LXXI International conference "NUCLEUS – 2021. Nuclear physics and elementary particle physics. Nuclear physics technologies"

The Penning trap with the combined functions of purification and measuremen

24 Sept 2021, 15:20

25m

Oral report Section 3. Modern nuclear physics methods and technologies. Section 3. Modern nuclear physics methods and technologies

Speaker

Olesia Bezrodnova (Saint Petersburg State University)

Description

A Penning trap is a powerful device for measuring properties of ions and subatomic particles. Presently it can reach the highest accuracy in the determination of the mass of a nuclide. The typical Penning-trap system for on-line mass measurements requires two dedicated traps. The first trap – preparation trap (PT) – serves for the purification and cooling of the captured ions via the conventional mass selective buffer-gas cooling technique. The second trap – measurement trap (MT) – which, in combination with the downstream MCP detector, serves for the determination of the ion’s cyclotron frequency and, therefore, its mass.

Such a configuration alows mass measurements with uncertainties of a few keV on medium-heavy nuclides with half-lives down to about a few hundred milliseconds. However, when captured, the ions are no longer well centered in the trap, acquiring coherent axial and magnetron motions, what in turn introduces additional systematic shifts in the measurement of eigenfrequencies and, thus, the systematic error of the measured mass. This effect is one of the limitations in the final precision for the PI-ICR detection technique[1]. For the sake of mass measurements of short-lived nuclides the issue can be circumvented by combining the features of both the PT and MT in a single ‘hybrid’ trap.

In the hybrid trap the buffer gas can be injected in the trap region in a pulsed manner using a fast piezo valve. In this way, the pressure in the trap volume is built up only for the cooling phase. After that, the valve is closed, allowing the buffer gas to be pumped out, and when the pressure drop is sufficient, finally the frequency measurement takes place. Besides the reduction of the systematic effects, such hybrid system lowers the overall cost of the apparatus, because it requires only one standard superconducting magnet instead of two or a special single magnet with two regions of highly homogeneous magnetic field.

This work presents the design of the proposed ‘hybrid’ Penning trap system, estimation of its capabilities, and its relevance to the future PITRAP project – the Penning-trap mass spectrometer at the PIK reactor in Gatchina[2].

1. S. Eliseev et al., Appl. Phys. B. 2014. V.114. p.107

2. Yu. Novikov et al., Exot.Nucl., Proc.Int.Conf., W. Sc. 2019. pp.417-426