Knocking on Heaven's Door - Lisa Randall [80]
The first milestone was to check whether the beams would actually circulate around the ring. And they could. Amazingly, after its long history of trials and tribulations, in September 2008, CERN fired up its two proton beams with so few hitches that the results exceeded expectations. On that day, for the first time, two proton beams in succession traversed the enormous tunnel in opposite directions. This single step involved commissioning the injection elements, starting the controls and instruments, checking that the magnetic field would keep the protons in the ring, and making sure all the magnets worked to spec and could run stimultaneously. The first time this sequence of events was ready was the evening of September 9. Yet everything worked as well as or better than planned when the tests took place the next day.
Everyone involved with the LHC describes September 10, 2008, as a day they will never forget. When I visited a month afterward, I heard many stories of the day’s euphoria. People followed the trajectory of two spots of light on a computer screen with unbelievable excitement. The first beam almost returned successfully on its first go-round, and with minor tweaking followed the exact path that was intended within the first hour of its being turned on. The beam at first went around the ring for a few turns. Then each successive burst of protons was adjusted slightly so that the beam was soon circulating hundreds of times. Not long after this, the second beam did the same—taking about one and a half hours to get exactly on track.
Lyn was just as happy that he didn’t know about the live video feed at the time from the control room, where the engineers were following the project, to the Internet, where the events were being broadcast for anyone to see. So many people watched those two dots on their screens that the sites were shut down for breaking capacity. People all over Europe—the CERN press office claims a couple of million—sat mesmerized as engineers modified the protons’ path to make them successfully circulate around the full circumference of the ring. Meanwhile, inside CERN, the thrill was palpable as physicists and engineers gathered in auditoriums to watch the same thing. At this point, the LHC outlook seemed more than extremely promising. The day was a wonderful success.
But a mere nine days later, euphoria transformed into despair. At the time, two important new features were to be tested. First, the beams were to be accelerated inside the LHC ring to higher energy than they had been during the first test, which used only the beam injection energy that protons have when first entering the LHC ring. The second part of the plan was to collide those beams, which would of course have been a huge milestone in LHC development.
However, at the last moment—on September 19—despite the engineers’ many considerations and precautions, the test failed. And when it did, it did so catastrophically. A simple soldering error in the copper casing connecting two magnets combined with too few functioning helium release valves caused a yearlong delay before protons would first collide.
The problem was that as scientists tried to ramp up the current and energy of the eighth and final sector, a joint between two magnets along the busbar that connects them broke. A busbar is a superconducting joint that connects a pair of superconducting magnets. (See Figure 27.) The splice that holds together a joint between two magnets was the culprit. The faulty connection created an electrical arc that punctured the helium enclosure and caused six metric tons of liquid helium—that would ordinarily be warmed up slowly—to be suddenly released. Superconductivity was lost in the quenching that occurred when the liquid helium heated up and reverted to gas.
[ FIGURE 27 ] A busbar connects different magnets together. A faulty solder in one was responsible for the unfortunate incident in 2008.
The enormous amount of helium released created a huge pressure wave that effectively caused an explosion. In less than 30 seconds, its energy