Nuclear Science

Talk about getting to the core of an issue. To probe the mysteries of an atom's nucleus is to seek answers to some of the most fundamental of questions about how the elements were formed and what keeps nuclei together.

Nuclear science pursues these big questions by colliding and examining the tiniest of particles. It's a meticulous science that explores the tiny microcosm at the center of the atom. Yet it is filled with the drama of collisions at half the speed of light, where new isotopes are created in a billionth of a trillionth of one second. To do this scientists need large machines, state-of-the-art computers, and often specially designed equipment that has no duplicate elsewhere in the world.

This is the science in which NSCL excels — exploring the wonders of the nucleus.

The Discovery of New Isotopes

The nuclear science research at NSCL concentrates on the study of exotic nuclei. Nuclei consist of neutrons and protons. “Normal” or stable nuclei prefer to have roughly equal numbers of neutrons and protons. However, it is possible to create rare isotopes with extra neutrons or extra protons. These nuclei transform over time — in some cases within a fraction of a second — back towards the stable nuclei. Although the short-lived nuclei do not exist on Earth, they play an important role in the formation of the elements in the cosmos. The Coupled Cyclotron Facility at NSCL produces large numbers of these exotic nuclei which can be used for experiments. The goal of the experiments is to measure the properties of such nuclei which are presently unknown but important for the understanding of nuclear synthesis and the forces that hold nuclei together.

The Properties of Exotic Nuclei

Thousands of the short-lived exotic nuclei that play a role in the formation of elements have never been observed, or very little is known about them. The Coupled Cyclotron Facility at NSCL is able to produce some of these nuclei for the first time. Many unknown properties of the exotic nuclei will be explored.

• How long do they live?
• How heavy are they?
• What is their shape?
• How fragile are they?
• Are the neutrons and protons uniformly distributed?

All these questions are important to understanding the fundamental underlying questions:

• How were the elements formed?
• What holds the nuclei together?

Hot Nuclear Systems

During the collision of two nuclei at high energies, the individual protons and neutrons can collide with each other many times. This increases the “temperature” of the nuclear system just as the temperature of water is increased by an increase of the collisions of the water molecules. If you increase the temperature by increasing the velocity of the projectile, the nucleus boils off (evaporates) nucleons. At even higher temperatures the nucleus can explode completely and break into smaller nuclear fragments and many protons and neutrons. By measuring the remnants of the compression and explosion of a nuclear collision, one can infer the densities and pressures that can be created within the nucleus.

Tools for Our Science

The K500/K1200 coupled cyclotrons are capable of producing exotic nuclei by fragmentation of a stable beam on a primary target. The A1900 fragment separator selects the nuclei of interest and focuses them into a beam which is then guided into a secondary target.

There are several different stations where this secondary target can be located. Each of these stations is equipped with highly sophisticated detector systems. They are specialized experimental devices, tuned to observe different particles resulting from the collisions of the exotic nuclei with the target.