Mark J. Devlin

Improved low frequency stability of bolometric detectors

An AC bridge readout system has been developed that greatly improves the low-frequency stability of bolometric detectors. The readout can be implemented with a simple circuit appropriate for use in space applications. A matched pair of detectors was used in the readout to achieve system noise within a factor of two of the fundamental noise limit of the detectors at frequencies as low as 10 mHz. The low-frequency stability of the readout system allows slower, more sensitive detectors to be used in many applications, and it facilitates observing strategies that are well suited to space-borne observations. >

A DC-coupled, high sensitivity bolometric detector system for the infrared telescope in space

The authors report the performance of an AC bridge readout system that has been developed for use on the Infrared Telescope in Space which is scheduled for launch in 1994. The AC bridge readout provides excellent DC stability, allowing observing strategies well-suited to space-borne observations. The ability to modulate the optical signal slowly allows the use of novel highly sensitive, long time-constant bolometers. At 300 mK, the bolometers have an electrical noise equivalent power of 3*10/sup -17/ W/ square root Hz. The total noise of the differential signal, including amplifier noise, is less than 8*10/sup -17/ W/ square root Hz at frequencies as low as 35 mHz.<<ETX>>

An arcminute-resolution search at 4.7 inverse centimeters for point source confusion to mesurements of CMB anisotropy

We have searched for millimeter-wave emission from compact objects in two fields, each approximately 1 sq deg in size, taken form regions of the sky in which degree-scale structure in the cosmic microwave background (CMB) has recently been reported. The observations were made at a frequency of 4.7 1 cm and an angular resolution of 1.7 min, using the Sunyaev-Zeldovich Infrared Experiment (SuZIE) bolometer array at the Caltech Submillimeter Observatory (CSO). The first field was centered on 14.92 hours, +82 deg (1994.0), one of two regions in which Cheng et al. (1994) identify the signature of an unresolved point source seen during 0.5 deg resolution observations at 5.6 1 cm with the Medium Scale Anisotropy Measurement (MSAM) experiment. The second field was centered on 15.47 hours, +72.4 deg (1994.0), part of the Gamma Ursae Minoris (GUM) region in which structure has been detected by Devlin et al. (1994) in 0.55 deg resolution observations at 3.5 and 6 1 cm with the Millimeter Anisotropy eXperiment (MAX). We find that there is no point source in either field that can account for the structure observed at 0.5 deg resolution, and that the structure must arise from objects with an angular size greater than 2 mins.

MAX searches for intermediate-scale anisotropy of the cosmic microwave background

Abstract The balloon-borne Millimeter-Wave Anisotropy Experiment (MAX) is designed to measure the fluctuations in the cosmic microwave background (CMB) on angular scales from 0.3 to several degrees. The long term goal is to measure many pixels on the sky at a level approaching ΔT/T(CMB) = 1 × 10−6. These angular scales fill an important gap between the angular scales ⩽10arcmin which are accessible from conventional radio telescopes and the angular scales ⩾ 7 deg which have been measured by the COBE satellite. They are of particular importance to scientific issues such as galaxy formation, dark matter, and the Sunyaev-Zeldovich effect.

100-mK bolometric receiver for low-background astronomy

The design and construction of 100 mK composite bolometers for low background submillimeter and millimeter-wave astronomy are discussed. The bolometers are cooled to 100 mK using an adiabatic demagnetization refrigerator. The bolometers consist of a silicon substrate suspended by nylon fibers, a bismuth film absorber, a neutron transmutation doped germanium thermometer with graphite fiber electrical leads, and a brass wire thermal strap. Heated JFET amplifiers located on the 1.5 K cold plate are used to read out the bolometer signals. Electrically measured noise equivalent powers as low as 2 X 10-17 W/(root)Hz have been achieved.