Scientists correct particle beam fluctuations at the speed of light, almost

Posted by Wolfgang Gruener

Upton (NY) - Physicists at the Relativistic Heavy Ion Collider (RHIC) have developed a method to keep particle beams tightly organized in order to increase the efficiency of collider experiments.

The best opportunity to observe matter to travel at the speed of light, or at least nearly at the speed of light, is to watch collider experiments. Last year, we have published a detailed article of how colliders work, using Fermilab’s fascinating Tevatron as an example. Collider experiments serve as tool to investigate the smallest building blocks of matter, by typically ion beams at each other. Travelling nearly at the speed of light, these beams set free enormous amounts of energy, helping scientist to discover new particles and getting more insight in matter, space and time.

One problem of these particle beams, which actually travel in bunches, is that magnets, which surround the beam pipe, heat up and as the beams accelerate, they tend to spread out. This reduces the effectiveness of a collision as scientists try keep the bunches tightly organized, providing an opportunity to create a direct collision with the least amount of scatter. The Tevatron uses liquid helium and liquid nitrogen as well as a lake as natural cooling source to reduce the temperature of the beam. Scatter is a typical event in a collision experiment, but if a cooling source actually fails, a beam can leave its path and has enough energy to cut through several feet of steel within nanoseconds.          

At the RHIC, a circular 2.4-mile collider that operates at a lower energy level than the Tevatron, physicists now have found a new method to keep particle beams more focused: Instead of a standard cooling, information about the beam is sent ahead of the beam to cooling devices to send that information ahead to “specialized devices” that smooth the fluctuations when the beam arrives. If you remember that the particle beam is travelling almost at the speed of light, sending information ahead of the beam is an astounding achievement. While we toured the Tevatron, we learned that - at least at this collider – the beams travel at a speed of 670,616,429 mph, which is about 200 mph slower than the actual speed of light.
 
"These corrections help to keep the beams focused and colliding, recreating thousands of times a second the conditions that existed just after the Big Bang," said Steven Vigdor, Brookhaven Lab's associate laboratory director for nuclear and particle physics, who manages the RHIC program.

The beam-correcting technique, called stochastic cooling, has been implemented at accelerators where the beams are made of a continuous stream of particles, but never before at a facility where the particles travel in discrete bunches."Its successful demonstration at RHIC provides an alternative path to the goal of increased collision rates, which would be much more costly and take longer to achieve via other proposed means," Vigdor said.