Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
Our knowledge of astronomical environments containing CO depends on accurate molecular data to re... more Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observations. The constant improvement in UV space instrumentation, both in sensitivity and resolution, requires increasingly detailed laboratory data. Following a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired complete datasets on the CO isotopologues in the vacuum ultraviolet. Absorption spectra were recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a resolving power R > 106 in the 8–12 eV range. Such resolution allows the analysis of individual line positions and strengths in electronic transitions and the location of perturbations. We continue our previous work on A–X bands of 12C16O and 13C16O, reporting here measurements for the 13C18O isotopologue.
Unlike transmission X-ray microscopy, scanning transmission X-ray microscopy (STXM), till now, do... more Unlike transmission X-ray microscopy, scanning transmission X-ray microscopy (STXM), till now, does not allow phase contrast. Several method have been suggested but no proof of practical feasibility has been yet given. Here we analyze the methods based on the detection of the small beam deflection induced by the object phase gradient, by a segmented detector. It is shown that structuring the zone plate illumination potentially improves the detection. A diffractive beam profiler has been constructed to condition the beam of the NSLS X1A STXM. Recent images are shown, which, compared to numerical simulations, indicate the presence of phase contrast
A VUV absorption spectroscopy facility designed for ultra-high spectral resolution is in operatio... more A VUV absorption spectroscopy facility designed for ultra-high spectral resolution is in operation as a dedicated branch on the DESIRS beamline at Synchrotron SOLEIL. This branch includes a unique VUV Fourier transform spectrometer (FTS) and a dedicated versatile gas sample chamber. The FTS instrument can cover a large UV–VUV spectral range from 4 to 30 eV, with an ultimate line width of 0.08 cm−1on a large spectral window, ΔE/E= 7%, over which all spectral features can be acquired in a multiplex way. The performance can be considered to be a middle ground between broadband moderate-resolution spectrometers based on gratings and ultra-high-spectral-resolution VUV tunable-laser-based techniques over very narrow spectral windows. The various available gaseous-sample-handling setups, which function over a wide range of pressures and temperatures, and the acquisition methodology are described. A selection of experimental results illustrates the performance and limitations of the FTS-bas...
We report on interferometric investigation of perturbed surfaces under high electric field by usi... more We report on interferometric investigation of perturbed surfaces under high electric field by using the 21.2 nm zinc soft X-ray laser operating in a half cavity configuration. DC electric fields of up to 100 MV/m were applied to the surface of a niobium sample. Both positive and negative polarizations of the electric field were examined. Single shot, high-quality X-ray interferograms
We propose a method for measuring directly the refractive index in the soft X-ray region using a ... more We propose a method for measuring directly the refractive index in the soft X-ray region using a wavefront division interferometer, the Fresnel twin mirrors. We discuss the design problems and requirements which are imposed by the application of this method to soft X-rays. This method of measurement has the advantage of being insensitive to absorption and is not based on any theory of condensed state. A simulation of the whole experiment is done.
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
Fourier transform spectrometers (FTS) are usually based upon amplitude division interferometers t... more Fourier transform spectrometers (FTS) are usually based upon amplitude division interferometers through beamsplitters (BS) as in the Michelson interferometer geometry. However, the manufacture of broadband BS is difficult and even impossible in the far VUV (below λ = 140 nm). We therefore conceived an instrument based upon an original design involving only reflective plane surfaces, giving access to the whole VUV range without the restrictions associated with BS. The VUV-FTS is a permanent endstation connected to one of the three experimental branches of the DESIRS beamline a and devoted to high resolution photoabsorption in the UV-VUV spectral range, typically between λ = 300 and 40 nm b. Since 2008, a large international community of users interested in laboratory measurements with applications in astrophysics, molecular physics or planetary atmospheres has been attracted by the VUV-FTS capabilities including its efficiency in terms of signal to noise ratio, even when high spectral resolution was not an issue. A large number of dedicated gas phase sample environments have been developed including a windowless cell that can be cooled down, a heated windowless cell, a free molecular jet setup and various windowed cells. Besides, a new discharge gas cell for production and study of transient species gave recently its first results. As an illustration, the VUV absorption spectrum of the CH 3 radical down to 140 nm will be shown in this presentation.
Using a recent technique of X-ray laser interferometry we performed the first 'in situ' probe of ... more Using a recent technique of X-ray laser interferometry we performed the first 'in situ' probe of defects induced on niobium surface by strong electric field. For the first time the modification of Nb surface state was observed during the growth of the electric field. The X-ray laser emits bright, 80ps-duration pulses at λ = 21.2 nm. The beam is reflected on the niobium surface under grazing incidence in a vacuum chamber. The interferometer is of the wave-front division type. Interferograms are single shot recorded, which affords us to probe 'instantaneous' defect morphology. We observed the appearance and the evolution of defects between 14 MV/m and 35 MV/m. The vertical set amplitude is of 100-200 Å. The observed position of a surface perturbed zone proved to be shifted by 500 µm under constant electric field (35 MV/m) between the instants of two laser shots (20 mn time interval).
