Performance of 1mm² Silicon Photomultipliers

A silicon photomultiplier (SPM) is a new type of semiconductor detector that has the potential to replace the photomultiplier tube (PMT) detector in many applications. In common with a PMT detector, the output of an SPM is an easily detectable current pulse for each detected photon and can be used in both photon counting mode and as an analogue (photocurrent) detector. However, the SPM also has a distinct advantage over PMT detectors. The photon-induced current pulse from a PMT varies greatly from photon to photon, due to the statistics of the PMT multiplication process (excess noise). In contrast, the current pulse from an SPM is identical from photon to photon. This gives the SPM a distinct advantage in photon counting applications as it allows the associated electronics to be greatly simplified. Identical pulses also mean that the SPM can resolve the number of photons in weak optical pulses, so-called photon number resolution. This is critical in a number of applications including linear-optics quantum computing.

Posted in: Articles, Features, ptb catchall, Photonics


Dr. William (Bill) Farrell, Scientist, Lunar Exploration Program

Goddard Space Flight Center, Greenbelt, MD Dr. William Farrell, a scientist with the Lunar Exploration Program at Goddard Space Flight Center, is an expert on the problem of lunar dust and its effects on astronauts and equipment.

Posted in: Who's Who


Advanced Position Sensors to Aid NASA in Future Spaceflight

Silicon carbide-based position sensors INPROX Technology Corp. Boston, MA 617-573-5158 www.inproxtechnology.com INPROX Technology Corp. (ITC) has entered into a Space Act Agreement (SAA) with NASA’s John H. Glenn Research Center in Ohio to develop advanced silicon carbide (SiC)- based position sensors aimed at potential uses in future spaceflight, turbine engine controls, and automotive engine applications. Under this SAA, high-temperature SiC electronics from NASA will be prototyped into ITC’s proprietary linear position sensor technology platform.

Posted in: Application Briefs


Simulated Models Test Design of Space Shuttles and Rocket Engines

Finite element modeling and analysis Dynamic Concepts Huntsville, AL 256-922-9888 www.dynamic-concepts.com NASA tasked Dynamic Concepts (DCI) with assessing the structural dynamics of the rollout process, whereby the space shuttle orbiter, external tank, and solid rocket booster assembly is moved via a crawler transporter from the Vertical Assembly Building to the launch pad. DCI used Femap finiteelement modeling software from Siemens PLM Software (Plano, TX) to create an integrated model of all the shuttle components, and used Siemens’ NX Nastran to analyze the simulated vibration environment. The analysis helped NASA resolve issues with support structures and determine target rollout speeds that minimized potentially damaging vibration.

Posted in: Application Briefs


The Virtual Becomes Reality at Iowa State University

The colonel has a problem. He has eight unmanned aerial vehicles (UAVs) flying over the outskirts of Baghdad, looking for potential insurgent activity. Are those people he sees moving through the streets insurgents or are they a US infantry patrol? If he alters the flight path of one UAV to loiter over the suspicious activity, how should he deploy the other seven UAVs to pick up the first’s original mission? How does he keep track of the positions of the eight UAVs, what they are seeing, and the locations of nearby US troops, all in real-time?

Posted in: Application Briefs, Application Briefs


Biomedical Imaging Using Ultrashort Laser Pulses

The field of optical microscopy experienced significant gains in resolution and speed following the introduction of lasers. Unfortunately, these gains came at the expense of sample degradation caused by the continuous flux of intense light. Taking advantage of the two-photon absorption process, Webb and Denk implemented a microscope based on the use of near-IR light pulses capable of causing simultaneous multiple fluorophore excitation. Two-photon microscopy is now widely applied in the biomedical imaging field due to the absence of out-of-focus photobleaching and reduced photodamage and fluorescence scattering. These advantages are brought about collectively by the inherent instantaneous peak intensity and narrow focal plane of excitation. Given that peak intensity increases with decreasing laser pulse duration, one would expect extensive use of available ultrashort (sub-10 fs) pulse laser systems in the field of biomedical imaging. However, most two-photon microscopes still use the same pulse duration that Webb and Denk used in 1990 (≈150 fs).

Posted in: Application Briefs, Applications, ptb catchall, Photonics


This Month in NASA History

This year, as NASA celebrates its 50th anniversary, we’ll be highlighting technology innovations and important moments in NASA history, leading to our special 50th Anniversary Issue in October.

Posted in: UpFront


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