The HERCULES laser at the University of Michigan is already the most intense laser in the world. Thanks to a $2 million grant from the National Science Foundation, it’s about to get a significant power upgrade as well.
The laser’s power, currently clocking in at 300 trillion watts (300 terawatts, or 300 TW), comes from a series of five embedded "pump" lasers that amplify ultrashort pulses of light. By replacing three of those pump lasers, researchers can bump the power to 500 or even 1,000 TW. That means a doubling or tripling of intensity, as well.
When it was first built a decade ago, HERCULES relied on commercial pump lasers that couldn’t reach the ambitious 300 TW goal; researchers had to build their own. Flash forward to a world where international demand for laser power has grown and levels of 10,000 TW or more are sought, and commercial lasers are now able to outpace their homemade cousins.
"This upgrade enables a wide variety of different experiments," said Prof. Karl Krushelnick, director of the Center for Ultrafast Optical Science, which houses HERCULES. “It also opens up a new regime at the very frontier of plasma physics, where quantum phenomena start to play an important role."
The upgrade will have a number of collateral benefits, including:
- Tabletop accelerators: While conventional particle accelerators can be hundreds of yards long, lasers can enable particle acceleration within a few square yards. These devices have myriad applications, including medicine (via radiation therapy), national security (by determining the presence of nuclear materials in shipping containers) and the exploration of new physics.
- Advanced X-ray imaging: Conventional X-rays are best at illuminating dense materials such as bone. The high-energy X-ray beams emitted by laser accelerators can find the boundaries between soft tissues, offering cheaper and faster results than an MRI.
- Probing advanced astrophysical questions: Quantum electrodynamics predicts that strong electric fields, such as those found in neutron star atmospheres, spontaneously create both matter and antimatter within the vacuum of space. Researchers can test the validity of these predictions by using HERCULES to accelerate electrons close to the speed of light, simulating strong-field environments. Theories about gamma ray bursts in space – currently thought to be produced by the breaking apart and reconnecting of magnetic field lines, such as those found near black holes - could also be explored.
Krushelnick, who is also a U-M professor of nuclear engineering and radiological science, anticipates that the expanded capabilities of HERCULES will enable researchers to do experiments that were previously impossible.