Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 60: Instrumentation VI, Detector Systems

HK 60.4: Gruppenbericht

Donnerstag, 19. März 1998, 15:00–15:30, A

The SHIPTRAP Project — •W. Quint¹ and SHIPTRAP² — ¹GSI, Planck-Str. 1, D-64291 Darmstadt — ²

The investigation of the properties of super heavy elements or of heavy doubly magic and neighbouring nuclei (e.g. ¹⁰⁰Sn) is a very important testing ground for the ability of the existing nuclear models to describe stabilisation effects of the underlying shell structure. The aim of the planned SHIPTRAP experiment is the precise mass measurement of radioactive heavy ions in a Penning trap spectrometer. In addition, the set-up presented here can deliver mass selected ion clouds of very high purity to other experiments, e.g. laser spectroscopy or β-spectroscopy. The system is designed to capture radioactive ions from the velocity filter SHIP at GSI and cool them into room temperature bunches of 5 mm³ with an overall efficiency of greater than 1 %.

In the experiment the radioactive ions to be investigated are separated from the primary beam projectiles in the SHIP detector. The energy of the recoil ions is reduced in degrader foils followed by a helium buffer gas cell (p < 1 bar) [1]. >From this stopping volume either the remaining singly charged ions or the neutralised and subsequently laser-ionised ions are extracted by electric fields and a gas flow through a nozzle. >From there the ions are captured with high efficiency (> 50 %) in two subsequent radio frequency quadrupole ion guides [2] forming differential pumping stages. The last section of the second ion guide is built as a RFQ rod trap where the ions are collected and cooled down to an energy of about 0.05 eV. Then the ions are extracted into the double Penning trap spectrometer, which will be similar to the ISOLTRAP facility at CERN [3,4]. In the trap the ions are mass selectively cooled in order to remove isobaric background. Alternatively, the ions can be delivered to other experiments using laser or nuclear spectroscopy.

In this report an overview of the physics goals and the techniques involved will be presented.

[1] H. Backe et al., Nucl. Instr. Meth. B 126 (1997) 406.

[2] M.D. Lunney et al., CSNSM 97-02, Orsay 1997.

[3] G. Bollen et al., Nucl. Instr. and Meth. A 368 (1996) 675.

[4] H. Raimbault-Hartmann et al., Nucl. Instr. and Meth. B 126 (1997) 378.