194 research outputs found
Modeling and simulation of a beam emission spectroscopy diagnostic for the ITER prototype neutral beam injector
A test facility for the development of the Neutral Beam Injection system for
ITER is under construction at Consorzio RFX. It will host two experiments:
SPIDER, a 100 keV H-/D- ion RF source, and MITICA, a prototype of the full
performance ITER injector (1 MV, 17 MW beam). A set of diagnostics will monitor
the operation and allow to optimize the performance of the two prototypes. In
particular, Beam Emission Spectroscopy will measure the uniformity and the
divergence of the fast particles beam exiting the ion source and travelling
through the beam line components. This type of measurement is based on the
collection of the H{\alpha}/D{\alpha} emission resulting from the interaction
of the energetic particles with the background gas. A numerical model has been
developed to simulate the spectrum of the collected emissions in order to
design this diagnostic and to study its performance. The paper describes the
model at the base of the simulations and presents the modeled
spectra in the case of MITICA experiment.Comment: 4 pages, 5 figures. Contributed paper for the HTPD 2014 conference.
Accepted manuscrip
Modeling and design of a BES diagnostic for the negative ion source NIO1
Consorzio RFX and INFN-LNL are building a flexible small ion source (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
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.Comment: 3 pages, 3 figures. Contributed paper for the ICIS 2013 conference.
Accepted manuscrip
First Beam Characterization by Means of Emission Spectroscopy in the NIO1 Experiment
The NIO1 experiment hosts a flexible RF H- ion source, developed by INFN-LNL
and Consorzio RFX to improve the present concepts for the production and
acceleration of negative ions. The source is also used to benchmark the
instrumentation dedicated to the ITER neutral beam test facility. Many
diagnostics are installed in NIO1 to characterize the source and the extracted
negative ion beam. Among them, Beam Emission Spectroscopy (BES) has been used
in NIO1 to measure the divergence and the uniformity of the beam, together with
the fraction of beam ions which was neutralized inside the acceleration system.
The diagnostic method is based on the analysis of the Doppler shifted
photons emitted by the fast beam particles and collected along a
line of sight. The article presents the experimental setup and the analysis
algorithms of the BES diagnostic, together with a discussion of the first
measurements and of their correlation with the operational parameters.Comment: 3 pages, 2 figures. Contributed paper for the ICIS 2017 conference.
Accepted manuscript of a published pape
Electron Density and Temperature in NIO1 RF Source Operated in Oxygen and Argon
The NIO1 experiment, built and operated at Consorzio RFX, hosts an RF
negative ion source, from which it is possible to produce a beam of maximum 130
mA in H- ions, accelerated up to 60 kV. For the preliminary tests of the
extraction system the source has been operated in oxygen, whose high
electronegativity allows to reach useful levels of extracted beam current. The
efficiency of negative ions extraction is strongly influenced by the electron
density and temperature close to the Plasma Grid, i.e. the grid of the
acceleration system which faces the source. To support the tests, these
parameters have been measured by means of the Optical Emission Spectroscopy
diagnostic. This technique has involved the use of an oxygen-argon mixture to
produce the plasma in the source. The intensities of specific Ar I and Ar II
lines have been measured along lines of sight close to the Plasma Grid, and
have been interpreted with the ADAS package to get the desired information.
This work will describe the diagnostic hardware, the analysis method and the
measured values of electron density and temperature, as function of the main
source parameters (RF power, pressure, bias voltage and magnetic filter field).
The main results show that not only electron density but also electron
temperature increase with RF power; both decrease with increasing magnetic
filter field. Variations of source pressure and plasma grid bias voltage appear
to affect only electron temperature and electron density, respectively.Comment: 7 pages 4 figures. Contributed paper for the NIBS 2016 conference.
