Positron production using a 9 MeV electron linac for the GBAR experiment

• DOI: 10.1016/j.nima.2020.164657
• Publication Date: 2020-09-16T15:34:03Z
• Authors: M. Charlton; J.J. Choi; M. Chung; P. Cladé; P. Comini; P.-P. Crépin; P. Crivelli; O. Dalkarov; P. Debu; L. Dodd; A. Douillet; S. Guellati-Khélifa; P.-A. Hervieux; L. Hilico; A. Husson; P. Indelicato; G. Janka; S. Jonsell; J.-P. Karr; B.H. Kim; E.-S. Kim; S.K. Kim; Y. Ko; T. Kosinski; N. Kuroda; B. Latacz; H. Lee; J. Lee; A.M.M. Leite; K. Lévêque; E. Lim; L. Liszkay; P. Lotrus; T. Louvradoux; D. Lunney; G. Manfredi; B. Mansoulié; M. Matusiak; G. Mornacchi; V.V. Nesvizhevsky; F. Nez; S. Niang; R. Nishi; S. Nourbaksh; K.H. Park; N. Paul; P. Pérez; S. Procureur; B. Radics; C. Regenfus; J.-M. Rey; J.-M. Reymond; S. Reynaud; J.-Y. Roussé; O. Rousselle; A. Rubbia; J. Rzadkiewicz; Y. Sacquin; F. Schmidt-Kaler; M. Staszczak; B. Tuchming; B. Vallage; A. Voronin; A. Welker; D.P. van der Werf; S. Wolf; D. Won; S. Wronka; Y. Yamazaki; K.-H. Yoo
• Keywords: safety; Antimatter; CERN Lab; Physics - Instrumentation and Detectors; tungsten; Positron; FOS: Physical sciences; 530; 01 natural sciences; 7. Clean energy; positron: particle source; Linear accelerator; electron: pair production; electron: linear accelerator; 0103 physical sciences; antimatter; [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det]; Antihydrogen; energy: low; antihydrogen; gravitation 2; Instrumentation and Detectors (physics.ins-det); linear accelerator; radioactivity; gravitation: acceleration; positron; performance; positron: yield; Gravitation

published in NIM A. 33 pages 9 figures<br/>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 $5\times10^7$ 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.<br/>