The advent of an ultra-strong high-voltage polarized electron gun that can accelerate electrons from zero to 80 percent of the speed of light

According to the American Association for the Advancement of Science on the 10th, scientists from the U.S. Department of Energy's Brookhaven National Laboratory designed and tested the world's highest voltage polarized electron gun, which is a key component required to build the world's first fully polarized electron-ion collider (EIC).

Brookhaven National Laboratory physicist Erdong Wang uses a high-voltage polarized electron gun in the Stony Brook University underground laboratory that will put the "e" (or electron) into the future electron-ion collider. Image credit: Brookhaven National Laboratory

The EIC is a cutting-edge nuclear physics facility currently under construction. The DC laser-driven polarized electron gun is the main component of the EIC, and its goal is to be the "starting gun" for a beam of colliding particles in the EIC, producing and firing electrons inside a circular collider with a circumference of about 38.6 kilometers. In theory, this should smash protons and neutrons in atomic nuclei and reveal the mechanism of their existence.

Wang Erdong, the chief architect of the device and a physicist at Brookhaven Laboratory, said that they can accelerate electrons to 80% of the speed of light. This means that in about one billionth of a second, the speed of electrons can be accelerated from zero to more than 800 million kilometers per hour (about 80% of the speed of light), and this process is completed in a space of only about 5 centimeters inside the electron gun.

However, accelerating electrons is only one of the tasks of the electron gun. Another task is to create tightly packed groups of particles and control their spin. To achieve this, the research team made a photocathode using ultrathin nanosheets of gallium arsenide crystals. Shining a laser on this cathode can release electrons and control whether they spin forward or backward.

Once the electrons have been freed from the crystal by the laser, the electron gun's job is to get them moving quickly. The team succeeded in doing this by building an anode opposite the cathode and applying an extremely high voltage. The electron energy was increased from zero to 320,000 electron volts in a gap of about 5 centimeters.

The team also found the best way to use the lasers. They found that short pulses of laser light produced groups of electrons with a high "bunch charge," meaning each bunch contained about 70 billion electrons. These bunches gave the particles the highest chance of colliding with nuclei flying in from the other direction in the accelerator.

The EIC accelerates polarized electrons and collides them with polarized protons and ions, allowing scientists to delve into the most basic building blocks of visible matter. Now, its key component, the electron gun, has not only exceeded the requirements of the EIC, but has also achieved quite impressive results. This is the world's highest voltage and most powerful polarized electron gun, and the team is still working on components that can further accelerate electrons inside the collider to bring them closer to the speed of light.