  Operation with ultra-low momentum-compaction factor (alpha) is a desirable
capability for many storage rings and synchrotron radiation sources. For
example, low-alpha lattices are commonly used to produce picosecond bunches for
the generation of coherent THz radiation and are the basis of a number of
conceptual designs for EUV generation via steady-state microbunching (SSMB).
Achieving ultra-low alpha requires not only a high-level of stability in the
linear optics but also flexible control of higher-order compaction terms.
Operation with lower momentum-compaction lattices has recently been
investigated at the IOTA storage ring at Fermilab. A procedure for lowering the
ring compaction using the linear optics along with compensations from the
higher-order magnets was developed with the aid of a model, and an experimental
technique for measuring the momentum compaction was developed. The lowest
momentum compaction achieved during the available run-time was
$3.4\times10^{-4}$, around 15 times lower than previously operated. These
feasibility studies ensure an improved experimental understanding of the IOTA
optics and potentially will enable new research programs at the facility.
