Alan W. Hoffman

Measurements of the Mechanical Q of Single-Crystal Silicon at Low Temperatures*

Measurements of the mechanical quality factor Q in a single crystal of silicon vs. temperature have been made. A value of 2 × 109 has been measured at T = 3.5K.

Development of infrared focal plane arrays for space

Space astronomy requires large-area cryogenic infrared focal plane arrays (FPAs) with high quantum efficiency, extremely low dark current, low power dissipation, and background limited noise performance. To meet these requirements, especially at temperatures of 5–15 K, Santa Barbara Research Center designed and fabricated a new multiplexer, CRC-744. The FPAs made by bonding InSb detector arrays to CRC-744 multiplexers were evaluated at the University of Rochester. The best array achieved the read noise of 5u2009e − with 12 s integration and 7u2009e − with 200 s integration with Fowler-64 sampling at 15 K, the average dark current of <0.2u2009e−/ s at both 15 and 29 K, and the average quantum efficiency of 87% at both 15 and 29 K. The 10%–90% rise time was 4 μs driving a 600 pF external load. The power dissipation was 0.3–0.4 mW when running flat-out (100% duty cycle). The full well capacity was 105u2009e− (230 mV) with 400 mV of applied bias. The above test results demonstrate that the FPAs meet background-limited space ...

ALADDIN: the 1024x1024 InSb array--design, description, and results

Seven Aladdin sensor chip assemblies (SCAs) have been produced and nine more are in production. In this paper we cover the design, description, and measured performance of the Aladdin SCA. At over 7.5 square cm Aladdin is the largest single chip infrared array in use today. It is a hybrid assembly made up from an InSb detector coupled, via indium bumps, to a silicon readout. An array of this size is only possible because the InSb detector material is thinned to less than 10 microns which allows it to accommodate the InSb/silicon thermal mismatch. The Aladdin development program is a success and the resulting devices met most of the original design goals. Experience with Aladdin I led to improvements in the readout multiplexer design and, with these changes, we expect to meet the remaining goals. The new readouts have completed processing but testing has just started. The ALADDIN program is a joint collaboration between the National Optical Astronomy Observatories (NOAO) and the U.S. Naval Observatory (USNO) with Santa Barbara Research Center (SBRC).

ALADDIN: the 1024 x 1024 InSb array test results

The ALADDIN 1024 X 1024 InSb array is now a fact rather than a concept, and the time has come to show test results. In this paper we present lab test data but we have also taken it to the telescope. The development program was a success and the array has met the design goals of the program. The few remaining problems involve hybridization and are expected to be solved soon. The ALADDIN program is a joint collaboration between the National Optical Astronomy Observatories (NOAO) and the U. S. Naval Observatory (USNO) with Santa Barbara Research Center (SBRC).

Next generation in very large InSb arrays: ALADDIN, the 1024x1024 InSb focal plane array readout evaluation results

The present state of the art for scientific InSb focal planes is the Santa Barbara Research Center (SBRC) 256 X 256 device. In this paper we will present the status of the 1024 X 1024 focal plane development effort, technical details on the design, and both warm and cryogenic test data on the readout multiplexer. As the largest InSb infrared hybrid focal plane in development, this information should be of great interest to many groups. The current status and test data are presented here so that those planning future space instrumentation projects can be brought up to date on this advanced technology.

Flux gradient accelerometer: Tests on a working model

A device to detect small vibrations, which we call a flux gradient accelerometer, has been constructed. We propose to use such a device as the transducer for a low‐temperature gravitational wave detector. The accelerometer is found to respond as predicted by a simple harmonic oscillator model with a sensitivity nearly equal to the sensitivity calculated theoretically. If the accelerometer signal were amplified by a SQUID (superconducting quantum interference device) having a flux noise of 1.4×10−12 Gu2009cm2u2009Hz−1/2, the signal should just equal the noise when Δxrms =9×10−18 (Δf)−1/2 cm where Δxrms is the rms displacement, and Δf is the amplifier bandwidth.

Next generation in InSb arrays: ALADDIN--the 1024x1024 InSb focal plane array development project status report

The present state of the art in scientific InSb focal plane arrays is defined by the Santa Barbara Research Center (SBRC) 256x256 device. In this paper we will discuss the status of the USNO-NOAO 1024x1024 focal plane development effort at SBRC. The project is in its ealy phases, and so this report consists of the device description, design goals, testing plans, and schedule. Drivers for even larger IR arrays include plans for large (8 meter class) telescopes, high resolution spectroscopy, astrometry of large fields, and wide field imaging amongst others. Focal planes of 640x480 have already been demonstrated, and so the step up to 124x1024 seems reasonable at this time.

High-background longwave Si:As IBC 320x240 IR focal plane array

Hughes has designed a large-area staring Si:As impurity band conduction (IBC) focal plane array specifically for high- background longwave infrared (LWIR) astronomy applications. We derived the design parameters by surveying leading astronomers for their requirements. This paper describes summary results of these requirements and how they were implemented in the design. We discuss preliminary detector and readout data that confirm satisfactory operation. We define current status and plans for fabrication and test of detector/readout hybrids.

Low-noise 256 x 256 10-kelvin staring FPA

Cryogenic spe telescopes such as the Space Infrared Telescope Faility (SIRTF) require large-area focal plane arrays (FPAs) with high sensitivity. This places large demands on readout arrays to simultaneously provide low noiseand high responsivity at low power dissipation. The Hughes Technology Center (HTC) has developed a low-noise 256x256-pixel readout array applicable to the SIRTF visible Fine Guidance Sensor (FGS), short-wavelength infrared array camera (IRAC), and Infrared Spectrometer (IRS). The readout is designed to operate at temperatures below 10 K. The unit cell employs a switched source follower-per-detector design wherein signals are multiplexed onto four outputs while row and column scanners can flexibly address small block portions of the array to conserve power. The readout has recently beenfabricated using the standard cryo-CMOS process developed at Hit specifically for low-temperawre, low-noise operation. The readout can be used with Si PIN, InSb, and Si impurity-band-conduction (IBC) detector arrays.

Overview of Astronomy Arrays at Raytheon Infrared Operations (RIO)

We review the various types of astronomy arrays currently available from RIO for wide-field imaging and spectroscopy. Arrays for infrared astronomy became available from RIO (previously the Santa Barbara Research Center) with the introduction of the 58×62 InSb in 1984. Since the introduction of this first array, RIO has developed and produced increasingly larger format arrays, including the 256×256 InSb array for SIRTF (Space Infrared Telescope Facility) and the Aladdin 1K×1K array. Over 70 Aladdin arrays have been delivered and are currently deployed on a number of major telescopes throughout the world. RIO is currently developing the next generation of 2K×2K format arrays. These include the 2K×2K ORION InSb array, and the VIRGO 2K×K SWIR HgCdTe array for ground-based applications and the 2K×2K InSb array for the NGST program. In addition, RIO is currently developing the next generation large format 1K×1K Si:As Impurity Band Conduction (IBC) arrays for the NGST MIR instrument.