bluuebunny/crossref_metadata_2025 huggingface dataset:
The EUTERPE facility
Authors: Botman J. I. M. , Xi Boling , Timmermans C. J. , Hagedoorn H. L.
Published: July 2002

The 400-MeV electron storage ring EUTERPE is a University project set up for studies of charged particle beam dynamics and applications of synchrotron radiation, and for the education of students in these fields. The ring has a relatively large circumference for the maximum beam energy contained, which is useful for accommodating insertion devices and diagnostic tools. The critical wavelength of the emitted photon spectrum is 8.3 nm for the regular dipole magnets and 1.2 nm corresponding to 1.03 keV for a 10-T wiggler. This provides useful radiation, e.g., for x-ray fluorescence up to 3.2 keV. An undulator with a periodicity distance of 2.5 cm is planned, to generate radiation of 40 nm. The major ring components are being constructed in the University workshop, including a 70-MeV injector microtron. The main characteristics of the machine and the present status are reported. Future options include a bypass system for microdevices.
Advances in precision mirror figure metrology (abstract)
Authors: Takacs Peter Z. , Furenlid Karen , Church Eugene L.
Published: July 2002

New developments in optical measurement techniques have made it possible to test the surface quality on grazing incidence optics with extreme precision and accuracy. An instrument developed at Brookhaven, the Long Trace Profiler (LTP), measures the figure of large (up to 1 m long) cylindrical aspheres with nanometer accuracy. The LTP optical system is based around a common-path interferometer design belonging to the class of slope measuring interferometers and, as such, it is very robust, stable, and vibration insensitive. A unique error correction technique removes the effect of tilt errors in the optical head as it traverses the air bearing, thus allowing one to accurately measure the absolute surface profile and radius of curvature. This is of critical importance to the manufacture of long-radius spherical optics used in high-resolution soft x-ray monochromators and in the testing of mirror bending systems. This talk will review the principle of operation of the LTP, probe the factors limiting the performance of the system, and will examine the current state of the art in synchrotron radiation mirror manufacturing quality (as viewed by our metrology techniques). This research was supported by the U.S. Department of Energy Contract No. DE-AC02-76CH00016.
Varied line-space gratings and applications (invited)
Authors: McKinney Wayne R.
Published: July 2002

This paper presents a straightforward analytical and numerical method for the design of a specific type of varied line-space grating system. The mathematical development will assume plane or nearly plane spherical gratings that are illuminated by convergent light, which covers many interesting cases for synchrotron radiation. The gratings discussed will have straight grooves whose spacing varies across the principal plane of the grating. Focal relationships and formulas for the optimal grating-pole-to-exit-slit distance and grating radius previously presented by other authors will be derived with a symbolic algebra system. It is intended to provide the optical designer with the tools necessary to design such a system properly. Finally, some possible advantages and disadvantages for application to synchrotron radiation beamlines will be discussed.
Plasma cleaning of beamline optical components: Contamination and gas composition effects
Authors: Rosenberg Richard A. , Smith James A. , Wallace Daniel J.
Published: July 2002

We have initiated a program to study the impact of gas composition on the carbon removal rate during plasma cleaning of optical components, and of possible contamination due to the plasma processing. The measurements were performed in a test chamber designed to simulate the geometry of the grating/Codling mirror section of a Grasshopper monochromator. Removal rates were determined for a direct-current (dc) (Al electrode) discharge using a quartz crystal microbalance coated with polymethylmethacrylate, located at the position of the grating. Auger electron spectroscopy analysis of strateg- ically located, gold-coated stainless steel samples was employed to determine contamination. The relative removal rates of the gases studied were 3% C2F6/O2≫ O2+H2O≳O2∼N2O≳H2≳N2. Although the C2F6/O2 gas mixture showed a 20 times greater removal rate than its nearest competitor, it also caused significant contamination to occur. Contamination studies were performed for both dc and radio-frequency (rf) discharges. For the dc discharge we found that great care must be taken in order to avoid Al contamination; for the rf discharge, significant Fe contamination was observed.
Separation of helium and deuterium peaks with a quadrupole mass spectrometer by using the second stability zone in the Mathieu diagram
Authors: Hiroki Seiji , Abe Tetsuya , Murakami Yoshio
Published: July 2002

