Simple analytic form of the relativistic Thomson scattering spectrum

Selden, A. C.

doi:10.1016/0375-9601(80)90276-5

Cited by 68 publications

(30 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Analytical forms of the TS form factor S(λ, T e , θ) are readily found in the literature. 9,10 To obtain expected signals from a TS detectors as a function of T e , we convolve the fully relativistic form factor with the detector spectral instrument response function f i (λ). To obtain a spectral calibration for a given TS detector, we fill the input fiber at F/3.5 with the output of a calibrated scannable Czerny-Turner monochromator.…”

Section: Calibrationsmentioning

confidence: 99%

Thomson scattering upgrades on Alcator C-Mod

Hughes

Mossessian

Zhurovich

et al. 2003

Review of Scientific Instruments

View full text Add to dashboard Cite

The Thomson scattering (TS) diagnostics set [Rev. Sci. Instrum. 70, 759 (1999); Rev. Sci. Instrum. 72, 1107 (2001)] on the Alcator C-Mod tokamak [Phys. Plasmas 1, 1511 (1994)] has been upgraded to deliver measurements of electron temperature (T e ) and density (n e ) with improved temporal and spatial resolution. Two 30 Hz, 1.3 J Nd-doped yttrium aluminum garnet (Nd:YAG) lasers share a vertical beam path through the tokamak plasma and are fired in alternating fashion, allowing collection of scattered light with a 60 Hz rep rate. Also, plasma variation occurring on faster time scales (10 −5 < ∼ τ (s) < ∼ 10 −2 ) can be studied by closely spacing the pulses from either laser for operation in 30 Hz burst mode. Eight compact polychromators [Rev. Sci. Instrum. 61, 2858 (1990)] have been added to the system, better than doubling the spatial resolution of core plasma TS measurements and allowing better diagnosis of core n e and T e gradients. Up to 14 fiber bundles view the core plasma, and a linear array of up to 22 single fibers of 1 mm diameter observes the plasma edge. Each fiber holder has been upgraded to incorporate a cam key and follower, so that the holders can be mounted to a cammed plate that automatically orients each holder to the correct viewing angle as its height is adjusted. This allows the fiber bundles to be repositioned easily between tokamak discharges, making it possible to concentrate core measurements in regions of particular interest, such as the vicinity of an internal transport barrier, with spatial resolution of ∼ 1 cm. The newly designed mount can be positioned with sub-millimeter precision, and its alignment with respect to the Nd-YAG beam can be adjusted between discharges using remotely controlled stepper motors. This capacity for correcting misalignment increases the reliability of density measurements. Cross-calibration of TS n e measurements with electron cyclotron emission (ECE) diagnostics is performed using dynamic ramps of both plasma density and magnetic field to force ECE signal cutoffs at known values of n e . This technique, which can be performed on any given day of an experimental campaign, supplements an absolute calibration based on Raman scattering in hydrogen and deuterium gas, which normally can not be done during a campaign.

show abstract

Section: Calibrationsmentioning

confidence: 99%

Thomson scattering upgrades on Alcator C-Mod

Hughes

Mossessian

Zhurovich

et al. 2003

Review of Scientific Instruments

View full text Add to dashboard Cite

show abstract

“…Table 2 summarizes the main parameters of the MTS system and also the present one (TS-1), assuming an electron temperature of 150 eV and a density of 2×10 19 m −3 . The number of scattered photons in the collection solid angle (Ω) was calculated by using Selden equations [7]. The number of photons that reach each channel was estimated taking into account the transmission of the optics and the polychromator spectral response.…”

Section: Fiber Optic Multiplex Upgrade Of the Thomson Scatteringmentioning

confidence: 99%

Thomson scattering diagnostic on the ETE tokamak: status and progress

Berni¹,

Bosco²,

Oliveira³

et al. 2004

Braz. J. Phys.

