Schematic of the one magnet Penning trap; the symmetry axis is horizontal. The NdFeB magnet is the central ring electrode, with its axial magnetization M indicated by the arrows. Characteristic dimensions of the trapping volume: r o = 9.525 mm is the inner radius of the NdFeB magnet; z o = ±8.385 mm is the distance from the midplane to one of the endcaps.
(Left) Magnetic flux density of a NdFeB magnet (N42 grade). The axis of the magnet is horizontal. Magnet size: 19.05 mm inner diameter, 38.10 mm outer diameter, and 19.05 mm length. (Right) Magnetic flux density for the two-magnet Penning trap shown in Fig. 3, which uses N40UH grade NdFeB magnets. The axis of rotational symmetry is horizontal. Colors indicate equal B-field contours, with the B-field inside the magnet arbitrarily pegged at 0.5 T to highlight the trapping region. The flux density inside a magnet is as high as ≈1.2 T.
Diagram of a Penning trap with two embedded NdFeB magnets; the symmetry axis is horizontal. The two magnets are seated tightly on opposite sides of the iron ring electrode with inner radius mm. Holes in this ring allow beam access. The iron endcaps have reentrant tubes extending into the NdFeB magnets and ending at mm from the midplane. The outer diameter is 5.08 cm, and the overall length is 6.10 cm.
(a) Comparison of the on-axis magnetic field calculated for the one-magnet trap (dash line) and the two-magnet trap (solid line); (b) magnification for finer comparison of the homogeneity within the trapping region. The reentrant edges of the trap endcaps are indicated by a pair of vertical lines; green dashed line for the one-magnet trap and blue solid line for the two-magnet trap. Hall probe measurements for the two magnet trap are also plotted: circle for N42 grade neomagnets, and square for N40UH neomagnets.
Circular motions of a Ne10 + ion in the midplane of the two-magnet Penning trap. The initial condition is chosen to illustrate the fast cyclotron motion undergoing a counter-clockwise magnetron drift (dashed circle) around the center of the trap.
Simplified diagram of the experimental apparatus. The two-magnet Penning trap is centered on the six-way cross. An ion pulse is steered and focused by orthogonal plates and an Einzel lens (right). Ions are counted using the time-of-flight (TOF) detector or the position-sensitive detector (PSD).
Diagram for ion detection scheme. A transistor-transistor logic (TTL) pulse triggers a high-voltage switch to eject stored ions, and simultaneously triggers a digital oscilloscope to begin data acquisition of the TOF detector signal.
Storage of highly charged ions in a two-magnet Penning trap. (Left) Number of ions detected on the fast MCP as a function of storage time in the two-magnet Penning trap with ΔV = 10 V applied between the ring and endcap electrodes. (Right) Output of the TOF detector versus arrival time, sampled for representative storage times: (a) 10 ms (b) 0.5 s (c) 1 s (d) 2 s (e) 3 s. The detector signal scale is magnified by ≈2 × stepwise from (a) through (e). The TOF peak for each charge state is converted to ion counts for (f). The number of ions decays exponentially as a function of the storage time, as illustrated in (f). Error bars represent 1σ uncertainty.
Dependence of observed ion number decay rate upon background gas pressure, for two potential well depths: ΔV = 10 V (circle) and ΔV = 40 V (square). Filled symbols are for Ne10 + only. Unfilled symbols are summed over charge states. Error bars represent 1σ uncertainty.
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