4He+ and D2+ have been separated with a conventional quadrupole mass spectrometer by using the second stability zone in the Mathieu diagram. The minimum resolving power needed for the separation of 4He+ and D2+ is 161. A resolution of 320 defined by the full width at half maximum was attained at an ion energy of 14.6 eV in the experiment.
Enhanced sensitivity for high-pressure EPR using dielectric resonators
Authors: Bromberg Steven E. , Chan I. Y.
Published: July 2002

We present a modified Merrill–Bassett diamond anvil cell for performing electron paramagnetic resonance (EPR) experiments under high pressure. The design centers on two mutually coupled TiO2 dielectric resonators mounted close to the diamonds. This configuration produces a tangential microwave magnetic field at the gasket, which is a prerequisite for a magnetic resonance experiment. Our simple device has a considerable advantage over previous approaches for EPR under pressure in both its compactness and sensitivity.
The spatial extent of gain depression for MCP-based photon detectors
Authors: Edgar Michael L. , Lapington J. S. , Smith Alan
Published: July 2002

We describe a technique to measure the spatial extent and magnitude of gain depression in the quiescent pores surrounding an active region of an MCP and present preliminary results. We find that significant gain depression occurs up to 1.5 mm from the center of the active region. The magnitude of the reduction in gain decreases linearly with radius and is proportional to the count rate. We evaluate two possible mechanisms for gain depression. We find that the pore deactivating model in which the electric field from the discharging of a pore distorts the electric fields in surrounding pores is more successful than the transfer of charge from quiescent pores.
Synchrotron radiation research center (SRRC) in Taiwan
Authors: Yen Edward
Published: July 2002

Aiming to upgrade the local research environment and to promote local technology, the government of the Republic of China on Taiwan endeavors to construct and establish the first synchrotron radiation facility in Taiwan. The main facility is a 1.3-GeV storage ring with full energy injection from a booster synchrotron. Design and procurement of accelerator components are progressing well. The start of installation is scheduled for February 1992. Commissioning with beam is projected toward the end of 1992.
Performance and upgrades of the NSLS storage rings and photon sources
Authors:   NSLS Department
Published: July 2002

The usefulness of synchrotron radiation sources is not only determined by current, energy, and magnetic field but also orbit stability and lifetime. The status and developments at NSLS in storage ring performance are discussed. Efforts at NSLS to look toward the future in source development are presented. In particular, small gap undulator development and studies toward development of an ultraviolet free-electron laser at the Accelerator Test Facility are described.
LURE (Laboratoire pour l’Utilisation du Rayonnement Electromagnétique)
Authors:   DCI
Published: July 2002

A status report is presented for LURE facility in Orsay, France. (AIP)
An automated system for testing surface acoustic wave gas sensors
Authors: Nederlof A. J. , Nieuwenhuizen M. S.
Published: July 2002

An automated, reliable, and safe system for the unattended and safe testing surface acoustic wave (SAW) gas sensors has been developed. The system includes the possibility to generate and/or dilute almost any gas or vapor and can easily be adapted for testing sensors or equipment other than SAW sensors. A large range of concentrations is achievable by the option of single-stage or two-stage dilution. The reliability of the gas generation system is guaranteed by the continuous monitoring of the concentration and the relative humidity of the gas generated as well as the temperature of the measuring cell. Aspecific sampling effects on the sensor response are excluded by using the same conditions (temperature, humidity, and flow rate) for the diluting and the reference gas flow.
An automated loop tracer for the study of the growth of ferroelectric hysteresis
Authors: Dias E. D. , Pragasam R. , Murthy V. R. K. , Viswanathan B.
Published: July 2002

