\section{Conclusions}
\label{sec:conclusions}

We have presented a study of a novel concept for sampling
electromagnetic calorimetry; namely a calorimeter with
binary readout. This requires very fine granularity and
a high level of sensor integration to handle the very
large number of pixels which are required.

We have produced a CMOS test sensor which demonstrates many
of the basic parameters required for a binary ECAL. Test
results show the sensor functions close to the expected
level.
As part of the sensor development, we worked with the
CMOS foundry to develop the INMAPS process, which enables
us to use a deep P-well implant to shield the signal
charge from the active PMOS circuit elements. Measurements
show this improved the signal efficiency by large factors
and makes the sensor viable.

The overall performance of 
a simulated full scale binary ECAL 
based on the test sensor results has been shown to give 
a better resolution
for electromagnetic showers than an equivalent analogue
readout ECAL. The dominating issue for the resolution
is the confusion of counting charged particles from the
hits and this will require real data from EM showers
at very fine granularity to be sure of the limiting
resolution of a binary ECAL.

A second round sensor is planned for the near future and
this will have a uniform pixel design throughout the
active area. This should enable the critical EM shower
measurements to be performed.
