Liquid crystal polymer receiver modules for electron cyclotron emission imaging on the DIII-D tokamak.

A new generation of millimeter-wave heterodyne imaging receiver arrays has been developed and demonstrated on the DIII-D electron cyclotron emission imaging (ECEI) system. Improved circuit integration, improved noise performance, and enhanced shielding from out-of-band emission are made possible by using advanced liquid crystal polymer (LCP) substrates and monolithic microwave integrated circuit (MMIC) receiver chips. This array exhibits ∼15 dB additional gain and >30× reduction in noise temperature compared to previous generation ECEI arrays. Each LCP horn-waveguide module houses a 3 × 3 mm GaAs MMIC receiver chip, which consists of a low noise millimeter-wave preamplifier, balanced mixer, and IF amplifier together with a local oscillator multiplier chain driven at ∼12 GHz. A proof-of-principle partial LCP instrument with 5 poloidal channels was installed on DIII-D in 2017, with a full proof-of-principle system (20 poloidal × 8 radial channels) installed and commissioned in early 2018. The enhanced shielding of the LCP modules is seen to greatly reduce the sensitivity of ECEI signals to out-of-band microwave noise which has plagued previous ECEI studies on DIII-D. The LCP ECEI system is expected to be a valuable diagnostic tool for pedestal region measurements, focusing particularly on electron temperature evolution during edge localized mode bursting.

Millimeter-wave system-on-chip advancement for fusion plasma diagnostics.

Recent advances in radio-frequency system-on-chip technology have provided mm-wave fusion plasma diagnostics with the capability to overcome major challenges such as space inefficiency, inflexible installation, sensitivity, susceptibility to EMI, and prohibitively high cost of conventional discrete component assemblies as higher imaging resolution and data accuracy are achieved by increasing the number of channels. Nowadays, shrinking transistor gate lengths on fabrication techniques have enabled hundreds of GHz operation, which is suitable for millimeter-wave diagnostics on current and future tokamaks. The Davis Millimeter Wave Research Center (DMRC) has successfully developed V-band (55-75 GHz) transmitter and receiver chips for Microwave Imaging Reflectometer (MIR) instruments. The transmitter can illuminate 8 different frequencies simultaneously within 55-75 GHz. Moreover, the receiver has the capability to amplify the reflected signal (>30 dB) while offering 10-30× reduction in noise temperature compared to current MIR instruments. Plasma diagnostics requires ultra-wideband (more than 20 GHz) operation which is approximately nine times wider bandwidth than the recent commercial impetus for communication systems. Current efforts are underway for gallium-arsenide monolithic microwave integrated circuit receiver chips at W-band (75-110 GHz) and F-band (90-140 GHz) permitting measurements at higher toroidal magnetic fields.

Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry.

The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

Congenital dilatation of extrahepatic bile ducts in children. Experience in the central hospital of Hue, Vietnam.

BACKGROUND/PURPOSE: The authors present a study of a series of cases in children with congenital dilatation of the extrahepatic bile ducts (CDEBD). METHODS: Between November 1998 and October 2002, 38 children aged between 50 days and 15 years suffering from CDEBD, admitted to the Central Hospital in Hue, Vietnam, were treated surgically with a minimum follow-up of one year. RESULTS: Diagnosis was based only on ultrasonography which was 100% accurate. According to Miyano's classification, 26 cases presented as cystic dilatation of the main bile duct (MBD) associated with dilatation of the intrahepatic bile ducts, while in the other 12 cases the dilatation of the MBD was of the fusiform type. The surgical treatment of choice was extensive excision of the dilatated extrahepatic bile ducts and biliary drainage according to the Roux-en-Y method in 36/38 patients. The other two patients underwent surgery for internal biliary drainage without removing the cysts. During follow-up we observed one case of pancreatitis out of the 36 patients who underwent excision of the dilatated extrahepatic bile ducts, while the two patients who had internal biliary drainage without removal of the cysts suffered from numerous attacks of cholangitis. CONCLUSIONS: The reflux of bile in the dilated biliary tree plays an important role in the etiopathogenesis of CDEBD. Excision of the extrahepatic bile ducts and internal biliary drainage by Roux-en-Y has proved a satisfactory surgical method.

Polysaccharase activity in Streptococcus agalactiae (group B streptococci).

Of 300 recently isolated strains of Streptococcus agalactiae from human sources, 97% degraded starch. Representative strains also degraded glycogen, pullulan, amylopectin and amylose. The polysaccharase activity is easily detected by clearing around growth on Columbia agar base medium. The activity is weaker than that of some S. pyogenes strains, and it does not appear to produce fermentable products but is inhibited by the presence of easily used sugars.