An automated ferroelectric hysteresis loop tracer, developed using an INTEL 8085 microprocessor is described. This setup can be used to study the growth of a hysteresis curve at any desired temperature instantaneously after the application of a field. Since the setup allows the storage of data for each cycle of the applied field, this can be used to study the response of ferroelectric domains in an applied alternating field with time on unpoled or poled samples. The setup is interfaced with a personal computer to obtain directly the values of loop parameters.
Simple laboratory instrumentation for measuring pointwise dimensions from chaotic time series
Authors: Namajūnas Audrius , Tamaševičius Arūnas
Published: July 2002

An analog instrumentation for estimating dimensions of chaotic dynamical systems has been developed. The technique employs time series of the Poincaré points successively displayed on the screen of an oscilloscope. It provides a rapid way to estimate the pointwise dimension from a single variable directly in an experiment. The instrumentation is easy to build and is convenient to employ. We have tested it by applying to periodic and quasiperiodic oscillators, and have verified by means of the fractal two-dimensional Poincaré map, simulated from the Duffing–Holmes differential equation. The measured values well agree with the computer calculated ones.
Using temporary cryostat support structure
Authors: Guillon F.
Published: July 2002

This paper describes a simple portable mechanical structure to support a medium size cryostat. The structure can provide adequate support for an helium-3 cryostat with an 8 T magnet while the Dewar can be stored between experiment in a pit hole area below the temporary structure.
Development of a single-longitudinal-mode, high-peak-power, tunable pulsed dye laser
Authors: Black J. F. , Valentini J. J.
Published: July 2002

A compact, high-peak-power, user-friendly, single-longitudinal-mode (SLM) tunable dye laser has been developed. The device yields ≳12 mJ pulses of 6 ns duration and ∼2.7×transform-limited linewidths of <200 MHz. Seamless single-mode tunability of ≳20 cm−1 is possible without resetting. The dye laser makes efficient use of the pump laser, with ∼10% conversion of the 532 nm pump energy to tunable dye power and occupies <4 m2 (including pump laser and all diagnostics). The linewidth of the device can be switched from <200 MHz SLM operation to <0.5 cm−1 broadband modeless operation by moving one mirror. This allows rapid interchange between high-resolution scanning and a ‘‘fast survey scan’’ mode of operation to isolate the spectral region of interest at low resolution.
On the conversion of a mass selective detector from gas chromatography/mass spectrometry application to stand-alone, on-line, real-time mass spectrometry application
Authors: Koch M.
Published: July 2002

Development of initial versions of hardware and software for a Hewlett-Packard HP-5971A mass selective detector (MSD) was performed in order to improve its capabilities for monitoring gaseous waste streams. The development allowed for initial evaluation of the feasibility of the conversion of the MSD from an integrated gas chromatography/mass spectrometry (GC-MS) detector to a stand-alone, on-line, real-time mass spectrometry (SOR-MS) detector. Chemical compound quantitation is accomplished via mass spectrometric step heights, rather than gas chromatographic peak areas or heights. Contributions of more than one chemical compound to a single M/Z ratio are accounted for by nonlinear deconvolution of the mass spectrum, provided a calibration can be obtained for all contributing chemical compounds. The enhanced MSD was tested by a number of calibration and monitoring experiments in order to evaluate the potential and limitations of the conversion. With sufficient care and awareness of the potential and limitations, it appears to be possible to convert the GC-MS detector to a SOR-MS detector. In particular, this conversion could allow for simple monitoring of reactive chemical compounds.
In situ characterization of plasma-deposited a-C:H thin films by spectroscopic infrared ellipsometry
Authors: Friedl A. , Fukarek W. , Möller W. , Koch A.
Published: July 2002

