Earlier this week, scientists and engineers at the US\u00a0Department of Energy\u2019s Fermi National Accelerator Laboratory\u00a0in Illinois loaded one of the most advanced superconducting radio-frequency cryomodules ever created onto a truck and sent it heading west.<\/p>\n
Today, that cryomodule arrived at SLAC National Accelerator Laboratory in California, where it will become the first of 37 powering a 3-mile-long machine that will revolutionize atomic X-ray imaging. The modules are the product of many years of innovation in accelerator technology<\/strong><\/a>, and the first cryomodule Fermilab developed for this project set a world record in energy efficiency.<\/p>\n These modules, when lined up end to end, will make up the bulk of the accelerator that will power a massive upgrade to the capabilities of the Linac Coherent Light Source<\/strong> at SLAC, a unique X-ray microscope that will use the brightest X-ray pulses ever made to provide unprecedented details of the atomic world. Fermilab will provide 22 of the cryomodules, with the rest built and tested at Thomas Jefferson National Accelerator Facility in Virginia.<\/p>\n The quality factor achieved in these components is unprecedented for superconducting radio-frequency cryomodules. The higher the quality factor, the lower the cryogenic load, and the more efficiently the cavity imparts energy to the particle beam. Fermilab\u2019s record-setting cryomodule doubled the quality factor compared to the previous state-of-the-art.<\/p>\n \u201cLCLS-II represents an important technological step which demonstrates that we can build more efficient and more powerful\u00a0accelerators,\u201d says Fermilab Director Nigel Lockyer. \u201cThis is a major milestone for our accelerator program<\/strong>, for our productive collaboration with SLAC and Jefferson Lab and for the worldwide\u00a0accelerator community.\u201d<\/p>\n Today\u2019s arrival is merely the first. From now into 2019, the teams at Fermilab and Jefferson Lab will build the remaining cryomodules, including spares, and scrutinize them from top to bottom, sending them to SLAC only after they pass the rigorous review.<\/p>\n \u201cIt\u2019s safe to say that this is the most advanced machine of its type,\u201d says\u00a0Elvin Harms, a Fermilab accelerator physicist working on the project. \u201cThis upgrade will boost the power of LCLS, allowing it to deliver X-ray laser beams that are 10,000 times brighter than it can give us right now.\u201d<\/p>\n With short, ultrabright pulses that will arrive up to a million times per second, LCLS-II will further sharpen our view of how nature works at the smallest scales and help advance transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions. Hundreds of scientists use LCLS each year to catch a glimpse of nature\u2019s fundamental processes.<\/p>\n To meet the machine\u2019s standards, each Fermilab-built cryomodule must be tested in nearly identical conditions as in the actual accelerator<\/strong>. Each large metal cylinder\u2014up to 40 feet in length and 4 feet in diameter\u2014contains accelerating cavities through which electrons zip at nearly the speed of light. But the cavities, made of superconducting metal, must be kept at a temperature of 2 Kelvin (minus 456 degrees Fahrenheit).<\/p>\n To achieve this, ultracold liquid helium flows through pipes in the cryomodule, and keeping that temperature steady is part of the testing process.<\/p>\n \u201cThe difference between room temperature and a few Kelvin creates a problem, one that manifests as vibrations in the cryomodule,\u201d says\u00a0Genfa Wu, a Fermilab scientist working on LCLS-II. \u201cAnd vibrations are bad for linear accelerator operation.\u201d<\/p>\n In initial tests of the prototype cryomodule, scientists found vibration levels that were higher than specification. To diagnose the problem, they used geophones\u2014the same kind of equipment that can detect earthquakes\u2014to rule out external vibration sources. They determined that the cause was inside the cryomodule and made a number of changes, including adjusting the path of the flow of liquid helium.\u00a0The changes worked, substantially reducing vibration levels to a 10th of what they were originally,\u00a0and have been successfully applied to subsequent cryomodules.<\/p>\n Fermilab scientists and engineers are also ensuring that unwanted magnetic fields in the cryomodule are kept to a minimum, since excessive magnetic fields reduce the operating efficiency.<\/p>\n \u201cAt Fermilab, we are building this machine from head to toe,\u201d Lockyer says. \u201cFrom nanoengineering the cavity surface to the integration of thousands of complex components, we have come a long way to the successful delivery\u00a0of LCLS-II\u2019s first cryomodule.\u201d<\/p>\n Fermilab has tested seven cryomodules, plus one built and previously tested at Jefferson Lab, with great success. Each of those, along with the modules yet to be built and tested, will get its own cross-country trip in the months and years to come.<\/p>\n