Bremsstrahlung at ELBE
The superconducting ELBE linac is currently the only machine worldwide delivering electron beams with energies above 10 MeV and driving a secondary radiation source for bremsstrahlung. This radiation has a variety of applications in nuclear physics and materials analysis.
- Photon-scattering, photodissociation and photofission experiments are performed to study electromagnetic strength functions and reaction rates for nuclear astrophysics and nuclear technology.
- In addition to fundamental and applied research in nuclear physics, the facility is used for positron annihilation lifetime studies in materials science. A variety of material types can be studied and defect concentrations and defect types in bulk materials, porous structures and the chemistry of radiolysis can be investigated at this setup.
- Tests of high-energy photon detectors are carried out, which also employ the ps timing resolution of the photon beam.
The γELBE facility for the production of bremsstrahlung and the detector setup are designed such that the production of neutrons and the scattering of photons from surrounding materials are strongly reduced.
Bremsstrahlung is produced by the electron beam hitting a niobium foil in the accelerator hall.
The photon beam is formed by a 2.60 m long collimator of high-purity aluminum installed in the concrete wall between accelerator hall and experimental cave. The exit of the collimator is visible at the left side of the photograph.
The beam hits the target placed inside the black plastic tube.
Emitted gamma rays are measured with four high-purity germanium detectors of 100% relative efficiency that are surrounded by escape-suppression shields consisting of bismuth-germanate scintillation detectors. Two of them are positioned at 127 degrees relative to the incident photon beam. The other two can be moved between 90 degrees and 127 degrees to the beam.
A description of the characteristics of the setup is given in