A computer-controlled rotating polarizer ellipsometer, operating in the infrared spectral region between 3.00 and 3.75 μm, has been developed for in situ characterization of amorphous hydrocarbon (a-C:H) thin films, deposited from methane in a rf plasma-enhanced chemical vapor deposition reactor. Spectroscopic IR ellipsometry permits insight into the chemical bonding structure of a-C:H coatings by the nondestructive detection of infrared stimulated C:H stretch vibrations. It is shown that the sp2CHx/sp3 CHx ratio, the content of bonded hydrogen, the infrared linewidth, and the real refractive index of the films depend on the negative self-bias voltage, which is formed at the samples during the deposition process. A transition from a-C:H films with polymerlike properties to hard a-C:H films was attained at a self-bias voltage of approximately −75 V.
A high inductance kHz resonator with a quality factor larger than 106
Authors: Falferi P. , Cerdonio M. , Franceschini L. , Macchietto R. , Vitale S. , Zendri J. P.
Published: July 2002

Electrical LC resonators with superconducting coils of ≊3.5 H inductance, operating in the frequency range 250–1500 Hz with quality factors up to Q≊1.6×106 are presented here. The coil has a reduced, <100 pF, stray capacitance and is housed in a superconducting case. Measurements are made with a low coupling SQUID readout. Some possible applications of the device are briefly discussed.
Spline-based deconvolution technique in electron paramagnetic resonance imaging
Authors: Placidi Giuseppe , Alecci Marcello , Sotgiu Antonello
Published: July 2002

The article presents a modification to the spline deconvolution technique. The method was developed within the framework of electron paramagnetic resonance imaging and is particularly useful in cases of low signal-to-noise ratio (S/N) and when the deconvolution kernel is a large fraction (about 50%) of the studied function. The modified spline deconvolution method works directly in the signal space and does not require a low-pass filter that causes loss of information and limits the resolution as is the case of Fourier deconvolution. The comparison was done with Fourier deconvolution and was based on three parameters that account for resolution, noise, and proportion stability. Experimental tests were done using two nitroxide-free radicals of different linewidths (0.05 and 0.16 mT, respectively) at different gradient values (between 0.05 and 0.2 mT/m). Modified spline deconvolution gave consistently better results in all the three parameters, particularly at the lower gradient values. For this reason the method is useful in in vivo experiments where the low S/N does not permit use of high gradient values.
Probehead with interchangeable loop-gap resonators and rf coils for multifrequency EPR/ENDOR
Authors: Christides T. , Froncisz W. , Oles T. , Hyde James S.
Published: July 2002

A probehead employing interchangeable loop-gap resonators and rf coils for multifrequency EPR/ENDOR spectroscopy from 1 to 10 GHz is described. A precision coupling mechanism allows accurate magnetic coupling of the microwaves to the resonators. The Rexolite© support of the resonator acts as a spool for the ENDOR coil. rf fields of 1.0 mT are generated. The coil and resonator can be easily changed to cover the range of 1–10 GHz. Liquid-phase ENDOR spectra of the stable free-radical galvanoxyl and of the spin label TEMPONE (4-oxo-2,2,6,6-tetramethyl-l-piperidine-N-oxyl) dissolved in n-heptane are shown. The ENDOR enhancement for nitrogen from TEMPONE is 15 times larger at 2.3 than at 9.3 GHz due to the rf enhancement.
A novel fiber-optic integrated cladding mode detector for displacement sensing
Authors: Sai S. Siva Sankara , Srinivasan K.
Published: July 2002

A novel fiber-optic cladding mode detector which uses the benefits of dark field detection in a fiber-optic sensor configuration is described. This detector integrates the microbender plate, and the photodetector. It facilitates the detection of cladding or radiation modes produced due to the microbends at the site of the bend itself thereby enhancing the signal strength. The design of this integrated detector along with the calibration curves are given. The detector performance is evaluated by using it in a displacement sensor configuration. Comparison of performance with core mode detection is also given.
A multiple-input digital correlator for the weak light scattering signals of chromatographic detectors
Authors: Lago P. , Rovati L. , Cuffaro D. , Corti M. , De Agostini A.
Published: July 2002

A simple digital correlator with four independent inputs is described. It gives 20 correlation points for each channel, with a maximum sampling frequency of 1 MHz, and is fully computer controlled. The correlator is designed to match the requirements of dynamic light scattering detectors in liquid chromatography.
A multipurpose electrical machining device with a unique control circuit
Authors: Ribaud L. , Mattocks P. G.
Published: July 2002

