Not sure how many , but he has been doing them for about 18 months. However, he has been doing ablations of other things for many years. He spoke very highly of the precision the TULSA system gives him.
Also found this online before my TULSA. A few years old but still valid for experience:

Focal therapy for the prostate began in the late 1990s; however, there is a very limited number of providers who are trained and skilled enough to perform this procedure. These 5 doctors have the most experience and have performed the most Focal Laser Ablation procedures:

Myself — Eric Walser, MD of Wavelength Medical by UTMB (Galveston, TX)
Dan Sperling, MD of Sperling Prostate Center (Boca Raton, FL)
Jurgen Futterer, MD, PhD of Radboud (The Netherlands)
David Woodrum, MD, PhD of Mayo Clinic (Rochester, MN)
John Feller, MD of Desert Medical Imaging (Indian Wells, CA)