Gabor holographic recording is an efficient way to collect information for soft x-ray imaging wit... more Gabor holographic recording is an efficient way to collect information for soft x-ray imaging with undulator synchrotron radiation sources. In addition to being well adapted to the radiative properties of these sources, the high simplicity and large field of the recording operation makes it akin to a particular kind of sample preparation. This is comparable to the conditions of contact microscopy. But, to take advantage of these properties, several difficult problems concerning hologram reconstruction have to be solved. We have investigated the theoretical performances and the practical implementation of Gabor holographic imaging with optical reconstruction, with the realization of a dedicated optical instrument in mind. Such an instrument is presently under construction; it is expected to provide low noise images, with a resolution better than 0.1 micrometers .
Proceedings of SPIE - The International Society for Optical Engineering, 2013
ABSTRACT The results of development and applications of the secondary sources at PALS Center will... more ABSTRACT The results of development and applications of the secondary sources at PALS Center will be presented. Currently the iodine system and the Ti:Sapphire system are operating at the PALS Center as driving lasers for generation of secondary sources. The iodine system with net energy of 1kJ is used for QSS X-ray lasing schemes. The most robust and most energetic QSS scheme with this driver is the Ne-like Zn X-ray laser, which is working here as standard user beamline for diverse applications. Recent experiment devoted to temporal coherence measurement shows possibility to amplify short duration X-rays. The second system with high rep rate is Ti: Sapphire laser chain with peak power 20TW. This laser system is used for generation high order harmonics and transient collisionally excited X-ray lasers.
We review our recent progress in the development of transient x-ray lasers and of their applicati... more We review our recent progress in the development of transient x-ray lasers and of their application to plasma diagnostic. The first observation of C-ray laser emission at the new PHELIX-GSI facility is reported. This TCE X-ray laser will be a promising tool for heavy-ion spectroscopy. We ...
Fourier Transform Spectroscopy: New Methods and Applications, 1999
Although there is a need for high resolution and/or accurate spectroscopy in the VUV-XUV spectral... more Although there is a need for high resolution and/or accurate spectroscopy in the VUV-XUV spectral range, it is remarkable that the Fourier transform spectroscopy (FTS) techniques never extended deeply toward high energy photons.
Large discrepancies in the published photoabsorption oscillator strengths of the vacuum-ultraviol... more Large discrepancies in the published photoabsorption oscillator strengths of the vacuum-ultraviolet (VUV) bands of CO hamper the interpretation of VUV astronomical observations. We report new oscillator strength measurements of the (0, 0) and (1, 0) bands of the CO B^1Sigma^+-X^1Sigma^+ electronic system determined from high-resolution (resolving power ~750,000) absorption spectra recorded with a tunable VUV laser system. The instrumental bandwidth
One of the processes controlling the interstellar CO abundance and the ratio of its isotopologues... more One of the processes controlling the interstellar CO abundance and the ratio of its isotopologues is photodissociation. Accurate oscillator strengths and predissociation rates for Rydberg transitions are needed for modeling this process. We present results on absorption from the E
The deeply saturated operation of a double-pass Ne-like zinc soft x-ray laser emitting at a wavel... more The deeply saturated operation of a double-pass Ne-like zinc soft x-ray laser emitting at a wavelength of 21.2 mm is reported, along with results of a study and optimization of its beam parameters and coherence. The active medium is a 3-cm-long plasma column produced by a separately delivered prepulse and a main pulse with a duration of ϳ450 ps, supplied by a 1.315-m laser. To generate plasma with reduced lateral density gradients, the ϳ130-m-wide main pulse focus, producing a pump irradiance of ϳ2.8ϫ10 13 W cm Ϫ2 , is placed on top of a much broader prepulse focus. The x-ray laser emission emerges as a narrowly collimated beam possessing high spatial quality and coherence. The dependence of the output on the prepulse conditions, the pump power, and the setup of the half-cavity mirror are investigated and discussed. The study of the beam transverse coherence demonstrates its strong dependence on pump energy. The large gain-length product attained through half-cavity operation allows for an efficient extraction of the energy stored in the active medium. With a small-signal gain of 7͑Ϯ0.5͒ cm Ϫ1 , the double-pass beam is deeply saturated and provides ϳ4 mJ of energy in one pulse, corresponding to peak power in excess of 40 MW, and implies that this system is the most powerful x-ray laser yet demonstrated. The inherent engineering conception of the device is compatible with a repetition rate in a hertz domain.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
Our knowledge of astronomical environments containing CO depends on accurate molecular data to re... more Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observations. The constant improvement in UV space instrumentation, both in sensitivity and resolution, requires increasingly detailed laboratory data. Following a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired complete datasets on the CO isotopologues in the vacuum ultraviolet. Absorption spectra were recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a resolving power R > 106 in the 8–12 eV range. Such resolution allows the analysis of individual line positions and strengths in electronic transitions and the location of perturbations. We continue our previous work on A–X bands of 12C16O and 13C16O, reporting here measurements for the 13C18O isotopologue.
