SBIR-STTR Award

It has become a general consensus that the development of better XAS detector systems is urgently needed to solve the problem of detectors are lagging behind synchrotron sources. The multilayer analyzer array detector (MAAD) using linearly graded multilayers has been successfully developed to handle the large photon flux from the third generation sources. However, this type of detector has limited detection solid angle restricted by its vertical and horizontal acceptance. The detectors will suffer large loss of throughput as well as degraded energy resolution if horizontal acceptance angle is increased from the current 0.4 radian level. The detection situation, with count rate limitation at one hand and the detection solid angle at the other, not only limits the effective use of the powerful third generation and beyond synchrotron sources, but also puts excess radiation burden on biological samples. We now propose to substantially increase the horizontal acceptance angle by using "radial gradient multilayers" (instead of linearly gradient multilayers) in the multilayer array detector design. This will give a 2.5 times of solid angle increase over the linearly graded MAAD without too much complication in the detector design. Furthermore, the radial gradient multilayer detector will have a substantial improvement in throughput, and a large reduction in energy resolution. Defining the Figure of Merit of the fluorescence detector as the product of solid angle and throughput divided by the energy resolution, the Improvement of the Figure of Merit of the new design is 5 to 10 times. The detector is very desirable in the soft x-ray region due to its superb energy resolution and large solid angle. In Phase I, we will fabricate a prototype detector consists of two radial gradient multilayers, and will evaluate its performance in 2-8 KeV energy range. The Phase II project will develop the array detectors to cover a 5-10% of total solid angle and to operate in a large energy region. Combining narrow bandwidth multilayers with dual multilayer analyzer technique, the system can be made with very high background rejection capability.

Thesaurus Terms:
biomedical equipment development, radiation detector, radiofluorescent probe

It has been repeatedly emphasized in various reports and workshops [1-2] that the development of better X- ray fluorescence detector systems is urgently needed to solve the saturation problems with the currently available detectors. The multilayer analyzer array detector (MAAD) using linearly graded multilayers has been successfully developed to handle the large photon flux from the third generation synchrotron sources. However, this type of detectors has limited detection solid angle restricted by its vertical and horizontal acceptance. The detectors will suffer largely degraded energy resolution and loss of throughput if horizontal acceptance angle is increased. In the Phase I proposal, we have proposed to develop multilayer array analyzer detectors using radially graded multilayers. By largely increasing the horizontal acceptance per multilayer, this new design provides a 2.5 times of collection solid angle increase. Furthermore, the new design substantially reduces the energy resolution and improves the throughput of the analyzers due to the preferred gradient design and optimized deposition material selection. Thus we have demonstrated 6-8 times of combined improvement of performance over the previous analyzer detector design. In a subsequent investigation after the completion of our Phase II project (RR015994), we have demonstrated that large background rejection, in excess of 10,000, can be achieved with a dual multilayer analyzer in }plus} configuration, rather than }minus} configuration that we have proposed previously. Thus we will combine the two technologies, namely the radially graded multilayer technology and the new dual multilayer analyzer configuration to fabricate very desirable fluorescence analyzer detectors to benefit the user community. In the Phase II project, we will design, fabricate and test one radially graded multilayer array analyzer detector (RMAAD) optimized for energies from 1.2 to 4 KeV, and one dual multilayer array analyzer detector (DMAAD) in the plus configuration optimized from 3.5 to 10 KeV. We will adopt a modular design for the RMAAD unit, where smaller unit containing 5 miltilayers can be added to form a full-scale unit. The DMAAD unit can work as a RMAAD when large background rejection is not required. The proposed DMAAD will allow for the elemental detection in ppb levels or in Physiologically relevant concentrations. In addition to the improved detection efficiency, the proposed analyzer detectors extend the current fluorescence detection capability in two crucial areas: very dilute system regime and intermediate to lower energy regions, which are most relevant to biology. The market of the new detectors will no longer be restricted to synchrotron beamlines with intense flux, but all the beamlines which are involved in spectroscopy and fluorescence analysis. The advances made in this proposal will enhance the capability of research for x-ray spectroscopy and fluorescence analysis under high count rate achievable at the current and next generation synchrotron sources.

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Thesaurus Terms:
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