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A coil-unit barrel for a helical coil electromagnetic launcher is described. It provides better features of high structural strength and flexible adjustability. It is convenient to replace the damaged coil units and easy to adjust the number of turns in the stator coils due to the modular design. In our experiments, the highest velocity measured for a 4.5-kg projectile is 47.3 m/s and the mechanical reinforcement of the launcher could bear 35 kA peak current. The relationship between the energy conversion efficiency and the inductance gradient of the launcher is also studied. In the region of low inductance gradient, the efficiency is positively correlated with the inductance gradient. However, in the region of high inductance gradient, the inter-turn arc erosion becomes a major problem of limiting the efficiency and velocity of the launcher. This modular barrel allows further studies in the inter-turn arc and the variable inductance gradient helical coil launcher.

A helical resonator serves as a key element for the detection of the trapped charged particles in a Penning trap. In order to compare the performance of the helical resonators, the concept of figure of merit (FOM) was introduced by Ulmer et al. [Nucl. Instrum. Methods Phys. Res., Sect. A 705, 55–60 (2013)]. In this work, we optimized the geometrical parameters of a resonator by numerical simulations keeping its outer dimensions and the diameter of the copper wire fixed and obtained the best possible value of FOM under these constraints. The corresponding 95 MHz helical resonator has been designed and fabricated, and its measured value of FOM is in good agreement with the simulated values. An empirical relationship between the total length of the wire to make the helical coil and the resonance frequency has been obtained. The simulations show that the FOM increases considerably with the increase in the conductivity of the building material, and this would be useful in detecting the feeble trap signal in cryogenic environment. [ABSTRACT FROM AUTHOR]

Narrow bandwidth and high voltage radio frequency (RF) is an essential requirement for stable confinement of ions within a RF trap and helical resonators are commonly used for that purpose. Effective capacitance and inductance of a helical resonator are estimated by measuring resonant frequencies for different external loads. Load capacitance of an ion trap can be estimated from this method and a resonator can be constructed for desired resonant frequency. We demonstrate a very simple method to achieve higher Q-factor of a resonator by optimizing mutual separation between the primary antenna and helical coil. We also formulate a set of analytical equations for calculating overall inductance, resistance, and Q-factor of a loaded helical resonator. [ABSTRACT FROM AUTHOR]

In this ECR ion source, the possibility of maintaining the plasma by slow wave structures (SWS), helical coil, and slotted line antennas, in the region where w[sub ce], w[sub pe] » w[sub rf] (w[sub ce], w[sub pe], and w[sub rf] are electron cyclotron, plasma, and microwave frequencies, respectively) is exploited. The plasma parameters, plasma density, and electron temperature are maximized by coupling microwave (frequency: 2.45 GHz; power: 650 W) at two places in a magnetic mirror machine (mirror ratio R[sub m] ... 1.45) to obtain higher beam current. Initially, the plasma is produced by coupling microwave to SWS at the mirror throat. The microwave is coupled by exciting the dominant slow wave field component of SWS, using an E-plane horn antenna. Then the plasma is brought to the region w[sub ce], w[sub pe] » w[sub rf] at the mirror throat by increasing the magnetic field. Simultaneously, the ECR region is shifted from mirror throat to the center where second microwave coupling is done at the resonant region using another horn antenna. The characterization of plasma parameters are presented for both helical coil and slotted line antennas. Enhancement of plasma parameters are observed in the present scheme. Also, the SLA is found to produce better plasmas (n[sub e] ∼ 7 × 10[sup 12] cm[sup -3] and T[sub e] ∼ 12 eV) than the helical coil and hence the SLA is chosen for the ion beam characterization. The extracted ion beam current density in the present scheme is ∼25 mA/cm² at 2-kV extraction voltage. [ABSTRACT FROM AUTHOR]

High voltage radio frequency (RF) supply is a critical part in an ion trapping system. The RF supply should have high Q-factor and relatively high driving frequency. A frequently used RF supply for an ion trap system is a helical resonator. In certain applications, it is advantageous to have a predictable resonant frequency and Q-factor when the helical resonator is connected to a capacitive load. We develop a model to describe the behavior of a helical resonator with capacitive load. With this model, we can correctly predict the loaded resonant frequency and the loaded Q-factor. To test our prediction, we construct a helical resonator, and measure its resonant frequencies and Q-factors under different capacitive loads. The experimental results agree with our prediction. [ABSTRACT FROM AUTHOR]

