Abstract: A method includes driving a component in an electromagnetic actuator back and forth during one or more cycles of the actuator, where the actuator includes a voice coil. The method also includes identifying a back electromotive force (EMF) voltage of the voice coil during at least one of the one or more cycles. The method further includes determining whether a stroke of the component is substantially centered using the back EMF voltage of the voice coil. In addition, the method includes, based on the determination, adjusting one or more drive signals for the voice coil during one or more additional cycles of the actuator. Determining whether the stroke of the component is centered could include determining whether the back EMF voltage of the voice coil is substantially maximized or determining whether times between extremes in the back EMF voltage are substantially equal.

Abstract: A method includes exposing a non-aqueous solution to ultraviolet illumination, where the non-aqueous solution includes one or more lanthanide elements and one or more photo-initiators. The method also includes producing lanthanide nanoparticles using the non-aqueous solution. The non-aqueous solution could be formed by mixing a first non-aqueous solution including the one or more lanthanide elements and a second non-aqueous solution including the one or more photo-initiators. The non-aqueous solution could include one or more metallic salts, where each metallic salt includes at least one lanthanide element. The one or more metallic salts could include erbium chloride, and the one or more photo-initiators could include benzophenone. The non-aqueous solution could include an organic solvent, such as an alcohol.

Abstract: A cryogenic assembly includes a platform configured to support at least one electronic component. A cryocooler is thermally connected to the platform to cool the platform to a cryogenic temperature. A vacuum unit includes a housing that surrounds a cavity configured to receive the platform. The vacuum unit is configured to thermally insulate the cavity from surrounding ambient air surrounding. At least one connector is configured to deliver an electrical signal from a power supply to the cryogenic assembly. The connector includes at least one carbon nanotube interconnect that inhibits heat flow into cryogenic assembly while delivering the electrical signal.

Abstract: A system includes a multi-stage cryocooler having multiple stages and a temperature control system configured to regulate temperatures of the multiple stages of the multi-stage cryocooler. The temperature control system includes an input interface configured to receive (i) temperature setpoints for the stages of the multi-stage cryocooler and (ii) temperature information corresponding to temperatures measured at the stages of the multi-stage cryocooler. The temperature control system also includes processing circuitry configured to determine temperature errors and calculate at least one of a compressor stroke error and a pressure-volume phase error. The temperature control system further includes at least one controller configured to adjust at least one of a compressor setting and a pressure-volume phase of the multi-stage cryocooler.

Abstract: Components within a cryocooler are scaled and/or configured for operation at a CMG operating frequency (e.g., 100 Hz) rather than at 30 to 70 Hz, matching the exported disturbances of control moment gyroscopes on the same platform and reducing line-of-sight jitter for electro-optic infrared focal plane array sensors. The smaller piston working volume and other reduced component sizes allow the cryocooler to be smaller and lighter than designs operating at lower frequencies. Combined with an advanced regenerator suitable for the higher frequency operation, the cryocooler has improved cooling efficiency over such lower frequency designs.

Abstract: An apparatus includes a regenerator configured to transfer heat to a fluid and to absorb heat from the fluid as the fluid flows between a warm end and a cold end of a cryocooler. The regenerator includes an anisotropic thermal layer configured to reduce a flow of heat axially along the regenerator and to spread the absorbed heat radially or laterally in a plane of the anisotropic thermal layer. The anisotropic thermal layer includes at least one allotropic form of carbon. The anisotropic thermal layer could have a higher radial or lateral thermal conductivity and a lower axial thermal conductivity. The anisotropic thermal layer could include carbon nanotubes and/or graphene. The regenerator could include multiple anisotropic thermal layers that divide the regenerator into multiple segments, where the anisotropic thermal layers are configured to reduce heat transfer between adjacent segments of the regenerator.