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The paper reviews the results from tokamak experiments and measurements on electron beam ion traps for the line ratios x/w, y/w, and z/w in the spectra of helium-like ions with Z in the range from 14 to 28. With the exception of the DITE experiments, where these line ratios were found to be in agreement with theoretical predictions, all other tokamak experiments yielded values that were significantly greater than predicted. The reasons for these discrepancies are not yet understood. It is possible that radial profile effects were not properly taken into account in the majority of the tokamak experiments. The paper also gives a short historical review of the X-ray diagnostic developments and presents very recent data from a new type of X-ray imaging crystal spectrometer, which records spatially resolved spectra with a spatial resolution of about 1 cm in the plasma. These new data can be Abel inverted, so that it will be possible to determine line ratios at each radial position in the plasma. Effects of radial profiles, which may have affected the chord-integrated measurements of the past, will thus be eliminated in the future. PACS Nos.: 52.55.Fa, 32.30.Rj

Research on the Alcator C-Mod tokamak has emphasized RF heating, self-generated flows, momentum transport, scrape-off layer (SOL) turbulence and transport and the physics of transport barrier transitions, stability and control. The machine operates with P-RF up to 6 MW corresponding to power densities on the antenna of 10 MW m(-2). Analysis of rotation profile evolution, produced in the absence of external drive, allows transport of angular momentum in the plasma core to be computed and compared between various operating regimes. Momentum is clearly seen diffusing and convecting from the plasma edge on time scales similar to the energy confinement time and much faster than neo-classical transport. SOL turbulence and transport have been studied with fast scanning electrostatic probes situated at several poloidal locations and with gas puff imaging. Strong poloidal asymmetries are found in profiles and fluctuations, confirming the essential ballooning character of the turbulence and transport. Plasma topology has a dominant effect on the magnitude and direction of both core rotation and SOL flows. The correlation of self-generated plasma flows and topology has led to a novel explanation for the dependence of the H-mode power threshold on the del B drift direction. Research into internal transport barriers has focused on control of the barrier strength and location. The foot of the barrier could be moved to larger minor radius by lowering q or B-T. The barriers, which are produced in C-Mod by off-axis RF heating, can be weakened by the application of on-axis power. Gyro-kinetic simulations suggest that the control mechanism is due to the temperature dependence of trapped electron modes which are destabilized by the large density gradients. A set of non-axisymmetric coils was installed allowing intrinsic error fields to be measured and compensated. These also enabled the determination of the mode locking threshold and, by comparison with data from other machines, provided the first direct measurement of size scaling for the threshold. The installation of a new inboard limiter resulted in the reduction of halo currents following disruptions. This effect can be understood in terms of the change in plasma contact with the altered geometry during vertical displacement of the plasma column. Unstable Alfven eigenmodes (AE) were observed in low-density, high-power ICRF heated plasmas. The damping rate of stable AEs was investigated with a pair of active MHD antennae.

The time evolution of toroidal rotation velocity profiles has been measured in Alcator C-Mod [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] plasmas using a tangentially viewing x-ray spectrometer array. The strong co-current toroidal rotation in enhanced Dα (EDA) high confinement mode (H-mode) plasmas is observed to propagate in from the edge on a time scale similar to the energy confinement time. The ensuing steady state rotation velocity profiles in both Ohmic and ion cyclotron range of frequencies (ICRF) heated EDA H modes, which are generated in the absence of any external momentum input, are found to be relatively flat. These profiles may be simulated by a simple diffusion model with the boundary condition of an edge rotation, which appears during the H-mode period. The observed profiles are well matched by the simulations using a momentum diffusivity of ∼0.1 m2/s, which is much larger than the calculated neo-classical value, and the momentum transport may be regarded as anomalous. The Alcator C-M...

To assess whether the sex of primary care physicians is associated with differing rates of cervical cancer and mammography screening in a contemporary multicultural context.Structured medical record review of a retrospectively defined cohort.Academic urban primary care clinic in Montreal, Que.Seven male physicians and 9 female physicians, and all female patients aged 14 to 69 years registered to one of the physicians (N = 1948).Screening compliance rates as measured by the elapsed time between the last visit and cervical cancer screening for all women in the study. In addition, in women aged 50 to 69 years, elapsed time between the last visit and mammography screening.Crude rates of Papanicolaou tests for patients of female primary care physicians were higher than for patients of male primary care physicians in all patient age groups. The lowest rates of Pap testing were among the youngest and oldest patients. After adjustment for patient age, first language, and region of birth, as well as physician age, the odds ratio of having a Pap test was 2.24 (95% CI 1.18 to 4.28) for the patients of female physicians, relative to those of male physicians. The adjusted odds ratio for mammography screening was 1.25 (95% CI 0.97 to 1.61) for patients of female physicians.Male primary care physician sex is associated with lower rates of cervical cancer screening in an urban multicultural context. The study did not detect a physician sex effect in the mammography cohort.

