Visible cameras as a non-invasive diagnostic to study negative ion beam properties.

Beam tomography is a non-invasive diagnostic that allows us to reconstruct the beam emission profile by measuring the light emitted by the beam particles interacting with the background gas, along an elevated number of lines of sight, which is related to the beam density by assuming a uniform background gas. In the framework of the heating and current drive of future nuclear fusion reactors, negative ion beams of hydrogen and deuterium are required for neutral beam injectors (NBIs) due to their elevated neutralization efficiency at high energy (in the MeV range). Beside the beam energy, beam divergence and homogeneity are two critical aspects in the design of future NBIs. In this paper, the characterization of the negative ion beam of the negative ion source NIO1 (a small-sized radio-frequency driven negative ion source, with 130 mA of total extracted H- current and 60 kV of maximum acceleration) using the tomographic system composed of two visible cameras is presented. The Simultaneous Algebraic Reconstruction Technique (SART) is used as an inversion technique to reconstruct the 3 × 3 matrix of the extracted beamlets, and the beam divergence and homogeneity are studied. The results are compared with the measurements of the other diagnostics and correlated with the source physics. The suitability of visible cameras as a diagnostics system for the characterization of the NIO1 negative ion beam is a small-scale experimental demonstration of the possibility to reconstruct more complicated multi-beamlet profiles, resulting in a powerful diagnostic for large NBIs.

Beam and installation improvements of the NIO1 ion source.

The NIO1 (Negative Ion Optimization phase 1) source can provide continuous beam operation, which is convenient for systematic parameter and equipment studies. Even in the pure volume production regime, the source yield was found to depend on conditioning procedures. Magnetic configuration tests continued adding magnets to the existing setup; the filter field component Bx has been progressively extended to span the -12 to 5 mT range, and as a trend, source performances improved with |Bx|. The progress of camera beam diagnostics and of the quality of the volume-produced H- beam is also shown. The status, off-line results, and reliability of a first NIO1 cesium oven are discussed; other upgrades in preparation (cavity ring down spectrometer, the end calorimeter, and conceptual tests of the energy recovery system) are also listed.

Beam energy recovery for fusion and collector design for tests on compact sources.

The next fusion project DEMO, which will be the evolution of the experimental fusion reactor [International Tokamak Experimental Reactor (ITER)], would require a high efficient energy production. As in ITER, DEMO will use fast Neutral Beam (NB) injectors to increase the plasma temperature needed for the fusion reaction. A way to recover the electric energy production efficiency in DEMO could be the beam energy recovery in the NB production, which is produced by a D- beam, neutralized by a gas cell with 60% efficiency. A compact energy recovery device with an axisymmetric cylindrical ion collector that uses only decelerating electric fields combined with the beam space charge effect has been recently proposed. It can be used for a test on the beam of the NIO1 (Negative Ion Optimization 1) source, a compact ion source (scaled down from ITER size sources) that has been developed at INFN-LNL and Consorzio RFX (Padua). The detailed collector design to be used on one of the beamlets of the NIO1 source within typical space limitation is presented and discussed here. Furthermore, a preliminary trajectory simulation for a beam with a rectangular geometry similar to the beam used in ITER to verify the beam recovery for a nonaxial symmetric geometry is also shown.

Development and installation of a radio frequency quadrupole cooler test.

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.

Sent Liver Grafts Do Not Have a Detrimental Impact on Post-transplant Outcome.

INTRODUCTION: "Sent livers" (SL) (interregional allocated organs) are considered extended donor criteria grafts. These grafts influence post-transplant outcome. In our donor allocation program, the number of allocated SLs is increasing. The aim of our study is to provide data supporting the possibility to enlarge the use of SLs through adequate donor-to-recipient matching. METHODS: A retrospective analysis was carried out from our prospective-collected database during 2014. RESULTS: Fifty-seven liver transplantations (LTs) were included: 22 SLs and 35 grafts procured by us (nSLs). Only donor risk index among donor characteristics showed a trend toward significant values (SL 1.901 vs nSL 1.726, P = .07). Among LT variables, the number of patients who received interleukin-2 inhibitor induction (SL 7 vs nSL 20, P < .05) and the presence of hepatocellular carcinoma (SL 50% vs nSL 34%, P < .05) reached statistical significance. One case of primary nonfunction occurred in the nSL group. No major retrieval injuries were observed. Retransplantation was performed in 6 cases (2 SLs and 4 nSLs). One patient in the SL group died after retransplantation. Graft survival rates at 1, 3, 6, and 12 months were 100%, 100%, 90%, 86% and 91%, 86%, 86%, 86% (P = .79) in SL and nSL groups, respectively. DISCUSSION: SL performance did not differ from that of nSL. SLs were usually allocated to noncritical candidates, and nSLs were transplanted more frequently in decompensated recipients. Despite this peculiar donor-recipient match, grafts survival was similar in the 2 groups of patients.