We present a laboratory-sized electrical discharge machining (EDM) device produced from a jeweler’s lathe with inexpensive modifications. The circuitry used to control the device is unique and simple in its operation. The device has been successfully used to machine spheres without contact. It can also perform other types of EDM machining.
A new atomic beam source: The ‘‘candlestick’’
Authors: Hau Lene Vestergaard , Golovchenko J. A. , Burns Michael M.
Published: July 2002

The design of a novel-type of atomic beam source which provides for long term, stable operation at high emission rates is reported. The heart of the design is the ‘‘candlestick’’ where liquid source material is transported by capillary action to a localized hot emission region. A surrounding cavity kept at the melting point for the source material shields the vacuum chamber walls from this region. The atomic beam escaping from the source is collimated, and uncollimated atoms are transported back to the liquid reservoir at the bottom of the ‘‘candlestick’’ by capillary action. This design has advantages over traditional oven designs: localized heating provides for large emission rates under high vacuum conditions, collimation is combined with recycling and conservation of source material, and the use of capillarity allows any orientation of the beam source. The source has been tested with sodium, and we believe that the design is useful for a broad range of applications including thin-film evaporation, molecular beam epitaxy, and semiconductor surface doping. With the low thermal mass of the emission section, the source could be optimized for pulsed mode operation. Furthermore, it is anticipated that the design ideas presented here could form the basis for a supersonic source with very high Mach numbers.
Optical pumping of a He(23S) metastable atom beam using a diode laser
Authors: Wallace C. D. , Bixler D. L. , Monroe T. J. , Dunning F. B. , Walters G. K.
Published: July 2002

Use of a commercial 1.083 μm laser diode to optically pump a collimated He (23S) metastable atom beam is described. Stable, efficient optical pumping is achieved resulting in polarizations that approach 100%.
ALTA: An automated lag-time apparatus for studying the nucleation of supercooled liquids
Authors: Barlow Thomas W. , Haymet A. D. J.
Published: July 2002

An automated apparatus for studying repeatedly the nucleation of a sample of supercooled liquid is designed and constructed. Many of the ideas are developed from an apparatus of M. Baldwin and B. Vonnegut [Rev. Sci. Instrum. 53, 1911 (1982)]. After preparation of a nonequilibrium state, ALTA measures repeatedly the ‘‘lag time’’ or ‘‘induction’’ time before nucleation and growth of the equilibrium state. A single sample is used in all experiments. The operation of the apparatus is demonstrated by generating a time series of lag times for the nucleation of supercooled water on (insoluble) AgI crystals at the temperature 269.2 K. The same sample is repeatedly frozen and thawed over 350 times. An average lag time τ can be measured precisely and reproducibly. However, nucleation of this sample is shown to be a stochastic process obeying ‘‘first-order’’ kinetics. Improved methods for analyzing time series of nucleation data are presented and tested.
New variable low-temperature scanning tunneling microscope for use in ultrahigh vacuum
Authors: Smith A. R. , Shih C. K.
Published: July 2002

We describe the design and characterization of a new variable low-temperature scanning tunneling microscope (STM) which has been proven to give atomic resolution at temperatures between 77 K and room temperature but which is also capable of performing experiments as low as 4 K. The STM ‘‘head’’ itself consists of a unique cold dewar made up of an upper and lower reservoir connected together by two tubes which pass through an 8 in. conflat flange. The STM stage is suspended in between the two reservoirs by three long springs which pass through holes in the upper reservoir and also attach to the top flange. An adjustable cold shroud surrounds the STM stage for radiation shielding while allowing sample and tip transfer when raised. It has the additional advantage of providing a controllable heat leak. By raising the shroud, the temperature can be increased; by lowering it, the temperature can be decreased. The cold reservoirs can be filled with either liquid nitrogen or liquid helium. In the case of liquid helium, an additional liquid nitrogen ‘‘jacket’’ surrounds the STM head. Everything is operated inside a customized ultrahigh vacuum chamber containing low-energy electron diffraction and various sample preparation facilities. A detailed description of the STM is presented together with performance results.
Wiggler x-ray beamlines at Synchrotron Radiation Research Center
Authors: Tsang K.-L. , Lee C.-H. , Jean Y.-C. , Dann T.-E. , Chen J.-R. , D’Amico K. L. , Oversluizen T.
Published: July 2002

