Scanning beam medium infra-red interferometry for plasma density measurements

The Frascati tokamak upgrade (FTU) Thomson scattering system is employed for the measurement of the electron temperature and density spatial profiles along the vertical torus diameter in 19 spatial points up to ten times in a single plasma discharge with a spatial resolution ranging from 2 cm in the central region to 4 cm in the plasma edge. The radiation source is a Nd:YLF laser at 1053 nm. The scattered radiation is collected by two objectives: the first looks at the plasma center, the second at the plasma edge. Bundles of optical fibers in the focal plane of the objectives carry the scattered light from the tokamak hall to a set of 19 interference filter polychromators, whose transmission is 70% and the rejection of the stray light at the laser wavelength is 1/107. The detectors are avalanche photodiodes with a NEP of the order of 10−13 W/(Hz)1/2 at 1053 nm. The absolute calibration for the electron density measurement has been carried out by Raman scattering on hydrogen and deuterium. Examples of temporal evolution of Te and ne spatial profiles are presented for ohmic plasma heating, lower hybrid current drive, and pellet injection experiment. A comparison between scattering data with interferometer for the density measurement, and ECE for the electron temperature shows agreement between the diagnostics. The system is controlled by two computers: a real-time computer for the laser settings, while the detection system parameters and data acquisition are managed using CAMAC by the data acquisition system of FTU.

There is a need for a real time, reliable density measurement compatible with the restricted access and radiation environment on International Thermonuclear Experimental Reactor (ITER). Due to the large plasma path length, high density and field, refraction, and Faraday rotation effects makes the use of contemporary long wavelength (≳50 μm) interferometers impractical. In this paper we consider the design of a short wavelength vibration compensated interferometer which allows operation without a prohibitively large vibration isolated structure and permits the optics to be conveniently mounted directly in or on the tokamak. A density interferometer design for ITER incorporating a 10.6 μm CO2 interferometer with vibration compensation provided by a 3.39 μm HeNe laser is discussed. The proposed interferometer design requires only a small intrusion into the ITER tokamak without a large support structure, refraction and Faraday rotation problems are avoided, and it provides a density resolution of at least 0.5%. Results are presented from an interferometer installed on the DIII-D tokamak incorporating essential elements of the proposed ITER design including 10.6 and 3.39 μm lasers, a retroreflector mounted on the vacuum wall of the DIII-D tokamak and real-time density feedback control. In this paper we consider a short wavelength interferometer design that incorporates vibration compensation for use on ITER. Our primary concern is to develop an interferometer design that will produce a reliable real time density monitor. We use the ITER conceptual design activity report as the basis of the design.

The SIRIO (Scanning InfraRed Interferometer) interferometer [1], recently disassembled together with the FTU (Frascati Tokamak Upgrade) experiment [2], worked continuously from 2004 to 2019.An extremely important contribution was made in all the experiments conducted on this tokamak. By virtue of its characteristics, in terms of spatial (1 cm) and temporal resolution (density profiles every 62 μs), combined with its capability to scan the entire plasma column. This interferometer produced all the density feedbacks for operations. Above all, it collected accurate density measurements in plasma physics, among the best data of all tokamak interferometers.In this review, it is reported the highly valuable experimental work of this powerful diagnostics. Indeed, high density observations were analyzed, as well as fast variations were measured; some examples: the detection of plasma instabilities (MARFE), the trace and the speed of the pellets, the measurement of the particle transport efficiencies in important transients etc.In order to improve the knowledge for future interferometry in plasma density measurements projects, some topics related to data analysis are also exposed, as well as local density reconstruction methods.

Diode-pumped solid-state (DPSS) ultraviolet lasers have been proven to be effective for dicing various types of glass in various applications and mainly thin substrates for microelectronics. The main varieties of glass are transparent to wavelengths above 300–350 nm. However, GW/cm2 intensities can be produced by tightly focusing short pulses (nanosecond to femtosecond) that will enable nonlinear interaction phenomena. High thermal stress induces cracks that might be prohibitive for precision engineering. As glass becomes absorptive below 300 nm, linear absorption and thermal ablation will occur without cracks by setting the right laser parameters (beam fluence, scanning speed, defocus, wavelength, and pulse width). In this paper we demonstrate the possibility of the crack-free laser dicing of borosilicate glass. The effect of a polymer layer is analysed on the laser (diode-pumped solid-state, 355 nm, nanosecond) dicing capability of a commercial glass (BorofloatO33) for backend packaging. The main drawbacks concerned the brittleness of glass and photothermal ablation, which induces thermal stresses responsible for chipping or cracks. It was assumed that a thick enough polymer would enhance the energy coupling between the beam and the target. The effect of pulse energy and speed on the scribing depth is provided in the present article. A numerical simulation using COMSOL Multiphysics® was performed in order to analyse the volume temperature distribution. It revealed that the temperature remained higher than the working point of glass (1500 K) between two pulses. The viscosity is thus low between two pulses, and thermal stresses are diminished compared to the processing of raw glass samples. A comparative study between SEM images and COMSOL based surface and in volume temperature will be finally discussed for the simulation validation according to the laser parameters.

