... more Understanding the ultrafast dynamics of matter under extreme conditions is relevant for structural studies and plasma physics with X-ray lasers. We used the pulses from free-electron lasers (FLASH in Hamburg and LCLS in Stanford) to trigger X-ray induced explosions in atomic atoms (Xe) and molecular clusters (CH 4 and CD 4 ). The explosion dynamics depends on cluster size and the intensity of the X-ray pulse, and a transition from Coulomb explosion to hydrodynamic expansion is expected with increasing size and increasing pulse intensity. In methane clusters experiments at FLASH, the time-of-flight spectrometry shows the appearance of molecular adducts which are the result of molecular recombination between ions and molecules. The recombination depends on the cluster size and the expansion mechanism and becomes significant in larger clusters. In Xenon cluster experiments at the LCLS, measurements of the ion charge states in clusters suggest a formation of Xe nanoplasma which expands hydrodynamically. The dominance of low charge states of Xe is due to three-body recombination processes involving electron and Xe ions, and it depends on the X-ray intensity and nanoplasma formation.

Proceedings of SPIE - The International Society for Optical Engineering, 2009

The beam of the Free-Electron Laser in Hamburg (FLASH) was focused by a grazing incidence ellipti... more The beam of the Free-Electron Laser in Hamburg (FLASH) was focused by a grazing incidence elliptical mirror (32.5 nm and 13.5 nm) and an off-axis parabolic mirror coated with a Si/Mo multilayer (13.5 nm) to 20-micron and 1-micron spot, respectively. The grazing incidence and normal incidence focusing of ~25-fs pulses with an energy of 10 PJ resulted in an irradiance of 10 13 W/cm 2 and 10 16 W/cm 2 , respectively, at the surface of various solids (:YAG, poly(methyl methacrylate) -PMMA, stainless steel, etc.). The optical emission of the plasmas produced under these conditions was registered by a grating (1200 lines/mm and/or 150 lines/mm) spectrometer MS257 (Oriel) equipped with iCCD head (iStar 720, Andor). Surprisingly, only lines belonging to the neutral atoms were observed at intensities around 10 13 W/cm 2 . No spectral lines of ions have been identified in UV-vis spectra emitted from the plasmas formed by the FLASH beam focused in a 20-micron spot. At intensities around 10 16 W/cm 2 , the OE spectra are again dominated by the atomic lines. However, a weak emission of Al + and Al 2+ was registered as well. The abundance ratio of Al/Al + should be at least 100. The plasma has an excitation temperature Downloaded from SPIE Digital Library on 12 Jan 2010 to 130.238.41.194. Terms of Use: http://spiedl.org/terms equivalent to 0.8 eV found by a computer simulation of the aluminum plasma OE spectrum. A broadband emission was also registered, both from the single-element plasmas (typical is for carbon; there were no spectral lines) and the scintillating slabs (on Ce:YAG crystal, both the luminescence bands and the line plasma emission were recorded by the spectrometer).

Damage To Vuv, Euv, and X-Ray Optics Iii, 2011

The recent commissioning of a X-ray free-electron laser triggered an extensive research in the ar... more The recent commissioning of a X-ray free-electron laser triggered an extensive research in the area of X-ray ablation of high-Z, high-density materials. Such compounds should be used to shorten an effective attenuation length for obtaining clean ablation imprints required for the focused beam analysis. Compounds of lead (Z=82) represent the materials of first choice. In this contribution, single-shot ablation thresholds

Optics Express, 2009

We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: λ = 13.5 nm, pulse length ... more We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: λ = 13.5 nm, pulse length 15 fs, pulse energy 10-40 μJ, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled sixaxis gimbal. Beam imprints on poly(methyl methacrylate) -PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of 1μm. Observations were correlated with simulations of best focus to provide further relevant information.

Advances in X-ray Free-Electron Lasers: Radiation Schemes, X-ray Optics, and Instrumentation, 2011

... and Karol Nass“ and Dusko Odie“ and Emanuele Pedersoli“ and Christian Reich“ and Daniel Rolle... more ... and Karol Nass“ and Dusko Odie“ and Emanuele Pedersoli“ and Christian Reich“ and Daniel Rollesci“ and Benedikt Rudek“'“ and Artem Rudenko“'“ and Carlo Schmidt“'“ and Joachim Schulz“ and M. Marvin Seibert“ and Robert L. Shoeman“ and Raymond G. Sierra“ and Heike ...

