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Jan 2001

Volume 72, Issue 1, pp. 1-1261

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Diagnostic first mirrors for burning plasma experiments (invited)

V. Voitsenya, A. E. Costley, V. Bandourko, A. Bardamid, V. Bondarenko, Y. Hirooka, S. Kasai, N. Klassen, V. Konovalov, M. Nagatsu, K. Nakamura, D. Orlinskij, F. Orsitto, L. Poperenko, S. Solodovchenko, et al.

Rev. Sci. Instrum. 72, 475 (2001); http://dx.doi.org/10.1063/1.1310580 (8 pages) | Cited 53 times

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The current state of investigations of the problem of providing first mirrors (FMs) for diagnostic systems in a reactor-grade fusion device is summarized. Results obtained in simulation experiments that have been conducted during recent years in several laboratories are presented. Attention is concentrated on two processes that can have an opposite effect but both can lead to degradation of mirror optical properties, namely: sputtering by charge exchange atoms which leads to erosion, and deposition which leads to surface contamination. It is shown in the analysis that when sputtering dominates, mirrors of monocrystalline refractory metals (Mo, W) can have a sufficiently long lifetime even for FMs that have to be located close to the first wall. Similarly, films of low sputtering yield metals on high thermal conductivity substrates (e.g., Rh on Cu) can be used for FMs in locations where the charge exchange flux is reduced to about a tenth of that at the first wall. However, deposition poses a serious threat to the lifetime of FMs but more modeling and experimental investigations are necessary before quantitative conclusions can be reached. Some mitigation methods are possible and these are briefly discussed. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.79.Bh Lenses, prisms and mirrors
28.52.Lf Components and instrumentation
52.55.Fa Tokamaks, spherical tokamaks

Overview of large helical device diagnostics (invited)

S. Sudo, Y. Nagayama, M. Emoto, M. Goto, Y. Hamada, K. Ida, T. Ido, H. Iguchi, S. Inagaki, M. Isobe, K. Kawahata, K. Khlopenkov, S. Masuzaki, T. Minami, S. Morita, et al.

Rev. Sci. Instrum. 72, 483 (2001); http://dx.doi.org/10.1063/1.1310581 (9 pages) | Cited 8 times

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The Large Helical Device (LHD) is the largest helical machine with superconducting coils. Key diagnostics issues for LHD are: (a) capability for multidimensional measurements because of the nonaxisymmetric toroidal plasma; (b) measurements of the electric field; (c) cross check of fundamental parameters using different methods; (d) advanced measurements appropriate for steady-state operation; and (e) a satisfactory data acquisition system. The design and research and development of plasma diagnostics were carried out taking these issues into consideration. As a result, the present status of diagnostics is described: diagnostics for LHD operation, fundamental diagnostics for plasma performance, diagnostics for physics subjects, innovative diagnostics and diagnostics for long-pulse operation. The LHD experiment started in March, 1998. Since then, the development of diagnostics has kept pace with the experimental campaigns. © 2001 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Jd Magnetic mirrors, gas dynamic traps
01.30.Rr Surveys and tutorial papers; resource letters

Target area and diagnostic interface issues on the National Ignition Facility (invited)

Perry Bell, Dean Lee, Alan Wootton, Bill Mascio, Joe Kimbrough, Noel Sewall, Wilthea Hibbard, Pat Dohoney, Mark Landon, George Christianson, John Celeste, and Jerry Chael

Rev. Sci. Instrum. 72, 492 (2001); http://dx.doi.org/10.1063/1.1310582 (7 pages) | Cited 2 times

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The National Ignition Facility (NIF) is under construction at Lawrence Livermore National Laboratory for the DOE Stockpile Stewardship Program. It will be used for experiments for inertial confinement fusion ignition, high energy density science, and basic science. Many interface issues confront the experimentalist who wishes to design, fabricate, and install diagnostics, and to help this process, a set of standards and guideline documents is being prepared. Compliance with these will be part of a formal diagnostic design review process. In this article we provide a short description of each, with reference to more complete documentation. The complete documentation will also be available through the NIF Diagnostics web page. Target area interface issues are grouped into three categories. First are the layout and utility interface issues which include the safety analysis report, target area facility layout; target chamber port locations; diagnostic interferences and envelopes; utilities and cable tray distribution; and timing and fiducial systems. Second are the environment interface issues which include radiation electromagnetic interference/electromagnetic pulse effects and mitigation; electrical grounding, shielding, and isolation; and cleanliness and vacuum guidelines. Third are the operational interface issues which include manipulator based target diagnostics, diagnostic alignment, shot life cycle and setup, diagnostic controllers; integrated computer control system; shot data archival; classified operations; and remote operations. © 2001 American Institute of Physics.
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28.52.Cx Fueling, heating and ignition
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.57.-z Laser inertial confinement
52.70.-m Plasma diagnostic techniques and instrumentation
28.52.Nh Safety