Unlike transmission X-ray microscopy, scanning transmission X-ray microscopy (STXM), till now, do... more Unlike transmission X-ray microscopy, scanning transmission X-ray microscopy (STXM), till now, does not allow phase contrast. Several method have been suggested but no proof of practical feasibility has been yet given. Here we analyze the methods based on the detection of the small beam deflection induced by the object phase gradient, by a segmented detector. It is shown that structuring the zone plate illumination potentially improves the detection. A diffractive beam profiler has been constructed to condition the beam of the NSLS X1A STXM. Recent images are shown, which, compared to numerical simulations, indicate the presence of phase contrast
A VUV absorption spectroscopy facility designed for ultra-high spectral resolution is in operatio... more A VUV absorption spectroscopy facility designed for ultra-high spectral resolution is in operation as a dedicated branch on the DESIRS beamline at Synchrotron SOLEIL. This branch includes a unique VUV Fourier transform spectrometer (FTS) and a dedicated versatile gas sample chamber. The FTS instrument can cover a large UV–VUV spectral range from 4 to 30 eV, with an ultimate line width of 0.08 cm−1on a large spectral window, ΔE/E= 7%, over which all spectral features can be acquired in a multiplex way. The performance can be considered to be a middle ground between broadband moderate-resolution spectrometers based on gratings and ultra-high-spectral-resolution VUV tunable-laser-based techniques over very narrow spectral windows. The various available gaseous-sample-handling setups, which function over a wide range of pressures and temperatures, and the acquisition methodology are described. A selection of experimental results illustrates the performance and limitations of the FTS-bas...
We report on interferometric investigation of perturbed surfaces under high electric field by usi... more We report on interferometric investigation of perturbed surfaces under high electric field by using the 21.2 nm zinc soft X-ray laser operating in a half cavity configuration. DC electric fields of up to 100 MV/m were applied to the surface of a niobium sample. Both positive and negative polarizations of the electric field were examined. Single shot, high-quality X-ray interferograms
We propose a method for measuring directly the refractive index in the soft X-ray region using a ... more We propose a method for measuring directly the refractive index in the soft X-ray region using a wavefront division interferometer, the Fresnel twin mirrors. We discuss the design problems and requirements which are imposed by the application of this method to soft X-rays. This method of measurement has the advantage of being insensitive to absorption and is not based on any theory of condensed state. A simulation of the whole experiment is done.
Proceedings of the 70th International Symposium on Molecular Spectroscopy, 2015
Fourier transform spectrometers (FTS) are usually based upon amplitude division interferometers t... more Fourier transform spectrometers (FTS) are usually based upon amplitude division interferometers through beamsplitters (BS) as in the Michelson interferometer geometry. However, the manufacture of broadband BS is difficult and even impossible in the far VUV (below λ = 140 nm). We therefore conceived an instrument based upon an original design involving only reflective plane surfaces, giving access to the whole VUV range without the restrictions associated with BS. The VUV-FTS is a permanent endstation connected to one of the three experimental branches of the DESIRS beamline a and devoted to high resolution photoabsorption in the UV-VUV spectral range, typically between λ = 300 and 40 nm b. Since 2008, a large international community of users interested in laboratory measurements with applications in astrophysics, molecular physics or planetary atmospheres has been attracted by the VUV-FTS capabilities including its efficiency in terms of signal to noise ratio, even when high spectral resolution was not an issue. A large number of dedicated gas phase sample environments have been developed including a windowless cell that can be cooled down, a heated windowless cell, a free molecular jet setup and various windowed cells. Besides, a new discharge gas cell for production and study of transient species gave recently its first results. As an illustration, the VUV absorption spectrum of the CH 3 radical down to 140 nm will be shown in this presentation.
Using a recent technique of X-ray laser interferometry we performed the first 'in situ' probe of ... more Using a recent technique of X-ray laser interferometry we performed the first 'in situ' probe of defects induced on niobium surface by strong electric field. For the first time the modification of Nb surface state was observed during the growth of the electric field. The X-ray laser emits bright, 80ps-duration pulses at λ = 21.2 nm. The beam is reflected on the niobium surface under grazing incidence in a vacuum chamber. The interferometer is of the wave-front division type. Interferograms are single shot recorded, which affords us to probe 'instantaneous' defect morphology. We observed the appearance and the evolution of defects between 14 MV/m and 35 MV/m. The vertical set amplitude is of 100-200 Å. The observed position of a surface perturbed zone proved to be shifted by 500 µm under constant electric field (35 MV/m) between the instants of two laser shots (20 mn time interval).