Neutron monitoring is quite important because fusion neutrons are a direct evidence of fusion reactions. In calibration experiments of a neutron monitoring system, Monte Carlo calculations play an important role to correct various effects. To perform Monte Carlo calculations for a helical type fusion device, we make a program that can automatically generate an input file of a helical coil geometry for the MCNP code. The neutron spatial distributions and spectra for the helical devices are calculated in the geometries automatically generated by this program. We also discuss in calibration experiments. [ABSTRACT FROM AUTHOR]

Presents results of a calibration experiment of the neutron counters of the Compact Helical System (CHS) to determine the calibration factor which relates the neutron-counter output to the extended neutron source of a torus plasma. Instruments employed in the experiment; Survey results of 64 toroidal angles; Poloidal cross section.

This paper describes a new method of exciting slow wave structures (SWS) for obtaining high-density electron cyclotron resonance plasmas. The electric field component corresponding to the slow wave mode (SWM) of SWS is excited by an E-plane horn antenna. The special features of the microwave transmission line are the stable tuning for a given antenna and no requirement for water cooling on any of the components. Two types of SWS, a helical coil and a slotted line antenna, are studied, and the experiments are carried out in nitrogen and argon. The plasma producing capability is examined for these systems in the region wce,wpe>=wrf, where wce, wpe, and wrf correspond to electron cyclotron, plasma, and microwave frequencies, respectively. A high-density, large-diameter plasma (n0∼5×1011 cm-3; diameter ∼8.0 cm) could be obtained and the plasma could be maintained in the region 1≤wce/wrf≤2. [ABSTRACT FROM AUTHOR]

This article is focused on a novel and practical production method for a uniform magnetic field generator. The method involves building of a surface coil template using a desktop 3D printer and winding of a conducting wire onto the structure using surface grooves as a guide. Groove pattern was based on the parametric spheroidal helical coil formula. The coil was driven by a current source and the magnetic field inside was measured using a Hall probe placed into the holes on the printed structure. The measurements are found to be in good agreement with our finite element analysis results and indicate a fairly uniform field inside. [ABSTRACT FROM AUTHOR]

We describe a high intensity metastable Kr source based on a helical resonator RF discharge. By adding an external B-field to the discharge source, the metastable Kr flux is enhanced. The effect of geometric configuration and magnetic field strength has been studied and optimized experimentally. Compared to the helical resonator discharge source without an external B-field, the new source showed an enhancement factor of 4–5 in producing metastable Kr beams. This improvement has a direct impact on the radio-krypton dating applications as it can increase the atom count rate, resulting in a higher analytical precision. [ABSTRACT FROM AUTHOR]

A new 320 GHz solid-state source interferometer is installed in the Heliotron J helical device to explore the physics of high-density plasmas (ne > 2–3 × 1019 m−3, typically) realized with advanced fueling techniques. This interferometry system is of the Michelson type and is based on the heterodyne principle, with two independent solid-state sources that can deliver an output power of up to 50 mW. A high time resolution measurement of <1 µs can be derived by tuning the frequency of one source in the frequency range of 312–324 GHz on the new system, which can realize the fluctuation measurement. We successfully measured the line-averaged electron density in high-density plasma experiments. The measured density agreed well with a microwave interferometer measurement using a different viewing chord, demonstrating that the new system can be used for routine diagnostics of electron density in Heliotron J. [ABSTRACT FROM AUTHOR]

We present a compact and gain-enhanced microwave helical antenna for manipulating ultracold 87Rb atoms coherently. By replacing the reflecting plate with an enhancing cup, the voltage standing wave ratio is reduced by 0.5 in the frequency range of 6.73–6.93 GHz, which covers the resonant frequency between the ground-state hyperfine levels of the 87Rb atom. The gain of the helical antenna is increased by 1.25–1.63 dBi, whose length is 89 mm. Applying the antenna to ultracold 87Rb atomic experiments, we achieve a Rabi frequency of 60(1) ×2π kHz of the oscillation between the hyperfine levels. [ABSTRACT FROM AUTHOR]