Deterioration of Lung Function in a Pig Model of Uncontrolled Cardiac Death.

INTRODUCTION: Uncontrolled donors after circulatory determination of death (uDCDD) represent a yet unexplored pool of organs potentially available for transplantation. The aims of this study were to validate a protocol of cardiac death in the pig and to investigate lung function during the process. MATERIALS AND METHODS: Cardiac death was induced in preanesthetized animals with an injection of 600 mg propofol; once systolic blood pressure was <50 mm Hg (Agonal Phase), a 20 mEq bolus of KCl was given and, after asystolia was documented, cardiopulmonary resuscitation (CPR) started, followed by 5 minutes no touch (end-CPR). Invasive blood pressure (BP) and heart rate (HR) were recorded; blood samples taken at baseline, 15 minutes after CPR, and after the no touch period (end-CPR). Computed tomography (CT) scans were taken at baseline and at end-CPR. RESULTS: Agonal phase was reached in 6 ± 1 minutes and lasted 3 ± 1 minutes; average HR was 49 ± 16 beats/min, and BP was 41 ± 12 mm Hg. CPR lasted 35 ± 3 minutes; average HR and BP were 113 ± 32 beats/min and 86 ± 63 mm Hg, respectively. PaO2/FiO2 decreased from 442 ± 31 mm Hg at baseline to 63 ± 36 at end-CPR (P < .001). pH decreased from 7.378 ± 0.045 to 6.931 ± 0.042 (P < .001), with a corresponding increase of lactate from 0.9 ± 0.2 to mmol/L to 12.8 ± 2.1 (P < .001). As assessed using CT scan, total lung volume decreased (baseline vs end-CPR 1107 ± 106 mL vs 617 ± 95; P < .001), whereas noninflated tissue (ie, atelectasis) significantly increased (46 ± 10 g vs 131 ± 89; P = .008). CONCLUSIONS: Lung function greatly deteriorated after cardiac death. The model we set may constitute a reproducible platform for future investigations on lung uDCDD.

Background gas density and beam losses in NIO1 beam source.

NIO1 (Negative Ion Optimization 1) is a versatile ion source designed to study the physics of production and acceleration of H- beams up to 60 keV. In ion sources, the gas is steadily injected in the plasma source to sustain the discharge, while high vacuum is maintained by a dedicated pumping system located in the vessel. In this paper, the three dimensional gas flow in NIO1 is studied in the molecular flow regime by the Avocado code. The analysis of the gas density profile along the accelerator considers the influence of effective gas temperature in the source, of the gas temperature accommodation by collisions at walls, and of the gas particle mass. The calculated source and vessel pressures are compared with experimental measurements in NIO1 during steady gas injection.

The characterization and optimization of NIO1 ion source extraction aperture using a 3D particle-in-cell code.

The geometry of a single aperture in the extraction grid plays a relevant role for the optimization of negative ion transport and extraction probability in a hybrid negative ion source. For this reason, a three-dimensional particle-in-cell/Monte Carlo collision model of the extraction region around the single aperture including part of the source and part of the acceleration (up to the extraction grid (EG) middle) regions has been developed for the new aperture design prepared for negative ion optimization 1 source. Results have shown that the dimension of the flat and chamfered parts and the slope of the latter in front of the source region maximize the product of production rate and extraction probability (allowing the best EG field penetration) of surface-produced negative ions. The negative ion density in the plane yz has been reported.

Ion collector design for an energy recovery test proposal with the negative ion source NIO1.

