Hybrid MKIDs with ground-side deposition - A novel method for microwave detection with a resonator separated from antenna H. Watanabe, M. Hazumi a, H. Ishino b, A. Kibayashi b, Y. Kibe b, S. Mima c, S. Oguri a, C. Otani c, N. Sato a, O. Tajima a, K. Takahashi c, and M. Yoshida a SOKENDAI, Tsukuba, Ibaraki, , Japan a High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, , Japan b Okayama University, Okayama, , Japan c Terahertz-wave Research Group, RIKEN, 2-1 Hirosawa, Wako, Saitama, , Japan Light satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection 1 ． LiteBIRD Quality factor as a function of physical temperature of Al-Nb hybrid MKIDs with ground-side deposition Microwave Kinetic Inductance Detectors (MKIDs) as a good candidate - High Q-value of resonance results in good NEP. - Many signals from detectors can be multiplexed. - No bias is required. Requirements for detectors MKIDs are superconducting cooper-pair breaking detectors. It’s very simple. It consists of three components: feed line, resonator, and antenna. Principle of signal detection 1.Reference RF (~5GHz) is fed into the feed line, which is coupled to resonators. Each resonator has individual resonance frequency, which is determined by inductance of the resonator, i.e. length of the resonator. The output microwave from the feed line has resonant peaks. 2.Millimeter waves (signals) that are picked up by the antenna break cooper-pairs in the resonator. It results in the variation of kinetic inductance (Mattis-Bardeen : anomalous skin effect). 3.The variation of the inductance induces change of the resonance frequency as well as change of the resonance phase. 2. MKIDs Frequency of RF (GHz) Resonance without any signal input Variation of kinetic inductance induces the shifts of resonance peaks. Millimeter waves above twice of gap energy, i.e. hν>2Δ, break cooper-pairs. As a result, the kinetic inductance changes. MKIDs Sorption refrigerator with pulse tube cooler Coaxial cable Equivalent diagram of LC-resonator circuit 4 ． Performance evaluations in the laboratory Inflation potential: V 1/4 ~ x (r/0.01) 1/4 GeV (with slow-roll approximation) “r” is Tensor-to-Scalar ratio (T/S), which is proportional to the B-modes intensity. Many models predict r = 0.01 ~ < 3  Karcmin with 2 years of full-sky observation  ~2,000 pixels x (WHz -1/2 ) NEP detectors Sensitive for multi-frequency bands for foreground removal  four or more frequency bands in GHz LiteBIRD is a small satellite for observation of the CMB B-mode polarization. The B-mode is a smoking-gun signature of inflationary universe. Generic prediction of the inflation models is generation of primordial gravitational waves, which results in the B-modes. Since the B-mode power is proportional to the intensity of the primordial gravitational waves, i.e. potential energy of the inflation, precise measurements of the CMB polarization could determine the energy scale of inflation. We evaluate the performance of developed MKIDs under the 0.3 Kelvin condition. We measured the quality factor by changing the physical temperature of MKIDs device; -Best Q~1,000,000 at 0.33K. Next step Measure the sensitivity and noise. Produce more MKIDs and evaluate a fraction of good channels. 5 ． Summary We have been developing MKIDs for LiteBIRD. We propose hybrid MKIDs with ground-side deposition. Advantages -Radiation loss due to leakage from the resonator to the antenna can be avoided. -This design can also adopt the easier millimeter wave filter design. -It’s simple design allows us to use a contact aligner for fabrication. Test results -Quality factors increase as temperature decreases. -Best Q ~ 1,000,000 at 0.33K. Poster P-19 Resonance with signal Cooper-pair Signals from antenna MaterialT C (Kelvin) Frequency corresponding to 2  (GHz) Niobium (Nb) Aluminum (Al) Microwave Resonator Dipole Antenna Feed Line 100μm ～ 5GHz Feed Line CMB signal (~100GHz) RF IN RF OUT λ/2 MKIDs RF OUT RF IN 3. Ground-side deposition Hybrid MKIDs Having a localized absorption area for deposition of input power from an antenna, which is often called “hybrid technique”, is a popular way to improve a sensitivity of the detector. Hybrid MKIDs are made using two different superconducting materials. Our hybrid MKIDs are fabricated using Al and Nb. 0.3K stage 左から Nb Si Al Nb SiO 2 Si Nb Al Nb SiO 2 Antenna Cross-section view Our proposal is to have an absorption area that is located on the ground-side of the coplanar waveguide (CPW). A microstrip line (MSL) connects the absorption area and the antenna. Ground Advantages -Radiation loss due to leakage from the resonator to the antenna can be avoided. -Antenna and resonator are not connected directly. -This design can also adopt the easier millimeter wave filter design. -It’s simple design allows us to use a contact aligner for fabrication. Hence radiation with 750 GHz> f >80 GHz traveling from the antenna into resonator will be absorbed only in the Al. The quasiparticles created by signals are confined within the Al due to the difference in superconducting gap between two materials. Nb Resist Al Etching Al ① ② ④ ③ ⑤ Lift off Nb No2 Quasiparticles