University logo High Energy Detector, HED

The ERNE High Energy Detector (HED) is a particle telescope which consists of the following detector layers:

1: S1x. The first layer consists of two parallel single-sided 33x70 mm² Si-strip detectors side by side with a 4 mm inactive area between. The total area is thus 70x70 mm² but an inactive region of 4x70 mm² goes through the layer. The thickness of the detector is 300 microns.

2: S1y. This layer is as S1x but the strip direction is perpendicular. The layers S1x and S1y are attached together and are used to give the energy deposited and the coordinates of the particle. Due to the inactive stripes there will be an inactive cross shaped region and thus we may assume that the structure S1x&S1y is composed of four 33x33 mm² detectors.

3 and 4: S2x & S2y. As S1x & S1y.

5: D1a. This is constructed of four 36x36 mm² Si detectors. The gap between the detectors is 3 mm thus giving the outer dimensions of 75x75 mm². The thickness of the layer is 0.5 mm.

6: D1b. As D1a. These two layers are electronically connected and are referred to as D1.

7: D2. This layer is a single 80x80x8 mm3 CsI(Tl) scintillator.

8: D3. This layer consists of five 80x16 mm² BGO scintillators. The thickness of the layer is 15 mm.

Plastic scintillators are used as anticoincidence shield in order to reject the particles which do not stop in the detector layer mentioned above. All scintillation detectors are read out by photodiodes.

The area of the thermal foil window (210 microns thick, surface density 30 mg/cm²) above S1x is 70x70 mm².

The main purpose of S1 and S2 is to determine the direction of incidence of charged particles. This information is used for two purposes. First, it is used to determine the trajectory path length which is needed for distinguishing elements and their isotopes from each other up to the iron group. Secondly, directional information and the large opening angle enable anisotropy measurements to be carried out. The triggering constraint is that a particle has to reach S2y; otherwise the trajectory cannot be determined and thus the identification of the particle is impossible.

HED Operational Characteristics:

Field of View: 120 degrees, squared
Energy Ranges:
Proton and Helium: 11-120 MeV/n
Other nuclei: 25-540 MeV/n
Electrons: 2-50 MeV
Geometrical Factor: from 25 cm² sr to 40 cm² sr
Temporal Resolution: 60 seconds, protons 10 seconds

Space Research Laboratory, Department of Physics and Astronomy
FI-20500 University of Turku, FINLAND