Commercial viability of thermonuclear fusion power plants depends also on minimizing the recirculation power used to operate the reactor. The neutral beam injector (NBI) remains one of the most important method for plasma heating and control. For the future fusion power plant project DEMO, a NBI wall plug efficiency at least of 0.45 is required, while efficiency of present NBI project is about 0.25. The D(-) beam from a negative ion source is partially neutralized by a gas cell, which leaves more than 40% of energy in residual beams (D(-) and D(+)), so that an ion beam energy recovery system can significantly contribute to optimize efficiency. Recently, the test negative ion source NIO1 (60 keV, 9 beamlets with 15 mA H(-) each) has been designed and built at RFX (Padua) for negative ion production efficiency and the beam quality optimization. In this paper, a study proposal to use the NIO1 source also for a beam energy recovery test experiment is presented and a preliminary design of a negative ion beam collector with simulations of beam energy recovery is discussed.

First hydrogen operation of NIO1: Characterization of the source plasma by means of an optical emission spectroscopy diagnostic.

NIO1 (Negative Ion Optimization 1) is a compact and flexible radio frequency H(-) ion source, developed by Consorzio RFX and INFN-LNL. The aim of the experimentation on NIO1 is the optimization of both the production of negative ions and their extraction and beam optics. In the initial phase of its commissioning, NIO1 was operated with nitrogen, but now the source is regularly operated also with hydrogen. To evaluate the source performances, an optical emission spectroscopy diagnostic was installed. The system includes a low resolution spectrometer in the spectral range of 300-850 nm and a high resolution (50 pm) one, to study, respectively, the atomic and the molecular emissions in the visible range. The spectroscopic data have been interpreted also by means of a collisional-radiative model developed at IPP Garching. Besides the diagnostic hardware and the data analysis methods, the paper presents the first plasma measurements across a transition to the full H mode, in a hydrogen discharge. The characteristic signatures of this transition in the plasma parameters are described, in particular, the sudden increase of the light emitted from the plasma above a certain power threshold.

First experiments with the negative ion source NIO1.

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW).

Integration of RFQ beam coolers and solenoidal magnetic fields.

Electromagnetic traps are a flexible and powerful method of controlling particle beams, possibly of exotic nuclei, with cooling (of energy spread and transverse oscillations) provided by collisions with light gases as in the Radio Frequency Quadrupole Cooler (RFQC). A RFQC prototype can be placed inside the existing Eltrap solenoid, capable of providing a magnetic flux density component B(z) up to 0.2 T, where z is the solenoid axis. Confinement in the transverse plane is provided both by B(z) and the rf voltage V(rf) (up to 1 kV at few MHz). Transport is provided by a static electric field E(z) (order of 100 V/m), while gas collisions (say He at 1 Pa, to be maintained by differential pumping) provide cooling or heating depending on V(rf). The beamline design and the major parameters V(rf), B(z) (which affect the beam transmission optimization) are here reported, with a brief description of the experimental setup.

Particle transport and heat loads in NIO1.

NIO1 is a compact radio frequency ion source designed to generate a 60 kV-135 mA hydrogen negative ion beam and it aims at continuous operation, which implies a detailed thermo-mechanical analysis of the beam-facing components, in particular, the accelerator grids. A 3D analysis of the entire NIO1 beam has been performed for the first time with a fully 3D version of EAMCC, a relativistic particle tracking code for the calculation of the grid power deposition induced by particle impacts. According to the results presented in this paper, secondary and co-extracted electrons cause a non-negligible heat load on the grids, where different high-power density regions, within reasonable sustainable standard limits, are calculated.

Simulation of space charge compensation in a multibeamlet negative ion beam.

Ion beam space charge compensation occurs by cumulating in the beam potential well charges having opposite polarity, usually generated by collisional processes. In this paper we investigate the case of a H(-) ion beam drift, in a bi-dimensional approximation of the NIO1 (Negative Ion Optimization phase 1) negative ion source. H(-) beam ion transport and plasma formation are studied via particle-in-cell simulations. Differential cross sections are sampled to determine the velocity distribution of secondary particles generated by ionization of the residual gas (electrons and slow H2 (+) ions) or by stripping of the beam ions (electrons, H, and H(+)). The simulations include three beamlets of a horizontal section, so that multibeamlet space charge and secondary particle diffusion between separate generation regions are considered, and include a repeller grid biased at various potentials. Results show that after the beam space charge is effectively screened by the secondary plasma in about 3 µs (in agreement with theoretical expectations), a plasma grows across the beamlets with a characteristic time three times longer, and a slight overcompensation of the electric potential is verified as expected in the case of negative ions.

Numerical simulations of the first operational conditions of the negative ion test facility SPIDER.