Singular spectrum analysis as a tool for plasma fluctuations analysis

L. Marrelli, R. Bilato, P. Franz, P. Martin, A. Murari, and M. O’Gorman

Rev. Sci. Instrum. 72, 499 (2001); http://dx.doi.org/10.1063/1.1323250 (4 pages) | Cited 4 times

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We describe the application of the singular spectrum analysis (SSA), an advanced adaptive statistical technique, to denoise experimental signals and to remove trends in order to isolate the relevant fluctuating components. We illustrate a fast denoising algorithm and show its performances relatively to synthetic and experimental signals of the soft x-ray (SXR) spectrometer and the polarimeter installed in the reversed field experiment (RFX) device. As a further application, we report a first estimate of the electron temperature fluctuations in the core of the RFX experiment. They have been performed with a multifilter SXR spectrometer and applying SSA for the first time in plasma physics the singular spectrum analysis. We find that temperature fluctuations are typically not larger than a few percent and are well correlated with magnetic fluctuations. © 2001 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Gj Fluctuation and chaos phenomena
02.70.Hm Spectral methods
52.55.Ez Theta pinch
84.40.Ua Telecommunications: signal transmission and processing; communication satellites

Application of the continuous wavelet transform to the fluctuations and electric field analysis in the H-1 heliac

X. Shi, J. Boman, and M. G. Shats

Rev. Sci. Instrum. 72, 503 (2001); http://dx.doi.org/10.1063/1.1310583 (3 pages) | Cited 3 times

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We apply the continuous wavelet transform (CWT) and a CWT spectral technique to the analysis of the time-resolved fluctuation-driven particle flux in the H-1 heliac. The results confirm that in some cases the outward radial flux reverses its direction. In addition, time-resolved frequency spectra of fluctuation signals obtained by CWT show that the dominant frequency component as a function of time closely follows changes in the radial electric field. This suggests that the VE×B drift velocity dominates the poloidal phase velocity of the fluctuations in the laboratory frame, in which case the time-resolved frequency can be used to characterize the radial electric field. © 2001 American Institute of Physics.
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52.70.Nc Particle measurements
52.70.Ds Electric and magnetic measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Gj Fluctuation and chaos phenomena

Observations of radial wild cables in tokamak plasmas (abstract)

A. B. Kukushkin and V. A. Rantsev-Kartinov

Rev. Sci. Instrum. 72, 506 (2001); http://dx.doi.org/10.1063/1.1323474 (1 page) | Cited 1 time

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The results of processing the plasma images with the help of the method of multilevel dynamical contrasting (MDC)1 are presented. The images are taken in visible light, with space resolution ∼100 μm and time resolution ∼10 μs, in various tokamaks (TM-2, T-4, T-6, and T-10). The presence of rigid-body filamentary structures is found. They are similar to those structures formerly found in a Z-pinch, whose long life was proven2 in tracing their dynamics. The reliability of results is supported by the rich statistics and considerable similarity of the structures in various facilities and regimes, as well as by the insensitivity of observed structuring to a specific way of imaging (strick camera, fast photography, etc.). Sometimes the structuring may be seen without MDC processing (in such cases, the MDC allows fine resolution of structuring). The most typical structure is a straight cylindrical block varying in length from few centimeters up to a diameter of plasma column. The diameter of such a block varies, respectively, from a few millimeters to several centimeters. The most attention is paid to radially directed filaments which, together with toroidal and poloidal filaments, form a network. Detailed analysis of individual cylindrical blocks of several centimeters in diameter revealed them to be a coaxial tubular structure with an inner rod (which may be of tubular form as well) of a few millimeters diameter. The similarity of the above structures to coaxial cables may appear to not be occasional: according to the hypothesis3 the elementary coaxial block of diameter not exceeding few millimeters, is a “wild cable” in which the propagating high-frequency (HF) electromagnetic wave produces a vacuum channel around the hypothetical microsolid skeleton2 and thus protects the skeleton from the ambient high-temperature plasma. An analysis of measurements of HF electric fields, both inside and outside the plasma column in tokamak T-10, reveals their reasonable agreement with predictions based on the hypothesis.3 © 2001 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Observations of radial wild cables in z-pinch plasma (abstract)

