The projected sensitivity of ADMX after the dilution refrigerator is added. ADMX will be sensitive to even the most pessimistically coupled dark matter axions in the range 1μeV to 10μeV (the most attractive mass range) in the very near future. Also shown is the sensitivity reach of a small apparatus ADMX-HF to explore next-generaton detector technologies.
Amplifier noise versus physical temperature for the SQUID amplifier in ADMX. SQUID amplifiers offer over a factor of 100 times lower noise than conventional amplifiers and a huge increase in experiment sensitivity.
A dilution refrigerator (at left) reaches temperatures below 100 milliKelvins and is crucial for this "Definitive Experiment".
ADMX is undergoing an upgrade to the "Definitive Experiment"; this is sensitive to even the most pessimistic range of plausible dark-matter axion masses and couplings.
Several years ago, the ADMX cavity temperature was around 1.2K and the amplifier noise was around 2K. Recently the amplifiers were replaced by SQUID amplifiers, which greatly lowered the noise and allowed a faster scan.
The addition of a dilution refrigerator is the main focus of the ADMX upgrade program. The dilution refrigerator allows cooling the apparatus down to 100mK or less which makes data taking 400 times faster. This makes it the "Definitive Experiment".