  Wakefield accelerators are under development in many laboratories worldwide.
They bring the promise of a high accelerating gradient, orders of magnitude
higher than current machines. The reduction in the overall length of the
accelerators will pave the way to a wider use of such machines, for industrial,
medical, research, and educational purposes. At the same time, all the
equipment must be reduced as well, to keep the dimensions of the machine as
small as possible. The two main challenges of the diagnostics for plasma
accelerated electron beams are the ability to measure the 6D phase space
properties with single shot techniques and the compactness to meet the
requirements of a `table-top' facility.
