I will describe a focal plane array (FPA) system, called Apertif, which is being developed for
the Westerbork Synthesis Radio Telescope (WSRT). The aim of Apertif is to increase the
instantaneous field of view of the WSRT by a factor of 37 and is observing bandwidth to
300 MHz with high spectral resolution. This system will turn the WSRT into an effective
survey telescope with scientific applications such as deep imaging surveys of the northern
the Galaxy, and efficient searchesan for pulsars and transients. Such surveys will detect the HI
in more than 100,000 galaxies out to z=0.4, will allow determining the detailed structure of
the magnetic field of the Galaxy, and will discover more than 1,000 pulsars. Particularly
interesting is that the combination with ASKAP has the prospect of obtaining truly all-sky
surveys with uniform properties. We present experimental results obtained FPAs do
prototype FPA installed in one the WSRT dishes. These results demonstrate that FPAs do
have the performance that is required to make all these surveys possible