This paper reports on the assembly of a compact, low-cost, pulsed-power facility used for plasma studies. The construction uses two modules placed on opposite sides of the test chamber to minimize the system impedance and improve access to test samples. The stored energy is 1 kJ with a peak current of 135 kA and a 1592 ns quarter-period time. Up until now, an imploding conical-wire array has been studied by using time-integrated (visible) imaging, and time-resolved laser imaging, providing a measure of the plasma jet speed in the range of 170 km/s. Our future plans will continue to investigate high-energy-density plasmas that are relevant to the space environment, fusion, and spectroscopy. [ABSTRACT FROM AUTHOR]

The Torsatron TJ-K is a toroidal device operated with a magnetically confined low-temperature plasma to study turbulence and wave propagation. The magnetic configuration is the same as for a fusion plasma device. However, the plasma parameters are such that probes can be used in the entire plasma cross section to measure the detailed spatiotemporal structure of the turbulence. At the same time, the dimensionless parameters governing turbulence are in the same range as those of the fusion plasma edge. The objective of the experiment is to obtain data, which allow a close comparison with drift-wave turbulence simulations. Furthermore, the propagation of the helicon heating wave in a toroidal geometry as well as excited gap Alfvén modes will be studied. The article presents the experimental setup and the diagnostics. It is demonstrated that the TJ-K plasma has parameters and profiles relevant to achieve the objectives of the project. First results of turbulence and wave studies are presented. [ABSTRACT FROM AUTHOR]

Neutron monitoring is important to manage safety of fusion experiment facilities because neutrons are generated in fusion reactions. Monte Carlo simulations play an important role in evaluating the influence of neutron scattering from various structures and correcting differences between deuterium plasma experiments and in situ calibration experiments. We evaluated these influences based on differences between the both experiments at Large Helical Device using Monte Carlo simulation code MCNP5. A difference between the both experiments in absolute detection efficiency of the fission chamber between O-ports is estimated to be the biggest of all monitors. We additionally evaluated correction coefficients for some neutron monitors. [ABSTRACT FROM AUTHOR]

If the major axes of the helical and vertical field coils of a torsatron plasma confinement device are not aligned to within ∼1% of their major radii, the resulting error field can break up closed magnetic flux surfaces and reduce the effective plasma confinement volume. A novel technique for accurately locating the magnetic symmetry axes of torsatron helical and vertical coil sets to within ∼1 mm using magnetic field measurements near the device major axis (i.e., away from the confinement volume) is described and applied to the URAGAN-3 torsatron. The axis of the vertical field coil set was found to be shifted by ∼1 cm relative to the axis of the helical coil set; this shift could account for the reduced confinement volume observed in previous experiments. The magnetic measurements were repeated after coil repositioning to verify correct alignment. [ABSTRACT FROM AUTHOR]

The magnetic flux surfaces of the Compact Auburn Torsatron have been experimentally mapped in a variety of magnetic configurations. The magnetic surface mapping was done using the phosphor screen technique. The results are compared with an extensive computer model in order to validate the design coil structure and determine what modifications are needed to correct any minor winding errors. In initial field mapping experiments, a large up–down asymmetry was identified in the vacuum magnetic surfaces. A set of mapping studies was used to characterize the error through addition of terms to the coil winding law. The error was corrected with the use of a radial trim coil. [ABSTRACT FROM AUTHOR]

We have conducted three tests of a new pulsed power device called the full function test. These tests represented the culmination of an effort to establish a high energy pulsed power capability based on high explosive pulsed power (HEPP) technology. This involved an extensive computational modeling, engineering, fabrication, and fielding effort. The experiments were highly successful and a new U.S. record for magnetic energy was obtained. [ABSTRACT FROM AUTHOR]