A. B. Kukushkin and V. A. Rantsev-Kartinov

Rev. Sci. Instrum. 72, 507 (2001); http://dx.doi.org/10.1063/1.1323475 (1 page)

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The results of processing the z-pinch plasma images with the help of the method of multilevel dynamical contrasting (MDC)1(a),1(b) are presented. This method was earlier used for: (i) analyzing the filaments (and their networks) in a gaseous z-pinch1(a),1(c) and (ii) characterization of long-living filaments2 of the lifetime comparable with the entire duration of discharge. The original images were taken in visible light, with space resolution ∼100 μm and time resolution ∼2–60 ns. The long-life structures are found, which are assembled from straight cylindrical blocks varying in length from a few millimeters to a few centimeters. Such blocks are of various orientation in space, and often they form a common frame. The most important phenomenon is the presence of radial (with respect to z-pinch axis) filaments directed from the periphery to the core, up to the z-pinch axis. An analysis of the fine structure of the above cylindrical blocks of few millimeter diameter reveals them to be a coaxial structure with the diameter of an inner rod (which may be of tubular form) approximately smaller by an order of magnitude. A comparison is made with similar structures recently observed in tokamak plasmas.3(a) The reliability of the above results is supported by the rich statistics and considerable similarity of the structuring in various regimes, and insensitivity to specific way of imaging. Sometimes the structuring may be seen without MDC processing (in such cases, the MDC allow fine resolution of structuring). The experimental results are analyzed from the viewpoint of the hypothesis3 about “wild cables” in plasmas of high-current electric discharges. The correlation is found between the measured values of the high-frequency electric fields in z-pinch plasma and the values of the Miller force needed to sustain vacuum channels in the plasma which are the essential elements of the wild cable © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Ez Theta pinch
52.80.Vp Discharge in vacuum

Multiparameter data acquisition system for spectroscopy

P. Beiersdorfer, G. V. Brown, L. Hildebrandt, K. L. Wong, and R. Ali

Rev. Sci. Instrum. 72, 508 (2001); http://dx.doi.org/10.1063/1.1310584 (5 pages) | Cited 13 times

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A powerful and versatile, simple to use multiparameter data acquisition system has been implemented for use in spectroscopy. In its standard configuration, the system can acquire signal from 16 time-to-digital converter channels, 16 analog-to-digital converter channels, and 12 scaler inputs. The system was put to use on the electron beam ion trap experiment to record the output from four position-sensitive proportional counters in two soft x-ray spectrometers together with the signal from an x-ray pulse height analyzer. Also recorded are the electron beam energy and the pulse height distribution of the proportional counters. All data are recorded as a function of time. Because the relevant parameters are recorded simultaneously, software gates instead of hardware gates are used to select the data of interest. This has led to a substantial cost saving over earlier data acquisition systems. Data are stored in binary or in ascii format for system-independent processing. The operation of the system is demonstrated in a measurement of the M-shell soft x-ray spectrum of gold. We used the system to record the 3–4 and 3–5 transitions of gold (Au44+–Au51+) excited with a simulated Maxwellian with electron temperature of 2.5 keV. © 2001 American Institute of Physics.
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29.30.Kv X- and γ-ray spectroscopy
07.05.Hd Data acquisition: hardware and software
07.85.Nc X-ray and γ-ray spectrometers

Newly developed double neural network concept for reliable fast plasma position control

Young-Mu Jeon, Yong-Su Na, Myung-Rak Kim, and Y. S. Hwang

Rev. Sci. Instrum. 72, 513 (2001); http://dx.doi.org/10.1063/1.1323251 (4 pages) | Cited 4 times

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Neural network is considered as a parameter estimation tool in plasma controls for next generation tokamak such as ITER. The neural network has been reported to be so accurate and fast for plasma equilibrium identification that it may be applied to the control of complex tokamak plasmas. For this application, the reliability of the conventional neural network needs to be improved. In this study, a new idea of double neural network is developed to achieve this. The new idea has been applied to simple plasma position identification of KSTAR tokamak for feasibility test. Characteristics of the concept show higher reliability and fault tolerance even in severe faulty conditions, which may make neural network applicable to plasma control reliably and widely in future tokamaks. © 2001 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.-m Plasma diagnostic techniques and instrumentation
07.05.Mh Neural networks, fuzzy logic, artificial intelligence

Mass data acquisition systems in JT-60 data processing system

T. Oshima, T. Matsuda, T. Tsugita, S. Sakata, M. Sato, and M. Koiwa

Rev. Sci. Instrum. 72, 517 (2001); http://dx.doi.org/10.1063/1.1319866 (3 pages)