Accepted manuscrip
Profile of deglutition speech evaluation in an intensive care unit
The combination of an increase in long-term survival and the availability
of a relatively sensitive parathyroid hormone (PTH) assay has led to
an increasing incidence of hyperparathyroidism (HPT) diagnosis in patients
on regular dialysis treatment (RDT). Hitherto the diagnosis has been
based on biochemical data and clinical grounds, as parathyroid (PT) imaging
is limited in accuracy, reproducibility, safety and invasiveness [1, 2].
Today, 201TI and 99mTc subtraction imaging (sq, high resolution ultrasonography
(US) and up-to-date computed tomography (CT) have been proposed
as sensitive and specific tests for primary HPT imaging [4-7]. The
aim of the present study was to assess on a group of patients on RDT the
accuracy of these methods in relation to the degree of HP
A novel plasma jet with RF and HF coupled electrodes
In order to achieve low processing temperature and efficient coatings deposition for manufacturing applications, a novel torch has been developed that couples in a double DBD design high frequency (HF ~17 kHz) and radio frequency (RF ~27 MHz) excitations. The design allows to obtain a stable RF plasma also in reactive processes and with the possibility to control on the treated substrates ions flux and surface charging, avoiding the micro-discharges. The plasma has been electrically and optically characterized by emission spectroscopy
First hydrogen operation of NIO1: characterization of the source plasma by means of an optical emission spectroscopy diagnostic
NIO1 is a compact and flexible radiofrequency H- ion source, developed by
Consorzio RFX and INFN-LNL. 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.Comment: 3 pages, 2 figures. Contributed paper for the ICIS 2015 conference.
Accepted manuscrip
Coherence-imaging approach to time-resolved charge-exchange recombination spectroscopy in high-temperature plasma
A coherence-based, or interferometric approach to spectral analysis of charge-exchange recombination (CXR) emission radiation from high-temperature plasma probed or heated using energetic neutral beams, offers a number of advantages over wavelength-domain instruments. The spectral-line shift and broadening are obtained from measurements of the spectralcoherence at a given fixed time delay. The coherence is monitored by first approximately isolating the spectral line of interest using an interference filter and subsequently imaging the spectral scene using a field-widened electro-optic path-delay-modulated polarization interferometer.Interferometers have the advantage of high-light throughput (no slit aperture). Moreover, because the spectral information is encoded at harmonics of the electro-optic modulation frequency, a single detector suffices to capture the spectral information, thereby opening the possibility for time-resolved two-dimensional spectralimaging. When unwanted spectral features are passed by the interference filter, the interpretation of the coherence phase and amplitude images can become ambiguous. By modulating the particle beam source, however, we show that coherence imaging using a single-delay modulatable interferometer can distinguish and characterize the Doppler-broadened CXR emission component against a significant background of continuum and intrinsic radiation, or pollution from nearby spectral features
Electromagnetic filaments and edge modifications induced by electrode biasing in the RFX-mod tokamak
Impur ity behaviour and r adiation patter n in the RFX-mod r ever sed field pinch
Intr oduction RFX-mod is the largest reversed field pinch operating nowadays, with 2 m in major radius, 0.459 m in minor radius and an installed power dimensioned to drive up to 2 MA of plasma current. In the long shutdown period completed at the end of 2004, several new features have been introduced. Above all, a closer resistive shell with external saddle coils has been installed to harness the rich spectrum of MHD modes. This paper describes the behaviour of the impurities in discharges with plasma current of about 600 kA, in terms of influxes from the wall, radiated power and effective charge; first results on the impurity toroidal velocity are also presented. In the former machine configuration, impurities did not represent a major problem. Despite the strong plasma wall interactions the effective charge was kept at reasonable levels (i.e. below 2), especially at high density. In this respect first observations on the restarted machine confirm the trend. In fact, the measured effective charge towards the plasma density is comparable or slightly lower than what found in the former machine. The effect on the influxes and on the emitted radiation of the strong poloidal and toroidal asymmetries associated with the plasma horizontal shift and with the wallmode locking have been investigated. Results and discussion The TV camera pictures of the inner wall in 600kA discharges show strong plasma wall interactions (PWI) in the region where the phase locked MHD modes form a local deformation in the plasma column (se
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