Superfluid Helium Drops Levitated in High Vacuum.

We demonstrate the trapping of millimeter-scale superfluid helium drops in high vacuum. The drops are sufficiently isolated that they remain trapped indefinitely, cool by evaporation to 330 mK, and exhibit mechanical damping that is limited by internal processes. The drops are also shown to host optical whispering gallery modes. The approach described here combines the advantages of multiple techniques, and should offer access to new experimental regimes of cold chemistry, superfluid physics, and optomechanics.

Cryogenic and hermetically sealed packaging of photonic chips for optomechanics.

We demonstrate a hermetically sealed packaging system for integrated photonic devices at cryogenic temperatures with plug-and-play functionality. This approach provides the ability to encapsulate a controlled amount of gas into the optical package allowing helium to be used as a heat-exchange gas to thermalize photonic devices, or condensed into a superfluid covering the device. This packaging system was tested using a silicon-on-insulator slot waveguide resonator which fills with superfluid 4He below the transition temperature. To optimize the fiber-to-chip optical integration 690 tests were performed by thermally cycling optical fibers bonded to various common photonic chip substrates (silicon, silicon oxide and HSQ) with a range of glues (NOA 61, NOA 68, NOA 88, NOA 86H and superglue). This showed that NOA 86H (a UV curing optical adhesive with a latent heat catalyst) provided the best performance under cryogenic conditions for all the substrates tested. The technique is relevant to superfluid optomechanics experiments, as well as quantum photonics and quantum optomechanics applications.

The quantum trajectory approach to quantum feedback control of an oscillator revisited.

We revisit the stochastic master equation approach to feedback cooling of a quantum mechanical oscillator undergoing position measurement. By introducing a rotating wave approximation for the measurement and bath coupling, we can provide a more intuitive analysis of the achievable cooling in various regimes of measurement sensitivity and temperature. We also discuss explicitly the effect of backaction noise on the characteristics of the optimal feedback. The resulting rotating wave master equation has found application in our recent work on squeezing the oscillator motion using parametric driving and may have wider interest.

Cavity optomechanical magnetometer.

A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400 nT Hz(-1/2) is achieved, with theoretical modeling predicting the possibility of sensitivities below 1 pT Hz(-1/2). This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation.

Mechanical squeezing via parametric amplification and weak measurement.

Nonlinear forces allow motion of a mechanical oscillator to be squeezed below the zero-point motion. Of existing methods, mechanical parametric amplification is relatively accessible, but previously thought to be limited to 3 dB of squeezing in the steady state. We consider the effect of applying continuous weak measurement and feedback to this system. If the parametric drive is optimally detuned from resonance, correlations between the quadratures of motion allow unlimited steady-state squeezing. Compared to backaction evasion, we demonstrate that the measurement strength, temperature and efficiency requirements for quantum squeezing are significantly relaxed.

Multisite saturation transfer using DANTE and continuous wave.

The DANTE pulse sequence was modified to produce selective resonance saturation similar to that produced by the continuous wave (CW) technique. A combined DANTE and CW saturation technique can be used to perform multisite saturation transfer experiments because of the similar saturation produced by the two techniques.

Employment-related administrative roentgenograms: characteristics of policy formulation and current practice.

A significant proportion of diagnostic medical procedures are used in response to public or private policy rather than in response to an individual patient-physician interaction. We have studied the system whereby such policies are developed and implemented in the case of employment-related chest and lumbar spine roentgenograms, which were found to account for about 11% of the total use of diagnostic radiographs in the state of Michigan. We observed that factors influencing formulation of policy are diverse and largely nonmedical, organizational policies developed in similar environments are often very dissimilar and are highly subject to external influence, and perceptions of policy success and examination utility are typically subjective and uncertain. It is concluded that considerable opportunity exists to enhance the efficacy of such radiographic examinations through leverage provided by their policy-driven nature.

Tantalum-178--a short-lived nuclide for nuclear medicine: production of the parent W-178.

The physical decay characteristics of the short-lived radionuclide Ta-178 (half-life 9.3 min) appear to be suitable for use in conjunction with low-energy detection systems such as the multiwire proportional camera. This camera is inefficient for emissions with energies greater than 100 keV. The gamma-ray spectrum of Ta-178 is dominated by the characteristic hafnium x-rays (55--65 keV), emitted as a result of electron-capture decay. The parent nuclide, W-178 (half-life 21.7 d), was produced in the Michigan State University cyclotron by proton bombardment of stacked natural tantalum-foil targets. Optimum production was found to occur with an incident proton energy of 34 MeV at an effective activity of 1.1 mCi/muA-hr per MeV of target thickness. Tungsten-178 was chemically separated from the Ta foils with a yield of 98%.

Tantalum-178--a short-lived nuclide for nuclear medicine: development of a potential generator system.

We describe a chemical separation that may form the basis of a generator system for the short-lived radionuclide Ta-178 (T 1/2 = 9 min). The parent nuclide W-178 (T 1/2 = 21.7 days) is loaded on an anion-exchange column and the daughter eluted with a mixture of dilute hydrochloric acid and hydrogen peroxide. The yields of tantalum and the breakthrough of the tungsten parent as a function of the eluting conditions are discussed, and preliminary animal distribution data are presented for various treatments of the eluant solution.