View full text Add to dashboard Cite

In order to measure the plasma temperature and density in the spherical tokamak ETE, a one-channel Thomson scattering system was implemented. During the upgrade of capacitor banks and optimization since the beginning of operation, the plasma pulse duration has increased from 1.5 ms up to 12 ms with plasma currents varying from 10 kA to 60 kA. During this phase, the electron temperature was increased from 20 eV to 160 eV with densities as high as 3.5×1019 m −3 . Presently, the Thomson scattering diagnostic is being upgraded based on the time-delay technique, that consists in using fibers of different lengths to transmit the scattered light signals to the same polychromator. This system will allow measurements of electron temperature and density profiles with ten spatial points per laser shot and per polychromator. This work describes in details the Thomson scattering system, presents a selection of results obtained by this system since the initial phase of operation, and shows details of the proposed upgrade of the Thomson scattering system. The ETE Spherical TokamakThe ETE (Experimento Tokamak Esférico) is a medium-size spherical torus with an aspect ratio of 1.5, major radius of 0.3 m, toroidal field of 0.4 T and plasma current of 0.22 MA for the first stage of operation [1]. The objectives of the project are focused on plasma edge investigation, development of diagnostics and training on tokamak operation. The vacuum vessel was manufactured with Inconel 625 with an external diameter and height of 1.2 m and an internal tube with a diameter of 0.18 m, which houses the ohmic solenoid and the inner legs of the toroidal coils. Good access for diagnostics is provided by 58 Conflat ports (12xCF14", 4xCF250 and 42xCF40). The vacuum system comprises three pumps: one turbo drag pump (1500 l/s) backed by an oilfree diaphragm (4 m 3 /h) and an auxiliary mechanical pump (30 m 3 /h). A base pressure of 7.8×10 −8 Torr was achieved after conditioning the vessel walls with baking (T < 150 o C) and DC glow discharge cleaning (GDC) with helium gas.There are three capacitor banks that storage energy for the toroidal, ohmic heating and equilibrium coils. The energy of the capacitor banks is being increased by adding more capacitors and increasing the maximum voltage rating. Presently, the acquisition system is based on CAMAC and oscilloscopes that, in a near future, will be replaced by VME technology [2]. Table 1 summarizes the status of the proposed diagnostics for ETE. For this initial phase a set of electromagnetic and optical diagnostics are already installed. For edge plasma investigation a 10 keV Fast Neutral Lithium Beam (FNLB) is under development with glassy β-eucryptite source that will furnish beam currents up to 1 mA/cm 2 [3]. To measure the electron temperature and density profiles a one-channel Thomson scattering (TS) system was implemented. Thomson Scattering Diagnostic in ETEThe TS is based on a 10 J Q-switched ruby laser (λ = 694.3 nm, pulse duration: 30 ns) that probes the plasma horizontally at the mid-plane. Th...

show abstract

“…Thus the integral TS intensity depends only on the electron density and the ratios of the signals in spectral channels depend only on electron temperature. Since the relativistic effects become important for T_>2 keV and the temperature in the plasma core of Alcator C-Mod can be as high as 5 keV, the relativistic spectral density function is used for data analysis as given in [6]. The spectral width of the spectrometers' channels varies from 100 A to 500 A and the spectral response of the detection system is nonuniform inside each channel.…”

Section: System Description and Data Analysis Proceduresmentioning

confidence: 99%

Performance of Alcator C-Mod core Thomson scattering system

Mossessian

Hubbard

Irby

1999

Review of Scientific Instruments

View full text Add to dashboard Cite

Design of the Alcator C-Mod Thomson Scattering (TS) diagnostic is discussed and the results of the measurements are presented. The TS system has 6 spatial channels with observation volumes evenly distributed between the midplane and the edge of the plasma. Each channel is capable of measuring the electron density in the range Ne = 5x 1019 m-3 -5x 1021 m-3 and temperature from Te = 200 eV -10 keV. A 30 Hz, 1.5 J per pulse Nd:YAG laser is employed allowing the measurements of evolution of Te and Ne yrofiles during plasma shot. A laser beam position control and feedback system provides for the beam alignment stability and reliable electron density measurements.Examples of the core density and temperature profiles measured at different stages of the plasma evolution are discussed.

show abstract

Simple analytic form of the relativistic Thomson scattering spectrum

Cited by 68 publications

References 2 publications

Thomson scattering upgrades on Alcator C-Mod

Thomson scattering upgrades on Alcator C-Mod

Thomson scattering diagnostic on the ETE tokamak: status and progress

Performance of Alcator C-Mod core Thomson scattering system

Contact Info

Product

Resources

About