  Accurately characterizing the intensity and duration of strong-field
femtosecond pulses within the interaction volume is crucial for attosecond
science. However, this remains a major bottleneck, limiting accuracy of the
strong-field, and in particular, high harmonic generation experiments. We
present a novel scheme for the in situ measurement and control of spatially
resolved strong-field femtosecond pulse intensity and duration within the
interaction focal region. Our approach combines conjugate focal imaging with in
situ ion measurements using gas densities pertinent to attosecond science
experiments. Independent measurements in helium and argon, accompanied by a
fitting to a strong field ionization dynamic model, yield accurate and
consistent results across a wide range of gas densities and underscores the
significance of double ionization, as well as barrier suppression ionization.
Direct spatially resolved characterization of the driving laser is a critical
step towards resolving the averaging problem in the interaction volume, paving
the way for more accurate and reliable attosecond experiments.
