The HiSCORE Detector

Extensive Air Showers & Cherenkov Effect

As many other experiments in the field (see Links section) the HiSCORE detector will make use of the fact that high energy particles (both photons and hadrons) that hit earth's atmosphere produce a so called air shower consisting of many secondary particles. Due to the high energy of the primary particle, many of these secondaries have kinetic energies that make them faster than the speed of light in air, therefore emitting cherenkov light. This light is weak, but can be detected on the surface of the earth with sensitive instruments.

Fig 2: Raytracing picture of the HiSCORE detector - click on this image to load an animation !

Fig 1: Simulation of an shower induced by a 167 TeV gamma photon. Indicated in red are all triggered stations (more than 100 p.e.), stations marked in cyan are read out even though they have not triggered. The stations are 150 meters apart and have a sensitive area of 0.5 sqm. Click for larger image.

Detector Setup

The HiSCORE Detector is planned to consist of a number of detector stations with a spacing of more than hundred meters and is designed to sample the Cherenkov light front. Each station will consist of four modules or channels.

Fig 3: Drawing of detector module. Click for larger image.

Each module consists of one large area photomultiplier looking upwards and the respective electronics and readout components. To increase the effective sensitive area of the detector, a Winston Cone will be placed on top of the PMT, concentrating the incoming light (see Fig 2 and 3). A useful side effect of the Winston Cone is the reduction of stray light from the horizon and the Night Sky Background (because photons with angles larger than a certain cutoff angle, say 30 deg, are not transmitted onto the PMT).

For a cutoff angle of 30 degrees the ratio of R1 and R2 must be about 2. At the moment, it is planned to use 20 cm (8 inch) PMTs as offered e.g. by Electron Tubes. In this case one module would have a sensitive area of about 0.125 sqm.

If one would use, for example, four modules per station, each station would have an effective sensitive area of about half a square meter. Currently simulation studies are ongoing to determine the optimal size of the detector stations.

Fig 4: 3D-schematics of a two-channel half-station encasing. Each station will consist of two such half-stations.

Currently the construction and testing of a prototype module is underway. Different photomultiplier modules are being tested in a test-bed and a slow-control concept was developed and implemented. We plan to soon start running a prototype station in Hamburg using scintillator material (for test purposes) inside the station. A 3D-schematics of the planned station mechanics is shown in Figure 4.

The first prototype Winston cone has been assembled by the workshop at the University of Hamburg. The Winston cone material is a reflective foil manufactured on a plastic-like support, easily cut and bent, and therefore ideal for implementation in the barrel-mount concept (Fig 6). Several Electron Tubes 8'' photomultipliers and Hamamatsu models with 8'' and 10'' are available and are being tested in our test-bed.

Fig 6: Prototype Winston Cone

Fig 5: Eletron Tubes 8'' photomultiplier