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In the data processing system for the JT-60 tokamak, a unique mass data acquisition system with fast sampling, a transient mass data storage system (TMDS), has been used since 1988. It is composed of a minicomputer and 61 channels of 4/6 MB memory modules with a sampling rate up to 200 kHz and about 300 MB of data are transferred to a main computer by using a special LAN developed by Fujitsu Ltd. TMDS can handle a large amount of data, but cannot be enlarged in its capability, such as CPU power or the number of channels. To solve the problems of TMDS, a new fast VME data acquisition system (FDS), has been developed. It can acquire 6 MB of data per channel with a sampling rate of 200 kHz or 1 MHz and consists of a workstation with VMEbus memory modules. Up to now there are three FDSs with 24 channels. The minicomputer of TMDS has been replaced with a new system based on the technology of FDS. To cope with mass data transfer to a data server, they are connected with a gigabit ethernet switch. © 2001 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Fa Tokamaks, spherical tokamaks
07.05.Hd Data acquisition: hardware and software
07.05.Wr Computer interfaces

4 K charge coupled device: A universal approach to diagnostic readout for the National Ignition Facility (abstract)

Noel Sewall, Darron Nielsen, James Moody, and Michel Vitalich

Rev. Sci. Instrum. 72, 520 (2001); http://dx.doi.org/10.1063/1.1323476 (1 page)

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This article describes an approach for data acquisition and retrieval to be used on several key diagnostics for experimental support on the National Ignition Facility. The major feature is a direct replacement for film with a large format, scientific grade charge coupled device (CCD) imager requiring minimum space in the diagnostic environment. Additionally, the system provides rapid data acquisition without film developing or digitizing time, equivalent or better resolution than film (9 μm pixel spacing), and compatibility with our existing diagnostic front ends. The CCD camera has been shown to provide very good linearity and signal to noise. Features of this camera include a modular design approach from the clocking state machine through the digitizer/data buffer including diagnostic controller software. Changing the imaging device will require only a change in the clock state machine and the pointers in the internal data buffer storage. Also the camera will provide digital output for transmission on a fiber optic line to provide better noise immunity and resistance to electromagnetic pulse. Results of the 4 K×4 K imaging front end used on laser experiments at the LLE Omega facility will be presented. © 2001 American Institute of Physics.
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28.52.Cx Fueling, heating and ignition
28.52.Lf Components and instrumentation
85.60.Gz Photodetectors (including infrared and CCD detectors)

Effect of film development on uniformity and modulation transfer function of the gated/fast x-ray imagers data

George A. Kyrala, Gottfried T. Schappert, and Scott C. Evans

Rev. Sci. Instrum. 72, 521 (2001); http://dx.doi.org/10.1063/1.1310585 (4 pages)

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We have been investigating the different phenomena that affect the modulation transfer function response of the gated x-ray imagers and fast x-ray imagers that we use to record subnanosecond x-ray images at different laser facilities. As part of that investigation, we noticed that there is definite nonuniformity to the recorded images, even when the incident radiation was uniform. After a significant effort to track down that effect we found that the automatic developing processors, which process the film along the length of the roll, cause the effect. Manual development, which depends primarily on transverse agitation in the developer, and automatic processors that do not use a feed mechanism but emulate this agitation, do not introduce such artifacts. We recommend that for absolutely critical missions, such as target symmetry measurements, certain automatic machines should not be used.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
42.79.Ls Scanners, image intensifiers, and image converters
52.70.La X-ray and γ-ray measurements

Accessing TJ-II data with remote procedure call

E. Sánchez, J. Vega, C. Crémy, and A. B. Portas

Rev. Sci. Instrum. 72, 525 (2001); http://dx.doi.org/10.1063/1.1316757 (5 pages) | Cited 2 times

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A new software, based on the de facto standard Open Network Computing Remote Procedure Call (ONC RPC) has been developed for TJ-II database access. This software solution replaces a previous development based on Berkeley sockets in which the client implementation had the drawback that was platform dependent. From the user point of view, the access to the TJ-II database can be done from codes running in the central server or from any other computer in the network in exactly the same way. From the development point of view, the ONC RPC tools allow to generate source code for the clients in an easy and flexible manner, thus reducing the work needed to maintain/upgrade the library for different platforms. The access to the database is managed by a concurrent server program, running on the central server, which implements each access routine as a service on the network. This allows controlling the accesses to the database. A client library has been developed to provide connection with the data server. This library implements a client routine per service, that interchanges parameters between client and server programs using External Data Representation. The client library has been installed in different UNIX and UNIX-like platforms, including ALPHA AXP/Digital UNIX, Sparc/SOLARIUS, INTEL/LINUX and CRAY/UNICOS and in Windows (NT/95/98) platforms. The support for Windows platforms allows autonomous PC-based acquisition systems to integrate experimental data into the data base. A basic in-house developed identification system is used to control client connections. An access policy has been defined in order to assign different permissions to different clients. © 2001 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Jd Magnetic mirrors, gas dynamic traps
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management

