Abstract
The residual activity induced in particle accelerators is a serious issue from the point of view of radiation safety as the long-lived radionuclides produced by fast or moderated neutrons and impact protons cause problems of radiation exposure for staff involved in the maintenance work and when decommissioning the facility. This paper presents activation studies of the magnets and collimators in the High Energy Beam Transport line of the European Spallation Source due to the backscattered neutrons from the target and also due to the direct proton interactions and their secondaries. An estimate of the radionuclide inventory and induced activation are predicted using the GEANT4 code.
Highlights
Activation induced by particle nuclear interactions in beam line components represents one of the main radiation hazards of high-energy accelerators
This layout includes (i) an ion source, (ii) a low energy beam transport system, (iii) a radio frequency quadrupole accelerating from 75 keV to 3 MeV, (iv) a medium energy beam transport system, (v) a warm linac section used for acceleration to 50 MeV, (vi) a superconducting linac section for acceleration to 2.5 GeV, and (vii) the highenergy beam transport system (HEBT) which will transport the proton beam from the underground linac to the spallation tungsten target at the surface level [15]
Predictions of the residual activity in the accelerator components is important for allowing access of maintenance personal after the beam is turned off
Summary
Activation induced by particle nuclear interactions in beam line components represents one of the main radiation hazards of high-energy accelerators. Elements such as targets, collimators, magnets, and beam dumps are built to withstand radiation, they become themselves highly radioactive as a result of induced activation. Induced radioactivity is due either to direct interactions of the incoming beam or indirect interactions of secondary particles in the accelerator components leading to radionuclides production. Nucleons at the surface in a less strongly bound state have binding energies of a few MeV, whereas nucleons in the deeper-lying shells need about 50 MeV to remove them from the nucleus Charged particles such as protons and pions (produced mainly in the decay of the Delta resonance) have to overcome the Coulomb barrier in addition. The total number of the disintegrations of all sorts occurring per unit time represents the activity of the activated material
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