Gabor holographic recording is an efficient way to collect information for soft x-ray imaging wit... more Gabor holographic recording is an efficient way to collect information for soft x-ray imaging with undulator synchrotron radiation sources. In addition to being well adapted to the radiative properties of these sources, the high simplicity and large field of the recording operation makes it akin to a particular kind of sample preparation. This is comparable to the conditions of contact microscopy. But, to take advantage of these properties, several difficult problems concerning hologram reconstruction have to be solved. We have investigated the theoretical performances and the practical implementation of Gabor holographic imaging with optical reconstruction, with the realization of a dedicated optical instrument in mind. Such an instrument is presently under construction; it is expected to provide low noise images, with a resolution better than 0.1 micrometers .
Proceedings of SPIE - The International Society for Optical Engineering, 2013
ABSTRACT The results of development and applications of the secondary sources at PALS Center will... more ABSTRACT The results of development and applications of the secondary sources at PALS Center will be presented. Currently the iodine system and the Ti:Sapphire system are operating at the PALS Center as driving lasers for generation of secondary sources. The iodine system with net energy of 1kJ is used for QSS X-ray lasing schemes. The most robust and most energetic QSS scheme with this driver is the Ne-like Zn X-ray laser, which is working here as standard user beamline for diverse applications. Recent experiment devoted to temporal coherence measurement shows possibility to amplify short duration X-rays. The second system with high rep rate is Ti: Sapphire laser chain with peak power 20TW. This laser system is used for generation high order harmonics and transient collisionally excited X-ray lasers.
We review our recent progress in the development of transient x-ray lasers and of their applicati... more We review our recent progress in the development of transient x-ray lasers and of their application to plasma diagnostic. The first observation of C-ray laser emission at the new PHELIX-GSI facility is reported. This TCE X-ray laser will be a promising tool for heavy-ion spectroscopy. We ...
Fourier Transform Spectroscopy: New Methods and Applications, 1999
Although there is a need for high resolution and/or accurate spectroscopy in the VUV-XUV spectral... more Although there is a need for high resolution and/or accurate spectroscopy in the VUV-XUV spectral range, it is remarkable that the Fourier transform spectroscopy (FTS) techniques never extended deeply toward high energy photons.
Large discrepancies in the published photoabsorption oscillator strengths of the vacuum-ultraviol... more Large discrepancies in the published photoabsorption oscillator strengths of the vacuum-ultraviolet (VUV) bands of CO hamper the interpretation of VUV astronomical observations. We report new oscillator strength measurements of the (0, 0) and (1, 0) bands of the CO B^1Sigma^+-X^1Sigma^+ electronic system determined from high-resolution (resolving power ~750,000) absorption spectra recorded with a tunable VUV laser system. The instrumental bandwidth
One of the processes controlling the interstellar CO abundance and the ratio of its isotopologues... more One of the processes controlling the interstellar CO abundance and the ratio of its isotopologues is photodissociation. Accurate oscillator strengths and predissociation rates for Rydberg transitions are needed for modeling this process. We present results on absorption from the E
The deeply saturated operation of a double-pass Ne-like zinc soft x-ray laser emitting at a wavel... more The deeply saturated operation of a double-pass Ne-like zinc soft x-ray laser emitting at a wavelength of 21.2 mm is reported, along with results of a study and optimization of its beam parameters and coherence. The active medium is a 3-cm-long plasma column produced by a separately delivered prepulse and a main pulse with a duration of ϳ450 ps, supplied by a 1.315-m laser. To generate plasma with reduced lateral density gradients, the ϳ130-m-wide main pulse focus, producing a pump irradiance of ϳ2.8ϫ10 13 W cm Ϫ2 , is placed on top of a much broader prepulse focus. The x-ray laser emission emerges as a narrowly collimated beam possessing high spatial quality and coherence. The dependence of the output on the prepulse conditions, the pump power, and the setup of the half-cavity mirror are investigated and discussed. The study of the beam transverse coherence demonstrates its strong dependence on pump energy. The large gain-length product attained through half-cavity operation allows for an efficient extraction of the energy stored in the active medium. With a small-signal gain of 7͑Ϯ0.5͒ cm Ϫ1 , the double-pass beam is deeply saturated and provides ϳ4 mJ of energy in one pulse, corresponding to peak power in excess of 40 MW, and implies that this system is the most powerful x-ray laser yet demonstrated. The inherent engineering conception of the device is compatible with a repetition rate in a hertz domain.
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Papers by Denis Joyeux