Oct. 1, 2019:
DM Radio Cubic Meter is a full-scale QCD axion search that will probe QCD axion dark matter over 1.5 orders of magnitude of mass. It is a collaboration of groups at SLAC, Stanford, UC Berkeley, LBNL, MIT, UNC Chapel Hill, and Princeton university.
Dark Matter is a term for matter that fills the universe, but interacts primarily through gravity. In the 1930's, astronomers first realized that there must be a substantial amount of non-luminous matter holding galaxy clusters together; stars and interstellar gas alone could not explain the huge observed mass in most clusters. Since the 1930's, evidence for dark matter has streamed in from all areas of astrophysics and cosmology. Dark matter plays a role in explaining galaxy cluster masses, anomalous galaxy rotation curves, and the formation of structure in the universe. Dark matter appears to be necessary to hold the universe together, but despite its ubiquity, nobody has ever directly detected a dark matter particle, though numerous theoretical candidates have been proposed.
The Irwin group is focused on searching for "light" dark matter that weighs so little that it acts more like a field than a particle. Field-like dark matter must be a boson. Two theoretically well motivated light-field dark matter candidates are the axion (spin 0) and the hidden photon (spin 1). Both couple weakly to photons. The Dark Matter Radio, or DM Radio for short, is an experiment that detects dark matter like an AM radio. But unlike a radio it uses exquisitely sensitive superconducting devices, including Superconducting Quantum Interference Devices (SQUIDs), and Quantum Sensors based on photon upconversion, to search for these elusive particles.
a) The 4K dip probe for the DM Radio Pilot detector. The superconducting shield is connected to the end of the probe and inserted into a dewar of liquid helium. b) CAD drawing of the DM Radio Pilot resonator inside the superconducting shield (green). The Nb slitted sheath (orange) is surrounded by a hexagonal Nb capacitor (red). PTFE wire guides placed on the top and bottom of the sheath are used route the inductor coil (not visible), which is wrapped around the sheath. The tuning system is made of sapphire dielectrics (blue) and PTFE supports (white), whose positions are controlled by room temperature stepper motors. An isolated annex for the SQUID electronics is located below the resonator (pink). c) Top: Photograph of the manufactured Nb slitted sheath, hex capacitor and PTFE wire guide. The slit is visible underneath the wire guide. Bottom: Photograph of the SQUID sensors mounted inside the annex.
An example resonant curve from the DM Radio. A dark matter signal would appear as a small spike in excess power on top of the resonator line shape. Unlike cavity-based searches, which operate at much higher frequencies, the thermal occupation of the resonator is visible in the noise.
Projected exclusion limits for axion and hidden photon couplings versus mass for the different phases of the DM Radio program. Limits are calculated assuming 1.5 years of integration time and noise performance at the Standard Quantum Limit, except for the Pilot detector which does not use a quantum-limited amplifier. Sensitivity below the SQL can be achieved through the use of squeezing, entanglement, and backaction evasion.
Saptarshi Chaudhuri, Kent D. Irwin, Peter W. Graham, and Jeremy Mardon,
arxiv:1803.01627 – Published 5 March 2018
M. Silva-Feaver, S. Chaudhuri, H.M. Cho, C. Dawson, P. Graham, K.D. Irwin, S. Kuenstner, D. Li, J. Mardon, H. Moseley, and R. Mule,
IEEE Trans. on Appl. Superc., 27, 1 – Published 21 November 2016
Saptarshi Chaudhuri, Peter W. Graham, Kent Irwin, Jeremy Mardon, Surjeet Rajendran, and Yue Zhao,
Phys. Rev. D 92, 075012 – Published 8 October 2015
Saptarshi Chaudhuri, Caltech HEP Seminar, 11 March 2019