We present a parallel network of 16 demagnetization refrigerators mounted ona cryofree dilution refrigerator aimed to cool nanoelectronic devices tosub-millikelvin temperatures. To measure the refrigerator temperature, thethermal motion of electrons in a Ag wire -- thermalized by a spot-weld to oneof the Cu nuclear refrigerators -- is inductively picked-up by asuperconducting gradiometer and amplified by a SQUID mounted at 4 K. The noisethermometer as well as other thermometers are used to characterize theperformance of the system, finding magnetic field independent heat-leaks of afew nW/mol, cold times of several days below 1 mK, and a lowest temperature of150 microK of one of the nuclear stages in a final field of 80 mT, close to theintrinsic SQUID noise of about 100 microK. A simple thermal model of the systemcapturing the nuclear refrigerator, heat leaks, as well as thermal and Korringalinks describes the main features very well, including rather high refrigeratorefficiencies typically above 80%.
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