Time-of-flight refractometry for robust line integral electron density measurements and control in ITER

Petrov, A. A.; Петров, В. Г.

doi:10.1063/1.1530389

Cited by 14 publications

(7 citation statements)

References 2 publications

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“…The refractometry concept was tested in T-11 [17], in T-10 and FTU in an ITER-like configuration, with 1-frequency [18], and with 2-frequency instruments [19].…”

Section: High Field Side Reflectometry (Hfsr)mentioning

confidence: 99%

Progress with the ITER project activity in Russia

Krasilnikov¹,

Abdyuhanov

Aleksandrov³

et al. 2015

Nucl. Fusion

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Due to the development of the ITER project, the requirements of the technical parameters of the ITER systems were more precisely and practically determined to be at higher levels. The essential increase of the ITER system characteristics happened recently. A number of prototypes were manufactured and tests were carried out. The results of the development and manufacture of 25 ITER systems, subject to the Russian Federation's obligations in the ITER project, are described.

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“…The refractometry concept was tested in T-11 [17], in T-10 and FTU in an ITER-like configuration, with 1-frequency [18], and with 2-frequency instruments [19].…”

Section: High Field Side Reflectometry (Hfsr)mentioning

confidence: 99%

Progress with the ITER project activity in Russia

Krasilnikov¹,

Abdyuhanov

Aleksandrov³

et al. 2015

Nucl. Fusion

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“…Another approach to determine the line average density (even with some information about profile flatness) comes from time delay refractometry [80], based on the measurement of the time delay of pulses launched across the plasma (with frequencies slightly above the cut-off frequency). The technique uses robust mirrors (like ECE and reflectometry) and in principle is free from fringe loss effects, which are typical for phase interferometers.…”

Section: Simultaneous Observation Of Several Ece Harmonics and (If Acmentioning

confidence: 99%

Chapter 7: Diagnostics

et al. 2007

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In order to support the operation of ITER and the planned experimental programme an extensive set of plasma and first wall measurements will be required. The number and type of required measurements will be similar to those made on the present-day large tokamaks while the specification of the measurements-time and spatial resolutions, etc-will in some cases be more stringent. Many of the measurements will be used in the real time control of the plasma driving a requirement for very high reliability in the systems (diagnostics) that provide the measurements.The implementation of diagnostic systems on ITER is a substantial challenge. Because of the harsh environment (high levels of neutron and gamma fluxes, neutron heating, particle bombardment) diagnostic system selection and design has to cope with a range of phenomena not previously encountered in diagnostic design. Extensive design and R&D is needed to prepare the systems. In some cases the environmental difficulties are so severe that new diagnostic techniques are required.The starting point in the development of diagnostics for ITER is to define the measurement requirements and develop their justification. It is necessary to include all the plasma parameters needed to support the basic and advanced operation (including active control) of the device, machine protection and also those needed to support the physics programme. Once the requirements are defined, the appropriate (combination of) diagnostic techniques can be selected and their implementation onto the tokamak can be developed. The selected list of diagnostics is an important guideline for identifying dedicated research and development needs in the area of ITER diagnostics.This paper gives a comprehensive overview of recent progress in the field of ITER diagnostics with emphasis on the implementation issues. After a discussion of the measurement requirements for plasma parameters in ITER and their justifications, recent progress in the field of diagnostics to measure a selected set of plasma parameters is presented. The integration of the various diagnostic systems onto the ITER tokamak is described. Generic research and development in the field of irradiation effects on materials and environmental effects on first mirrors are briefly presented. The paper ends with an assessment of the measurement capability for ITER and a forward of what will be gained from operation of the various diagnostic systems on ITER in preparation for the machines that will follow ITER. Performance assessment relative to requirements Design meets requirements S339 A.J.H. Donné et alPhysics Basis [7] and remains essentially the same. However, for ITER, the specific limits have changed. 2.1.2.Measurements needed for plasma control and evaluation. The measurements needed for plasma control and evaluation are naturally directly linked to the experimental programme, and particularly to the operating phase (i.e. H, D or D/T) and the operating scenario (H-mode, hybrid, etc). Since there is expected to be a phased introduction of po...

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“…This is also true when applying the PTFR diagnostics at an extraordinary (low fre quency) wave, because, in this case, a rather narrow transparency window is used (50-100 GHz in ITER and 45-120 GHz in FTU) and the measured time delay depends nonlinearly on the plasma density. To solve this problem, it was proposed in [3] to probe the plasma at several frequencies simultaneously.…”

Section: Introductionmentioning

confidence: 99%

“…When probing with an extraordinary wave, when the plasma frequency satisfies the inequalities f p Ӷ f c , f, where k is the numerical factor, f is the probing fre quency, N(z) is the plasma electron density, f c is the electron cyclotron frequency in the center of the plasma column, f p is the plasma electron frequency, z is the current coordinate along the probing direction, and l is the path length along the trajectory of the prob ing beam in plasma [3]. Probing with an extraordinary (low frequency) wave makes it possible to use microwaves with rela tively low frequencies, thereby substantially simplify ing the problem of "the first mirror," typical of ITER diagnostics applying electromagnetic waves in the IR and optical frequency ranges.…”

Section: Introductionmentioning

confidence: 99%

“…The development of reliable methods for mea suring the mean plasma density that are highly resis tant to vibrations and radiation loads, have a simple optical scheme, and do not require vast access to the plasma is of great importance. One such method, which was suggested and tested on the T 11M toka mak, is pulsed time of flight plasma refractometry (PTFR) [1][2][3], based on direct measurements of the propagation time of microwave pulses through the plasma, which is uniquely associated with linear plasma density along the probing chord. Since phase measurements are not used in this instrument, there is no problem of "phase jumps," which is inherent in most classical phase interferometers.…”

Section: Introductionmentioning

confidence: 99%

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First results from plasma density measurements in the FTU tokamak by means of a two-frequency pulsed time-of-flight refractometer

et al. 2012

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A pulsed time of flight refractometer was developed and tested to determine the mean plasma density in the T 11M tokamak by measuring the propagation time of nanosecond microwave pulses in plasma. Later, it was also proposed to use such an instrument to measure and control the mean plasma density in the ITER tokamak by probing the plasma with an extraordinary wave, the electric field of which is perpen dicular to the magnetic field in plasma, in the transparency window at frequencies of 50-100 GHz. To avoid the effect of the density profile shape on the measurement results in the nonlinear mode of refractometer operation (near the cutoff), a system operating at two different probing frequencies was developed and tested. Such a system provides two values of the time delay, which can be used to estimate the peaking factor of the density distribution α and correctly determine the linear density 〈Nl〉, regardless of the density profile (assum ing a smooth density profile of the form of N(ρ) = N(0)(1 -ρ 2 ) α , where N(0) is the central plasma density and ρ = r/a is the normalized plasma radius). The first experiments on density measurements in the FTU tokamak performed with this refractometer are described, and results from these experiments are presented. The formation of a thin dense plasma layer in the zone of a strong magnetic field (the so called MARFE layer) at a relatively low (for FTU) plasma density of ~6 × 10 19 m -3 was detected. The thickness of this layer, deter mined from the refractometry data, agrees well with the data obtained using a digital camera.

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Time-of-flight refractometry for robust line integral electron density measurements and control in ITER

Cited by 14 publications

References 2 publications

Progress with the ITER project activity in Russia

Progress with the ITER project activity in Russia

Chapter 7: Diagnostics

First results from plasma density measurements in the FTU tokamak by means of a two-frequency pulsed time-of-flight refractometer

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