The ITER neutral beam (NB) injectors are the first injectors that will have to operate under conditions and constraints similar to those that will be encountered in a fusion reactor. These injectors ...will have to operate in a hostile radiation environment and they will become highly radioactive due to the neutron flux from ITER. The injectors will use a single large ion source and accelerator that will produce 40 A 1 MeV D − beams for pulse lengths of up to 3600 s. Significant design changes have been made to the ITER heating NB (HNB) injector over the past 4 years. The main changes are: Modifications to allow installation and maintenance of the beamline components with an overhead crane. The beam source vessel shape has been changed and the beam source moved to allow more space for the connections between the 1 MV bushing and the beam source. The RF driven negative ion source has replaced the filamented ion source as the reference design. The ion source and extractor power supplies will be located in an air insulated high voltage (−1 MV) deck located outside the tokamak building instead of inside an SF 6 insulated HV deck located above the injector. Introduction of an all metal absolute valve to prevent any tritium in the machine to escape into the NB cell during maintenance. This paper describes the status of the design as of December 2008 including the above mentioned changes. The very important power supply system of the neutral beam injectors is not described in any detail as that merits a paper beyond the competence of the present authors. The R&D required to realize the injectors described in this paper must be carried out on a dedicated neutral beam test facility, which is not described here.
The heating neutral beam injectors (HNBs) of ITER are designed to deliver 16.7 MW of 1 MeV D0 or 0.87 MeV H0 to the ITER plasma for up to 3600 s. They will be the most powerful neutral beam (NB) ...injectors ever, delivering higher energy NBs to the plasma in a tokamak for longer than any previous systems have done. The design of the HNBs is based on the acceleration and neutralisation of negative ions as the efficiency of conversion of accelerated positive ions is so low at the required energy that a realistic design is not possible, whereas the neutralisation of H− and D− remains acceptable ( 56%). The design of a long pulse negative ion based injector is inherently more complicated than that of short pulse positive ion based injectors because: negative ions are harder to create so that they can be extracted and accelerated from the ion source; electrons can be co-extracted from the ion source along with the negative ions, and their acceleration must be minimised to maintain an acceptable overall accelerator efficiency; negative ions are easily lost by collisions with the background gas in the accelerator; electrons created in the extractor and accelerator can impinge on the extraction and acceleration grids, leading to high power loads on the grids; positive ions are created in the accelerator by ionisation of the background gas by the accelerated negative ions and the positive ions are back-accelerated into the ion source creating a massive power load to the ion source; electrons that are co-accelerated with the negative ions can exit the accelerator and deposit power on various downstream beamline components. The design of the ITER HNBs is further complicated because ITER is a nuclear installation which will generate very large fluxes of neutrons and gamma rays. Consequently all the injector components have to survive in that harsh environment. Additionally the beamline components and the NB cell, where the beams are housed, will be activated and all maintenance will have to be performed remotely. This paper describes the design of the HNB injectors, but not the associated power supplies, cooling system, cryogenic system etc, or the high voltage bushing which separates the vacuum of the beamline from the high pressure SF6 of the high voltage (1 MV) transmission line, through which the power, gas and cooling water are supplied to the beam source. Also the magnetic field reduction system is not described.
Bioorthogonal cleavable linkers are attractive building blocks for compounds that can be manipulated to study biological and cellular processes. Sodium dithionite sensitive azobenzene‐containing ...(Abc) peptides were applied for the temporary stabilization of recombinant MHC complexes, which can then be employed to generate libraries of MHC tetramers after exchange with a novel epitope. This technology represents an important tool for high‐throughput studies of disease‐specific T cell responses.
