A detailed understanding of the physics of space-charge dominated beams is vital for many advanced accelerators that desire to achieve high beam intensity. In that regard, low-energy, high-intensity electron beams provide an excellent model system. The University of Maryland Electron ring (UMER), currently under construction, has been designed to study the physics of space-charge dominated beams with extreme intensity in a strong focusing lattice with dispersion. The tune shift in UMER will be more than an order of magnitude greater than exiting synchrotrons and rings. The 10-keV, 100 mA, UMER beam has a generalized perveance in the range of 0.0015, and a tune shift of 0.9. Though compact (11-m in circumference), UMER is a very complex device, with over 140 focusing and bending magnets. We report on the unique design features of this research facility, the beam physics to be investigated, and early experimental results.

The University of Maryland Electron Ring (UMER), currently under construction, has been designed to study the physics of space-charge dominated beams at extremely large values of the betatron tune shift which exceed those of existing strong-focusing synchrotrons and rings by more than an order of magnitude. In this paper, the unique design features of this research facility, the new beam physics to be investigated, and recent experimental results in the injector prototype as well as simulation studies will be reviewed.

A two-year study of recirculating induction heavy ion accelerators as low-cost driver for inertial-fusion energy applications was recently completed. The projected cost of a 4 MJ accelerator was estimated to be about $500 M (million) and the efficiency was estimated to be 35%. The principal technology issues include energy recovery of the ramped dipole magnets, which is achieved through use of ringing inductive/capacitive circuits, and high repetition rates of the induction cell pulsers, which is accomplished through arrays of field effect transistor (FET) switches. Principal physics issues identified include minimization of particle loss from interactions with the background gas, and more demanding emittance growth and centroid control requirements associated with the propagation of space-charge-dominated beams around bends and over large path lengths. In addition, instabilities such as the longitudinal resistive instability, beam-breakup instability and betatron-orbit instability were found to be controllable with careful design.

Articles you may be interested in Relativistic solutions for one-and two-dimensional space-charge limited current in coaxial diode Phys. Plasmas 20, 053103 (2013); 10.1063/1.4804403 Amended conjecture on an upper bound to time-dependent space-charge limited current A fully kinetic model for the electron flow in a crossed field device is derived and used to determine the system stationary states. It is found that for low injection temperatures, there is a simultaneous presence of distinct stationary solutions and an abrupt transition between accelerating and space-charge limited regimes. On the other hand, for high injection temperatures, there is only a single stationary solution branch and the change between the regimes becomes continuous. For intermediate temperatures, it is then identified a critical point that separates the abrupt and continuous behaviors. It is also investigated how intrinsic space-charge oscillations may drive stationary states unstable in certain parameter regimes. The results are verified with N-particle self-consistent simulations. V C 2014 AIP Publishing LLC. [http://dx.

Results are presented for electron beam transport experiments in a 1-m-long straight section consisting of a solenoid and five short printed-circuit quadrupoles. A linear computer code for rms envelope matching, SPOT, is used for channel design, while final simulations with more realistic elements are obtained with a 2 1 2 D version of WARP, a particle-in-cell code. Reasonable agreement is found between calculations and the effective beam envelope obtained from pictures of the beam on a movable phosphor screen. The results validate, within experimental errors, the use of short magnetic quadrupoles for the transport of space-charge dominated beams. The straight section constitutes the prototype matching section for an electron recirculator to be built at the University of Maryland. [S1098-4402(98)