Design of the National Ignition Facility diagnostic instrument manipulator

W. J. Hibbard, M. D. Landon, M. D. Vergino, F. D. Lee, and J. A. Chael

Rev. Sci. Instrum. 72, 530 (2001); http://dx.doi.org/10.1063/1.1316758 (3 pages) | Cited 3 times

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The diagnostic instrument manipulator (DIM) provides a diagnostic platform to insert and retract a variety of instruments into and out of the National Ignition Facility target chamber. The DIM is a two-stage telescoping system, designed to fit on any of the DIM designated diagnostic ports on the target chamber, and will provide precision radial positioning, pointing, and alignment-to-target capability. The DIM provides a standard set of utilities, and cables to support the operation of instruments that require insertion into the target chamber. The DIM provides for positioning of diagnostic packages, and enables exchange of manipulator diagnostics between fusion laboratories. Principal design requirements for the DIM are presented. A half-length prototype of the DIM was designed and fabricated by Atomic Weapons Establishment in England and is being tested at Lawrence Livermore National Laboratory. The results of this testing are presented. © 2001 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
07.07.Tw Servo and control equipment; robots
06.60.Sx Positioning and alignment; manipulating, remote handling
52.57.-z Laser inertial confinement
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Precision metrology of NSTX surfaces using coherent laser radar ranging

H. W. Kugel, D. Loesser, A. L. Roquemore, M. M. Menon, and R. E. Barry

Rev. Sci. Instrum. 72, 533 (2001); http://dx.doi.org/10.1063/1.1310586 (4 pages) | Cited 1 time

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A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 μm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of <100 μm at distances of up to 22 m. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
52.40.Hf Plasma-material interactions; boundary layer effects
42.79.Qx Range finders, remote sensing devices; laser Doppler velocimeters, SAR, and LIDAR

Debris characterization diagnostic for the NIF

M. C. Miller, J. R. Celeste, M. A. Stoyer, L. J. Suter, M. T. Tobin, J. Grun, J. F. Davis, C. W. Barnes, and D. C. Wilson

Rev. Sci. Instrum. 72, 537 (2001); http://dx.doi.org/10.1063/1.1310587 (3 pages) | Cited 2 times

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Generation of debris from targets and by x-ray ablation of surrounding materials will be a matter of concern for experimenters and National Ignition Facility (NIF) operations. Target chamber and final optics protection, for example debris shield damage, drive the interest for NIF operations. Experimenters are primarily concerned with diagnostic survivability, separation of mechanical versus radiation induced test object response in the case of effects tests, and radiation transport through the debris field when the net radiation output is used to benchmark computer codes. In addition, radiochemical analysis of activated capsule debris during ignition shots can provide a measure of the ablator 〈ρr〉. Conceptual design of the Debris Monitor and Rad-Chem Station, one of the NIF core diagnostics, is presented. Methods of debris collection, particle size and mass analysis, impulse measurement, and radiochemical analysis are given. A description of recent experiments involving debris collection and impulse measurement on the OMEGA and Pharos lasers is also provided. © 2001 American Institute of Physics.
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52.70.Nc Particle measurements
52.57.-z Laser inertial confinement
28.52.Lf Components and instrumentation

Optical characterization of plasma facing mirrors for a Thomson scattering system of a burning plasma experiment

F. P. Orsitto, D. Del Bugaro, M. DiFino, A. Maiolo, M. Montecchi, E. Nichelatti, C. Gowers, and P. Nielsen

Rev. Sci. Instrum. 72, 540 (2001); http://dx.doi.org/10.1063/1.1316759 (5 pages) | Cited 8 times

