Optically trapped nanospheres in high-vaccum experience little friction and hence are promising for ultra-sensitive force detection. Here we demonstrate measurement times exceeding $10^5$ seconds and zeptonewton force sensitivity with laser-cooled silica nanospheres trapped in an optical lattice. The sensitivity achieved exceeds that of conventional room-temperature solid-state force sensors, and enables a variety of applications including electric field sensing, inertial sensing, and gravimetry. The optical potential allows the particle to be confined in a number of possible trapping sites, with precise localization at the anti-nodes of the optical standing wave. By studying the motion of a particle which has been moved to an adjacent trapping site, the known spacing of the lattice anti-nodes can be used to calibrate the displacement spectrum of the particle. Finally, we study the dependence of the trap stability and lifetime on the laser intensity and gas pressure, and examine the heating rate of the particle in high vacuum in the absence of optical feedback cooling.Comment: 5 pages, 4 figures, minor changes, typos corrected, references adde

We describe the implementation of laser-cooled silica microspheres as force sensors in a dualbeam optical dipole trap in high vacuum.Using this system we have demonstrated trap lifetimes exceeding several days, attonewton force detection capability, and wide tunability in trapping and cooling parameters. Measurements have been performed with charged and neutral beads to calibrate the sensitivity of the detector. This work establishes the suitability of dual beam optical dipole traps for precision force measurement in high vacuum with long averaging times, and enables future applications including the study of gravitational inverse square law violations at short range, Casimir forces, acceleration sensing, and quantum opto-mechanics.

Our collaboration has designed, installed, and operated a compact antineutrino detector at a nuclear power station, for the purpose of monitoring the power and plutonium content of the reactor core. This paper focuses on the basic properties and performance of the detector. We describe the site, the reactor source, and the detector, and provide data that clearly show the expected antineutrino signal. Our data and experience demonstrate that it is possible to operate a simple, relatively small, antineutrino detector near a reactor, in a non-intrusive and unattended mode for months to years at a time, from outside the reactor containment, with no disruption of day-to-day operations at the reactor site. This unique real-time cooperative monitoring capability may be of interest for the International Atomic Energy Agency (IAEA) reactor safeguards program and similar regimes.

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Abstract:We present the multiplexed readout of two gamma-ray microcalorimeters made from transition-edge sensors. We use a frequency-domain multiplexing scheme in which each sensor is biased at an identifying frequency. We show that the energy resolution of the sensors is unaffected by multiplexing, and that cross-talk between the sensors is negligible. Our results indicate the feasibility of multiplexing 30 sensors or more to one readout line.1 preprint -submitted to Applied Physics Letters Transition-Edge Sensors (TESs) are a promising technology for precision measurements of electromagnetic radiation at gamma-ray, x-ray, optical, and far-infrared to millimeter wavelengths 1,2,3,4 . These sensors consist of superconducting thin films electrically biased in the resistive transition. Their sensitivity is a result of the strong dependence of resistance on temperature in the transition and the low specific heat and thermal conductivity of materials at typical operating temperatures near 100 mK. Because TES sensors can be reliably fabricated using well-established thin-film techniques, they are likely to be used in several important upcoming measurement programs which require imaging arrays of 10 3 -10 4 sensors. These programs include studies of the polarization of the cosmic microwave background, the planned x-ray satellites XEUS and Constellation-X, and the sub-millimeter array SCUBA II. Large sensor arrays also provide increased collection area for applications in materials analysis.However, the undegraded measurement of signals from thousands of sensors and the transport of these signals from below 1 K to room temperature pose significant technical challenges. In order to realize the next-generation instruments mentioned above, techniques to minimize the number of interconnects and read-out amplifiers are required. Two proposed methods for reading out large arrays of TES sensors are time and frequency-domain multiplexing 5,6,7 . While timedomain multiplexing has been successfully demonstrated 8 , frequency-domain multiplexers that combine all of the features needed for a practical system are still under development.In this letter, we present a frequency-domain multiplexing measurement in which two sensors are measured with a single amplifier. As shown in Fig. 1, each TES is biased at an identifying frequency and operated in a series resonant circuit to suppress out-of-band noise.The current through each sensor couples inductively to a superconducting loop and the summed 3 preprint -submitted to Applied Physics Letters signal in the loop is measured with a Superconducting QUantum Interference Device (SQUID).We demonstrate that the energy resolution of the sensors is unaffected by multiplexing and that cross-talk between the sensors is negligible. In addition, we discuss the optimal selection of circuit parameters and the limits on the number of sensors that can be measured in this manner.The calorimeters used in this study are designed to analyze radioactive materials via high-resolution measurements of gamma-r...