Optics Express, 2012

We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to... more We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 s after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems.

Conference on Lasers and Electro-Optics 2010, 2010

JM Glownia1, J. Cryan1, O. Kornilov2, M. Hertlein2, O. Gessner2, A. Belkacem 2, R. Wilcox2, G. Hu... more JM Glownia1, J. Cryan1, O. Kornilov2, M. Hertlein2, O. Gessner2, A. Belkacem 2, R. Wilcox2, G. Huang2, J. White1, V. Petrovic1, C. Raman3, H. Merdji4, D. Ray5, J. Andreasson6, J. Hajdu6, J. Frisch1, W. White1, C. Bostedt1, PH Bucksbaum1, and R. Coffee1 1 Stanford ...

Nature Photonics, 2014

ABSTRACT We overcome two of the most daunting challenges in single-particle diffractive imaging: ... more ABSTRACT We overcome two of the most daunting challenges in single-particle diffractive imaging: collecting many high-quality diffraction patterns on a small amount of sample and separating components from mixed samples. We demonstrate this on carboxysomes, which are polyhedral cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min with the Linac Coherent Light Source running at 120 Hz. We separate different structures directly from the diffraction data and show that the size distribution is preserved during sample delivery. We automate phase retrieval and avoid reconstruction artefacts caused by missing modes. We attain the highest-resolution reconstructions on the smallest single biological objects imaged with an X-ray laser to date. These advances lay the foundations for accurate, high-throughput structure determination by flash-diffractive imaging and offer a means to study

Optics express, Jan 17, 2014

We use a Mach-Zehnder type autocorrelator to split and delay XUV pulses from the FLASH soft X-ray... more We use a Mach-Zehnder type autocorrelator to split and delay XUV pulses from the FLASH soft X-ray laser for triggering and subsequently probing the explosion of aerosolised sugar balls. FLASH was running at 182 eV photon energy with pulses of 70 fs duration. The delay between the pump-probe pulses was varied between zero and 5 ps, and the pulses were focused to reach peak intensities above 10¹⁶W/cm² with an off-axis parabola. The direct pulse triggered the explosion of single aerosolised sucrose nano-particles, while the delayed pulse probed the exploding structure. The ejected ions were measured by ion time of flight spectrometry, and the particle sizes were measured by coherent diffractive imaging. The results show that sucrose particles of 560-1000 nm diameter retain their size for about 500 fs following the first exposure. Significant sample expansion happens between 500 fs and 1 ps. We present simulations to support these observations.

Physical Review Letters, 2010

Intense and ultrashort x-ray pulses from free-electron lasers open up the possibility for near-at... more Intense and ultrashort x-ray pulses from free-electron lasers open up the possibility for near-atomic resolution imaging without the need for crystallization. Such experiments require high photon fluences and pulses shorter than the time to destroy the sample. We describe results with a new femtosecond pump-probe diffraction technique employing coherent 0.1 keV x rays from the FLASH soft x-ray free-electron laser. We show that the lifetime of a nanostructured sample can be extended to several picoseconds by a tamper layer to dampen and quench the sample explosion, making <1 nm resolution imaging feasible.

Physical Review Letters, 2010

Physical Review Letters, 2010

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have create... more By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

Physical Review Letters, 2012

Explosions of large Xe clusters (<N> ~ 11,000) irradiated by femtos... more Explosions of large Xe clusters (<N> ~ 11,000) irradiated by femtosecond pulses of 850 eV x-ray photons focused to an intensity of up to 10(17) W/cm(2) from the Linac Coherent Light Source were investigated experimentally. Measurements of ion charge-state distributions and energy spectra exhibit strong evidence for the formation of a Xe nanoplasma in the intense x-ray pulse. This x-ray produced Xe nanoplasma is accompanied by a three-body recombination and hydrodynamic expansion. These experimental results appear to be consistent with a model in which a spherically exploding nanoplasma is formed inside the Xe cluster and where the plasma temperature is determined by photoionization heating.

Physical Review E, 2011

Studies of materials under extreme conditions have relevance to a broad area of research, includi... more Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10 17 W/cm 2 were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10 16 W/cm 2 . This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.