Generation of incoherent picosecond x-ray pulses: resonant production and advantage of using thin films (original) (raw)
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The generation of femtosecond X-ray pulses will have important scientific applications by enabling the direct measurement of atomic motion and structural dynamics in condensed matter on the fundamental time scale of a vibrational period. Interaction of femtosecond laser pulses with relativistic electron beams is an effective approach to generating femtosecond pulses of X-rays. In this paper we present recent results from proof-of-principle experiments in which 300 fs pulses are generated from a synchrotron storage ring by using an ultrashort optical pulse to create femtosecond time structure on the stored electron bunch. A previously demonstrated approach for generating femtosecond X-rays via Thomson scattering between terawatt laser pulses and relativistic electrons is reviewed and compared with storage-ring based schemes.
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The efficient conversion of optical laser light into bright ultrafast x-ray pulses in laser created plasmas is of high interest for dense plasma physics studies, material science, and other fields. However, the rapid hydrodynamic expansion that cools hot plasmas has limited the x-ray conversion efficiency (CE) to 1% or less. Here we demonstrate more than one order of magnitude increase in picosecond x-ray CE by tailoring near solid density plasmas to achieve a large radiative to hydrodynamic energy loss rate ratio, leading into a radiation loss dominated plasma regime. A record 20% CE into hν > 1 keV photons was measured in arrays of large aspect ratio Au nanowires heated to keV temperatures with ultrahigh contrast femtosecond laser pulses of relativistic intensity. The potential of these bright ultrafast x-ray point sources for table-top imaging is illustrated with single shot flash radiographs obtained using low laser pulse energy. These results will enable the deployment of brighter laser driven x-ray sources at both compact and large laser facilities.
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Journal of The Optical Society of America B-optical Physics - J OPT SOC AM B-OPT PHYSICS, 1996
Short-pulse high-intensity laser-plasma interactions are investigated experimentally with temporally and spectrally resolved soft-x-ray diagnostics. We demonstrate that, by adjustment of the incident laser flux, the pulse width of the laser-produced x rays emitted from solid targets may be varied to as short as the picosecond time scale. Bright, picosecond, broadband emission characteristic of a short-scale-length high-density plasma is produced only when a high laser contrast (1010) is used. The results are found to be in qualitative agreement with both the predictions of a simple model of radiation from a collisionally dominated atomic system and the results obtained from a numerical simulation. 52.40.Nk.
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Bright picosecond x-rays from intense sub-picosecond laser-plasma interactions
1995
Short-pulse, high-intensity laser-plasma interactions are investigated experimentally with temporally and spectrally resolved soft x-ray diagnostics. The emitted x-ray spectra from solid targets of various Z are characterized for a range of laser intensities (I~100 ps, characteristic of a long-scale-length, low-density plasma. Bright, picosecond, continuum emission, characteristic of a short-scalelength, high-density plasma, is produced only when a high laser contrast (1010) is used. It is demonstrated experimentally that the pulsewidth of laser-produced x-ray radiation may be varied down to the picosecond time-scale by adjusting the incident ultrashort-pulse laser flux. This controls the peak electron temperature relative to the ionization potential, corresponding to the emitted x-ray photon energy of interest. The results are found to be consistent with the predictions of a hydrodynamics code coupled to an average atom model only if non-local thermodynamic equilibrium (NLTE) is as...
Quantum Electronics, 2000
The effect of intensity, length, and wavelength of an ultrashort laser pulse on the formation of a hot electron component in a dense laser-produced plasma was first investigated in a single experiment. For a pulse length of 1 ps (or 200 fs, but with an energy contrast ratio of $ 20), it was shown that the principal mechanism of generation of hot electrons is the resonance absorption of laser radiation and that the temperature of hot electrons depends on the laser pulse intensity I and the wavelength l as T h $ (I l 2) 1a3. The homogenisation of the nanostructures of porous silicon due to a poor contrast ratio or a long duration (1 ps) of the laser pulse lowers the yield of hard x-ray radiation compared to the case of high-contrast 200-fs pulses.