  The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is a
co-planar interferometer array operating at a wavelength of 3mm to measure the
Sunyaev-Zeldovich effect (SZE) of galaxy clusters. In the first phase of
operation -- with a compact 7-element array with 0.6m antennas (AMiBA-7) -- we
observed six clusters at angular scales from 5\arcmin to 23\arcmin. Here, we
describe the expansion of AMiBA to a 13-element array with 1.2m antennas
(AMiBA-13), its subsequent commissioning, and our cluster SZE observing
program. The most important changes compared to AMiBA-7 are (1) array
re-configuration with baselines ranging from 1.4m to 4.8m covering angular
scales from 2\arcmin to 11.5\arcmin, (2) thirteen new lightweight
carbon-fiber-reinforced plastic (CFRP) 1.2m reflectors, and (3) additional
correlators and six new receivers. From the AMiBA-13 SZE observing program, we
present here maps of a subset of twelve clusters. In highlights, we combine
AMiBA-7 and AMiBA-13 observations of Abell 1689 and perform a joint fitting
assuming a generalized NFW pressure profile. Our cylindrically integrated
Compton-y values for this cluster are consistent with the BIMA/OVRA, SZA, and
Planck results. We report the first targeted SZE detection towards the
optically selected galaxy cluster RCS J1447+0828, and we demonstrate the
ability of AMiBA SZE data to serve as a proxy for the total cluster mass.
Finally, we show that our AMiBA-SZE derived cluster masses are consistent with
recent lensing mass measurements in the literature.
