Manipulating large-area, heavy metal ion beams with a high-current electrostatic plasma lens

High-Current Heavy Ion Beams in the Electrostatic Plasma Lens

“…For the case of tantalum beam with diameter 10 cm, the maximum beam compression at the lens focus was approximately a factor of 30, with current density up to 32 mA/cm 2 . Similar results were obtained for a copper ion beam on the Kiev set-up, where the compression was a factor 15 -25 depending on the total ion beam current passing through the lens and the current density was up to 170 mA/cm 2 (see [6][7][8] for details).…”

“…The experimental results depend on the particular externally-applied potential distribution along the lens electrodes (see [8] for more details). The optimal "O"-distribution minimizes lens spherical aberrations, as established empirically.…”

“…Moderate energy, large area, high current, heavy ion beams can be focused in this way, as has been well demonstrated in a number of experiments carried out at Kiev and at Berkeley in recent years [7][8]. The lens used in these experiments employed a magnetic field that was established by conventional current-driven electromagnetic coils.…”

“…The experiments were carried out at Kiev using the set-up described in detail in [6] and at Berkeley described in [7,8]. For ion beam formation we use a two-chamber MEVVA ion source with grid anode and a three-electrode, multi-aperture, accel-decel ion extraction system.…”

“…In the absence of spherical aberrations the maximum compression of low-divergence beams may be restricted by a finite phase volume, uncompensated beam space charge, and momentum aberrations due to a finite azimuthal twist of beam particles in the lens magnetic field. Estimates made in [3,8] show that the main reason for the low compression of the light hydrogen ion beams, under the experimental conditions employed [3,4], are momentum aberrations. For heavy ions the role of momentum aberrations, that lead to space charge separation and limitation of beam compression, decreases rapidly for higher ion mass and energy.…”