LCLS-II Cryomodules (IMAGE) DOE/SLAC National Accelerator Laboratory Caption Now that the cavities have been cooled, the next step is to pump them with more than a megawatt of microwave power to accelerate the electron beam from the new source. Electrons passing through the cavities will draw energy from the microwaves so that by the time the electrons have passed through all 37 cryomodules, they'll be moving close to the speed of light. Credit Greg Stewart/SLAC National Accelerator Laboratory Usage Restrictions No restrictions. License Public Domain 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.