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The general requirements for a plasma facing mirror (PFM) of a Thomson scattering system (TS) for a burning plasma experiment are (i) high and approximately constant reflectivity in the wavelength spectral range 400–800 nm; (ii) low sputtering yield and low erosion; (iii) high power damage threshold; (iv) good thermo-mechanical properties to preserve quality imaging. Rhodium-coated mirrors are chosen because they meet these requirements. Rhodium coated mirror were realized with substrates of copper and vanadium. The detailed optical characterization of these mirrors is presented: i.e., surface planarity measurements as well as roughness and reflectivity figures are presented. These data can be used for the choice of the PFM of a TS system for international thermonuclear experimental reactor. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.79.Bh Lenses, prisms and mirrors

Plasma diagnostics for INTER-FEAT

K. Ebisawa, A. E. Costley, A. J. H. Donne, G. Janeschitz, S. Kasai, A. Malaquias, G. Vayakis, C. I. Walker, S. Yamamoto, and V. Zaveriaev

Rev. Sci. Instrum. 72, 545 (2001); http://dx.doi.org/10.1063/1.1310588 (6 pages) | Cited 6 times

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A comprehensive set of diagnostics is planned for ITER-FEAT. The design of the systems is a substantial technical challenge because of the combination of the harsh environment with the demanding measurement requirements. Through a combination of careful choice of technique, materials, and design, supported by dedicated research and development, an extensive diagnostic set has been developed. The designs are based on existing techniques as much as possible but in some cases novel approaches have to be adopted. In the article the requirements for measurements are outlined and representative diagnostic designs are presented. Key issues in the design are identified and areas requiring further development are highlighted. © 2001 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Fa Tokamaks, spherical tokamaks
28.52.Lf Components and instrumentation

Diagnostic requirements for high power auxiliary heating on NSTX (abstract)

A. L. Roquemore, D. Johnson, and R. Kaita

Rev. Sci. Instrum. 72, 551 (2001); http://dx.doi.org/10.1063/1.1323478 (1 page)

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National Spherical Torus Experiment (NSTX) has recently completed its first phase of operation. The primary objective for the baseline diagnostic1 set during this phase has been to aid in plasma control and machine operation, which successfully led to attainment of 1 MA of plasma current and some encouraging initial results with coaxial helicity injection (CHI). This first set of diagnostics relied on techniques previously established on tokamaks and related plasma devices. In the next phase of operation, strong auxiliary heating will become available in the form of rf heating through high harmonic fast waves (HHFWs) and neutral beam injection (NBI) for a combined total power of 11 MW. With intense auxiliary heating, accurate and reliable measurements of the plasma parameters for both machine operation and characterization of the plasma performance over a wide range of conditions will require an extended set of diagnostics. Profile diagnostics will be particularly important in this phase, and in some cases this capability can be achieved by upgrading existing diagnostics. However, many new diagnostic approaches must be implemented which take into account the constraints of a spherical torus device. An overview of the full complement of diagnostics planned for NSTX will be presented, and issues related to implementing each diagnostic will be discussed. © 2001 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams
52.70.-m Plasma diagnostic techniques and instrumentation

Diagnostics for a magnetized target fusion experiment

G. A. Wurden, T. P. Intrator, D. A. Clark, R. J. Maqueda, J. M. Taccetti, F. J. Wysocki, S. K. Coffey, J. H. Degnan, and E. L. Ruden

Rev. Sci. Instrum. 72, 552 (2001); http://dx.doi.org/10.1063/1.1310589 (4 pages) | Cited 8 times

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We are planning experiments using a field reversed configuration plasma injected into a metal cylinder, which is subsequently electrically imploded to achieve a fusing plasma. Diagnosing this plasma is quite challenging due to the short timescales, high energy densities, high magnetic fields, and difficult access. We outline our diagnostic sets in both a phase I study (where the plasma will be formed and translated), and phase II study (where the plasma will be imploded). The precompression plasma (diameter of only 8–10 cm, length of 30–40 cm) is expected to have n ∼ 1017 cm−3, T ∼ 100–300 eV, B ∼ 5 T, and a lifetime of 10–20 μs. We will use visible laser interferometry across the plasma, along with a series of fiber-optically coupled visible light monitors to determine the plasma density and position. Excluded flux loops will be placed outside the quartz tube of the formation region, but inside of the diameter of the θ-pinch formation coils. Impurity emission in the visible and extreme ultraviolet range will be monitored spectroscopically, and fast bolometers will measure the total radiated power. A 20 J Thomson scattering laser beam will be introduced in the axial direction, and scattered light (from multiple spatial points) will be collected from the sides. Neutron diagnostics (activation and time-resolved scintillation detectors) will be fielded during both phases of the DD experiments.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Ez Theta pinch
52.70.Ds Electric and magnetic measurements
52.70.Nc Particle measurements

Plasma diagnostics for the sustained spheromak physics experiment

H. S. McLean, A. Ahmed, D. Buchenauer, D. Den Hartog, C. W. Domier, D. N. Hill, C. Holcomb, E. B. Hooper, E. C. Morse, M. Nagata, Y. Roh, B. Stallard, R. D. Wood, S. Woodruff, G. Wurden, et al.

