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Gentile T.R.,U.S. National Institute of Standards and Technology | Bales M.,University of Michigan | Arp U.,U.S. National Institute of Standards and Technology | Dong B.,Sotera Defense Solutions | Farrell R.,RMD Inc
Review of Scientific Instruments | Year: 2012

For an experiment to study neutron radiative beta-decay, we operated large area avalanche photodiodes (APDs) near liquid nitrogen temperature to detect x rays with energies between 0.2 keV and 20 keV. Whereas there are numerous reports of x ray spectrometry using APDs at energies above 1 keV, operation near liquid nitrogen temperature allowed us to reach a nominal threshold of 0.1 keV. However, due to the short penetration depth of x rays below 1 keV, the pulse height spectrum of the APD become complex. We studied the response using monochromatic x ray beams and employed phenomenological fits of the pulse height spectrum to model the measurement of a continuum spectrum from a synchrotron. In addition, the measured pulse height spectrum was modelled using a profile for the variation in efficiency of collection of photoelectrons with depth into the APD. The best results are obtained with the collection efficiency model. © 2012 American Institute of Physics. Source

Gentile T.R.,U.S. National Institute of Standards and Technology | Bass C.D.,U.S. National Institute of Standards and Technology | Nico J.S.,U.S. National Institute of Standards and Technology | Breuer H.,U.S. National Institute of Standards and Technology | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

We present results for detection of X-rays by large area avalanche photodiodes (APDs) in strong magnetic fields and at cryogenic temperatures. Whereas at room temperature we observe essentially no effects on the response, at cryogenic temperature we observe significant distortion when the magnetic field is in the plane of the APD surface (and thus perpendicular to the electric field in the APD). At all temperatures, effects are minor when the magnetic field is normal to the APD surface (and thus parallel to the electric field in the APD). We performed measurements of the response of an APD to illumination by X-rays in fields between 0 and 4.6 T, for temperatures between 77 and 250 K. Measurements were performed using 241Am and 55Fe sources, and 1.5 keV X-rays produced by aluminum fluorescence. The data indicate that the effects are associated with those X-rays that are absorbed in the drift region of the APD. © 2010 Elsevier B.V. Source

Rmd Llc | Date: 2012-07-24

heat and acoustical composite insulating shield for automobiles, trucks, boats, watercraft, HVAC, appliances and machinery; insulating tapes; adhesive sealant and caulking compound.

Tian L.,Massachusetts Institute of Technology | Tian L.,University of California at Berkeley | Petruccelli J.C.,Massachusetts Institute of Technology | Miao Q.,Massachusetts Institute of Technology | And 4 more authors.
Optics Letters | Year: 2013

We develop and implement a compressive reconstruction method for tomographic recovery of refractive index distribution for weakly attenuating objects in a microfocus x-ray system. This is achieved through the development of a discretized operator modeling both the transport of intensity equation and the x-ray transform that is suitable for iterative reconstruction techniques. © 2013 Optical Society of America. Source

Kim H.,RMD Inc | Kargar A.,RMD Inc | Cirignano L.,RMD Inc | Churilov A.,RMD Inc | And 4 more authors.
IEEE Transactions on Nuclear Science | Year: 2012

In recent years, progress in processing and crystal growth methods have led to a significant increase in the mobility-lifetime product of electrons in thallium bromide (TlBr). This has enabled single carrier collection devices with thickness greater than 1-cm to be fabricated. In this paper we report on our latest results from pixellated devices with depth correction as well as our initial results with Frisch collar devices. After applying depth corrections, energy resolution of approximately 2% (FWHM at 662 keV) was obtained from a 13-mm thick TlBr array operated at-18°C and under continuous bias and irradiation for more than one month. Energy resolution of 2.4% was obtained at room temperature with an 8.4-mm thick TlBr Frisch collar device. © 2012 IEEE. Source

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