Most tokamak-based reactor concepts require the use of noble gases to form either a radiative mantle or divertor to reduce conductive heat exhaust to tolerable levels for plasma facing components. Predicting the power loss necessary from impurity radiation is done using electron temperature-dependent 'cooling-curves' derived from ab initio atomic physics models. We present here a technique to verify such modeling using highly radiative, argon infused discharges on Alcator C-Mod. A novel x-ray crystal imaging spectrometer is used to measure spatially resolved profiles of line-emissivity, constraining impurity transport simulations. Experimental data from soft x-ray diodes, bare AXUV diodes and foil bolometers are used to determine the local emissivity in three overlapping spectral bands, which are quantitatively compared to models. Comparison of broadband measurements show agreement between experiment and modeling in the core, but not over the entire profile, with the differences likely due to errors in the assumed radial impurity transport outside of the core. Comparison of Ar{sup 16+} x-ray line emission modeling to measurements suggests an additional problem with the collisional-radiative modeling of that charge state.

Plasma flow drive via ICRF mode conversion (MC) has been demonstrated on Alcator C‐Mod. The toroidal rotation in these D(3He) MC plasmas is typically more than twice above the empirically determined intrinsic rotation scaling in ICRF minority heated plasmas. In L‐mode plasmas at 3 MW ICRF power input, up to 90 km/s toroidal rotation and 2 km/s localized ( r/a∼0.4) poloidal rotation has been observed. The MC ion cyclotron wave (ICW) was detected by a phase contrast imaging system in heterodyne setup. Through TORIC 2‐D full wave simulation, and comparison with other experimental evidence, we hypothesize that the interaction between the MC ICW and the 3He ions may be the mechanism for the observed MC flow drive. TORIC simulation suggests that similar flow drive scenario may be realized on JET D(3He) plasmas. The promising scenarios on ITER are the inverted minority scenario (T)D and high field launch for T‐D‐(3He) plasma. In non‐radioactive phase, these correspond to (3He)‐H and 4He(3He) plasmas respectively.

LHCD on Alcator C‐Mod is being used in plasmas with parameters similar to those expected on ITER for the purpose of tailoring the plasma current profile. LHCD experiments have also produced intriguing results related to momentum transport and edge pedestal physics that affect the toroidal rotation profile and the temperature and density profiles. Quantitative comparisons between local measurements and theory/simulation have been performed, confirming the off‐axis localization of the current drive, as well as its magnitude and location dependence on the launched n‖ spectrum and electron temperature. Applying LHCD during the current ramp saves volt‐seconds and delays the peaking of the current profile. Counter current toroidal rotation during LHCD has been observed in both L and H‐mode plasmas. In H‐mode plasmas the edge pedestal collisionality is reduced while the overall pressure in the pedestal increases slightly.

A new spatially resolving x-ray crystal spectrometer capable of measuring continuous spatial profiles of high resolution spectra (lambda/d lambda6000) of He-like and H-like Ar K alpha lines with good spatial (approximately 1 cm) and temporal (approximately 10 ms) resolutions has been installed on the Alcator C-Mod tokamak. Two spherically bent crystals image the spectra onto four two-dimensional Pilatus II pixel detectors. Tomographic inversion enables inference of local line emissivity, ion temperature (T(i)), and toroidal plasma rotation velocity (upsilon(phi)) from the line Doppler widths and shifts. The data analysis techniques, T(i) and upsilon(phi) profiles, analysis of fusion-neutron background, and predictions of performance on other tokamaks, including ITER, will be presented.

The use of high resolution x-ray crystal spectrometers to diagnose fusion plasmas has been limited by the poor spatial localization associated with chord integrated measurements. Taking advantage of a new x-ray imaging spectrometer concept [M. Bitter et al., Rev. Sci. Instrum. 75, 3660 (2004)], and improvements in x-ray detector technology [Ch. Broennimann et al., J. Synchrotron Radiat. 13, 120 (2006)], a spatially resolving high resolution x-ray spectrometer has been built and installed on the Alcator C-Mod tokamak. This instrument utilizes a spherically bent quartz crystal and a set of two dimensional x-ray detectors arranged in the Johann configuration [H. H. Johann, Z. Phys. 69, 185 (1931)] to image the entire plasma cross section with a spatial resolution of about 1 cm. The spectrometer was designed to measure line emission from H-like and He-like argon in the wavelength range 3.7 and 4.0 A with a resolving power of approximately 10,000 at frame rates up to 200 Hz. Using spectral tomographic techniques [I. Condrea, Phys. Plasmas 11, 2427 (2004)] the line integrated spectra can be inverted to infer profiles of impurity emissivity, velocity, and temperature. From these quantities it is then possible to calculate impurity density and electron temperature profiles. An overview of the instrument, analysis techniques, and example profiles are presented.

