A proton source in the ALPHA apparatus for precision measurements of antihydrogen and hydrogen

Abstract

The apparent lack of antimatter within our local solar system, the Milky Way, and at Galactic boundaries is inconsistent with the Big Bang hypothesis. This disagreement has motivated many experiments to compare the properties and behaviour of antimatter and matter. The ALPHA (Antihydrogen Laser PHysics Apparatus) experiment produce, trap and study antihydrogen. This synthesis involves antiprotons sourced from the limited schedule of the Antiproton Decelerator facility. The restricted availability hinders the number of novel antiproton experiments, which could potentially increase the number of trapped antihydrogen atoms per Antiproton Decelerator cycle. Some of these studies can be performed using a substitute for antiprotons, such as protons, allowing the limited antiprotons to be used during the implementation of their results. This research demonstrates a method that adapts an existing Penning trap to produce protons on demand within reasonable operating time scales of minutes. The availability of protons enables the consideration of new physics studies within ALPHA, including hydrogen formation, trapping, and possibly in situ hydrogenantihydrogen comparisons. The study produced protons from radiofrequency-driven electrons through electron impact ionisation of the cryogenic Penning trap residual gas. The resulting positive ions were sympathetically cooled and compressed by positrons. All positive ions, except protons, were ejected from the trapping potentials using the autoresonance method. The remaining trapped population is approximately (0.9 − 1.2) × 10 6 protons. This research proves the feasibility of generating protons within the ALPHA apparatus, paving the way for future prospects of hydrogen generation.

Laser-cooled Be+ for improved antihydrogen trapping and magnetometry

“…Recently ALPHA has applied the laser cooling technique to antihydrogen atoms [2], which is very promising for future improvement of precision antihydrogen measurements. There is ongoing work to introduce a hydrogen [42][43][44] inside the ALPHA trap to perform a direct CPT symmetry test using the same experimental protocol, in the same apparatus and at the same time.…”

“…This is challenging because the antimatter community would have to either develop the same measurement technique as MPQ and other groups measuring hydrogen beams or hydrogen would have to be trapped in an antihydrogen trap. ALPHA is currently looking for ways to introduce hydrogen atoms into their Ioffe-Pritchard trap in a few independent ways: a. synthesis from protons and electrons in a similar way as antihydrogen is produced [44],…”

“…Hydrogen ions generated from the background gas could be used in the ALPHA Experiment. A large amount of protons could serve as an antiproton mock-up for a plasma dynamics study and they could also be used for hydrogen formation in an analogue scheme to antihydrogen formation [44].…”