Positron production using a 9 MeV electron linac for the GBAR experiment
Résumé
For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN’s Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5×107 slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux.
Mots clés
positron
linear accelerator
antimatter
antihydrogen
gravitation 2
Positron
Linear accelerator
Antimatter
Antihydrogen
Gravitation
electron: linear accelerator
positron: particle source
positron: yield
energy: low
radioactivity
electron: pair production
gravitation: acceleration
performance
CERN Lab
tungsten
safety
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