The paper describes a new scheme for wide-angle point-to-point x-ray imaging with almost arbitrarily large angles of incidence by a matched pair of spherically bent crystals to eliminate the astigmatism, which is a well-known imaging error of spherical mirrors. In addition to x rays, the scheme should be applicable to a very broad spectrum of the electromagnetic radiation, including microwaves, infrared and visible light, as well as UV and extreme UV radiation, if the crystals are replaced with appropriate spherical reflectors. The scheme may also be applicable to the imaging with ultrasound.

Strong toroidal flow (Vphi) and poloidal flow (Vtheta) have been observed in D-3He plasmas with ion cyclotron range of frequencies (ICRF) mode-conversion (MC) heating on the Alcator C-Mod tokamak. The toroidal flow scales with the rf power Prf (up to 30 km/s per MW), and is significantly larger than that in ICRF minority heated plasmas at the same rf power or stored energy. The central Vphi responds to Prf faster than the outer regions, and the Vphi(r) profile is broadly peaked for r/aor =0.5. Localized (0.3or = r/aor =0.5) Vtheta appears when Prfor =1.5 MW and increases with power (up to 0.7 km/s per MW). The experimental evidence together with numerical wave modeling suggests a local flow drive source due to the interaction between the MC ion cyclotron wave and 3He ions.

In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to $60\text{ }\text{ }\mathrm{km}/\mathrm{s}$ in the central region of the plasma ($r/a\ensuremath{\sim}l0.4$). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time ($\ensuremath{\sim}100\text{ }\text{ }\mathrm{ms}$) but longer than the energy and momentum confinement times ($\ensuremath{\sim}20\text{ }\text{ }\mathrm{ms}$). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch.

In this paper, a new spatially resolving X-ray crystal spectrometer (XCS) capable of measuring continuous spatial profiles of high resolution spectra (lambda/dlambda > 6000) of He-like and H-like Ar Kalpha lines has been installed on the Alcator C-Mod tokamak. The spectrometer has an improved measurements on ion temperature (Ti), intrinsic rotation-velocity profiles (vphi) with excellent spatial (~1 cm) and temporal resolution, and on the atomic physics of highly charged ions.The data analysis techniques, (Ti) and (vphi) profile results, analysis of background resulting from fusion neutrons, and predictions of performance on the international tokamak ITER and other tokamaks is presented.

This tutorial gives a brief introduction into passive spectroscopy and describes the working principles of bolometers, a high‐resolution grating spectrometer, and a novel X‐ray imaging crystal spectrometer, which is also of particular interest for profile measurements of the ion temperature and plasma rotation velocity on ITER and future burning plasma experiments.

A new type of X-ray imaging crystal spectrometer for Doppler measurements of the radial profiles of the ion temperature and plasma rotation velocity in tokamak plasmas is presently being developed in a collaboration between various laboratories. The spectrometer will consist of a spherically bent crystal and a two-dimensional position sensitive detector; and it will record temporally and spatially resolved X-ray line spectra from highly-charged ions. The detector must satisfy challenging requirements with respect to count rate and spatial resolution. The paper presents the results from a recent test of a PILATUS II detector module on Alcator C-Mod, which demonstrate that the PILATUS II detector modules will satisfy these requirements.

High-quality spectra of hydrogen-like Ar(17+) have been obtained from Alcator C-Mod tokamak plasmas using a spatially imaging high-resolution x-ray spectrometer system in an extensive study of the ...

This paper consists of two parts: part I describes the working principle of a recently developed x-ray imaging crystal spectrometer, where the astigmatism of spherically bent crystals is being used with advantage to record spatially resolved spectra of highly charged ions for Doppler measurements of the ion-temperature and toroidal plasma-rotation-velocity profiles in tokamak plasmas. This type of spectrometer was thoroughly tested on NSTX and Alcator C-Mod, and its concept was recently adopted for the design of the ITER crystal spectrometers. Part II describes imaging schemes, where the astigmatism has been eliminated by the use of matched pairs of spherically bent crystals or reflectors. These imaging schemes are applicable over a wide range of the electromagnetic radiation, which includes microwaves, visible light, EUV radiation and x-rays. Potential applications with EUV radiation and x-rays are the diagnosis of laser-produced plasmas, imaging of biological samples with synchrotron radiation and lithography.