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Journal ArticleDOI

Pilot experiments for the International Thermonuclear Experimental Reactor active beam spectroscopy diagnostic

01 Oct 2004-Review of Scientific Instruments (American Institute of Physics)-Vol. 75, Iss: 10, pp 3458-3461

AbstractSupporting pilot experiments and activities which are currently considered or already performed for the development of the International Thermonuclear Experiment Reactor active beam spectroscopy diagnostic are addressed in this article. Four key issues are presented including optimization of spectral instrumentation, feasibility of a motional Stark effect (MSE) evaluation based on line ratios, “first-mirror” test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE diagnostic.

Summary (2 min read)

Introduction

  • Four key issues are presented including optimization of spectral instrumentation, feasibility of a motional Stark effect(MSE) evaluation based on line ratios, “first-mirror” test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE diagnostic.
  • A comprehensive package of active beam based spectroscopy tools for the International Thermonuclear Experimental Reactor(ITER) has been developed and a final summary was recently completed.
  • More quantitative studies and modeling will be required in this field.
  • The effects of carbon and beryllium coatings on reflectivity and polarization characteristics of metallic mirrors have been modeled and presented at several meetings(e.g., Ref. 7).

II. CXRS AND BES INSTRUMENTATION

  • Very early on it has been recognized that the substantial attenuation of the diagnostic beam requires high-optical throughput spectrometers in order to compensate for a low CX signal in the presence of huge background of continuum radiation.
  • The system’s etendue sA·V=4310−1 mm2 srd is preserved by the periscope fiber bundle assembly, and a DNB slab of about 1003100 mm is imaged for each radial channel onto the entrance slits1 35 mmd of individual spectrometers.
  • The role of the CXRS/ BES diagnostic as a multi-tasking requires the simultaneous measurement of the main ion species: helium ash at 468 nm, intrinsic impurities C and Ne at 529 nm, and bulk D and T ions at 650 nm(cf. Fig. 1).
  • The proposed scheme is to make use of color filters and different orders of the TRINITI echelle grating instruments for different representative wavelengths.
  • The detection of nonthermal broadband features depends critically on clear distinction of CX induced features and passive background.

III. MSE MEASUREMENTS BY RATIOMETRY

  • The combination of CXRS and beam emission spectroscopy5 is seen today as the sole path to obtain absolute ion densities(helium ash) on ITER.
  • A natural spin-off of BES on the DNB is to exploit the D-alpha spectrum and its amplitudes for magnetic diagnosis.
  • In fact, the complementary exploitation of the entire MSE polarization pattern will ultimately optimize signal accuracy and spatial resolution.
  • The pitch angleBp/Bt derived from the dipole intensity ratio of s andp group in MSE spectrum, which, in the case of statistical population, is determined by the angleq between direction of l.o.s. and Lorentz-vectorEL=v3B.
  • Is for the case of a simplified circular magnetic flux surface and the ITER CXRS top-port periscope.

IV. FIRST-MIRROR EXPERIMENTS ON TEXTOR

  • Metallic mirrors which are foreseen for ITER optical periscopes were recently investigated on TEXTOR.
  • The aim of the experiments was to investigate optical properties of plasma-facing mirrors in dependence on erosion, deposition, and particle implantation.
  • Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp.
  • The wavelength regime of measurements ranged from 250 to 2500 nm.
  • First experimental evaluations14 can be summarized as: (1) after plasma exposure the reflectivity was decreased by up to 35% in the deposition areas.

V. ACTIVE BEAM SPECTROSCOPY DATA ANALYSIS: CHEAP FOR ITER

  • A collateral activity to ongoing conceptual design and feasibility studies is dedicated to the development of suitable data analysis packages including spectral analysis and physics evaluation.
  • For ITER the concept of integrated data CX analysis implies a comprehensive diagnostic coverage of the main plasma ions(intrinsic and seeded impurities and bulk ions).
  • A new concept is to involve a full set of spectra representing, for example, a complete ion temperature profile and solve all spectra in one go.
  • Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp.