We have designed three x-ray beamlines extracted out from one 25-pole 1.8 T wiggler insertion device. This wiggler insertion device at the Synchrotron Radiation Research Center 1.3 GeV storage ring will increase the usable x-ray photons with an energy up to 15 keV. In order to satisfy the big x-ray user community at Taiwan, we need to have at least three different types of beamlines to cover various kinds of experiments. Due to limitation of radiation source and space, we have specially designed three x-ray beam lines sharing the 13 mrad horizontal radiation output from the insertion device. The design and construction of these three beamlines will be described in this article.
High-sensitivity scintillating-fiber imaging detector for high-energy neutrons
Authors: Ress D. , Lerche R. A. , Ellis R. J. , Heaton G. W. , Lehr D. E.
Published: July 2002

We have created a detector to image the neutrons emitted by imploded inertial-confinement fusion targets. The 14 MeV neutrons, which are produced by deuterium–tritium fusion events in the target, pass through an aperture to create an image on the detector. The neutron radiation is converted to blue light (430 nm) with a 20 cm2 array of plastic scintillating fibers. Each fiber is 10 cm long with a 1 mm2 cross section; approximately 35 000 fibers make up the array. The resulting blue-light image is reduced in size and amplified by a sequence of fiber-optic tapers and image intensifiers, then acquired by a charge-coupled device camera. The fiber-optic readout system was tested separately for overall throughput and spatial resolution; the throughput was 0.22 electrons/photon, and the resolution was 0.8 mm. We also characterized the overall efficiency of the detector using the DT-fusion neutrons emitted by inertial confinement targets; the measured value was 14 electrons/pixel/neutron. Several neutron images of laser-fusion targets have been obtained with the detector. We describe the detector, present characterization results, and give examples of the neutron images.
New alpha-particle diagnostic using knock-on ion tails (abstract)
Authors: Fisher R. K. , Parks P. B. , McChesney J. M. , Rosenbluth M. N.
Published: July 2002

We propose a new method of measuring the fast confined α-particle distribution in a reacting plasma. The presence of α particles in a D-T plasma will create a high-energy tail on the deuterium and tritium ion energy distributions. A 3.5 MeV alpha can transfer 3.4 MeV to a tritium ion in a single elastic scattering interaction. Calculations of the size of these knock-on tails in tokamaks such as TFTR, JET, and ITER show that it may be possible to measure these tails and provide information on the fast confined alphas. The knock-on tail ions will produce D-T neutrons with energies up to 20.7 MeV, so that D-T neutron spectroscopy can be used to monitor the alpha population. Neutron spectroscopy looks especially attractive for ITER. A collimated array of threshold neutron activation detectors could be used to deduce the confined alpha density profile. Tests of this diagnostic can also be done on TFTR and JET. Existing high-energy neutral particle analyzers may allow observation of the ion tails directly via passive and/or active charge exchange.
Direct experimental evidence for trap-state mediated excitation of Er3+ in silicon
Authors: Shin Jung H. , van den Hoven G. N. , Polman A.
Published: July 2002

The time evolution of the 1.54 μm Er3+ photoluminescence intensity of Er-doped silicon following a 30 μs excitation pulse is investigated. It is found that at 9 K, the 1.54 μm luminescence from Er3+ continues to increase up to 50 μs after the pulse is terminated, when excess photocarriers no longer exist. This provides the first direct experimental evidence that a state in the forbidden gap of silicon acts as the gateway to the excitation of Er3+. Further analysis indicates recombination of bound excitons to be the most likely excitation mechanism.
An intense proton beam diagnostic using the 7Li(p,γ)8Be →141Pr(γ,n)140Pr(β+) nuclear reaction sequence
Authors: Evans C. Brad , Cooper G. W. , Ruiz C. L. , Leeper R. J.
Published: July 2002

