  The acceleration of super-heavy ions (SHIs) from plasmas driven by ultrashort
(tens of femtoseconds) laser pulses is a challenging topic waiting for
breakthrough. The detecting and controlling of the ionization process, and the
adoption of the optimal acceleration scheme are crucial for the generation of
highly energetic SHIs. Here, we report the experimental results on the
generation of deeply ionized super-heavy ions (Au) with unprecedented energy of
1.2 GeV utilizing ultrashort laser pulses (22 fs) at the intensity of 10^22
W/cm2. A novel self-calibrated diagnostic method was developed to acquire the
absolute energy spectra and charge state distributions of Au ions abundant at
the charge state of 51+ and reaching up to 61+. The measured charge state
distributions supported by 2D particle-in-cell simulations serves as an
additional tool to inspect the ionization dynamics associated with SHI
acceleration, revealing that the laser intensity is the crucial parameter for
the acceleration of Au ions over the pulse duration. The use of double-layer
targets results in a prolongation of the acceleration time without sacrificing
the strength of acceleration field, which is highly favorable for the
generation of high-energy super heavy ions.
