Longitudinal confinement and matching of an intense electron beam

Abstract

An induction cell has successfully been demonstrated to longitudinally confine a space-charge dominated bunch for over a thousand turns ͑Ͼ11.52 km͒ in the University of Maryland Electron Ring ͓Haber et al., Nucl. Instrum. Methods Phys. Res. A 606, 64 ͑2009͒ and R. A. Kishek et al., Int. J. Mod. Phys. A 22, 3838 ͑2007͔͒.With the use of synchronized periodic focusing fields, the beam is confined for multiple turns overcoming the longitudinal space-charge forces. Experimental results show that an optimum longitudinal match is obtained when the focusing frequency for containment of the 0.52 mA beam is applied at every fifth turn. Containment of the beam bunch is achievable at lower focusing frequencies, at the cost of a reduction in the transported charge from the lack of sufficient focusing. Containment is also obtainable, if the confinement fields overfocus the bunch, exciting multiple waves at the bunch ends, which propagate into the central region of the beam, distorting the overall constant current beam shape.

Excitation of transverse dipole and quadrupole modes in a pure ion plasma in a linear Paul trap to study collective processes in intense beams

“…In order to study the dynamics of particle beams in large accelerator systems, many experimental studies have been carried out in compact, laboratory-scale, and experiments. 5,6,[9][10][11][12][13][14][15][16][17] A linear Paul trap 18 is suitable for studying the transverse dynamics of such a system because the self-fields and spatially periodic force that a slice of a long charge bunch in the transport system experiences are the Lorentz transforms of the self-field and time oscillating electrostatic force that a long trapped charge column experiences in a linear Paul trap. The transverse dynamics of particles in the two systems are equivalent.…”

Research and development toward heavy ion driven inertial fusion energy

“…The cost vs benefit of these experiments is attractive because they are able to address important physics questions at relatively low cost. Some experiments might be able to answer key questions related to HIF drivers, and we illustrate this with two examples: Paul traps (e.g., at PPPL and at Hiroshima University [79][80][81]), and UMER [21][22][23]82] are able, in principle, to achieve high space-charge tune depression and transport the beam over the equivalent of thousands of lattice periods.…”

“…Particle-in-cell (PIC) codes for beam and beam-plasma interaction have both guided and been validated by comparison to the above experiments [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Computational tools were developed for the self-consistent modeling of the beams (and plasma if present) subject to the externally applied focusing field, acceleration field, self-field of the beam, as well as the fields from induced image-charge and currents.…”

“…This was measured and modeled with and without the neutralization of the beam space charge with electron distributions in the scaled final focusing experiment [17], neutralized transport experiment [18], and with simultaneous longitudinal compression of the beam in the neutralized drift compression experiment (NDCX) [19,20]. (e) Experiments on bending and studying high spacecharge beams in circular machines are being explored with electrons at the University of Maryland Electron Ring (UMER) [21][22][23] and were studied with heavy ions in the recirculator experiment [24,25]. (f) Current amplification by longitudinal compression of a few to % 50 times has been demonstrated.…”

Experimental and simulation study of barrier compression on the University of Maryland Electron Ring

“…To prevent this expansion and maintain the initial rectangular bunch shape, a barrier bucket system was developed that employs an inward field at the bunch ends to confine the beam, allowing us to store the uniform beam bunch for more than 1000 turns [1].…”