Fig. 1
From: Antihydrogen accumulation for fundamental symmetry tests
The ALPHA-2 central apparatus. a ALPHA-2 geometry, drawn to scale except for the radial extent of the annihilation detector. The inner diameter of the Penning–Malmberg electrodes is 44.35 mm in the central region of the atom trap and 29.6 mm at either end. Antiprotons enter from the left in this view, while positrons and electrons are loaded from the right. b Magnetic field strength on axis with the atom trap energised (the external solenoid responsible for producing a uniform 1 T field is not shown). The solid curve (red) shows the flattened atom trap field used in ref. 5. The dashed curve (blue), shows the on-axis field during stacking; the left and right solenoids a, b increase the field from 1 to 3 T for enhanced capture, cyclotron cooling and rotating wall efficiency of, as appropriate, positrons, electrons and antiprotons
