We describe a 60W, 70fs, 20kHz Ti:sapphire CPA laser system using cryogenically-cooled amplifiers, currently
operating at the Advanced Light Source at LBNL. The system consists of an oscillator, a 20 kHz regenerative preamplifier,
and two power amplifiers to produce two output beams, each at 30W. Each power amp can be pumped by two
90 Watt, 10 kHz, diode-pumped, doubled YLF lasers simultaneously (for 10 kHz) or interleaved in time (for 20 kHz).
The regen is pumped at 20 kHz and 60W, producing 8W output which is split between the power amps. To maintain the
crystals near the thermal conductivity peak at ~50°K, we used 300 Watt cryorefrigerators mechanically decoupled from
the optical table. Pulses are compressed in a quartz transmission grating compressor, to minimize thermal distortions of
the phase front typical of gold coated gratings at high power density. Transmission through the compressor is >80%,
using a single 100 x 100mm grating. One of the 30W output beams is used to produce 70fs electron bunches in the
synchrotron light source. The other is delayed by 300ns in a 12-pass Herriot cell before amplification, to be
synchronized with the short light pulse from the synchrotron.