Development of Superconducting Detectors for Measurements of Cosmic Microwave Background. Mr. MIMA, SatoruMr. MIMA, Satoru (Okayama University) Co-Authors: ISHINO, Hirokazu (Okayama University) KIMURA, Nobuhiro (High Energy Accelerator Research Organization (KEK)) KAWAI, Masanori (High Energy Accelerator Research Organization (KEK)) NOGUCHI, Takashi (National Astronomical Observatory of Japan) WATANABE, Hiroki (The Graduate University for Advanced Studies) HATTORI, Kaori (Okayama University) KIBAYASHI, Atsuko (Okayama University) HAZUMI, Masashi (High Energy Accelerator Research Organization (KEK)) YOSHIDA, Mitsuhiro (High Energy Accelerator Research Organization (KEK)) SATO, Nobuaki (High Energy Accelerator Research Organization (KEK)) TAJIMA, Osamu (High Energy Accelerator Research Organization (KEK)) OKAMURA, Takahiro (High Energy Accelerator Research Organization (KEK)) TOMARU, Takayuki (High Energy Accelerator Research Organization (KEK)) 09/Jun/20111TIPP11

Contents Motivation: LiteBIRD STJ (Superconducting Tunnel Junction) ◦ About STJ ◦ Antenna coupled STJ detectors  Parallel-connected Twin Junction  Microstrip Junction MKID (Microwave Kinetic Inductance Detector) Summary 09/Jun/2011TIPP112

LiteBIRD Lite (light) Satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection Purpose and concept ◦ B-mode polarization detection ◦ Whole sky scan ◦ Small & compact design ◦ Orbit ： L2 or LEO Detector requirements ◦ 2,000 Detectors ◦ Frequency GHz ◦ Noise Equivalent Power ~ W/√Hz 09/Jun/2011TIPP113 Weight : 391kg electricity : 480W LiteBIRD

LiteBIRD Collaboration ISAS/JAXA: TAKEI Yoh, FUKE Hideyuki, MATSUHARA Hideo, MITSUDA Kazuhisa, YAMASAKI Noriko, YOSHIDA Tetsuya ARD/JAXA: SATO Yoichi, SHINOZAKI Keisuke, SUGITA Hiroyuki Okayama Universiry: ISHINO Hirokazu, KIBAYASHI Atsuko, HATTORI Kaori, MISAWA Naonori, MIMA Satoru UC Berkeley: Adnan Ghribi, William Holzapfel, Bradley Johnson, Adrian Lee, Paul Richards, Aritoki Suzuki, Huan Tran LBNL: Julian Borrill Kinki University: OHTA Izumi ACCL/KEK: YOSHIDA Mitsuhiro IPNS/KEK: ISHIDOSHIRO Koji, KATAYAMA Nobuhiko, SATO Nobuaki, SUMISAWA Kazutaka, TAJIMA Osamu, NAGAI Makoto, NAGATA Ryo, NISHINO Haruki, HAZUMI Masashi, HASEGAWA Masaya, HIGUCHI Takeo, MATSUMURA Tomotake CSC/KEK: KIMURA Nobuhiro, SUZUKI Toshikazu, TOMARU Takayuki SOKENDAI: YAGINUMA Eri UT Austin: Eiichiro Komatsu ATC/NAOJ: UZAWA Yoshinori, SEKIMOTO Yutaro, NOGUCHI Takashi Tohoku University: CHINONE Yuji, HATTORI Makoto Tsukuba University: TAKADA Suguru RIKEN: OTANI Chiko Yokohama National University: TAKAGI Yuta, NAKAMURA Shogo, MURAYAMA Satoshi

Superconducting detectors Antenna coupled STJ ◦ fast response  can reduce the dead time caused by the cosmic ray attack ◦ wide frequency range  achievable for GHz using either photon assisted tunneling or Cooper pair breaking with a pure Al STJ MKID ◦ frequency domain readout  thousand detectors can be readout with a single line ◦ easy to fabricate ◦ no bias TES ◦ UC Barkley 09/Jun/2011TIPP115

The STJ has a structure of SIS with the insulator thickness of about 1nm. 09/Jun/2011 Quasiparticle(electron) Superconductor Insulator Cooper Pair STJ Superconducting Tunnel Junction S S I S S I Direct Cooper pair breaking Photon assisted Tunneling A photon having energy greater than 2  can break a Cooper pair and generate two quasiparticles, which penetrate the insulator layer by the tunnel effect and are detected as an electric current. A photon having energy less than 2  can also be detected using photon assisted tunneling effect. The valence electron can directly penetrate the insulator and go up to the conducting band with the assist of the photon energy. E gap =2 