Radioactive ion beams produced using the isotope separation on-line method in the Rare isotope Accelerator complex for ON-line (RAON) experiment are to be delivered with a beam emittance of around 3 π mm mrad, an energy spread of less than 10 eV, and a short beam bunch width of around 10 µs to meet the requirements of an electron beam ion source charge breeder. A radio frequency quadrupole cooler buncher (RFQ-CB) will be used to meet the beam quality requirements mentioned above. Our target bunching capacity of RFQ-CB is 108 ions/bunch for various ion species. Such a high bunching capacity requires an RF amplitude of ∼3 kV and a frequency range of 1.5–4.5 MHz in our RFQ-CB design. We designed and tested the prototype RF system composed of a helical resonator, a high-power RF amplifier, and high-voltage probes. To reduce heat load to the high voltage probes, we employed vacuum capacitors serially connected to the ends of helical resonators. In the experiment, we confirmed that our 4.5-µH helical resonators made of a 12-mm copper tube and variable vacuum capacitor with a capacitance range of 120–1120 pF can produce required voltages and frequencies using a 100-W RF amplifier. As a result, with 2.5-W RF output power, we obtained the maximum voltage amplitude of 1 kV at 4.5 MHz, which is equivalent to 6.4 kV with 100-W RF output power. [ABSTRACT FROM AUTHOR]

An injection barrel was designed and fabricated for a small size 0.8 mm cryogenic pellet with a low speed of 200-300 m/s in medium-sized plasma fusion devices. Pellet injection with pneumatic acceleration was examined using a conventional in situ technique. A tapered structure was applied in the downstream side of the injection barrel to satisfy the requirement of pellet speed reduction by expansion of the propellant gas. Shadowgraph and light gate measurements show that the intact pellets have speeds of 260 ± 30 m/s and a typical size of 1.1-1.2 mm. The pellet ablation code based on a neutral gas shielding model shows that the penetration depth of the measured pellet parameters does not cross the plasma center, even in medium-sized plasma devices such as the Heliotron J helical device. The injection barrel with a tapered structure developed in this study is feasible for low speed pellet injection. [ABSTRACT FROM AUTHOR]

We actively stabilize the harmonic oscillation frequency of a laser-cooled atomic ion confined in a radiofrequency (rf) Paul trap by sampling and rectifying the high voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz atomic oscillation frequency to be better than 10 Hz or 10 ppm. This represents a suppression of ambient noise on the rf circuit by 34 dB. This technique could impact the sensitivity of ion trap mass spectrometry and the fidelity of quantum operations in ion trap quantum information applications. [ABSTRACT FROM AUTHOR]

A radio-frequency coil for the experimental investigation of the magnetic properties of thin superconducting films under microwave fields at different values of temperature and dc magnetic field has been developed. The system has been used for low-temperature microwave frequency-dependent magnetization measurements in a Pb thin film with an engineered periodical antidot array. The characteristic frequencies and the electric and magnetic fields of the resonant system formed by a multi-turn coil with a sample loaded in its core are estimated using the helical approach. A good agreement of the calculated values with those recorded in swept-frequency spectra is obtained. The relation between the characteristics of the resonant structure and the frequency-driven magnetic response of the sample at different nominal microwave powers documents the capability and sensitivity of the layout. [ABSTRACT FROM AUTHOR]

We describe a liquid jet injector system developed to deliver fully solvated microscopic target species into a probe beam under either vacuum or ambient conditions. The injector was designed specifically for x-ray scattering studies of biological nanospecies using x-ray free electron lasers and third generation synchrotrons, but is of interest to any application in which microscopic samples must be delivered in a fully solvated state and with microscopic precision. By utilizing a gas dynamic virtual nozzle (GDVN) to generate a sample-containing liquid jet of diameter ranging from 300 nm to 20 μm, the injector avoids the clogging problems associated in this size range with conventional Rayleigh jets. A differential pumping system incorporated into the injector shields the experimental chamber from the gas load of the GDVN, making the injector compatible with high vacuum systems. The injector houses a fiber-optically coupled pump laser to illuminate the jet for pump-probe experiments and a hermetically sealed microscope to observe the liquid jet for diagnostics and alignment during operation. This injector system has now been used during several experimental runs at the Linac Coherent Light Source. Recent refinements in GDVN design are also presented. [ABSTRACT FROM AUTHOR]

