A full-field modular gamma camera.

A modular gamma ray camera is described that gives useful image information over its entire crystal face. The lack of dead area on the periphery of the camera is made possible by a unique application of digital electronics and optimal position estimation using maximum likelihood (ML) estimates. The ML estimates are calculated directly from photomultiplier tube responses and stored in a lookup table, so the restriction of calculating the position estimates in separate circuitry is removed. Each module is designed to be optically and electronically independent, so that many modules can be combined in a large system. Results from a prototypical module, which has an active crystal area of 10 cm X 10 cm, are presented.

In situ microviscoelastic measurements by polarization-interferometric monitoring of indentation depth.

new type of computer-controlled instrument has been developed to measure microviscoelastic properties of thin materials. It can independently control and measure indentation loads and depths in situ revealing information about material creep and relaxation. Sample and indenter positions are measured with a specially designed polarization interferometer. Indenter loadings can be varied between 0.5 and 10 g and held constant to +/-41 mg. The resulting indentation depths can be measured in situ to +/-1.2 nm. The load required to maintain constant indentation depths from 0.1 to 5.0 microim can be measured in situ to +/-3.3 mg and the depth held constant to +/-15 nm.