Antenna coupled STJ: Parallel-connected twin junction PCTJ (Parallel-Connected Twin Junction ） ◦ The twin parallel STJs and the inductance form a resonant circuit. ◦ The circuit accumulates the millimeter wave power that generates the quasiparticles. TIPP11709/Jun/2011 Log-Periodic antenna ( Nb ) wire STJ Transmission line Log-Periodic antenna STJ PCTJ

09/Jun/2011TIPP μ m φ STJ screen with a pattern horn polyethylene lens the screen pattern an obtained image STJ output current millimeter wave input STJ bias optics 0.3K refrigerator Fabrication and test for the PCTJ detector illuminating 80GHz signature of the photon assisted tunneling

Problems on the PCTJ detector We have successfully detected 80GHz millimeter wave with the photon assisted tunneling effect using the PCTJ detector. However, there are some difficulties on fabricating the PCTJ detector. ◦ The impedance matching between the antenna and the PCTJ is not easy.  We need a fine tuning control for the fabrication on the insulator thickness and character.  related with the Josephson current control  It is not easy to increase the bandwidth.  the current design up to ~10%  LiteBIRD requires 30% bandwidth, however. 2011/03/ 年日本物理学会年次大会 9

Microstrip STJ 2011/03/ 年日本物理学会年次大会 10 The microstrip STJ has been proposed by Prof. T. Noguchi (NAO). ◦ The condition to match the impedances between the antenna and the STJ is easier for the microstrip STJ than the PCTJ. ◦ In addition, we have found the microstrip STJ can have wider bandwidth than the PCTJ. frequency: 150GHz bandwidth: 30% strip width :2um antenna coupled Microstrip STJ antenna coupled PCTJ simulation results frequency

Antenna-coupled Microstrip STJ Design ◦ The microstrip STJ has a width of 2  m and a length of /4 at the resonant frequency. 09/Jun/2011TIPP1111 antenna （ Nb) readout line Al- ＳＴＪ Nb transmission line

Fabrication of antenna coupled Microstrip STJ TIPP111209/Jun/2011 SEM images Microstrip STJ design 100GHz 60GHz 150GHz Freque ncy[G Hz] Length [um] 60~60 100~40 150~20 We have successfully fabricated a pure Al microstrip STJ. Three different detectors are fabricated for central frequencies of 60, 100 and 150GHz.

First look at the microstrip pure Al STJ performance 09/Jun/2011TIPP1113 The IV curve seems to be good : the gap energy is measured to be 0.34mV, consistent with the pure Al SIS behavior. But we found the normal resistance is higher than expected by an order. We need more tuning on the fabrication. 0.35K

09/Jun/2011TIPP1114 Typical Absorption CPW-MKIDs Microwave feed line Microwave Resonator Frequency shift P. K. Day et al., Nature 425 (2003) 817.

Absorption(typical) and Transmission MKIDs Z0Z0 Z0Z0 Z0Z0 Z0Z0 Z0Z0 Z0Z0 Z0Z0 Z0Z0 2 Δ f = 0.04MHz => Q=150,000 Q = 90,000 This leads to enable feedback readout

CPW Al-MKIDs 96GHz Irradiation => Improving quality of process : EV, Wet etching, Target purity etc… Microstrip Nb-MKIDs Nb Si 基板 SiO 2 Microstrip CPW CPW Feed-line Microstrip Resonator => Adjusting coupling etc. CPW resonator Aluminum : Tc = 1.1K f > 88 GHz Multichroic Detector Array

Design for Multichroic MKIDs ↑ 4 Polarization×4 Frequency×5 Antenna = 80 ch Microwave Readout Sinuous Antenna Transmission MKIDs Microstrip Nb-MKIDs Nb Si substrate Al 2 O 3 Al From antenna ・ Diffusion length 100mm >> Penetration depth ・ No diffusion from Al to Nb SiO 2 Based on Transmission Microstrip Nb-MKIDs Final target : - Multichroic ch

Summary LiteBIRD requires 2,000 superconducting detectors We are developing STJ and MKID: ◦ PCTJ STJ has detected 80GHz successfully. ◦ Microstrip STJ has been newly developed. ◦ An antenna coupled MKID has been proposed for the multichroic readout. 09/Jun/2011TIPP1118

09/Jun/2011TIPP1119 backup slides

Nb Si substrate Al 2 O 3 Al SiO 2 ＳＴＪ＋ＭＫＩＤｓ Microstrip Nb-MKIDs Al-STJ == Merit == ・ design is easy (can use current design) ・ keep up the Q factor ・ we can inject electromagnetic wave arbitarily place == Problem == ・ increasing layer Diffusion type MKIDs readout 2010/12/ 年ＫＥＫ年末発表会 From Antenna ・ Diffusion length 100mm >> Penetration depth ・ No diffusion from Al to Nb