Superconductors

An ultralow-noise superconducting radio-frequency ion trap for frequency metrology with highly charged ions

“…On its both ends, additional electrostatic mirror electrodes are used to capture injected HCI (R2). All conducting parts are made of high-purity, massive niobium, a type-II superconductor with a critical temperature of T c = 9.25 K. 57 For high mechanical stability (R3), the monolithic resonator tank supporting the quadrupole rods is machined from a single piece. During cooldown, this suppresses differential contraction, which could lead to electrode misalignment.…”

“…Its concentric rings and spokes transmit 83.2% of the light from the trap center that is emitted within a solid angle of Ω/4π 0.106. A superconducting connection between these parts is established with high-purity 99.99% lead wire with T c = 7.2 K. 57 Twelve narrow bores through the side walls of the tank give access to the trap center in the horizontal plane (R1). For suppressing RF leakage from the cavity, their diameter of 7 mm, or 3.5 mm for the two axial ports, is chosen much smaller than the wavelength of the resonant mode, λ 0 ≈ 8.7 m.…”