An indirect nuclear activation diagnostic was developed to measure the proton fluence onto a thick target of lithium metal located in the diode region of pulsed power accelerators. This diagnostic uses the nuclear reaction sequence 7Li(p,γ)8Be→141Pr(γ,n)140Pr(β+) to relate the proton fluence to induced 140Pr activity. This diagnostic was calibrated using a Van de Graaff accelerator. Energetic protons were focused onto a thick lithium target driving the 7Li(p,γ)8Be reaction. The resulting prompt gamma rays activated a secondary 141Pr target via the reaction 141Pr(γ,n)140Pr(β+). A NaI gamma-gamma coincidence detector system was used to measure the induced 140Pr activity as a function of proton energy and proton fluence. These data yielded a calibration curve for proton energies ranging from 2 to 12 MeV. Since deuterium impurities can interfere with this diagnostic by driving the reaction sequence 7Li(d,n)8Be→141Pr(n,2n)140Pr, a similar calibration experiment was conducted using deuterium ions. These data yielded a correction factor that can be used to determine the deuterium contribution to the 140Pr activity, providing that the deuterium beam fraction is known.
A linear electric motor to study turbulent hydrodynamics
Authors: Dimonte Guy , Morrison Jim , Hulsey Scott , Nelson Don , Weaver Sam , Susoeff Allan , Hawke Ron , Schneider Marilyn , Batteaux Jan , Lee Dean , Ticehurst Judy
Published: July 2002

A linear electric motor has been built to study hydrodynamic instabilities at the interface between fluids subjected to acceleration. The facility is powered by 16 independent capacitor banks to provide arbitrary acceleration profiles up to 1000 times earth’s gravity. Electrical measurements include the current, magnetic field, acceleration, and projectile trajectory. The instability is observed with flash shadowgraphy. The shot turnaround time is <15 min and over 100 shots can be taken before replacing the armature and rails.
Very high Q frequency-locked Fabry–Perot cavity
Authors: De Riva A. M. , Zavattini G. , Marigo S. , Rizzo C. , Ruoso G. , Carugno G. , Onofrio R. , Carusotto S. , Papa M. , Perrone F. , Polacco E. , Cantatore G. , Della Valle F. , Micossi P. , Milotti E. , Pace P. , Zavattini E.
Published: July 2002

We report measurements on a 1.75 m long Fabry–Perot cavity locked to a Nd:YAG tunable laser using the Pound–Drever technique. The cavity decay time was measured to be about 291 μs corresponding to a quality factor Q of about 5×1011, the highest value ever reported for an optical resonant cavity.
1 W plasma x-ray source for lithography at 1 nm wavelength
Authors: Turcu I. C. E. , Ross I. N.
Published: July 2002

A picosecond excimer laser-plasma source is used to generate average x-ray powers of 1.5 and 0.9 W at 1.4 and 1 nm wavelength, respectively. These wavelengths are required for proximity x-ray lithography in the semiconductor industry. The laser system uses a commercial KrF excimer amplifier for trains of 8 ps laser pulses which are focused to power densities of ≳1015 W/cm2 on steel and copper tape targets, in atmospheric pressure helium gas. The laser to x-ray energy conversion efficiency is 10.4% at 1.4 nm and 5.4% at 1 nm x-ray wavelength. By using several, larger, commercial, excimer laser amplifiers, the x-ray power output of the laser-plasma source can be scaled up to the tens of watts required by the semiconductor industry.
Fusion Neutronic Source deuterium–tritium neutron spectrum measurements using natural diamond detectors
Authors: Krasilnikov A. V. , Kaneko J. , Isobe M. , Maekawa F. , Nishitani T.
Published: July 2002

