The VEGA project

VEGA will provide Versatile and Efficient GAmma-Detectors for experimental nuclear structure studies at the limits of stability.

Main physics issues

N=Z

proton-neutron residual interaction

structure at and beyond the p-dripline

p-decay from excited states

Coulomb distortion effects

astrophysical rp-process

N>>Z

shell quenching effects

rapid shape changes

K isomerism

astrophysical r-process

Large A,Z

shell structure at and beyond Z=92 and N=164

structure of Trans-Einsteinium nuclei

Experimental requirements

To perform the physics program gamma-detectors are necessary providing

Large efficiency (epsilon>0.3)
High granularity (Doppler correction up to v/c=0.5)
Modularity (experiment specific set-ups)
Mobility (different experimental sites)
Compatibility (exchange with other Ge-Arrays)

Two types of composite, segmented detectors are appropriate: the large Segmented Clover providing the largest efficiency, best P/T-ratio and superior polarisation sensitivity and the Segmented Cluster detector currently being developped within the MINIBALL project. The Segmented Cluster has a higher granularity and enables different geometrical arrangements due to the encapsulated crystals.

Realization

The main emphasis of the planned physics program is on decay studies. Therefore VEGA will provide in a collaboration with JYFL and UK institutes four large Segmented Clover detectors to build compact set-ups, e.g. the VEGA-box. For in-beam experiments, particularily at relativistic energies, the MINIBALL array -being supplied with one Segmented Cluster detector by VEGA- may be used.

VEGA-box

The VEGA-box is a compact, box-like configuration of four large Segmented Clover detectors. The minimal distance of the Ge detectors to the target is only 7 cm.

The VEGA-box provides a very large total photopeak efficiency up to gamma energies above 10 MeV and is particularily well suited for low and medium multiplicity applications.

last update march 1st, 1999 / Euroball at GSI / HJW