A Possible Beam Dump Design for Intense Electron Beams
B. Naumann, W. Neubert, H. Prade and D.Pröhl1
Experiments at the radiation source ELBE
require beam dumps fulfilling the safety conditions
up to the maximum electron beam current of @ 1 mA.
The construction materials have to meet
requirements
as
low specific energy deposition, heat resistance combined with sufficient
thermal conductivity, modest neutron production rate and a low level of
produced long-living nuclides. Here, we present a possible layout for
a power dissipation of 50 kW. The core is proposed to be built from
purified graphite covered by a water cooled copper coating.
The construction shown in Fig. 1 was imaged by a corresponding GEANT geometry
including the material parameters [1]. The origin of the electron beam
characterized by a spatial distribution of sx,y =2 mm and a
divergence of sx¢,y¢=12 mrad was assumed to be at a distance of
2 m in front of the entrance of the graphite core.
Under these conditions, the
incident beam strikes completely the cone-shaped hole of the beam dump.
section | DE/Ekin [%] | DP [kW] |
beam line | 0.072 | 0.036 |
Al separation foil (50mm) | 0.049 | 0.024 |
graphite core | 92.175 | 46.087 |
copper coating (20 mm) | 3.271 | 1.635 |
Fe shielding plate (15 cm) | 3.973 | 1.987 |
concrete wall | 0.459 | 0.230 |
air gap | 8.0·10-4 | 4.0·10-4 |
Table 1
Energy deposition in the dump materials
The slowing-down of the
electrons and the production of bremsstrahlung
as well as the associated energy release were
simulated with the GEANT 3.21 package. In this way,
we calculated the energy deposition
in all construction materials involved (see Table 1). The power dissipation
in the graphite core is plotted in Fig. 2.
Dose calculations were performed with a cubic water phantom ( l = 20 cm )
which was positioned at the downstream position 2.20 m, i.e. 20 cm backward
the simulated beam origin. The expected dose from the photons and electrons
backscattered by the graphite core amounts to 9 Gy/h provided
that the incident beam current is 1 mA.
A complete representation of the Monte Carlo
simulations is published in [2].
1
Department of Research and Information Technology
References
[1] GEANT - CERN Program Library W5013, March 1994
[2] B. Naumann. W. Neubert, D. Pröhl, FZR Report FZR-267, Juli 1999.
|
|