In view of the realization of the negative ion beam injectors for ITER, a test facility, named SPIDER, is under construction in Padova (Italy) to study and optimize production and extraction of negative ions. The present paper is devoted to the analysis of the expected first operations of SPIDER in terms of single-beamlet and multiple-beamlet simulations of the hydrogen beam optics in various operational conditions. The effectiveness of the methods adopted to compensate for the magnetic deflection of the particles is also assessed. Indications for a sequence of the experimental activities are obtained.

Negative Pressure Wound Treatment of Infections Caused By Extensively Drug-Resistant Gram-Negative Bacteria After Liver Transplantation: Two Case Reports.

Although survival after liver transplantation (LT) has progressively improved over the last years, an increased prevalence of clinically relevant infections in LT patients is well documented. In particular, the spread of infections sustained by extensively drug-resistant bacteria (XDR) produced an increase in the incidence of wound infections. Implementation of treatments for these life-threatening events is mandatory. This study describes 2 LT patients in whom XDR wound infection was effectively treated using negative pressure wound treatment (NPWT) combined with targeted local and systemic antibiotic therapy. Over the last 3 years, 2 of 8 patients with XDR infection admitted to our unit developed wound infection caused by XDR Klebsiella pneumoniae (KP-XDR). Positive results of the abdominal fluid culture and of the wound swab for KP-XDR were followed by sepsis. In both cases wound debridement was required and deep fascial layer dehiscence was detected. Combination antibiotic therapy was administered for sepsis treatment and, after failure of conventional NPWT, a NPWT with local instillation (NPWTi; V.A.C.-Ulta/VeraFlo-Instillation Therapy-KCI USA, Inc., San Antonio, TX, USA) of colistin-rifampicin was applied. After NPWTi application a reduction in bacterial load and exudate was observed with reduction in inflammatory markers. A complete healing of wound was achieved and both patients are currently alive. Instillation and NPWT are widely discussed in the literature. Results of the present study indicate beneficial effects of NPWT combined with targeted local and systemic antibiotic therapy; in both cases a life-threatening complication was cured. We consider local instillation of selected antibiotics applied to NPWTi a valuable tool for deep wound infection sustained by XDR bacteria.

Installation of a versatile multiaperture negative ion source.

Neutral Beam Injectors (NBI), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact RF ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, is being installed at Padua, in Consorzio RFX, to provide a test bench for source optimizations in the framework of the accompanying activities in support to the ITER NBI test facility. NIO1 construction and status of the overall installation, including a high voltage deck and an optical cavity ring down spectrometer are here summarized and reported. Plasma and low voltage beam operations are discussed. Development of a sampling beam calorimeter (with small sampling holes, and a segmented cooling circuit) is also discussed.

Modeling and design of a beam emission spectroscopy diagnostic for the negative ion source NIO1.

Consorzio RFX and INFN-LNL are building a flexible small ion source (Negative Ion Optimization 1, NIO1) capable of producing about 130 mA of H(-) ions accelerated at 60 KeV. Aim of the experiment is to test and develop the instrumentation for SPIDER and MITICA, the prototypes, respectively, of the negative ion sources and of the whole neutral beam injectors which will operate in the ITER experiment. As SPIDER and MITICA, NIO1 will be monitored with beam emission spectroscopy (BES), a non-invasive diagnostic based on the analysis of the spectrum of the Hα emission produced by the interaction of the energetic ions with the background gas. Aim of BES is to monitor direction, divergence, and uniformity of the ion beam. The precision of these measurements depends on a number of factors related to the physics of production and acceleration of the negative ions, to the geometry of the beam, and to the collection optics. These elements were considered in a set of codes developed to identify the configuration of the diagnostic which minimizes the measurement errors. The model was already used to design the BES diagnostic for SPIDER and MITICA. The paper presents the model and describes its application to design the BES diagnostic in NIO1.

A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators.

Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

Advancements in ion diode and triode design.

Selfconsistent laminar flow models, which enable to predict the optimal cathode and anode geometry in simple diodes, must be modified to account for the anode aperture and the effect of other electrodes. An equation for charge coupled to arbitrary laminar flows is here first presented and its numerical solutions are obtained with a new method, based on mesh transformations. It is found that a close match to theoretical flows requires an increase of the simple diode voltage v0 by an amount vδ, which, for a typical case designed for zero exit angle condition, are v0 = 0.7465 and vδ = 0.0294 in adimensional units. States "in" and "out" for the anode lens are also shown, where "out" is a new and nonlinear solution for the beam expansion in a drift tube.