As easy as Abc: Replacement of an azobenzene‐containing (Abc) peptide with novel MHC ligands can be triggered by sodium dithionite. The Abc peptide (turquoise) is cleaved into two fragments, which are released from the binding groove. A novel epitope (orange) can then reoccupy the protein complex. This strategy enables the parallel generation of an array of MHCs with novel antigen‐specificities for use in high‐throughput studies of T cell responses.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In parallel to the developments dedicated to the ITER neutral beam (NB) system, CEA-IRFM with laboratories in France and Switzerland are studying the feasibility of a new generation of NB system able ...to provide heating and current drive for the future DEMOnstration fusion reactor. For the steady-state scenario, the NB system will have to provide a high NB power level with a high wall-plug efficiency ( ∼ 60%). Neutralization of the energetic negative ions by photodetachment (so called photoneutralization), if feasible, appears to be the ideal solution to meet these performances, in the sense that it could offer a high beam neutralization rate (>80%) and a wall-plug efficiency higher than 60%. The main challenge of this new injector concept is the achievement of a very high power photon flux which could be provided by 3 MW Fabry-Perot optical cavities implanted along the 1 MeV D− beam in the neutralizer stage. The beamline topology is tall and narrow to provide laminar ion beam sheets, which will be entirely illuminated by the intra-cavity photon beams propagating along the vertical axis. The paper describes the present R&D (experiments and modelling) addressing the development of a new ion source concept (Cybele source) which is based on a magnetized plasma column. Parametric studies of the source are performed using Langmuir probes in order to characterize and compare the plasma parameters in the source column with different plasma generators, such as filamented cathodes, radio-frequency driver and a helicon antenna specifically developed at SPC-EPFL satisfying the requirements for the Cybele (axial magnetic field of 10 mT, source operating pressure: 0.3 Pa in hydrogen or deuterium). The paper compares the performances of the three plasma generators. It is shown that the helicon plasma generator is a very promising candidate to provide an intense and uniform negative ion beam sheet.
The ATP-binding cassette (ABC) transporters ABCC2 multidrug resistance-associated protein (MRP) 2, ABCC3 (MRP3), and ABCG2 (breast cancer resistance protein) are involved in the efflux of potentially ...toxic compounds from the body. We have shown before that ABCC2, ABCC3, and ABCG2 together influence the pharmacokinetics of the anticancer and antirheumatic drug methotrexate (MTX) and its toxic metabolite 7-hydroxymethotrexate (7OH-MTX) after intravenous MTX administration. We now have used Abcc2;Abcc3;Abcg2(-/-) and corresponding single and double knockout mice to investigate the relative impact of these transporters on MTX and 7OH-MTX pharmacokinetics after oral MTX administration (50 mg/kg). The plasma areas under the curve (AUC(plasma)) in Abcg2(-/-) and Abcc2;Abcg2(-/-) mice were 1.7- and 3.0-fold higher than those in wild-type mice, respectively, suggesting additive effects of Abcc2 and Abcg2 on oral MTX pharmacokinetics. However, the AUC(plasma) in Abcc2;Abcc3;Abcg2(-/-) mice was not different from that in wild-type mice, indicating that Abcc3 protein is necessary for increased MTX plasma concentrations in the absence of Abcc2 and/or Abcg2. Furthermore, 2 h after administration, MTX liver levels were increased in Abcg2-deficient strains and MTX kidney levels were 2.2-fold increased in Abcc2;Abcg2(-/-) mice compared with those in wild-type mice. The absence of Abcc2 and/or Abcg2 also led to significantly increased liver and kidney levels of 7OH-MTX. Our results suggest that inhibition of ABCG2 and/or ABCC2, genetic polymorphisms or mutations reducing expression or activity of these proteins may increase the oral availability of MTX. Such conditions may also present risk factors for increased MTX-related toxicity in patients treated with oral MTX.
The ITER Neutral Beam Test Facility (PRIMA) is presently under construction at Consorzio RFX (Padova, Italy). PRIMA includes two experimental devices: an ITER-size ion source with low voltage ...extraction, called SPIDER, and the full prototype of the whole ITER Heating Neutral Beams (HNBs), called MITICA. The purpose of MITICA is to demonstrate that all operational parameters of the ITER HNB accelerator can be experimentally achieved, thus establishing a large step forward in the performances of neutral beam injectors in comparison with the present experimental devices. The design of the MITICA extractor and accelerator grids, here described in detail, was developed using an integrated approach, taking into consideration at the same time all the relevant physics and engineering aspects. Particular care was taken also to support and validate the design on the basis of the expertise and experimental data made available by the collaborating neutral beam laboratories of CEA, IPP, CCFE, NIFS and JAEA. Considering the operational requirements and the other physics constraints of the ITER HNBs, the whole design has been thoroughly optimized and improved. Furthermore, specific innovative concepts have been introduced.