The study of thermophysical properties is of great importance in several scientific fields. Among them, the heat capacity, for example, is related to the microscopic structure of condensed matter and plays an important role in monitoring the changes in the energy content of a system. Calorimetric techniques are thus of fundamental importance for characterizing physical systems, particularly in the vicinity of phase transitions where energy fluctuations can play an important role. In this work, the ability of the Photopyroelctric calorimetry to study the versus temperature behaviour of the specific heat and of the other thermal parameters in the vicinity of phase transitions is outlined. The working principle, the theoretical basis, the experimental configurations, and the advantages of this technique, with respect to the more conventional ones, have been described and discussed in detail. The integrations in the calorimetric setup giving the possibility to perform, simultaneously with the calorimetric studies, complementary kind of characterizations of optical, structural, and electrical properties are also described. A review of the results obtained with this technique, in all its possible configurations, for the high temperature resolution studies of the thermal parameters over several kinds of phase transitions occurring in different systems is presented and discussed. [ABSTRACT FROM AUTHOR]

A low speed single barrel pellet injector, using a mechanical punch device has been developed for alternative injection in the large helical device. A pellet is injected by the combined operation of a mechanical punch and a pneumatic propellant system. The pellet shape is cylindrical, 3 mm in diameter and 3 mm in length. Using this technique the speed of the pellet can be controlled flexibly in the range of 100-450 m/s, and a higher speed can be feasible for a higher gas pressure. The injector is equipped with a guide tube selector to direct the pellet to different injection locations. Pellets are exposed to several curved parts with the curvature radii Rc = 0.8 and 0.3 m when they are transferred in guided tubes to the respective injection locations. Pellet speed variation with pressure at different pellet formation temperatures has been observed. Pellet intactness tests through these guide tubes show a variation in the intact speed limit over a range of pellet formation temperatures from 6.5 to 9.8 K. Pellet speed reduction of less than 6% has been observed after the pellet moves through the curved guide tubes. [ABSTRACT FROM AUTHOR]

A new high repetition rate Nd:YAG Thomson scattering system has been designed for the Heliotron J helical device. The main purpose of installing the new Thomson scattering system is an investigation of an improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (>550 mJ at 50 Hz) realize the measurement of the time evolution of the plasma profile with 10 ms time interval. Scattered light is collected with a large concave mirror (D=800 mm, f/2.25) with a solid angle of ∼100 msr. The laser beam is injected from obliquely downward to upward, and obliquely backscattered light is detected (scattering angle is 20°). Model simulation of the polychromator shows the measurable electron temperature and density range are from10 eV to 10 keV, >5×1018 m-3 within 3% error for the temperature measurement, respectively. [ABSTRACT FROM AUTHOR]

A high explosive pulsed power generator called the advanced helical generator (AHG) has been designed, built, and successfully tested. The AHG incorporates design principles of voltage and current management to obtain a high current and energy gain. Its design was facilitated by the use of modern modeling tools as well as high precision manufacture. The result was a first-shot success. The AHG delivered 16 MA of current and 11 MJ of energy to a quasistatic 80 nH inductive load. A current gain of 160 times was obtained with a peak exponential rise time of 20 μs. We will describe in detail the design and testing of the AHG. [ABSTRACT FROM AUTHOR]

We describe a simple slow atom source for loading a rubidium magneto-optical trap. The source includes an effusive oven with a long heated collimation tube. Almost all components are standard vacuum parts. The heating elements and thermocouples are external to the vacuum, protecting them from the hostile hot alkali environment and allowing repair without breaking vacuum. The thermal source is followed by a Zeeman slower with a single-layer coil of variable winding pitch. The single-layer design is simple to construct and has low inductance which allows for rapid switching of the magnetic field. The coil pitch was determined by fitting the analytic form of the magnetic field for a variable winding pitch to the desired magnetic field profile required to slow atoms. The measured magnetic field for the constructed coil is in excellent agreement with the desired field. The source produces atoms at 35 m/s with a flux up to 2×1010 cm-2 s-1 at 200 °C. [ABSTRACT FROM AUTHOR]

A Doppler reflectometer system has recently been installed in the stellarator TJ-II. The system is optimized for the Q-band (33–50 GHz) and the high-curvature plasmas produced in TJ-II. The launch angle of the microwave beam can be controlled by a steerable mirror to obtain angles between ±20° enabling the measurement of perpendicular wave numbers in the range of 3–15 cm-1. The available angular range allows for comparisons between positive and negative values and additionally for calibration of the system. Localization and k⊥-estimation is done via the three-dimensional ray/beam-tracing code TRUBA. First measured spectra and radial profiles of the perpendicular velocity of plasma density fluctuations are presented. [ABSTRACT FROM AUTHOR]

