The imaging speed of optical resolution photoacoustic microscopy (OR-PAM) using pulsed excitation is fundamentally limited by the range ambiguity condition, which defines the maximum laser pulse repetition frequency (PRF). To operate at this theoretical upper limit and maximize acquisition speed, a custom-built fiber laser capable of operating at a PRF of up to 2 MHz was combined with a fast laser scanning optical OR-PAM system based on a stationary fiber-optic ultrasound sensor. A large area (10 mm × 10 mm) of the mouse ear was imaged within 8 s, when acquiring 16 million A-lines and operating the laser at a PRF of 2 MHz. This corresponds to a factor of four improvement in imaging speed compared to the fastest OR-PAM system previously reported. The ability to operate at high-imaging frame rates also allows the capture of hemodynamic events such as blood flow. It is considered that this system offers opportunities for high throughput imaging and visualizing dynamic physiological events using OR-PAM.

No abstract

In [1, Sec. II-B], the last sentence should read as follows: "Voltage taps VS84 and VS85 are those at the top and bottom of strand #44.

CERN's twisted-pair superconducting cable is a novel design which offers filament transposition, low cable inductance and is particularly suited for tape conductors such as 2G YBCO coated conductors, Ag-sheathed Bi2223 tapes and Ni/Monel-sheathed MgB 2 tapes. A typical design of such twistedpair cables consists of multiple superconducting tapes intercalated with thin copper tapes as additional stabilizers. The copper tapes are typically not soldered to the superconducting tapes so that sufficient flexibility is retained for the twisting of the tape assembly. The electrical and thermal contacts between the copper and superconducting tapes are an important parameter for current sharing, cryogenic stability and quench propagation. Using an MgB 2 twisted-pair cable assembly manufactured at CERN, we have carried out minimum quench energy (MQE) and propagation velocity (v p ) measurements with point-like heat deposition localized within a tape. Furthermore, different contacts between the copper and superconductor around the hot spot have also been studied, including the co-twisted assembly in Kapton wrapping and locally separated tapes. The measurements have been performed in cooling helium gas at temperatures between 20 K and 35 K, with different current fractions with respect to the thermal runaway current. The results suggest a potential optimization strategy, compromising between: a higher stabilization with better contact between the copper and superconducting layers; and a faster propagation velocity and easier quench detection with a higher contact resistance.Index Terms-High-temperature superconductors, minimum quench energy, power transmission, propagation velocity, quench detection.