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
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
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