Single-sided CZT strip detectors

We report progress in the study of thick CZT strip detectors for 3-d imaging and spectroscopy and discuss two approaches to device design. We present the spectroscopic, imaging, detection efficiency and response uniformity performance of prototype devices. Unlike double-sided strip detectors, these devices feature both row and column contacts implemented on the anode surface. This electron-only approach circumvents problems associated with poor hole transport in CZT that normally limit the thickness and energy range of double-sided strip detectors. These devices can achieve similar performance to pixel detectors. The work includes laboratory and simulation studies aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma radiation measurements. The low channel count strip detector approach can significantly reduce the complexity and power requirements of the readout electronics. This is particularly important in space-based coded aperture or Compton telescope instruments requiring large area, large volume detector arrays. Such arrays will be required for NASA\u27s Black Hole Finder Probe (BHFP) and Advanced Compton Telescope (ACT)

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Continued Studies of Single-Sided Charge-Sharing CZT Strip Detectors

In this paper, we report progress in the study of thick single-sided charge-sharing cadmium zinc telluride (CZT) strip detector modules designed to perform gammaray spectroscopy and 3-D imaging. We report on continuing laboratory and simulation measurements of prototype detectors with 11×11 unit cells (15×15×7.5mm3 ). We report preliminary measurements of the 3-D spatial resolution. Our studies are aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma measurements while minimizing the number and complexity of the electronic readout channels. This is particularly important in space-based coded aperture and Compton telescope instruments that require large area, large volume detector arrays. Such arrays will be required for the NASA’s Black Hole Finder Probe (BHFP) and Advanced Compton Telescope (ACT). This design requires an anode pattern with contacts whose dimensions and spacing are roughly the size of the ionization charge cloud. The first prototype devices have 125µm anode contacts on 225µm pitch. Our studies conclude that finer pitch contacts will be required to improve imaging efficiency

A Survey Addressing on High Performance On-Chip VLSI Interconnect

With the rapid increase in transmission speeds of communication systems, the demand for very high-speed lowpower VLSI circuits is on the rise. Although the performance of CMOS technologies improves notably with scaling, conventional CMOS circuits cannot simultaneously satisfy the speed and power requirements of these applications. In this paper we survey the state of the art of on-chip interconnect techniques for improving performance, power and delay optimization and also comparative analysis of various techniques for high speed design have been discussed

Development of a telescope for medium-energy gamma-ray astronomy

The Advanced Energetic Pair Telescope (AdEPT) is being developed at GSFC as a future NASA MIDEX mission to explore the medium-energy (5–200 MeV) gamma-ray range. The enabling technology for AdEPT is the Three- Dimensional Track Imager (3-DTI), a gaseous time projection chamber. The high spatial resolution 3-D electron tracking of 3-DTI enables AdEPT to achieve high angular resolution gamma-ray imaging via pair production and triplet production (pair production on electrons) in the medium-energy range. The low density and high spatial resolution of 3-DTI allows the electron positron track directions to be measured before they are dominated by Coulomb scattering. Further, the significant reduction of Coulomb scattering allows AdEPT to be the first medium-energy gamma-ray telescope to have high gamma-ray polarization sensitivity. We review the science goals that can be addressed with a medium-energy pair telescope, how these goals drive the telescope design, and the realization of this design with AdEPT. The AdEPT telescope for a future MIDEX mission is envisioned as a 8 m3 active volume filled with argon at 2 atm. The design and performance of the 3-DTI detectors for the AdEPT telescope are described as well as the outstanding instrument challenges that need to be met for the AdEPT mission

3-Dimensional Intracortical Neural Interface For The Study Of Epilepsy

Epilepsy is a chronic disease characterized by recurrent, unprovoked seizures, where seizures are described as storms of uncontrollable neuro-electrical activity within the brain. Seizures are therefore identified by observation of electrical spiking observed through electrical contacts (electrodes) placed on the scalp or the cortex above the epileptic regions. Current epilepsy research is identifying several specific molecular markers that appear at specific layers of the epilepsy-affected cortex. However, technology is limited in allowing for live observation of electrical spiking across these layers. The underlying hypothesis of this project is that electrical interictal activity is generated in a layer- and lateral-specific pattern. This work reports a novel neural probe technology for the manufacturing of 3D arrays of electrodes with integrated microchannels. This new technology is based on a silicon island structure and a simple folding procedure. This method simplifies the assembly or packaging process of 3D neural probes, leading to higher yield and lower cost. Various types of 3D arrays of electrodes, including acute and chronic devices, have been successfully developed. Microchannels have been successfully integrated into the 3D neural probes via isotropic XeF2 gas phase etching and a parylene resealing process. This work describes in detail the development of neural devices targeted towards the study of layer-specific interictal discharges in an animal model of epilepsy. Devices were designed utilizing parameters derived from the rat model of epilepsy. The progression of device design is described from 1st prototype to final chronic device. The fabrication process and potential pitfall are described in detail. Devices have been characterized by SEM (scanning electron microscope) imaging, optical imaging, various types of impedance analysis, and AFM (atomic force microscopy) characterization of the electrode surface. Flow characteristics of the microchannels were also analyzed. Various animal tests have been carried out to demonstrate the recording functionality of the probes, preliminary biocompatibility studies, and the reliability of the final chronic device package. These devices are expected to be of great use to the study of epilepsy as well as various other neurological diseases

Fault Tolerance in Programmable Metasurfaces: The Beam Steering Case

Metasurfaces, the two-dimensional counterpart of metamaterials, have caught great attention thanks to their powerful control over electromagnetic waves. Recent times have seen the emergence of a variety of metasurfaces exhibiting not only countless functionalities, but also a reconfigurable or even programmable response. Reconfigurability, however, entails the integration of tuning and control circuits within the metasurface structure and, as this new paradigm moves forward, new reliability challenges may arise. This paper examines, for the first time, the reliability problem in programmable metamaterials by proposing an error model and a general methodology for error analysis. To derive the error model, the causes and potential impact of faults are identified and discussed qualitatively. The methodology is presented and instantiated for beam steering, which constitutes a relevant example for programmable metasurfaces. Results show that performance degradation depends on the type of error and its spatial distribution and that, in beam steering, error rates over 10% can still be considered acceptable