Rev. Sci. Instrum. 72, 556 (2001); http://dx.doi.org/10.1063/1.1318246 (6 pages) | Cited 21 times

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In this article we present an overview of the plasma diagnostics operating or planned for the sustained spheromak physics experiment device now operating at Lawrence Livermore National Laboratory. A set of 46 wall-mounted magnetic probes provide the essential data necessary for magnetic reconstruction of the Taylor relaxed state. Rogowski coils measure currents induced in the flux conserver. A CO2 laser interferometer is used to measure electron line density. Spectroscopic measurements include an absolutely-calibrated spectrometer recording extended domain spectrometer for obtaining time-integrated visible ultraviolet spectra and two time-resolved vacuum monochrometers for studying the time evolution of two separate emission lines. Another time-integrated spectrometer records spectra in the visible range. Filtered silicon photodiode bolometers provide total power measurements, and a 16 channel photodiode spatial array gives radial emission profiles. Two-dimensional imaging of the plasma and helicity injector is provided by gated television cameras and associated image-processing software. An array of fiber-coupled photodetectors with H alpha filters view across the midplane and in the injector region to measure neutral hydrogen concentrations. Several novel diagnostics are being fielded including a transient internal probe (TIP) and an ultrashort-pulse reflectometer (USPR) microwave reflectometer. The TIP probe fires a very high velocity optical bullet through the plasma and will provide fairly nonpertabative internal magnetic field and current measurements to compare with an equilibrium code model fitted to wall-mounted probes. The USPR is being designed to study edge density and turbulent fluctuations. A multipoint Thomson scattering system is currently being installed to give radial temperature and density profiles. © 2001 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Jd Magnetic mirrors, gas dynamic traps
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Gw Radio-frequency and microwave measurements

Calibration facilities at Bechtel Nevada–Livermore operations (abstract)

T. S. Perry, D. Hargrove, C. Diamond, K. Piston, T. Sammons, and P. M. Bell

Rev. Sci. Instrum. 72, 562 (2001); http://dx.doi.org/10.1063/1.1323479 (1 page) | Cited 1 time

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Since moving to a new location in March of 1999, Bechtel Nevada–Livermore Operations has established a modern laboratory for the characterization of optical and x-ray diagnostics for high temperature plasmas. Some of the facilities include a short pulse laser facility, a streak tube production facility, a microchannel plate characterization laboratory, an optical streak camera calibration laboratory, and a charge coupled device calibration laboratory. Descriptions of the facilities will be presented as well as examples of data taken at the laboratory. Future upgrades to the facility will be discussed. © 2001 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.La X-ray and γ-ray measurements
01.52.+r National and international laboratory facilities

Detection of radio frequency perturbations using an ion beam diagnostic (abstract)

S. Howard, J. Si, T. P. Crowley, K. A. Connor, P. M. Schoch, and J. G. Schatz

Rev. Sci. Instrum. 72, 563 (2001); http://dx.doi.org/10.1063/1.1323480 (1 page)

