  Nonlinear integrable optics (NIO) are a promising novel approach at improving
the stability of high intensity beams. Implementations of NIO based on
specialized magnetic elements are being tested at the Integrable Optics Test
Accelerator (IOTA) at Fermilab. One method of verifying proper implementation
of these solutions is by measuring the analytic invariants predicted by theory.
The initial measurements of nonlinear invariants were performed during IOTA run
in 2019/20, however the covid-19 pandemic prevented the full-scale experimental
program from being completed. Several important improvements were implemented
in IOTA for the 2022/23 run, including the operation at higher beam energy of
150 MeV, improved optics control, and chromaticity correction. This report
presents the results of improved measurements of nonlinear invariants.