2.09 - Standard Normal Variate, Multiplicative Signal Correction and Extended Multiplicative Signal Correction Preprocessing in Biospectroscopy

Detailed magnetic measurements of Field-reversed configurations (FRC) from the Translation Confinement Sustainment Upgrade (TCSU) experiment are presented. A two-axis probe inserted transversely at the axial midplane provides 24 independent measurements of B z (r) and B x (r). Two single-axis 29 channel probes provide axial profiles at the plasma edge. The B x (r) field profiles, oriented to measure Bθ from the rotating magnetic field (RMF), provide details about RMF penetration into the FRC. B z (r) profiles, when combined with the high beta nature of the FRC, interferometric density measurements, and assuming uniform temperature, yield radial density and pressure profiles. Time evolution of these profiles gives insight into plasma dynamics and the n = 1 (wobble) and n = 2 instabilities. Data from 123 and 172 kHz RMF frequencies is presented.

Plant biology is currently experiencing a growing demand for easy and reliable mRNA and protein localisation techniques. Here, we present novel whole mount in situ hybridisation and immunolocalisation protocols, suitable to localise mRNAs and proteins in Arabidopsis seedlings. We demonstrate that these methods can be used in different organs of Arabidopsis seedlings as well as in other plant species. In order to achieve better reproducibility and higher throughput, we modified these protocols for automation to be performed by a liquid handling robot. In addition, we show that other procedures such as reporter enzyme assays and tissue clearing can be similarly automated. We present examples of application of our protocols including mRNA localisation and proteins and epitope tag (co)localisations which demonstrate that these methods provide reliable and versatile tools for expression, localisation and anatomical studies in plants.

Validation and robustness testing of a CEC method used to determine impurities in a pharmaceutically active compound

Due to several favorable atomic properties (including a simple spectral structure, the existence of a visible resonance line, large excitation cross section, and ease of beam formation), beams of atomic lithium have been used for many years to diagnose various plasma parameters. Using techniques of active (beam‐based) spectroscopy, lithium beams can provide localized measurements of plasma density, ion temperature and impurity concentration, plasma fluctuations, and intrinsic magnetic fields. In this paper we present recent results on polarization spectroscopy from the LIBEAM diagnostic, a 30 keV, multi‐mA lithium beam system deployed on the DIII‐D National Fusion Facility tokamak. In particular, by utilizing the Zeeman splitting and known polarization characteristics of the collisionally excited 670.8 nm Li resonance line we are able to measure accurately the spatio‐temporal dependence of the edge current density, a parameter of basic importance to the stability of high performance tokamaks. We discuss the basic atomic beam performance, spectral lineshape filtering, and polarization analysis requirements that were necessary to attain such measurements. Observations made under a variety of plasma conditions have demonstrated the close relationship between the edge current and plasma pressure, as expected from neoclassical theory.

Precision displacement laser interferometry is crucial in various applications such as microlithography, high-performance profilometry, and gravitational wave detection. We are currently developing a fiber-based heterodyne laser interferometer that features compact size and low noise floor. Laser beams at two different wavelengths are utilized to construct a fiberbased interferometer system. Narrow band spectral filters are used to separate the beams of different wavelengths and to control their optical paths. The highly common optical paths between the two interferometers provide a high commonmode rejection ratio to instrument and environmental noise sources. In this paper we present the interferometer design, benchtop prototype system, and preliminary measurement results obtained in the lab environments. A benchtop prototype shows sub-nm/√Hz displacement sensitivities in air at frequencies above 100 mHz in our lab.

Optical Emission Spectroscopy (OES) represents a very reliable technique to carry out non-invasive measurements of plasma density and plasma temperature in the range of tens of eV. With respect to other diagnostics, it also can characterize the different populations of neutrals and ionized particles constituting the plasma. At INFN-LNS, OES techniques have been developed and applied to characterize the plasma generated by the Flexible Plasma Trap, an ion source used as "testbench" of the proton source built for European Spallation Source. This work presents the characterization of the parameters of a hydrogen plasma in different conditions of neutral pressure, microwave power and magnetic field profile, along with perspectives for further upgrades of the OES diagnostics system.

Mitigation of edge localised modes with magnetic perturbations in ASDEX Upgrade