Fig. 1: Experimental set-up.
From: Observation of the 1S–2P Lyman-α transition in antihydrogen
a, The three-layer silicon vertex annihilation detector is shown schematically in green; the external solenoid magnet for the Penning traps is not shown in this diagram. Laser light enters from the positron (e+) side (right) and is transmitted to the antiproton (\(\bar{p}\)) side (left) through vacuum-ultraviolet-grade MgF2 ultrahigh-vacuum windows. The laser beam crosses the trap axis at an angle of 2.3°. The transmitted 121.6-nm pulses are detected by a photomultiplier at the antiproton side. b, Axial magnetic well formed by the five mirror coils and responsible for the axial confinement of cold (less than 0.5 K) anti-atoms. c, Radial magnetic octupole field profile. PMT, photomultiplier tube; THG, third-harmonic generation.
