Hollow Waveguide (image) National Science Foundation Caption This image depicts the experimental setup used to create a coherent version of the Roentgen tube in the soft X-ray region of the spectrum. When a long-wavelength, femtosecond laser is focused into this hollow waveguide filled with high-pressure helium gas, part of the laser is converted into an ultrafast, laser-like, X-ray beam. Credit Tenio Popmintchev, JILA and University of Colorado at Boulder Usage Restrictions Credit must be used. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.