Semiconductor detectors in the low countries

Several milestones in the development of semiconductor radiation imaging detectors are attributed to scientists from the Low Countries, the Netherlands and Belgium, and a few historical details will be highlighted. The very first usable semiconductor nuclear detector was made in Utrecht, around 1943, in the form of an AgCl crystal. The earliest large-scale application of monolithic, double- sided silicon strip detectors was in the BOL experiment around 1968 at IKO, now NIKHEF, in Amsterdam. The technology developed and patented by Philips and IKO was adapted by the author and coworkers in 1980 to produce the first silicon microstrip detector used for the reconstruction of events in a CERN fixed target experiment. An avalanche of developments then led to worldwide use of silicon microstrip detectors in elementary particle physics, motivated by the capability to reconstruct particles with lifetime similar to 10**- **1**2s, which decay on sub-millimeter scale. The intensive activity in silicon detector R&D culminated in 1991 in the construction of fine-grained 2D monolithic and hybrid pixel detectors that incorporate sophisticated electronic functions in each microscopic detection element, with typical dimensions of 25-100mum. Besides being a powerful high intensity tracker for particle physics, this device can also be designed as a new X-ray imager, which allows selective counting of individual photons in each pixel at MHz frequency.