A multichannel system of the Hα-line emission detector is developed in order to investigate the neutral particle transport in the Heliotron J plasma. The application of a multianode photomultiplier tube to the filter measurement system enables us to observe the Hα emission profile with 32 chords. The absolute calibration with a standard lamp is performed and the cross-talk between each of the adjoining channels is evaluated to be less than 6%, while the photomultiplier tube has a typical cross-talk of 3% in nominal value. The temporal and spatial profiles of the Hα emission are measured in detail in the plasma breakdown by electron cyclotron heating (ECH). The Hα emission profile in the ECH plasma is calculated by the Monte Carlo simulation using a three-dimensional mesh model. The fueling rates of the wall recycling and the gas puffing are estimated by means of the simulation and the measurement. [ABSTRACT FROM AUTHOR]

The design and first results from an electrically isolated and plasma-shielded Rogowski probe, used in the reconnection scaling experiment (RSX), are presented. The probe is designed to withstand extreme thermal shock, plasma corrosion, and be vacuum sanitary, which is accomplished with a machinable boron nitride shell. The novel miniature design, with an inner detecting area of 0.79 cm[sup 2], allows accurate position detection of plasma current channels with ≈2 cm radius and to measure local current density profiles. The temporal resolution (<1 μs) is sufficiently high to resolve the dynamic evolution of RSX plasma current channels. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A Johann-type x-ray crystal spectrometer has been designed using a ray tracing calculation and constructed for ion temperature measurement in the plasma center of a large helical device (LHD) using Doppler broadening of a He-like resonance line of ArXVII, TiXXI, CrXXIII, or FeXXV. Four curved quartz (2020), (2023), (3140), and (2243) crystals are set in a quadrangular rotary crystal holder for measuring the x-ray line from such four different elements. Each of the crystals can be externally selected through a computer network. The curved crystals with a radius of 3 m are fabricated by gluing thin quartz (0.7 mm[SUPt) on an accurately ground cylindrical blue glass plate. The curvature of the crystals was checked by scanning a sharp pin along the crystal surface. As a result, an excellent agreement with the designed cylindrical curvature was obtained with an accuracy of 1 μm. A secular change of the curved crystal surface structure was found by measuring the curvature of the curved crystal fabricated 15 years earlier. A charge-coupled-device (CCD) detector is used instead of a usually used proportional counter to increase the count rate and to avoid the influence of magnetic field leakage from the LHD. The influence of magnetic fields on the proportional counter was investigated in a range of B&les;1.5 kG. The use of the CCD brought us a large increment of more than ten times in the count rate compared with the multiwire proportional counter. The ion temperature thus has been successfully observed in a time interval of 20 ms with small error bars. The lowest measured ion temperature was 0.2-0.3 keV for ArXVII and TiXXI, which indicates an excellent spectral resolution of the crystal spectrometer. Finally, the influence of the chord integration on the measured ion temperature is discussed as a function of central electron temperature and density profile with analysis from impurity transport calculations. [ABSTRACT FROM AUTHOR]

The H-1NF heliac regularly operates using the ion cyclotron range of frequencies at 0.5 T to produce plasmas with a mixture of hydrogen and helium gases. Due to the complex three-dimensional structure of the magnetic flux surfaces, these plasmas require sophisticated diagnostic systems, with good spatial coverage, to extract meaningful physical information. This article presents a study of the dependence of the plasma density profile on resonant heating conditions and magnetic configuration, using a far-infrared scanning interferometer. Recent modifications to the system and data that illustrate the performance of the interferometer will be discussed. [ABSTRACT FROM AUTHOR]