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Pilot experiments for the International Thermonuclear Experimental
Reactor active beam spectroscopy diagnostic
M. von Hellermann,
a)
M. de Bock, R. Jaspers, and K. Jakubowska
FOM-Institute for Plasma physics “Rijnhuizen,” Association EURATOM, Trilateral Euregio Cluster, 3430 BE
Nieuwegein, NL
R. Barnsley, C. Giroud, N. C. Hawkes, and K. D. Zastrow
UKAEA Culham Laboratory Euratom Association, Abingdon, United Kingdom
P. Lotte and R. Giannella
CEA Cadarache, Association Euratom, France
A. Malaquias
IAEA, Vienna, Austria
E. Rachlew
Euratom Association-VR, KTH Stockholm, Sweden
S. Tugarinov and A. Krasilnikov
TRINITI Troitsk, Russia
A. Litnovsky, V. Philipps, and P. Wienhold
Institute for Plasma Physics, FZ-Juelich, Euratom Association, 52425 Juelich, Germany
P. Oelhafen and G. De Temmerman
Institut für Physik, University of Basel, 4056 Basel, Switzerland
L. Shmaenok
Phystex, Vaals, NL and loffe Physical Technical Institute, St. Peterburg, Russia
(Presented on 19 April 2004; published 1 October 2004)
Supporting pilot experiments and activities which are currently considered or already performed for
the development of the International Thermonuclear Experiment Reactor active beam spectroscopy
diagnostic are addressed in this article. Four key issues are presented including optimization of
spectral instrumentation, feasibility of a motional Stark effect (MSE) evaluation based on line ratios,
“first-mirror” test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data
analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE
diagnostic. © 2004 American Institute of Physics. [DOI: 10.1063/1.1787950]
I. INTRODUCTION
A comprehensive package of active beam based spec-
troscopy tools for the International Thermonuclear Experi-
mental Reactor (ITER) has been developed and a final sum-
mary was recently completed.
1
The package encompasses
charge exchange recombination spectroscopy (CXRS)
2,3
for
the measurement of the main impurity ion densities (includ-
ing helium ash), ion temperature and torodial as well as po-
loidal plasma rotation. Quantitative use of beam emission
spectroscopy (BES)
4
based on comprehensive atomic model-
ing is proposed as an indispensable cross-calibration tool for
absolute local impurity density measurements
5
and monitor-
ing of the neutral beam power deposition profile. Finally, a
full exploitation of the motional Stark effect (MSE) pattern is
proposed to deduce local pitch angles, total magnetic fields
6,7
and radial electric fields. CXRS on slowing-down alphas as
demonstrated. on the Tokamak Fusion Test Reactor
8
is also
considered for the ITER DNB and HNB (100 keV/amu,
2.2 MW diagnostic neutral beam and 500 keV/amu, 17 MW
heating neutral beam respectively) and was discussed
recently.
2
More quantitative studies and modeling will be
required in this field. A similar diagnostic challenge refers to
the measurement of slowing-down beam ions as produced by
the HNB. Medium energy velocity distribution functions rep-
resenting slowing-down helium beam ions were observed at
the Joint European Tours (JET).
9
A number of issues have
been recognized over the last years which need to be ad-
dressed in advance of the next stage, the diagnostic “procure-
ment phase.” Four of those are addressed in this article.
(1) The optimization of spectral instruments and detectors
for the active beam spectroscopy diagnostic package
needs to be tested on existing fusion devices in order to
establish suitable combinations for high-resolution and
broadband applications. Moreover, multi-tasking recom-
mends practical maintainable instrumental solutions.
(2) A converging interest in motional Stark diagnostics,
beam emission spectroscopy, and charge exchange spec-
a)
Author to whom correspondence should be addressed; electronic mail:
mgvh@rijnh.nl
REVIEW OF SCIENTIFIC INSTRUMENTS VOLUME 75, NUMBER 10 OCTOBER 2004
0034-6748/2004/75(10)/3458/4/$22.00 3458 © 2004 American Institute of Physics
Downloaded 02 Jan 2007 to 134.94.122.39. Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp

troscopy has highlighted the needs for characterization
of the polarization transfer properties of optical
periscopes.
(3) A central issue is the survival and protection of the first
mirrors used in observation periscopes. The effects of
carbon and beryllium coatings on reflectivity and polar-
ization characteristics of metallic mirrors have been
modeled and presented at several meetings (e.g., Ref. 7).
First results describing erosion effects of monocrystal-
line molybdenum mirrors were reported recently.
10
(4) Finally, data evaluation procedures are closely linked to
feasibility studies and will ultimately decide on achiev-
able performances.
II. CXRS AND BES INSTRUMENTATION
Very early on it has been recognized that the substantial
attenuation of the diagnostic beam requires high-optical
throughput spectrometers in order to compensate for a low
CX signal in the presence of huge background of continuum
radiation. For the case of a modulated DNB the effective
signal to noise is then determined by the ratio of CX signal
and fluctuation of the background. A crucial criterion for the
acceptance of CXRS as a viable tool for ITER is the capa-
bility of measuring local helium ash densities in the plasma
core. At TRINITI a high-optical-throughput, high-resolution
spectrometer was developed especially for CXRS
application.
11
A unique combination of a large f-number
F/3,f =480 mm, and high linear dispersion value D
=0.250.3 nm/mm make it a particularly suited instrument
for the envisaged ITER CXRS system. The system’s etendue
A· =4 10
−1
mm
2
sr is preserved by the periscope fiber
bundle assembly, and a DNB slab of about 100 100 mm is
imaged for each radial channel onto the entrance slit 1
5mm of individual spectrometers. The role of the CXRS/
BES diagnostic as a multi-tasking requires the simultaneous
measurement of the main ion species: helium ash at 468 nm,
intrinsic impurities C and Ne at 529 nm, and bulk D and T
ions at 650 nm (cf. Fig. 1). The proposed scheme is to make
use of color filters and different orders of the TRINITI ech-
elle grating instruments for different representative wave-
lengths. Pilot experiments are required addressing achievable
sensitivities, stray-light suppression, and color control. A
critical issue will also be the spectral purity of the underlying
continuum radiation and its quantum noise photon statistics
in order to verify predicted spectral signal-to-noise reactor
(SNR) values (cf Ref. 1). The detection of nonthermal broad-
band features depends critically on clear distinction of CX
induced features and passive background.
III. MSE MEASUREMENTS BY RATIOMETRY
The combination of CXRS and beam emission
spectroscopy
5
is seen today as the sole path to obtain abso-
lute ion densities (helium ash) on ITER. BES refers here
explicitly to a quantitative exploitation of measured and
modeled line intensities and wavelength separations and not
to the measurement of plasma fluctuations. A natural spin-off
of BES on the DNB is to exploit the D-alpha spectrum and
its amplitudes for magnetic diagnosis. This will be comple-
mentary to MSE polarimetry on the HNB.
6,12,13
In fact, the
complementary exploitation of the entire MSE polarization
pattern will ultimately optimize signal accuracy and spatial
resolution. Whereas the viewing geometry of the HNB MSE
periscopes is optimized for a maximum sensitivity to a rota-
tion of the polarization pattern, the DNB periscopes will only
be sensitive to changes of the angle between Lorentz-field
vector and viewing line. For the ITER magnetic field B
t
=5.2 T, and a DNB energy of 100 keV/amu, the MSE com-
ponents (6
and 3
components, respectively) will be well
separated and the SNR compared to the background
fluctuation level (assuming photon statistics of continuum
radiation) should be in excess of 50 (see also Refs. 1 and 2).
The pitch angle B
p
/B
t
derived from the dipole intensity
ratio of
and
group in MSE spectrum, which, in the case
of statistical population, is determined by the angle
be-
tween direction of l.o.s. and Lorentz-vector E
L
=
v
B
I
I
=
sin
2
1 + cos
2
.
Maximum sensitivity for observation angles
close to 45°.
For the ITER CXRS top-port periscope the angle
on axis
B
p
=0 is 32.6°. Figure 2 shows q values derived from ratio
I
/I
for the case of a simplified circular magnetic flux sur-
face and the ITER CXRS top-port periscope. In contrast to
polarimetry, no active or passive polarizing element is in-
volved in ratiometry. However, a key issue will be isotropic
reflection factors ensuring the preservation of I
/I
for the
entire observation system including multiple mirrors in the
periscope, the fiber link, and finally in the spectrometer it-
self. A MSE ratiometry pilot experiment is presently imple-
mented on TEXTOR in ITER-like geometry.
IV. FIRST-MIRROR EXPERIMENTS ON TEXTOR
Metallic mirrors which are foreseen for ITER optical
periscopes were recently investigated on TEXTOR. The aim
of the experiments was to investigate optical properties of
plasma-facing mirrors in dependence on erosion, deposition,
and particle implantation.
FIG. 1. Schematic layout of CXRS/
BES/MSE spectroscopic instrumenta-
tion. Multi-tasking of periscopes for
simultaneous evaluation of CXRS
(impurity and bulk ions), BES on
injected neutrals and finally for MSE
ratiometry.
Rev. Sci. Instrum., Vol. 75, No. 10, October 2004 Plasma diagnostics 3459
Downloaded 02 Jan 2007 to 134.94.122.39. Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp

Large polycrystalline metal mirrors (molybdenum and
tungsten) on inclined target holders were exposed in the
scrape-off layer (SOL) plasma of TEXTOR in both erosion
and deposition-dominated zones. The accumulated plasma
exposure time of mirrors was about 900 s. Particle energies
and particle affluence were of the same order of magnitude
as those expected for ITER. Figure 3 shows a schematic
layout of the mirror test and one sample exposed in the
deposition-dominated zone. The reflectivity was measured
before and after exposure in the SOL. The wavelength re-
gime of measurements ranged from 250 to 2500 nm. First
experimental evaluations
14
can be summarized as:
(1) after plasma exposure the reflectivity was decreased by
up to 35% in the deposition areas. The reflectivity was
increased by 12% in the plasma near zones (erosion
zones);
(2) fringes due to constructive and destructive interference
are observed if /4 corresponds to the optical thickness
of a deposited film;
(3) the degradation of reflectivity of the exposed mirror
samples is likely due to film growth observed on the
mirror surface; and
(4) the increase of reflectivity of mirrors noticed on some
areas is possibly due to annealing effects during the tem-
perature excursions and/or cleaning by plasma ions.
V. ACTIVE BEAM SPECTROSCOPY DATA ANALYSIS:
CHEAP FOR ITER
A collateral activity to ongoing conceptual design and
feasibility studies is dedicated to the development of suitable
data analysis packages including spectral analysis and phys-
ics evaluation. At JET the self-consistent CX evaluation
package CHEAP (charge exchange analysis package) is
used routinely and is potentially applicable in inter-shot
performance.
The CHEAP concept is based on a comprehensive
atomic modeling
15
of all emission processes (beam emission,
active and passive charge exchange recombination) making
use of a full set of data for the plasma environment. An
essential first step is the introduction of a common mapping
grid for all physical parameters. This strategy has enabled us
to treat the beam-plasma interaction (i.e., beam stopping and
beam emission processes) in a consistent fashion. Multiple
step processes and contributions from excited states are taken
into account. For ITER the concept of integrated data CX
analysis implies a comprehensive diagnostic coverage of the
main plasma ions (intrinsic and seeded impurities and bulk
ions). From this point of view, the issue of CX measurement
of helium ash densities on ITER is inseparable from a simul-
taneous measurement of all ions. Moreover, the issue of a
density measurement is linked directly to a measurement of
ion temperature and plasma rotation.
Highlights of future activities in this field are listed
below:
(1) Super Fit: The present strategy of spectral analysis is
usually based on a step-by-step process addressing each
spectrum individually. A new concept is to involve a full
set of spectra representing, for example, a complete ion
temperature profile and solve all spectra in one go.
(2) Integrated Data Analysis: From a similar point of view, a
spectral analysis is ultimately to be seen as part of a
global data consistency strategy. Ion temperature and
density lead to ion pressure and combined with electron
pressure to a match of kinetic and diamagnetic energy
which can be used as a constraint on spectral analysis.
(3) The stochastic occurrence of plasma edge line emission,
e.g., edge localized modes ELMs is a potential hazard to
a perfect background suppression scheme using beam
modulation. In this case, complex spectra will have to be
evaluated requiring advanced atomic modeling and suit-
able extraction tools.
1
M. von Hellermann, “Active Charge Exchange Spectroscopy (CXRS) and
Beam Emission Spectroscopy BES+MSE with Diagnostic Neutral
Beam (DNB) (under EFDA contract; not publicly available, contact:
mgvh@rijnh.nl)
2
M. von Hellermann, C. Giroud, N. C. Hawkes, R. Jaspers, A. Krasilnikov,
P. Lotte, G. McKee, A. Malaquias, M. O’. Mullane, E. Rachlew, S.
FIG. 2. Safety factor q as derived from MSE intensity ratio for different
minor radii and ITER top-portconfiguration. Note, a simplified case off cir-
cular flux geometry has been assumed for illustration purposes.
FIG. 3. (Color) Large polycrystalline metal mirrors (molybdenum and tung-
sten) on inclined target holders were exposed in the SOL plasma of TEX-
TOR in both erosion and deposition-dominated zones.
3460 Rev. Sci. Instrum., Vol. 75, No. 10, October 2004 von Hellermann
et al.
Downloaded 02 Jan 2007 to 134.94.122.39. Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp

Tugarinov, and K.-D. Zastrow, 30th EPS Conf. Contr. Fus. Pl. Phys., St.
Petersburg, 2003, ECA Vol. 27A, O-4.2D.
3
A. Malaquias, A. Costley, A. Gorshkov, N. Hawkes, M. v. Hellermann,
M. Kuldkepp, P. Lotte, E. Rachlew, S. Tugarinov, G. Vayakis, and C.
Walker, 15th Topical Conference on High Temperature Plasma Diagnos-
tics, San Diego, 19 April 2004.
4
W. Mandl, R. Wolf, M. von Hellermann, and H. P. Summers, Plasma Phys.
Controlled Fusion 35, 1373 (1993).
5
M. von Hellermann, R. Jaspers, H. P. Summers, and K-D. Zastrow, Ad-
vanced Diagnostics for Magnetic and Inertial Fusion, edited by P. E.
Stott, A. Wootton, G. Gorini, E. Sindoni, and D. Batani (Plenum, New
York, 2001),p.205.
6
P. Lotte, M. Von Hellermann, A. Malaquias, R. Giannella, N. Hawkes, E.
Rachlew, R. Jaspers, P. Nielsen, S. Tugarinov, and C. Walker, in Ref. 2,
P1–183.
7
A. Malaquias, M. von Hellermann, P. Lotte, S. Tugarinov, and V. Voit-
senya, in Ref.2 .
8
G. McKee, R. J. Fonck, B. Stratton, R. Budny, Z. Chang, and A. Ramsey,
Nucl. Fusion 37, 501 (1997).
9
M. von Hellermann, W. G. F. Core, J. Frieling, L. D. Horton, R. W. T.
König, W. Mandl, and H. P. Summers, Plasma Phys. Controlled Fusion
35, 799 (1993).
10
K. Vukolov and V. Voitsenya, Sixth ITPA Topical Group Meeting on ITER
Diagnostics, Part I, Naka, Japan, February 2004.
11
S. Tugarinov, A. Krasilnikov, V. Dokouka, R. Khayrutidinov, I. Beigman,
I. Tolstikhina, L. Vainshtein, M. von Hellermann, and A. Malquias, Rev.
Sci. Instrum. 74, 2075 (2003).
12
N. C. Hawkes, A. Malaquias, P. Lotte, M. von Hellermann, M. Brix, R.
Giannella, M. Kuldkepp, E. Rachlew, C. Negus, and E. Surrey, Fifth ITPA
Topical Group Meeting on ITER Diagnostics, St. Petersburg, Russia, 16
July 2003.
13
F. Levinton, R. Fonck, G. Gammel, R. Kaita, H. Kugel, E. Powell, and D.
Roberts, Phys. Rev. Lett. 63, 2060 (1989).
14
P. Wienhold, A. Litnovsky, V. Philipps, P. Oelhafen, G. De Temmerman,
W. Schneider, and B. Emmoth. (unpublished).
15
http://adas.phys.strath.ac.uk..
Rev. Sci. Instrum., Vol. 75, No. 10, October 2004 Plasma diagnostics 3461
Downloaded 02 Jan 2007 to 134.94.122.39. Redistribution subject to AIP license or copyright, see http://rsi.aip.org/rsi/copyright.jsp
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Abstract: 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. a Author to whom any correspondence should be addressed.

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Cites background from "Pilot experiments for the Internati..."

  • ...Large polycrystalline metal mirrors of Mo and W have been exposed in the SOL plasma of TEXTOR mounted on inclined target holders [269]....

    [...]

  • ...Experiments have shown that thin films (10 nm) of C-H or Be can strongly modify the reflectance of mirrors as well as its polarization characteristics [268, 269]....

    [...]


