  We present the design and performance of an ultra-high vacuum (UHV) scanning
tunneling microscope (STM) that uses adiabatic demagnetization of electron
magnetic moments for controlling its operating temperature in the range between
30 mK and 1 K with the accuracy of up to 7 $\mu$K. The time available for STM
experiments at 50 mK is longer than 20 h, at 100 mK about 40 h. The single-shot
adiabatic demagnetization refrigerator (ADR) can be regenerated automatically
within 7 hours while keeping the STM temperature below 5 K. The whole setup is
located in a vibrationally isolated, electromagnetically shielded laboratory
with no mechanical pumping lines penetrating through its isolation walls. The
1K pot of the ADR cryostat can be operated silently for more than 20 days in a
single-shot mode using a custom-built high-capacity cryopump. A high degree of
vibrational decoupling together with the use of a specially-designed
minimalistic STM head provides an outstanding mechanical stability,
demonstrated by the tunneling current noise, STM imaging, and scanning
tunneling spectroscopy measurements all performed on atomically clean Al(100)
surface.
