Some readers might remember the news article, "A compact synchrotron light source driven by pulse laser", in X-ray Spectrometry, Vol. 37, No.2 (2008). The essential point is that a table top pulse laser can be used as an alternative to a linear or circular electron accelerator. The article above reported the first successful synchrotron radiation generation from laser-plasma-accelerated electrons, but the wavelength was only in the visible to infrared region. Recently, an international team led by Professors S. Karsch and F. Grunera achieved a new breakthrough. The team belongs to Munich's Cluster of Excellence "Munich Centre for Advanced Photonics" (MAP), in the Laboratory for Attosecond Physics (LAP) of Ludwig-Maximilians-Universitat (LMU) in Munich and the Max Planck Institute of Quantum Optics (MPQ) in Garching. In their experiment, the electron accelerator is driven by pulses from a 20 TW (850 mJ in 37 fs) laser system. Focused into a hydrogen-filled gas cell with a length of 15 mm, the laser pulses produce stable electron beams showing a quasi-monoenergetic energy spectrum with a stable peak in the range of 200-220 MeV and 7 pC of charge in the whole spectrum. In order to transport the electron beam from the plasma accelerator, the scientists employed a pair of miniature permanent-magnet quadrupole lenses, which have been found to be critical for stability. The spectrum of their 30cm-long undulator typically consists of a main peak at a wavelength of 18 nm (fundamental), a second peak near 9 nm (second harmonic) and a high-energy cutoff at 7 nm. For more information, see the paper, "Laser-driven soft-X-ray undulator source", M. Fuchs et al., Nature Physics. 5, 826 (2009).
