Operating experience of the United States National High Magnetic Field Laboratory 60 T Long Pulse Magnet
The 60 T Long-Pulse (60 T LP) magnet system has provided controlled power magnetic field pulses to experimentalists since August 3, 1998. This magnet system is installed as part of the user facility research equipment at the National High Magnetic Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory. The 60 T LP magnet is the first of its kind in the United States and produces the highest field in its class, routinely providing a 60 T pulsed field of 100 ms flat-top duration in a 32 mm diameter bore. In addition, numerous other controlled pulse shapes at 60 T and lower fields have been provided. Since the start of commissioning on September 17, 1997 the magnet has been pulsed in excess of 800 times at various field levels. More than 600 magnet pulses have been provided to experiments and almost 400 of these were at 60 T. Operating statistics including coil system and inductance and resistance histories are presented. Operating and maintenance experience and issues are discussed as well as realizable improvements and upgrades to the magnet.
Design and Analysis of a Combined Power Supply for High-Field Quasi-Continuous Magnets
The high-field quasi-continuous magnets (QCM) are of great interest for scientific experiments that require long pulse duration and in particular a field pulse with a flat-top. For the QCM, the power supply is a real challenge. At the Wuhan National High Magnetic Field Center (WHMFC), it is planned to realize a 45 T/500 ms flat-top field by the series combination of a 0.6 kV/35 kA battery bank and a 12-pulse rectifier that is powered by a 100 MVA/100 MJ flywheel pulse generator (FPG). In order to reduce the dc current ripple, a dc passive filter is connected in parallel with the rectifier. The simulation of the pulse shape with respect to the voltage profile supplied by the power supply takes the resistance of the magnet into account; this increases with temperature as a function of coil current. The configuration and the associated control strategy are presented in this paper. A simulation model of the combined power supply system is developed and compared with the model of a single rectifier supply system. Results are provided to validate the proposed method.
Diagnostic and therapeutic studies on chronic diarrhea in dairy animals
The study was conducted to determine the etiology of chronic diarrhea in dairy animals. Seven causes of chronic diarrhea were established in dairy cattle and buffaloes. Balantidiasis in 37.6 per cent, dietary diarrhea in 9.9 per cent, chronic salmonellosis in 6.9 per cent cases of chronic diarrhea, secondary copper deficiency and amphistomiasis in 6.9 per cent, clinical Johne‘s disease in 3.9 per cent and chronic peritonitis in 2.97 per cent of dairy animals, manifest chronic diarrhea. The precise diagnosis could not be established in 24.50 per cent of animals. Lymphosarcoma was confirmed in one of the dairy cattle. Body condition score was associated to the etiology of chronic diarrhea. B. coli infected cattle and buffalo revealed cysts in 32.3 per cent cases while 5 per cent positive cases revealed both cysts and trophozoites. Mean cyst count was 2.73±0.91 hpf in diarrheic animals compared to 0.11±0.447 hpf in healthy animals. Clinical Johne‘s disease was confirmed in four animals. Hematological changes revealed anemia and neutrophilia with morphological changes suggestive of regenerative to degenerative left shift. High plasma phosphorus, hypoproteinaemia and hypoalbuminaemia was seen in clinical Johne‘s disease. Salmonella isolates showed higher in-vitro sensitivity to enrofloxacin (87%), ciprofloxacin (87%), gentamicin (75%), and tetracycline (66.7 %) and were resistant to ampicillin and amoxicillin. Mean cyst count reduction from 2.41±1.16 to 0.11±.33 was observed in oral metronidazole treated group where as reduction of mean cyst count from 2.73±0.918 to 0.18±0.44 in intravenous metronidazole treated group. Recovery rate with oral and intravenous metronidazole was 42.1 and 63.1 per cent respectively. Recovery results in significant decrease in eiosionphil count and increase in total plasma protein in both oral and intravenous treatment groups. Complete recovery response approaches 60 per cent in balantidiasis affected adult dairy animals. Balantidiasis was the major cause of chronic diarrhea and intravenous administration of metronidazole was more effective than oral metronidazole.