The VORTEX project: first results and perspectives

(abridged) Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations. They feature a very small inner working angle, a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric subwavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about $6\times 10^{-5}$ at $2 \lambda/D$. Three of them have now been installed on world-leading diffraction-limited infrared cameras (VLT/NACO, VLT/VISIR and LBT/LMIRCam). During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit ($0.1''$). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imagers and on future extremely large telescopes (ELTs).Comment: To appear in SPIE proceedings vol. 914

Demonstration of radon removal from SF6 using molecular sieves

The gas SF6 has become of interest as a negative ion drift gas for use in directional dark matter searches. However, as for other targets in such searches, it is important that radon contamination can be removed as this provides a source of unwanted background events. In this work we demonstrate for the first time filtration of radon from SF6 gas by using a molecular sieve. Four types of sieves from Sigma-Aldrich were investigated, namely 3Å, 4Å, 5Å and 13X. A manufactured radon source was used for the tests. This was attached to a closed loop system in which gas was flowed through the filters and a specially adapted Durridge RAD7 radon detector. In these measurements, it was found that only the 5Å type was able to significantly reduce the radon concentration without absorbing the SF6 gas. The sieve was able to reduce the initial radon concentration of 3875 ± 13 Bqm−3 in SF6 gas by 87% when cooled with dry ice. The ability of the cooled 5Å molecular sieve filter to significantly reduce radon concentration from SF6 provides a promising foundation for the construction of a radon filtration setup for future ultra-sensitive SF6 gas rare-event physics experiments

A hall plate based instrument to measure the snapback in the Large Hadron Collider superconducting dipole magnets

The decay and snapback of the magnetic field multipoles in superconducting particle accelerators like the Large Hadron Collider (LHC) could result in a significant particle beam loss unless adequately compensated. Whilst standard instrumentation used to measure the field quality of the superconducting magnets is good enough to measure the harmonic decay, it is not fast enough to measure the snapback. Therefore, a state of the art instrument was recently developed at CERN to measure the most important harmonics with a high measurement frequency and hence improve the understanding of the snapback phenomenon. In this paper we describe the instrument's principle of operation, its mechanical arrangement, its compensation system and its digital acquisition system. We also compare the performance of two different techniques implemented to achieve the necessary measurement resolution of 6 orders of magnitude lower than the main superimposed dipole field.peer-reviewe

Selective Cytopheretic Inhibitory Device With Regional Citrate Anticoagulation and Portable Sorbent Dialysis

Selective cytopheretic inhibitory device (SCD) therapy is an immunomodulatory treatment provided by a synthetic biomimetic membrane in an extracorporeal circuit, which has shown promise in preclinical large animal models of severe sepsis as well as in clinical trials treating patients with acute kidney injury and multiple organ failure. During SCD therapy, citrate is administered to lower ionized calcium levels in blood for anticoagulation and inhibition of leukocyte activation. Historically, citrate has been known to interfere with sorbent dialysis, therefore, posing a potential issue for the use of SCD therapy with a portable dialysis system. This sorbent dialysis SCD (sorbent SCD) would be well suited for battlefield and natural disaster applications where the water supply for standard dialysis is limited, and the types of injuries in those settings would benefit from SCD therapy. In order to explore the compatibility of sorbent and SCD technologies, a uremic porcine model was tested with the Allient sorbent dialysis system (Renal Solutions Incorporated, Fresenius Medical Care, Warrendale, PA, USA) and concurrent SCD therapy with regional citrate anticoagulation. The hypothesis to be assessed was whether the citrate load required by the SCD could be metabolized prior to recirculation from systemic blood back into the therapeutic circuit. Despite the fact that the sorbent SCD maintained urea clearance without any adverse hematologic events, citrate load for SCD therapy caused an interaction with the sorbent column resulting in elevated, potentially toxic aluminum levels in dialysate and in systemic blood. Alternative strategies to implement sorbent‐SCD therapy will be required, including development of alternate urease‐sorbent column binding chemistry or further changes to the sorbent‐SCD therapeutic circuit along with determining the minimum citrate concentration required for efficacious SCD treatment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96390/1/aor1541.pd

On Replacing Peer Review with Legal Challenge in Scientific Research: An Opinion

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74869/1/j.1525-139X.1994.tb00817.x.pd