Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS).

A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam transport line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezo-driven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 µrad (horizontal) to 4 µrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.

Institutional variability of intraoperative red blood cell utilization in coronary artery bypass graft surgery.

The variability in frequency of allogeneic blood transfusion during coronary artery bypass surgery (CABG) is a concern. Evidence-based guidelines support minimizing the use of blood during open heart surgery. The Hospital Clinical Services Group quality indicator database was queried for intraoperative red blood cell (RBC) transfusions in 17 252 isolated CABG surgery cases during 2007. Institutional variability was observed in the frequency of intraoperative RBC transfusion rates, which ranged from 0% to 85.7%. The institution mean RBC transfusion rate was 40.8%. Regional geographic and cardiac program size variations were observed in RBC transfusion rates and volume with significant variation. Notable institutional variability persists with respect to intraoperative RBC transfusion in isolated CABG surgery despite clear evidence and guidelines to support techniques to minimize RBC transfusion. Such results support the hypothesis that incorporating evidence-based transfusion-related practices in open heart surgery are not uniformly adopted.

A 300 GHz collective scattering diagnostic for low temperature plasmas.

A compact and portable 300 GHz collective scattering diagnostic employing a homodyne detection scheme has been constructed and installed on the hot helicon experiment (HELIX). Verification of the homodyne detection scheme was accomplished with a rotating grooved aluminum wheel to Doppler shift the interaction beam. The HELIX chamber geometry and collection optics allow measurement of scattering angles ranging from 60 degrees to 90 degrees. Artificially driven ion-acoustic waves are also being investigated as a proof-of-principle test for the diagnostic system.