Low-current, space-charge dominated beam transport at the University of Maryland Electron Ring (UMER)

The University of Maryland Electron Ring (UMER) is designed for the transport of low energy (10 keV), high current (100 mA) electrons in a 72-magnetic-quadrupole lattice over an 11.5 m circumference. With these parameters, and a typical single-particle phase advance per period of 76deg, space charge is extreme. However, high current is not necessary for establishing space charge dominated transport in UMER. In fact, low current (0.6 mA) beam transport in combination with longer full-lattice period can yield strong space charge conditions. All 72 quadrupoles are needed, though, to yield beams with relatively small cross sections, as required for emittance-dominated transport. We present design calculations for the low-current, high space charge regime in UMER, including the use of Collins-type insertions for matching into the ring lattice.