Vibration characteristics of a continuously rotating superconducting magnetic bearing and potential influence to TES and SQUID

Kavli Affiliate: Nobuhiko Katayama

| First 5 Authors: Shinya Sugiyama, Tommaso Ghigna, Yurika Hoshino, Nobuhiko Katayama, Satoru Katsuda

| Summary:

We measured the vibration of a prototype superconducting magnetic bearing
(SMB) operating at liquid nitrogen temperature. This prototype system was
designed as a breadboard model for LiteBIRD low-frequency telescope (LFT)
polarization modulator unit. We set an upper limit of the vibration amplitude
at $36~mathrm{mu m}$ at the rotational synchronous frequency. During the
rotation, the amplitude of the magnetic field produced varies. From this setup,
we compute the static and AC amplitude of the magnetic fields produced by the
SMB magnet at the location of the LFT focal plane as $0.24~mathrm{G}$ and
$3times10^{-5}$$~mathrm{G}$, respectively. From the AC amplitude, we compute
TES critical temperature variation of $7times10^{-8}$$~mathrm{K}$ and
fractional change of the SQUID flux is $delta
Phi/Phi_0|_{ac}=3.1times10^{-5}$. The mechanical vibration can be also
estimated to be $3.6times 10^{-2}$$~mathrm{N}$ at the rotation mechanism
location.

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