Sarcocysts of Sarcocystis rommeli were found for the first time in 6 of 34 (17.6%) cattle (Bos taurus) in China. With light microscopy, sarcocysts of S. rommeli were up to 1,130 μm long, with a ...striated, 4–8-μm-thick cyst wall. Using transmission electron microscopy, the villar protrusions (vp) were 4.7–5.2 × 0.2–0.3 μm, and 0.3–0.5 μm apart from each other. The vp contained microtubules extending from the top of the vp to the middle of the ground substance layer (gsl). A BLAST search of the near full-length 18S rRNA and partial mitochondrial cox1 sequences of S. rommeli revealed 98.7% identity and 99.2% identity with sequences of Sarcocystis bovini in GenBank, respectively. Two domestic cats (Felis catus) fed sarcocysts of S. rommeli shed oocysts/sporocysts in their feces with a prepatent period of 14 to 15 days; the partial mitochondrial cox1 sequences of these oocysts/sporocysts shared the high identities, that is, 99.4% and 99.5%, with cox1 sequences of S. rommeli sarcocysts and S. bovini sarcocysts, respectively. This is the first demonstration of a definitive host for S. rommeli.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The soy isoflavone daidzein (DAI) is known to undergo metabolism to equol (EQO) and to 3′-hydroxy-DAI (3′-HO-DAI) and 6-hydroxy-DAI (6-HO-DAI) in humans. In order to better understand the ...implications of soy diets for human health, the hormonal and genotoxic activities of these DAI metabolites were studied in cultured human endometrial carcinoma cells. When the estrogenicity was tested by cell-free binding to recombinant human estrogen receptor (ER) α and β as well as by the induction of enzyme activity and gene expression of alkaline phosphatase (ALP) in Ishikawa cells, the ranking order was EQO
>
DAI
>
3′-HO-DAI
>
6-HO-DAI. All compounds had a higher affinity to ERβ than to ERα. No significant anti-estrogenic effects of the DAI metabolites were observed in the cells at non-cytotoxic concentrations. The in vitro genotoxicity was assessed by analyzing effects on cell cycle distribution and cell morphology as well as the induction of micronuclei (MN). EQO caused a slight increase in G1 and decrease in S phase of the cell cycle, and slightly but significantly induced kinetochore-positive as well as kinetochore-negative MN and an elevated proportion of abnormal mitotic spindles. 3′-HO-DAI, but not 6-HO-DAI, induced kinetochore-negative MN. The observation that major human metabolites of DAI exhibit estrogenic and genotoxic potential may be of relevance for the safety evaluation of diets containing soy isoflavones.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this paper, the capacitances of the two-stage bushing that is installed in the 1-MV test bed for neutral beam injectors in the future fusion reactors are calculated by modeling the bushing in a ...3-D electrostatic code. One of the modeling results is the stored energy in the bushing, which corresponds to 1/2 CV 2 . After evaluating the bushing capacitance, a MATLAB/Simulink model is presented to model the possible breakdown in the bushing and between the electrodes in the 1-MV test bed. When a breakdown occurs between anode and cathode, an overcurrent is drawing that can cause damage in the electrode surfaces while an overvoltage takes place when the breakdown happens between the bushing stages. Such damage has been observed experimentally in the past. This paper also presents some of the possible protection against the breakdown in the 1-MV test bed to dissipate the stored energy in order to protect the electrode surfaces and the bushing. The suggested protections presented in this paper are damping resistors, surge arrester individually, and both of them. Also, a coil can be added to the DR either in series or in parallel.
At JAEA, as the Japan Domestic Agency (JADA) for ITER, a MAMuG (multi-aperture multi-grid) accelerator has been developed to perform the required R&D for the ITER neutral beam (NB) system. As a ...result of countermeasures to handle excess heat load to the ion source by backstreaming positive ions, H
−
ion beam current was increased to 0.32 A (the ion current density of 140 A m
−2
) at a beam energy of 796 keV. This high power beam acceleration simulated the ITER operation condition maintaining the perveance (H
−
ion current density/beam energy
3/2
) of the ITER accelerator. After the high power beam operation, the pulse length was successfully extended from 0.2 to 5 s at 550 keV, which yielded a 131 mA H
−
ion beam as an initial test of the long pulse operation. A test of a single-aperture single-gap (SINGAP) accelerator was performed at JAEA under an ITER R&D task agreement. The objective of this test was to compare two different accelerator concepts (SINGAP and MAMuG) at the same test facility. As a result, the MAMuG accelerator was defined as the baseline design for ITER, due to advantages in its better voltage holding and less electron acceleration. In three-dimensional beam trajectory analyses, the aperture offset at the bottom of the extractor was found to be effective for compensation of beamlet deflection due to their own space charge. It has been analytically demonstrated that these compensated beamlets can be focused at a focal point by adopting the aperture offset at the final grid of the accelerator.
PDF
