Search

A RF-driven, Cs-enhanced H- ion source feeds the SNS accelerator with a high current (typically >50 mA), ~1.0 ms pulsed beam at 60 Hz. To achieve the persistent high current beam for several weeks long service cycles, each newly installed ion source undergoes a rigorous conditioning and cesiation processes. Plasma conditioning outgases the system and sputter-cleans the ion conversion surfaces. A cesiation process immediately following the plasma conditioning releases Cs to provide coverage on the ion conversion surfaces. The effectiveness of the ion source conditioning and cesiation is monitored with plasma emission spectroscopy using a high-sensitivity optical spectrometer. Plasma emission spectroscopy is also used to provide a means for diagnosing and confirming a failure of the insulating coating of the ion source RF antenna which is immersed in the plasma. Emissions of composition elements of the antenna coating material, Na emission being the most significant, drastically elevate to signal a failure when it happens. Plasma spectra of the developmental ion source with an AlN (aluminum nitrite) chamber and an external RF antenna are also briefly discussed. [ABSTRACT FROM AUTHOR]

Recent measurements of the H- beam current show that SNS is injecting about 55 mA into the RFQ compared to ~45 mA in 2010. Since 2010, the H- beam exiting the RFQ dropped from ~40 mA to ~34 mA, which is sufficient for 1 MW of beam power. To minimize the impact of the RFQ degradation, the service cycle of the best performing source was extended to 6 weeks. The only degradation is fluctuations in the electron dump voltage towards the end of some service cycles, a problem that is being investigated. Very recently, the RFQ was retuned, which partly restored its transmission. In addition, the electrostatic low-energy beam transport system was reengineered to double its heat sinking and equipped with a thermocouple that monitors the temperature of the ground electrode between the two Einzel lenses. The recorded data show that emissions from the source at high voltage dominate the heat load. Emissions from the partly Cs-covered first lens cause the temperature to peak several hours after starting up. On rare occasions, the temperature can also peak due to corona discharges between the center ground electrode and one of the lenses. [ABSTRACT FROM AUTHOR]

A new Allison-type emittance scanner has been built to characterize the ion sources and low energy beam transport systems at Spallation Neutron Source. In this work, the emittance characteristics of the H- beam produced with the external-antenna rf-driven ion source and transported through the two-lens electrostatic low energy beam transport are studied. The beam emittance dependence on beam intensity, extraction parameters, and the evolution of the emittance and twiss parameters over beam pulse duration are presented. [ABSTRACT FROM AUTHOR]

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30^0 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ~55 mA of H- beam current (~1ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electro-static Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H- yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented. [ABSTRACT FROM AUTHOR]

Mulberry leaf was first recorded in the Shennong Bencao Jing ( The Classic of Herbal Medicine )《》 on the list of drugs affixed, and first separate recorded in the Bencao Shiyi ( Supplement to Materia Medica )《》. By checking Chinese herbs' literature of the harvest processing and application of mulberry leaves, we found that Mulberry leaves can be harvested in Summer and autumn before the Qing dynasty, but from Qing dynasty to present, those harvested in autumn and winter, which were called frost mulberry leaves or winter mulberry leaves, were seen as better. Before the Republic of China, mulberry leaves were dried in shade or on the fire, after that, they were dried in the sun. It can be found that the harvest processing of mulberry leaves was changing as time went on. The clinical application of mulberry leaves had multiplicity, depending on different picking time and different processing method. It is suggested that research of mulberry leaves on chemistry and pharmacology of picking time, processing method can result in new scientifically clinical application.

Jixuecao was first recorded in the Shennong bencaojing . The variety of plant referred to is undefined because of a lack of detailed description in the medical books of the Han and Tang dynasties. From the Song dynasty to the Republican period Jixuecao refers to Glechoma longituba (Nakai) Kupr. The name was also recorded as Jinqiancao instead of Jixuecao in the Bencao gangmu shiyi from the Qing dynasty to the Republican period, though it refers to the same plant. In recent times, Jixuecao has evolved to refer to Centella asiatica (L.) Urb, Jinqiancao now refers to Lysimachia christinae Hance, while G . longituba (Nakai) Kupr. is now called Lianqiancao . It is thus determined that G . longituba (Nakai) Kupr. alone is unequivocally the original plant referred to as Jixuecao, and has the longest medicinal history.

Herba Schizonepetae was firstly recorded in the Sheng nong ben caojing (Shennong's Materia Medica) with the title Jiasu. It could be sure that the original plant of Jiasu is Ocimumbasilicum L. ofLabiatae based on the record of Jiasu's name, morphology, edible property before the Song Dynasty. Beginning from the Ben cao tu jing (Illustrated Classic of Materia Medica) in the Song Dynasty, the source of this drug evolved as SchizonepetatenuisfoliaBriq. ofLabiatae, and it has been in use until now. Hence, the sources of Jiasu should be both O. basilicum L. and the co-existence of S. tenuisfolia Briq in the Qing Dynasty. It is claimed that the hometowns of those herb writers who considered the source ofOcimumbasilicum L. to be the producing areas of cultivation of the edible Ocimumbasilicum L. It was found that the source of Jiasu recorded in the Sheng nong ben cao jing should be O. basilicum L. , hence, it is suggested the title Jiasu should be recorded for the source of O. basilicum L, and the original plant of Herba Schizonepetae was Schizonepetatenuisfolia Briq. of Labiatae, and this medicine should be separately recorded. In fact, Jiasu and Herba Schizonepetae were two different kinds of medicines.