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Feb 2007

Volume 78, Issue 2, pp. 1-029901-1

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Rev. Sci. Instrum. 78, 021101 (2007); http://dx.doi.org/10.1063/1.2437069 (25 pages)

Seth M. Foreman, Kevin W. Holman, Darren D. Hudson, David J. Jones, and Jun Ye
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A new method of observing weak extended x-ray sources with the Reuven Ramaty High-Energy Solar Spectroscopic Imager

Iain G. Hannah, Gordon J. Hurford, Hugh S. Hudson, and Robert P. Lin

Rev. Sci. Instrum. 78, 024501 (2007); http://dx.doi.org/10.1063/1.2437120 (6 pages) | Cited 2 times

Online Publication Date: 7 February 2007

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We present a new method, fan-beam modulation, for observing weak extended x-ray sources with the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). This space-based solar x-ray and γ-ray telescope has much greater sensitivity than previous experiments in the 3–25 keV range, but is normally not well suited to detecting extended sources since their signal is not modulated by RHESSI’s rotating grids. When the spacecraft is offpointed from the target source, however, the fan-beam modulation time-modulates the transmission by shadowing resulting from exploiting the finite thickness of the grids. In this article we detail how the technique is implemented and verify its consistency with sources with clear known signals that have occurred during RHESSI offpointing: microflares and the Crab Nebula. In both cases the results are consistent with previous and complementary measurements. Preliminary work indicates that this new technique allows RHESSI to observe the integrated hard x-ray spectrum of weak extended sources on the quiet Sun.
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95.75.-z Observation and data reduction techniques; computer modeling and simulation
95.55.Ka X- and γ-ray telescopes and instrumentation
95.55.Ev Solar instruments
96.60.qe Flares
98.70.Qy X-ray sources; X-ray bursts
07.85.-m X- and γ-ray instruments

Electrical and optical measurements on the first SCUBA-2 prototype 1280 pixel submillimeter superconducting bolometer array

Adam L. Woodcraft, Peter A. R. Ade, Dan Bintley, Julian S. House, Cynthia L. Hunt, Rashmi V. Sudiwala, William B. Doriese, William D. Duncan, Gene C. Hilton, Kent D. Irwin, Carl D. Reintsema, Joel N. Ullom, Michael D. Audley, Maureen A. Ellis, Wayne S. Holland, et al.

Rev. Sci. Instrum. 78, 024502 (2007); http://dx.doi.org/10.1063/1.2436839 (7 pages) | Cited 7 times

Online Publication Date: 9 February 2007

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SCUBA-2 is a submillimeter camera being built for the James Clerk Maxwell Telescope in Hawaii. Bringing CCD style imaging to the submillimeter for the first time, with over 10 000 pixels, it will provide a revolutionary improvement in sensitivity and mapping speed. We present results of the first tests on a prototype 1280 pixel SCUBA-2 subarray; the full instrument will be made up of eight such subarrays. The array is made up of transition edge sensor (TES) detectors, with Mo/Cu bilayers as the sensing element. To keep the number of wires reasonable, a multiplexed readout is used. Unlike previous TES arrays, an in-focal plane multiplexer configuration is used, in which the multiplexing elements are located beneath each pixel. To achieve the required performance, the detectors are operated at a temperature of approximately 120 mK. We describe the results of a basic electrical and optical characterization of the array, demonstrating that it is fully operational. Noise measurements were made on several pixels and gave a noise equivalent power below 2.5×10−17 W HZ−0.5, within the requirements for SCUBA-2. The construction of the testbed used to carry out these measurements is also described.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors

Determining the absolute efficiency of a delay line microchannel-plate detector using molecular dissociation

B. Gaire, A. M. Sayler, P. Q. Wang, Nora G. Johnson, M. Leonard, E. Parke, K. D. Carnes, and I. Ben-Itzhak

Rev. Sci. Instrum. 78, 024503 (2007); http://dx.doi.org/10.1063/1.2671497 (5 pages) | Cited 2 times

Online Publication Date: 27 February 2007

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We present a method to measure the absolute detection efficiency of a delay-line microchannel-plate detector using the breakup of diatomic molecular ions. This method provides the absolute total detection efficiency, as well as the individual efficiency for each signal of the detector. The method is based on the fact that molecular breakup always yields two hits on the detector, but due to finite detection efficiency some of these events are recorded as single particles while others are detected in pairs. We demonstrate the method by evaluating the detection efficiency for both timing and position signals of a delay-line detector using laser-induced dissociation of molecular ions. In addition, the detection efficiency as a function of position has been determined by dividing the detector into sectors.
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33.80.Gj Diffuse spectra; predissociation, photodissociation
29.40.Gx Tracking and position-sensitive detectors
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