A special two-period insertion device is considered in terms of useful properties of spontaneous emission. General idea of the geometry can be interpreted as helical transformation applied to an original linear undulator structure to provide superimposed fast and slow transverse oscillations of the electron beam. Periodic sextupolar focusing effect of the device is calculated analytically. Three-dimensional hybrid magnetic design is treated numerically on the base of traditional and specially modified feasible structures. Main properties of the spontaneous emission of single electron were studied using a derived analytical form and numerical computations. The following features of the radiation are outlined: (i) reduction of relative content of higher odd harmonics as the "slow" imposed helical field increases; (ii) radiation enhancement as the number of helical turns increases; (iii) spectral line splitting and intensity adjustment; and (iv) opposite directions of circular polarization for adjacent spectral lines. In particular, unlike most insertion devices this structure does not require any magnetic readjustments or electromagnetic switching to provide opposite polarization. Potential technical advantages in application for single pass superradiant free electron lasers are also discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Coated paramagnetic particles (PMPs) with diameters typically 1-10 μm are widely used in biomedical investigations, including immunoassays and molecular biology. In this article we describe an investigation into a measuring system to determine rapidly the concentration of PMPs in suspension in a buffer solution in a pot. The measuring system is based on a coil in a parallel resonant circuit with a capacitor. The sample pot is placed in the coil, causing the inductance of the coil to increase and the resonant frequency to decrease. The decrease in resonant frequency is directly related to the concentration of PMPs in the pot. Using a circuit based on a Colpitts oscillator it is possible to determine the concentration of PMPs in the pot with an error of about 10% over the range 0-9 mg g-1. Much more accurate measurements (error <1%) are possible using a circuit design based on a phase-locked loop. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The neutral beam (NB) shine-through profile is routinely monitored on the Large Helical Device (LHD) both to calibrate the port-through power of the NB and to evaluate the NB-deposition power to LHD plasmas. The profile is measured with a calorimeter (CM) array on an armor plate of the NB counter wall inside the LHD vacuum vessel. An infrared camera is also used to check the beam profile where CMs are not located, and measures a temperature increase of the armor plate due to the NB heat load. The measured beam profile is compared to the calculated NB profile at the armor plate. The measurement indicates that the beam is not uniform at the exit of the ion source and that the steering angle of the beam in the horizontal direction is not the same as the designed value. It is found that the monitoring of the NB shine-through profile is important to estimate the NB port-through power and the NB deposition power, especially when the neutral beam injector (NBI) is based on a large negative-hydrogen ion source. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Soft x-ray (SX) detector array systems are installed on the Large Helical Device (LHD). Two types of systems are in operation: An 80 ch array for detailed profile measurement and two sets of 40 ch array installed inside the vacuum vessel suitable for fluctuation studies. Recent results of the profile and fluctuation measurement with this system are discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes a dual-mode calorimetry capable of high resolution operation in a conventional alternating current and in nonadiabatic ramped relaxation mode. Modified version of relaxation technique; Characterization of the first- and second-order phase transition; Use in the study of liquid crystal phase transition.

Describes a complete design for a versatile nuclear magnetic resonance cryostat/probe systems specifically adapted for small 32 millimeter bore bitter magnets. Two main problems solved by the probe in association with constrained environments; Implementation of a system with an evacuated space for tuning capacitors to avoid high voltage breakdown.

Presents a study that probed the electric fields of the helical resonator using metallic copper and heavily doped silicon (Si):phosphorous (P) disks. Fundamental frequency and odd harmonics; Measurement of the relative frequency shift and the change in quality factor; Insertion of the disk as a probe mounted on a dielectric support rod.

Explores different types of ion sources used for specific industrial applications and the future trends in this area. Ion-beam processing; Ion-beam etching; Ion-beam cleaning; Ion-beam deposition; Ion-beam assisted deposition; Automatic control of the source for its utilization in complex processes; Neutralization of the ion beam in a reactive gas environment.

Describes the design of a grating polarizer with rectangular grooves for the 106.4 GHz electron cyclotron heating (ECH) system on the Heliotron-E helical device. Grating polarizer in the HE[sub 11] transmission line; Effect of magnetic shear on wave propagation through plasma; TE-like mode; TM-like mode.

In magnetic fusion toroidal confinement devices, the confining magnetic fields may have errors which produce magnetic islands. The standard method of investigating magnetic field errors involves measuring the maximum radial spatial extent of a given magnetic island at a fixed toroidal location and calling this measurement the island width. However, because of magnetic flux conservation inside an island, the spatial width of the island is not toroidally invariant. Magnetic error fields and their associated islands have been investigated in the Compact Auburn Torsatron through the measurement of the local rotational transform about the fixed points of the island. This method of magnetic field error investigation is valid at any poloidal or toroidal angle because the local rotational transform is spatially invariant. The technique of measuring the local rotational transform is described and the results are compared to those obtained using standard methods of measuring island widths. [ABSTRACT FROM AUTHOR]