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of reaching base temperatures below 100 mK. A coaxial feedline drives the device through a 30 dB attenuator at 4 Kelvin, and a high electron mobility (HEMT) amplifier with a noise temperature T$_{n}$ ≈ 5 . 5 K is used to boost the output signal. A cryoperm magnetic shield is used to shield the device, and a Helmholtz Coil internal to the magnetic shield is used to apply a magnetic field normal to the surface of the chip. 

Microstrip resonators, like larger CPW resonators[18], appear to be quite sensitive to the magnetic field normal to the metal surface during cooling through the superconducting transition temperature T$_{c}$ . Figure 2 shows the applied magnetic field during cooling and the resulting quality factors of the lowest Q$_{m}$ resonator on the device. Despite the magnetic shield the best quality factor is achieved with an applied magnetic field of around 30 mG. 

