Edinburgh Germanium Telescope

|| Introduction || Drawings || Photos ||

|| Photonuclear Reactions ||

This detector type has been designed to accurately measure the energy of charged particles. It consists of six cylindrical germanium crystals stacked one on top of another. Protons of up to 260MeV and pions of up to 130MeV stop within the germanium material.

schematical arrangement - click for PS page

prototype presently manufactured by DSG, Mainz

EURISYS prototype

In contrast to gamma rays (measuring them with germanium detectors is well established) the charged particles deposit energy all along their path until they come to a stop. Ideally one wants to measure the energy deposited in all material the particles go through. Conventional technology has been using a thick 1/2mm rear contact on the crystals, degrading the energy resolution for particles punching through as the energy loss in this layer cannot be measured.

A novel technology has been developed to be able to use thin contacts on the rear side of the crystals, too, which has required a considerable effort but in the end has been successful. Two such detectors are now on order for some time and delivery is expected in the near future.

The energy resolution is expected to be of a few 100 keV, this limit being due to the necessary thickness of the detector entrance window with vacuum on one side and ambient pressure on the other side.

The first step of particle identification will use the well established dE/E technique. As there are several crystals, the requirement for consistent energy deposition will also allow to identify (and discard) events where a nuclear reaction or a hard scattering has taken place in a crystal.

Pions of positive charge decay into muons and finally positrons after being stopped in the material. These afterpulses can serve to identify these particles. The technique has successfully been used previously, for example with the PiP detector in a number of experiments at the MAMI accelerator in Mainz.

The halo nuclei with real photons experiment will be one of the first to use these detectors.

|| Introduction || Drawings || Photos ||

|| Photonuclear Reactions ||