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Presently, experiments are underway at the Plasma Dynamics Laboratory at Rensselaer Polytechnic Institute to demonstrate that the techniques developed for heavy ion beam probe diagnostics (HIBP) can be used to measure radio frequency (rf) fluctuations in plasmas. We hope to measure fluctuations in plasma density and magnetic and electric fields. This will provide a direct measurement of the electric and magnetic fields in the plasma during ICRF heating and thereby improve understanding of heating deposition and wave physics. In addition, the field and the density measurements will be used to determine the plasma reaction to the heating experiments. It is expected that the density measurements will be easiest to interpret, while the electric field measurement will be the most difficult to interpret. The diagnostic issues that will be important in taking data at rf frequencies include faster electronics, signal levels, and path effects. We have used a current to voltage amplifier design to measure 0–500 kHz fluctuations in several previous experiments. By reducing the gain and changing some components, a very similar design is capable of operation at rf frequencies. The modified circuit has been tested up to 15 MHz and worked well. The number of beam ions striking the detector plate in one rf period will be too small to obtain good enough statistics for fluctuation measurements, and therefore, averages over many cycles will be required. We expect to be able to achieve millisecond time resolution in the experiments. The global nature of the modes will tend to make path effects important in the HIBP signals. On the other hand, since the beam will take more than one period to cross the plasma, phase shifts may cancel some of these effects. In addition, a path effect term due to dA/dt will be much more important relative to the electric potential than in lower frequency experiments. The initial experimental plan is to do a series of measurements in which a lithium ion beam passes through an argon helicon plasma. The helicon plasma was chosen because its high density (of order 1019 m−3) will produce a larger HIBP signal than can be obtained from other small plasmas. The helicon plasma is formed within a solenoidal magnetic field of 1 kG on axis. The plasma is excited by an rf antenna that is a modification of the type used in Boswell’s experiments.1 The rf power source is presently a 500 W, 13.56 MHz generator. From calculation of final trajectories we have determined that 16–29 keV Li ions can be used to probe a plasma with 1 kG magnetic field on axis. If the signal levels with a lithium beam are too small, a molecular hydrogen source will be used. For testing the basic operation of the ion beam probe we will use a simple plate detector mounted on the output flange. These preliminary experiments will be used to determine the feasibility of measuring density and magnetic field fluctuations. A second set of experiments using a more traditional HIBP energy analyzer as a detector is also planned. This detector will also be able to measure electric field effects on the probing ions. It will also be less sensitive to UV noise from the plasma. © 2001 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Gj Fluctuation and chaos phenomena
52.50.Gj Plasma heating by particle beams

Calibration and initial operation of the HIBP on the MST

J. Lei, U. Shah, D. R. Demers, K. A. Connor, and P. M. Schoch

Rev. Sci. Instrum. 72, 564 (2001); http://dx.doi.org/10.1063/1.1310590 (4 pages) | Cited 7 times

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For the first time, a heavy ion beam probe (HIBP) has been installed on a reversed field pinch, i.e., Madison symmetric torus (MST), to measure the plasma potential profile, potential, and electron density fluctuations, etc. The application of a HIBP on MST has presented new challenges for this diagnostic. The primary sources of difficulty are small access ports, high plasma, and, ultraviolet (UV) flux and a confining magnetic field produced largely by plasma currents. The requirement to keep ports small so as to avoid magnetic field perturbations led to the development of the cross-over sweep system. The effectiveness and calibration of this sweep system will be reported. In addition, this diagnostic is now operating with greater plasma/UV loading effects than most previous Rensselaer HIBPs. The plasma flux is reduced by using a magnetic suppression structure. The UV flux appears to be the dominant cause of the remaining loading, which is substantial. The magnetic field being largely produced by the plasma makes determination of measurement locations exclusively from trajectory calculations difficult. Initial operation results have shown that the magnetic field model we are using to calculate our ion trajectories has an inaccuracy of about 10%, and thus subsequent development of improved confining field models is important. Secondary signals have been detected, and the levels are smaller than that from the UV induced noises. Methods to increase the signal levels are discussed. A very rough estimation of the potential at a typical MST core location is 0.8–2 kV. Fluctuations in the frequency range 100–20 kHz have also been observed. © 2001 American Institute of Physics.
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52.55.Ez Theta pinch
52.70.Nc Particle measurements

Suppression of plasma electrons in the diagnostic ports of the MST

D. R. Demers, K. A. Connor, J. Lei, P. M. Schoch, and U. Shah

Rev. Sci. Instrum. 72, 568 (2001); http://dx.doi.org/10.1063/1.1318247 (4 pages) | Cited 2 times

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The recent application of a heavy ion beam probe (HIBP) to the Madison Symmetric Torus (MST) has motivated the development of permanent magnet plasma suppression structures. Unconfined plasma at the MST diagnostic ports is free to flow out the ports and into adjoining diagnostic chambers. The HIBP system incorporates seven pairs of high voltage, electrostatic steering plates. Stray charged particles that exit the MST-HIBP ports are attracted to these biased steering plates, loading down the power supplies, and detrimentally affecting the desired operation of the plates. A second source of loading is electron current generated by UV light emitted from the MST plasma. Structures comprised of steel keepers and nickel plated magnets were designed to conform to the walls of the two HIBP diagnostic ports. The magnetic fields in the keeper aperture are able to suppress most of the plasma that would otherwise flow into the HIBP chambers. The fields external to the keeper structure are sufficiently small to avoid perturbing the confining fields at the plasma edge. Analysis indicates that electron current from UV radiation dominates the remaining loading of the HIBP steering plates. © 2001 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Ez Theta pinch
07.77.Ka Charged-particle beam sources and detectors
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