Search

We describe the Fourier Transform Spectrometer (FTS) used for in-field testing of the POLARBEAR receiver, an experiment located in the Atacama Desert of Chile which measures the cosmic microwave background (CMB) polarization. The POLARBEAR-FTS (PB-FTS) is a Martin-Puplett interferometer designed to couple to the Huan Tran Telescope (HTT) on which the POLARBEAR receiver is installed. The PB-FTS measured the spectral response of the POLARBEAR receiver with signal-to-noise ratio >20 for ∼69% of the focal plane detectors due to three features: a high throughput of 15.1 sr cm2, optimized optical coupling to the POLARBEAR optics using a custom designed output parabolic mirror, and a continuously modulated output polarizer. The PB-FTS parabolic mirror is designed to mimic the shape of the 2.5 m-diameter HTT primary reflector, which allows for optimum optical coupling to the POLARBEAR receiver, reducing aberrations and systematics. One polarizing grid is placed at the output of the PB-FTS and modulated via continuous rotation. This modulation allows for decomposition of the signal into different harmonics that can be used to probe potentially pernicious sources of systematic error in a polarization-sensitive instrument. The high throughput and continuous output polarizer modulation features are unique compared to other FTS calibrators used in the CMB field. In-field characterization of the POLARBEAR receiver was accomplished using the PB-FTS in April 2014. We discuss the design, construction, and operation of the PB-FTS and present the spectral characterization of the POLARBEAR receiver. We introduce future applications for the PB-FTS in the next-generation CMB experiment, the Simons Array.

Multisensor-based fire alarm systems have been developed as an automatic fire detection technology. However, only two or three fire signatures do not suffice to recognize a fire. Conventional fire detectors must touch sufficient targets (heat or smoke) so that they respond slowly to the alarm. This article proposes several approaches that use the radiation-sensing technologies to detect fire behaviors. Four features, temperature, hot CO2 gas, flicker, and the UV energy of the flame are adopted in the system to analyze the fire traits. Four kinds of sensors and one IR transducer are used successfully to evaluate these features. Experimental results show that the use of two pyroelectric sensors can accurately “see” the appearance of combustion by detecting the CO2 emission instead of the particle density of smoke. The combination of a blue and an UV sensor is used effectively to pickup the UV component of the flame. The information is presented on a personal computer using LABVIEW software and a data-acquisition interface. Although this article focuses on techniques for measuring IR and UV energies, in off-line work, a trained back-propagation network verifies that the measuring system is effective in collecting the information on fire behaviors. Results of this study provide a valuable reference for designers in developing a novel fire detector. [ABSTRACT FROM AUTHOR]

A quasi-steady-state (pulse duration of 30 s) ion source of the duoPIGatron type has been developed for fusion applications. It was designed to deliver an 80-keV hydrogen ion beam of low beamlet divergence (Θrms= 0.26°) at a current density of 0.19 A cm-2. Hydrogen ion beams of 40 to 48 A were extracted at beam energies of 77 to 80 keV for 30-s-long pulses. The reliability and stability of the ion source operation were demonstrated by extracting about 600 beam pulses at full power and full pulse length. The ion source was also operated with deuterium as the working gas, and the optimum current at 80 keV was found to be about 33 A, in agreement with the expected inverse square-root scaling of current density with atomic mass. [ABSTRACT FROM AUTHOR]

A high-heat-flux target has been developed for intercepting multimegawatt, multisecond neutral beams at Oak Ridge National Laboratory (ORNL). Water-cooled copper swirl tubes are used for the heat transfer medium; these tubes exhibit an enhancement in burnout heat flux over conventional axial flow tubes. The target consists of 126 swirl tubes [each 0.95 cm in outside diameter (o.d.) with 0.16-cm-thick walls and ≊1 m long] arranged in a V shape and inclined with respect to the beam axis. In tests with the ORNL long-pulse ion source (13×43-cm grid), the target has handled up to 3-MW, 30-s beam pulses with no deleterious effects. The peak power density was estimated at ≊15 kW/cm2 normal to the beam axis (>5 kW/cm2 maximum on tube surfaces). The water flow rate through the tubes was 0.33 l/s (5.2 gal/min) per tube (axial flow velocity=11.6 m/s) with a corresponding pressure drop of 1.14 MPa (165 psi). To date, the target has absorbed an estimated 25 000 full-power (≊3 MW) pulses for a cumulative time of ≊100 000 beam seconds without failure. Other potential applications for swirl tube technology in the fusion area include plasma limiters, divertor collector plates, rf launchers, and Faraday shields. [ABSTRACT FROM AUTHOR]