Another technique we are interested in exploiting for the use in these type of measurement is the electrostatic ion trap invented by Prof. Daniel Zajfman as the Weizmann Institute. Unlike conventional ion traps, which localize ions in place using combinations of RF, electric, and magnetic fields, this trap confines ions is stable orbits inside an “ion resonator” which acts in the same way as a light resonator does for trapped light. The ions in this setup bounce back an forth between sets of electrostatic mirrors (so they are in fact not “trapped” with respect to their position in space). A schematic of this trap can be seen in the following figure

This type of trap seems to offer several advantages for beta decay studies of trapped rare ions:

• Most of the trap volume is field free so the ions suffer no external interference as the decay.
• Due to the motion of the ions in the lab frame as they decay the recoil nucleus is kinematically focused forward toward the edge of the trap, which can be easily instrumented with detectors.
• Since the trap does not require optical access (for laser beams) it is possible to instrument a large solid angle with detectors, leading to a large detection efficiency for the decays.
• Trapping ions relies on their interaction with EM fields and does require a resonant light source (lasers), so that a large number of ion species can be trapped.

Our group has collaborated in the construction of such at trap at the Lawrence Berkeley National Lab, and is also collaborating with groups at the Weizmann Institute who have built such traps. Together with these research groups we plan to pursue a program to perform &beta decay studies of ions in these traps. We are also involved in the development of a large area, position and energy sensitive, &beta detector which we plan to instrument these traps with.

The figure below shows the Berkeley trap under construction, the trap is being held by Andrew Wong, an undergraduate student from UC Berkeley who worked with us on the trap construction.

References:

• D. Zajfman et al. High resolution mass spectrometry using a linear electrostatic ion beam trap. Int J Mass Spectrom (2003) vol. 229 (1-2) pp. 55-60

• D. Strasser et al. Negative Mass Instability for Interacting Particles in a 1D Box: Theory and Application. Phys. Rev. Lett. (2002) vol. 89 (28) pp. 283204
• H. Pedersen et al. Stability and loss in an ion-trap resonator. Phys. Rev. A (2002) vol. 65 (4) pp. 042703