Biomedical subjects

J Barraza

Publications and source records attributed to J Barraza.

3 recordsLinked to original sources

PubMed1998

Smart X-ray beam position monitor system using artificial-intelligence methods for the Advanced Photon Source insertion-device beamlines.

At the Advanced Photon Source (APS), each insertion-device (ID) beamline front end has two X-ray beam position monitors (XBPMs) to monitor the X-ray beam position for both vertical and horizontal directions. Performance challenges for a conventional photoemission-type XBPM during operations are contamination of the signal from the neighbouring bending-magnet sources and the sensitivity of the XBPM to the insertion-device gap variations. Problems are exacerbated because users change the ID gap during their operations, and hence the percentage level of the contamination in the front-end XBPM signals varies. A smart XBPM system with a high-speed digital signal processor has been built at the Advanced Photon Source for the ID beamline front ends. The new version of the software, which uses an artificial-intelligence method, provides a self-learning and self-calibration capability to the smart XBPM system. The structure of and recent test results with the system are presented in this paper.

Journal Article↗

PubMed1998

Synthetic diamond-based position-sensitive photoconductive detector development for the Advanced Photon Source.

A novel X-ray beam-position detection device that we call a position-sensitive photoconductive detector (PSPCD) is designed to have synthetic diamond as its substrate material. We proved that it is feasible to use synthetic diamond to make a hard X-ray position-sensitive detector based on the photoconductivity principle and that it acts as a solid-state ion chamber. Experiments on different PSPCD samples using synthetic diamond with a high-heat-flux white undulator beam, as well as with monochromatic hard X-ray beams, have been performed at the Advanced Photon Source. Recent test results with the PSPCD in the quadrant configuration as an X-ray beam-position monitor and in a multipixel array as an X-ray beam profiler are presented in this paper.

Journal Article↗

PubMed1998

Optical design for laser Doppler angular encoder with sub-nrad sensitivity.

A novel laser angular-encoder system has been developed based on the principles of radar, the Doppler effect, optical heterodyning and self-aligning multiple-reflection optics. Using this novel three-dimensional multiple-reflection optical path, an increase in resolution of 10 to 20 times has been reached compared with commercially available laser Doppler displacement meters or laser interferometer systems. With the new angular encoder, sub-nrad resolution has been attained in the 8 degrees measuring range in a compact set-up [about 60 (H) x 150 (W) x 370 mm (L)] for high-energy-resolution applications at the Advanced Photon Source undulator beamline 3-ID.

Journal Article↗