Efficient injection of an intense positron beam into a dipole magnetic field

Abstract

We have demonstrated efficient injection and trapping of a cold positron beam in a dipole magnetic field configuration. The intense 5 eV positron beam was provided by the NEutron induced POsitron source MUniCh facility at the Heinz Maier-Leibnitz Zentrum, and transported into the confinement region of the dipole field trap generated by a supported, permanent magnet with 0.6 T strength at the pole faces. We achieved transport into the region of field lines that do not intersect the outer wall using the E B drift of the positron beam between a pair of tailored plates that created the electric field. We present evidence that up to 38% of the beam particles are able to reach the intended confinement region and make at least a 180°rotation around the magnet where they annihilate on an insertable target. When the target is removed and the E B plate voltages are switched off, confinement of a small population persists for on the order of 1 ms. These results lend optimism to our larger aims to apply a magnetic dipole field configuration for trapping of both positrons and electrons in order to test predictions of the unique properties of a pair plasma.

Characterization of the NEPOMUC primary and remoderated positron beams at different energies

“…For the remoderated beam with energies of 5, 12 and 22 eV we observed intensities in the range of (2-6)·10 7 e + /s, comparable to previous measurements close to the source [11]. The diameter of this beam was found to be less than 4 mm (FWHM) and independent of the beam energy, which is convenient, e.g., for the investigation of positron injection into a magnetic dipole field [8]. The energy spread of the remoderated beam is found to exceed expectations from thermal broadening perhaps due to surface properties of the remoderation crystal and the remoderator geometry.…”

“…Another novel topic is the creation of an electronpositron plasma in the laboratory, as suggested by some of the current authors [7,8]. Many of these projects benefit from the use of high-flux, high-brightness positron beams where the beam brightness is defined as flux normalized to the product of the beam diameter squared and the perpendicular energy [9].…”

Manipulation of positron orbits in a dipole magnetic field with fluctuating electric fields

“…Prior to the construction of the accumulator and SC levitated dipole devices, we are conducting studies to develop injection and manipulation methods of positrons in the dipole magnetic field. In a prototype dipole field trap operated at NEPOMUC, so far we have realized efficient injection of positron beam with a E × B drift scheme [14,15]. Recent optimization work realized almost loss-less (close to 100 % efficiency) injection.…”

“…Experimental setup, single particle orbit analysis, and initial results on the compression experiments are reported in the following sections. The experiments were performed in a prototype dipole field trap [15], shown in Figure 1, at the open beam port of the NEPOMUC facility [8]. The positron beam was transported into the trap with a 5 mT guiding field through an injection port located at the top of the chamber.…”

Simulations on the Mixing Processes of Electrons and Positrons in a Magnetic Mirror Trap

“…Currently, there are projects to confine low energy ep plasmas in a magnetic dipole field [18] and a stellarator [19] with the use of low energy positrons from a nuclear reactor [20]. Also, the simultaneous confinement of low energy electrons and positrons with a compact magnetic mirror trap has been planned [21].…”