  We propose a quantum-circuit refrigerator (QCR) based on photon-assisted
quasiparticle tunneling through a single
normal-metal--insulator--superconductor (NIS) junction. In contrast to previous
works with multiple junctions and an additional charge island for the QCR, we
galvanically connect the NIS junction to an inductively shunted electrode of a
superconducting microwave resonator making the device immune to low-frequency
charge noise. At low characteristic impedance of the resonator and parameters
relevant to a recent experiment, we observe that a semiclassical impedance
model of the NIS junction reproduces the bias voltage dependence of the
QCR-induced damping rate and frequency shift. For high characteristic
impedances, we derive a Born--Markov master equation and use it to observe
significant non-linearities in the QCR-induced dissipation and frequency shift.
We further demonstrate that in this regime, the QCR can be used to initialize
the linear resonator into a non-thermal state even in the absence of any
microwave drive.
