The plasma images measure the z-averaged radial density profile n(r,t), from which we compute N(t), the integrated signal within some arbitrary radius, R. By comparing the time evolution of the central density with the quadrupole field on and off, we can separate the effects of the quadrupole field from other plasma loss mechanisms.įrom a series of images taken at successive times, we measure the diffusion coefficient, D. At the point indicated by the arrow in Figure 12(b), the diffusion becomes greatly enhanced.įigure 12. However, because the plasma density decreases over time the electrons become resonant. Indeed, for B o = 20 G (Figure 12(b)), we see that the diffusion is suppressed at first. Well below resonance, when the plasma is rotating quickly, there are few resonant electrons and there should not be a large effect due to the quadrupole field. There are higher order resonances in which the electron makes N/4 (N odd) revolutions as it travels across the plasma, but these are less important.Ībove resonance, when the plasma is rotating slowly, there are many resonant electrons and the quadrupole field has an immediate effect as shown in Figure 12(a). Diffusion due to this mechanism can be very large. Resonant and near-resonant electrons traveling outwards can leave the plasma very quickly. The trajectory (red lines) of a resonant electron as it moves outwards. If only set#1 is used, then $$\vec$$įigure 11. The total field is the axial field, B o, plus the transverse field. This photograph shows the various coils used to produce magnetic fields. The two sets of coils are rotated 45° from one another so that by varying the relative current in the coils, quadrupole patterns with arbitrary angles about the z-axis can be created.įigure 2. We add an axially invariant transverse magnetic quadrupole field using the coils shown in Figure 2. When the right ring is grounded, the electrons stream along the magnetic field lines and strike the phosphor screen. The right ring is grounded to image plasma. The left ring is grounded to load electrons into the trap. The plasma is confined radially by an axial magnetic field and axially by potentials on the ends of the trap.įigure 1. The plasma is confined in a cylindrical region as shown in Figure 1. Our plasma is comprised of electrons thermionically emitted from a tungsten filament. Malmberg-Penning traps will be used to confine positrons and anti-protons before creating anti-hydrogen, and quadrupole traps will be used to confine the neutral anti-hydrogen. The results of this research apply directly to anti-hydrogen creation experiments proposed by the ATHENA and ATRAP collaborations. We have also measured the equilibrium shape of plasmas when a magnetic quadrupole perturbation is present. ![]() We have found experimental evidence for resonant particle transport when we apply a quadrupole magnetic field to our system. Resonant particle transport has long been suspected as the primary cause of plasma loss in Malmberg-Penning traps, but there is no conclusive experimental evidence to support this claim.
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