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Abstract: We describe a version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of Stark split D(alpha) emission from the neutral beams. This system, named B-Stark, has been recently installed on the DIII-D tokamak. To find the magnetic pitch angle, we use the ratio of the intensities of the pi(3) and sigma(1) lines. These lines originate from the same upper level and so are not dependent on the level populations. In future devices, such as ITER, this technique may have advantages over diagnostics based on MSE polarimetry. We have done an optimization of the viewing direction for the available ports on DIII-D to choose the installation location. With this placement, we have a near optimal viewing angle of 59.6 degrees from the vertical direction. All hardware has been installed for one chord, and we have been routinely taking data since January 2007. We fit the spectra using a simple Stark model in which the upper level populations of the D(alpha) transition are treated as free variables. The magnitude and direction of the magnetic field obtained using this diagnostic technique compare well with measurements from MSE polarimetry and EFIT.

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TL;DR: A version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of Stark split D(alpha) emission from the neutral beams, recently installed on the DIII-D tokamak.
Abstract: We describe a version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of Stark split Dα emission from the neutral beams. This system, named B-Stark, has been recently installed on the DIII-D tokamak. To find the magnetic pitch angle, we use the ratio of the intensities of the π3 and σ1 lines. These lines originate from the same upper level and so are not dependent on the level populations. In future devices, such as ITER, this technique may have advantages over diagnostics based on MSE polarimetry. We have done an optimization of the viewing direction for the available ports on DIII-D to choose the installation location. With this placement, we have a near optimal viewing angle of 59.6° from the vertical direction. All hardware has been installed for one chord, and we have been routinely taking data since January 2007. We fit the spectra using a simple Stark model in which the upper level populations of the Dα transition are treated as free variables. The magnitude and direction of the magnetic field obtained using this diagnostic technique compare well with measurements from MSE polarimetry and EFIT.

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TL;DR: Polarimetry measurements of the Doppler-shifted H{sub {alpha}} emission from a neutral hydrogen beam on the PBX-M tokamak have been employed in a novel technique for obtaining {ital q}({ital r}) and magnetic field pitch-angle profiles using the Stark effect.
Abstract: Polarimetry measurements of the Doppler-shifted H{sub {alpha}} emission from a neutral hydrogen beam on the PBX-M tokamak have been employed in a novel technique for obtaining {ital q}({ital r}) and magnetic field pitch-angle profiles using the Stark effect. The resulting {ital q}({ital r}) profile is very broad and its central value, {ital q}(0), is significantly below 1, which has important implications for theoretical models of sawteeth.

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Abstract: This book is a collection of papers, written by specialists in the field, on advanced topics of nuclear fusion diagnostics. The 78 contributions were originally presented at the International Conference on Advanced Diagnostics for Magnetic and Inertial Fusion held at Villa Monastero, Italy in September 2001. Both magnetically confined and inertial fusion programmes are quite extensively covered, with more emphasis given to the former scheme. In the case of magnetic confinement, since the present international programme is strongly focused on next-step devices, particular attention is devoted to techniques and technologies viable in an environment with strong neutron fluxes. Indeed, in the first section, the various methods are considered in the perspective of performing the measurements of the relevant parameters in conditions approaching a burning plasma, mainly in the Tokamak configuration. The most demanding requirements, like the implications of the use of tritium and radiation resistance, are reviewed and the most challenging open issues, which require further research and development, are also clearly mentioned. The following three sections are devoted to some of the most recent developments in plasma diagnostics, which are grouped according to the following classification: `Neutron and particle diagnostics', `Optical and x-ray diagnostics' and `Interferometry, Polarimetry and Thomson Scattering'. In these chapters, several of the most recent results are given, covering measurements taken on the most advanced experiments around the world. Here the developments described deal more with the requirements imposed by the physical issues to be studied. They are therefore more focused on the approaches adopted to increase the spatial and time resolution of the diagnostics, on some methods to improve the characterisation of the turbulence and on fast particles. Good coverage is given to neutron diagnostics, which are assuming increasing relevance as the plasma parameters approach ignition. Spectroscopic systems and their recent developments are well represented, whereas edge diagnostics are somewhat thin on the ground. A dedicated section is devoted to the latest tests on radiation effects and technological issues. The problems of damage to optical components and the difficulties presented by the determination of the tritium inventory are described. In the last part, the new diagnostic systems of the most recent experiments (under construction or recently operated) are reported. Various aspects of some diagnostics not included in the three previous sections are also covered, with particular emphasis on microwaves and infrared diagnostics. The book is well suited for specialists and, more generally, for people involved in nuclear fusion, who need information about the most recent developments in the field of plasma diagnostics. The papers cover many aspects of the challenges and possible solutions for performing measurements in fusion machines approaching reactor conditions. On the other hand, the contributions are in general quite advanced and would be challenging for people without a significant background in plasma diagnostics and nuclear fusion. The quality of the paper is more than satisfactory both from the point of view of clarity and of graphics. Moreover, at the beginning of the book, several papers make a considerable effort to put diagnostic issues in the wider context of present day nuclear fusion research. For those topics, which are too involved to be completely described in a conference contribution, in general adequate references are provided for deeper investigation. A Murari Approximately one third of the papers included in this volume deal with diagnostics related to inertial confinement fusion plasmas (i.e., laser-produced plasmas and pulsed-power). These papers discuss recent developments in charged particle diagnostics, neutron diagnostics, optical and x-ray measurements along with laser and particle probing diagnostics. The resulting collection of papers is comprehensive and wide-ranging and all of the major laboratories in Europe, the US, and Japan are represented. There is important discussion on the development of diagnostics for the National Ignition Facility, LMJ, and future ultra-high intensity laser experiments as well as papers on wire array z-pinch experiments. It is especially useful to have the contributions from inertial confinement fusion experiments intermingled with those from magnetic confinement fusion. The separation between these two approaches to fusion is often unfortunately large, so one of the pleasing things about this book is that it is very easy for readers familiar with experimental research in one area to compare `state of the art' plasma diagnostics in the other area. Hopefully this will facilitate the development of new ideas in both areas. This book is a conference proceedings and as such, almost all of the papers included are quite brief and are highly technical. Consequently, the book is not particularly pedagogical and would be most useful to researchers already working in this area of physics. For these readers, however, Advanced Diagnostics for Magnetic and Inertial Confinement Fusion is an excellent overview of the present status of fusion plasma diagnostics. K Krushelnick

