CERN's Antiproton Decelerator Facility Research Articles

Probing electric and magnetic fields with a Moiré deflectometer

A new contact-free approach for measuring simultaneously electric and magnetic field is reported, which considers the use of a low energy ion source, a set of three transmission gratings and a position sensitive detector. Recently tested with antiprotons (Aghion et al., 2014) [1] at the CERN Antiproton Decelerator facility, this paper extends the proof of principle of a moiré deflectometer (Oberthaler et al., 1996) [2] for distinguishing electric from magnetic fields and opens the route to precision measurements when one is not limited by the ion source intensity. The apparatus presented, whose resolution is mainly limited by the shot noise is able to measure fields as low as 9mVm−1Hz−1/2 for electric component and 100μGHz−1/2 for the magnetic component. Scaled to 100nm pitch for the gratings, accessible with current state-of-the-art technology [3], the moiré fieldmeter would be able to measure fields as low as 22μVm−1Hz−1/2 and 0.2μGHz−1/2.

Multiple Aperture-Based Antihydrogen Parallel Plate Gravity Experiment

An experiment is described that could be carried out at the CERN Antiproton Decelerator facility to determine the direction of acceleration of antihydrogen in the earth's gravitational field. The experiment would use two plates separated by a small distance and oriented parallel with the earth's surface. Multiple cylindrical barriers would be used with gaps that allow the antihydrogen to pass through. Shadow regions are created where, with linear motion, the antihydrogen cannot annihilate. However, with parabolic paths, such as those of objects under the influence of gravity, antihydrogen can annihilate within a shadow region. The probability of an atom annihilating in one of the shadow regions is determined. For simplicity the model considers the antihydrogen source as a point and at a temperature of 4 K.

Positron cross-field transport due to quasibound states of antihydrogen

Within the past few years, experiments have been reported in which antiprotons produced at the CERN Antiproton Decelerator facility were slowed, trapped in nested Penning traps and made to interact with a positron plasma such that antihydrogen was formed. Classical trajectory simulations of the interactions between the antiprotons and positrons have been reported to indicate that positive-energy, quasibound states of antihydrogen can form at a rate that exceeds the rate of formation of stable Rydberg states. The formation of quasibound states may affect the rate of diffusion of positrons across the magnetic field that confines them in the nested Penning trap. Simulations indicate that a binary interaction associated with the formation and disintegration of a quasibound state can cause a shift of the positron’s guiding center that is much larger than the positron cyclotron radius before the interaction. A theory is presented that describes positron cross-magnetic-field diffusion due to quasibound states of antihydrogen.