  Superconducting tunnel junctions (STJs) are able to measure the energy of
single photons in the range from near infrared to X-rays. They provide
simultaneous information of the impact time and wavelength of an absorbed
photon. The main difficulty of these detectors compared with conventional
imaging detectors lies in their limited pixel number. Each STJ has to be
connected independently and therefore the wiring becomes technologically more
demanding as the number of STJs increases. One approach to solving this problem
is to use a single large absorber and to distribute STJs for position sensitive
signal readout. This configuration is able to detect single optical photons
with an energy resolution close to that of a single STJ pixel.
  We have produced a Ta absorber strip with Ta/Al/AlOx/Al/Nb/Ta junctions at
either end. The energy and position of single photons were measured
simultaneously. The energy resolving power approaches the theoretical limit. We
will present a simple Monte Carlo simulation which reproduces the measurement
exactly.
