The Next Particle Collider is Taking Shape
The Tevatron, Fermilab's particle smasher will be shut down next month, largely due to the fact that CERN's LHC has assumed the role of the default collider for high-energy physics.
However, Fermilab scientists are preparing the road toward the next big collider, which they hope will be built on their site in Illinois and become a nearly 22 mile long linear collider 300 feet beneath the surface.
These are emotional days at Fermilab as its main attraction to the physics world, the Tevatron, will close its doors in September after an amazing 27-year run. The experiments are already being scaled back and at least one member of the staff, Ron Stevens, who was in charge of the Tevatron operation, announced his departure. It is an end that began when the LHC was approved and Fermilab staff in fact helped to build the accelerator at CERN. Reality set it when LHC was in full operation and it was clear that LHC would be running the high-profile experiments and that discoveries are more likely at LHC due to its higher energy level.
Stuart Henderson, who is responsible for all accelerators at Fermilab said that running experiments at the Tevatron now can be "emotionally disappointing" for scientists. The sight is now set on the next big collider, beyond the LHC, which Fermilab wants to have on its 6800 acre property in Batavia, Illinois. However, the cost of the ILC, so far estimated at about $7 billion but likely to exceed well more than $10 billion, almost killed the project due to the recession in late 2008. Fermilab isn't giving up and is taking smaller steps toward the ILC - and is building its technology on a much smaller scale in a test facility.
For the past four years, Fermilab has been constructing a Superconducting RF (SRF) test facility, which will house a small collider for SRF testing purposes. Phase 1 has just been completed and includes a proton gun, an injector as well as the first of six accelerator modules in a 210 ft building that was extended with a tunnel to a length of 420 ft. So far, Fermilab spent about $60 million on the SRF facility and expects to have the system up and running for $70 - $75 million in 2013 or 2014.
The completion of cryomodule 1 is special as it represents the key building block of a future planned collider system called Project X as well as a potential future ILC. Project X will house about 30 - 40 cryomodules, while the ILC would hold between 1600 and 2200. Each module holds eight 3-foot long "cavities", which are produced from purified niobium, a superconductor that has the highest critical temperature of the elemental superconductors (9.2 K) and features a very high melting point of 2477 degrees Celsius, or 4491 degrees Fahrenheit, as well as a power gradient of 35 MV/m (megavolts per meter).
The cavities receive a charge of 300 KW each and exposed to a pulsating electric field clocked at 1.3 GHz to accelerate the proton beam to a total of about 1.5 GeV when all six cryomodules are in place. Liquid helium is used to cool the niobium cavities, which consist of a string of 9 cells, which are bathed in liquid helium at a temperature of 2K, while additional cooling layers on the outside have a temperature of 5K and 80K. The first cryomodule carried a cost of about $6 million, but the scientists hope that the cost will eventually come down to about $1 million - and, remember, the ILC will need at least 1600 of these.
At the end of 2012, Fermilab plans to test-fire the collider and hit an initial energy level of 300 MeV.
As a side note it is critical to slow down the powerful 1.5 GeV beam as well. Fermilab will be using a tomb built from a graphite core as well as aluminum plates that is equipped with a water cooling system and is encased in a 20ft x 20ft x 20ft steel and concrete container - to hold the radiation caused by the beam. I was told that the graphite and aluminum layers are designed to quickly transfer the heat created to water that is running through the metals via drilled holes and is transported away through its pipe system. Fermilab scientists said that the water is estimated to heat up from about 80 to 110 degrees Fahrenheit in the process.
It is unclear whether Fermilab will get approval for the ILC, while scientists are optimistic to get funding for Project X, which will also use SRF technology developed and tested at the facility for a 120 GeV neutrino collider. Scientists are currently making amazing progress toward a much more efficient future collider and it appears to be common sense that the ILC is just a matter of time and that it will, at some point, be replacing the LHC, depending on the results the CERN collider delivers. Given Fermilab's expertise, it appears reasonable to assume that it is the natural choice for a location of this new accelerator.