65 citations


Journal ArticleDOI
Abstract: The first experimental results are reported of anisotropic slowing-down features observed in JET helium beam fuelling experiments. Two independent observation ports, one with a view perpendicular to the magnetic field in the centre of the plasma and a second multichord viewing arrangement, approximately tangential to the toroidal field, provide radially and temporally resolved information on the velocity distribution function comprising the populations of both fast and thermalized alpha particles. The fuelling process is characterized by a change-over from a distinctly non-Maxwellian distribution function to a dominantly Maxwellian distribution and also by a broadening of the deduced fast ion density radial profile. The fast particle component in the observed composite charge exchange spectrum is found to be in excellent agreement with predictions are based on anisotropic velocity distribution functions obtained from the analytical solution of the neutral injection Fokker-Planck equation. Signal-to-noise levels in the measurement of fast alpha particle in the JET helium fuelling campaign are extrapolated to thermonuclear-fusion alpha particle density levels expected for the D-T phase of JET. It is shown that beam penetration and not competing continuum radiation is a major constraint, and that acceptable (hydrogen or helium) neutral beam power and energy requirements promise a feasible CX alpha particle diagnosis in the core of next-step devices such as ITER.

56 citations


Journal ArticleDOI
Abstract: Fusion produced non-thermal alpha particle radial profile measurements are obtained with the α-CHERS diagnostic in deuterium-tritium (DT) supershot plasmas on the Tokamak Fusion Test Reactor (TFTR). Alpha particles in the energy range 0.15 ≤ Eα ≤ 0.6 MeV are observed spectroscopically over a five point radial profile. The extracted non-thermal alpha signal is ≤ 1% of the background bremsstrahlung intensity for typical total fast alpha densities in the range (0.5-1.0) × 1017 m-3. The profiles obtained in two sets of discharges vary slightly, and are best described by a slowing down alpha distribution subject to neoclassical diffusion plus a small anomalous cross-field diffusion. The data are consistent with an effective anomalous diffusion coefficient in the range 0.00 ≤ Dα,a ≤ 0.10 m2/s, where Dα ,a is constant with alpha energy and with radius

23 citations


Frequently Asked Questions (1)
Q1. What contributions have the authors mentioned in the paper "Pilot experiments for the international thermonuclear experimental reactor active beam spectroscopy diagnostic" ?

Supporting pilot experiments and activities which are currently considered or already performed for the development of the International Thermonuclear Experiment Reactor active beam spectroscopy diagnostic are addressed in this article.