  An array of Parallel Plate Avalanche Counters (PPAC) for the detection of
heavy ions has been developed. The new device, NIFF (Nuclear Instrument for
Fission Fragments), consists of four individual detectors and covers $60\%$ of
2$\pi$. It was designed to be used in conjunction with the SiRi array of
${\Delta}E-E$ silicon telescopes for light charged particles and fits into the
CACTUS array of 28 large-volume NaI scintillation detectors at the Oslo
Cyclotron Laboratory. The low-pressure gas-filled PPACs are sensitive for the
detection of fission fragments, but are insensitive to scattered beam particles
of light ions or light-ion ejectiles. The PPAC detectors of NIFF have good time
resolution and can be used either to select or to veto fission events in
in-beam experiments with light-ion beams and actinide targets. The powerful
combination of SiRi, CACTUS, and NIFF provides new research opportunities for
the study of nuclear structure and nuclear reactions in the actinide region.
The new setup is particularly well suited to study the competition of fission
and $\gamma$ decay as a function of excitation energy.
