ISOLDE gets a new laser system

It's action stations at ISOLDE, the On-Line Isotope Mass Separator at CERN. The Laboratory is preparing to add a second laser ion source system to its arsenal. By alternating between two laser systems, the ISOLDE team will be able to switch from one type of beam to another in record time.


Bruce Marsh, from the EN-STI Group, with one of the lasers from ISOLDE's current system.

The first laser source for producing radioactive ion beams (see box) was installed in the ISOLDE hall in the 1990s. This method, which was highly innovative for its time, has since been adopted by several laboratories all over the world. "This laser system allows us to control the ionisation wavelength with precision and thus to select specific atoms in order to produce very pure radioactive ion beams," explains Valentin Fedosseev of the EN Department. "These beams are then used for various experiments, in nuclear astrophysics and biology, for example. With two laser systems we will be able to do more experiments by producing more beams of different types in a given amount of time."

The new laser system during recent tests.

The new lasers, which have been built by CERN in collaboration with the University of Mainz, are due to be installed at ISOLDE before the summer and will be used in conjunction with the existing lasers. "The new equipment will enable us to produce totally new beams," explains Valentin Fedosseev. "We will also be able to switch from one isotope to another a lot more quickly. While one laser system is operating with one type of nucleus, our team will be able to parameter the other system for another experiment. We hope to be able to switch beams in half a day in future, compared to three days at present."

In its current configuration, ISOLDE can produce 700 different beams from the isotopes of 70 chemical elements. The fields of application are already very varied, ranging from nuclear structure physics to nuclear astrophysics, atomic physics, solid-state physics and biology, and can only increase further with the arrival of the new system.

The laser as a selection tool

ISOLDE produces radioactive nuclei by bombarding a target element with protons from the PS Booster, which have an energy of between 1 and 1.4 GeV. When the target reaches a high enough temperature, the isotopes created disperse and then decay.

In order to produce a pure beam, the desired isotopes have to be "captured". This is where the laser ion sources come in. Before being concentrated inside the beams, the selected nuclei are ionised by the laser and extracted in the form of ions, then separated from the other isotopes by a magnetic field.


by Anaïs Schaeffer