Two natural diamond detectors (NDDs) operating at room temperature were used for Fusion Neutronics Source (FNS) deuterium–tritium (DT) neutron spectra measurements at different points around the tritium target and for different deuteron beam energies. Energy resolution of both NDDs were measured, with values 1.95% and 2.8%. Due to the higher energy resolution of one of the two NDDs studied it was possible to measure the shape of the DT neutron energy distribution and its broadening due to deuteron scattering inside the target. The influence of pulse pileup on the energy resolution of the combined system (NDD+electronics) at count rates up to 3.8×105 counts/s was investigated. A 3.58% energy resolution for the spectrometric system based on NDD and a 0.25 μs shaping time amplifier has been measured at a count rate of 5.7×105 counts/s. It is shown that special development of a fast pulse signal processor is necessary for NDD based spectrometry at count rates of approximately 106 counts/s.
Use of a charge coupled device camera for low-angle elastic light scattering
Authors: Ferri Fabio
Published: July 2002

A charge coupled device (CCD) camera has been successfully used to implement a low-angle elastic light scattering setup. A novel optical detection layout brings all the light scattered by the sample directly onto the CCD, optimizing the instrument sensitivity. The detectable angular range covers ∼2 decades, from ∼0.1° to ∼10°. The calibration of the instrument, as well as the estimate of its sensitivity, accuracy, dynamic range and linearity, can be carried out by using single pinholes. Experimental results from pinholes and diluted suspensions of polystyrene spheres are presented.
Fine temperature stabilizer for x-ray diffraction measurements
Authors: Kojima A. , Ishii C. , Tozaki K. , Matsuda S. , Nakayama T. , Tsuda N. , Yoshimura Y. , Iwasaki H.
Published: July 2002

A simple and versatile method of high-temperature stability is presented for x-ray diffraction measurements near room temperature. The small sample cell for the measurements possesses coaxial multishells to guarantee the temperature homogeneity in the shells. It is capable of being directly and easily mounted on the commercially available goniometer head. A double-stage temperature control is adopted using both a heater and a thermoelectric module. The temperature is regulated by an optimized proportional integral derivative (PID) control. The base-line stability of the temperature at the sample stage in the cell is within ±0.5 mK. X-ray precession patterns of PbCsCl3 single crystal were taken at two temperatures separated by 30 mK across the phase transition point, showing the appearance and disappearance of a diffraction spot from the superstructure.
A new method for imaging of carbon monoxide in combustion environments
Authors: Meneses J. , Briz S. , de Castro A. J. , Meléndez J. , López F.
Published: July 2002

Infrared imaging of CO in combustion environments is made difficult by cross-talk effects due to the high emission of CO2. A new method for discriminating CO emission, to be implemented in thermal cameras, is proposed. This method is based on a new family of infrared multilayer filters, denominated solid-state Fabry–Pérot (SSFP) filters. The design and spectral parameters of these filters are developed on the basis of the optical properties of the multilayers and substrate, and specific designs for CO imaging are presented. The application of this method to CO emission imaging in a flame is described, as an illustration of the wide range of applicability of SSFP filters in the detection and imaging of gases with a regularly spaced fine structure emission spectrum.
A technique for obtaining spatial and temporal mass flux measurements of a pulsed spray: A description of the hardware and methodology
Authors: Hoffman Jeffrey A. , Martin Jay K. , Coates Sam W.
Published: July 2002

This article provides a description of a diagnostic developed to allow spatial and temporal measurements of the average vertical liquid mass flux within a pulsing spray. The diagnostic incorporates a patternator similar to that used in spray research for measuring mass distributions within sprays. For this application, the patternator section consists of a row of sample tubes oriented normal and intersecting the injector axis. However, in addition to the patternator section, the diagnostic incorporates a rotating shutter mechanism, which allows phased or transient sampling of the mass within transient spray plumes. To date, the technique has been successfully applied to a number of pulsing injection systems to produce spatially resolved measurements of transient mass flux. To illustrate the capabilities of this diagnostic, sample mass flux data are provided for a pulsed fuel injector. In this case, mass flux was a strong function of time and space, and measurements were possible for all regions of the spray, independent of spray number density or liquid void fraction.
A new simple and low cost scattered transmission accessory for commercial double beam ultraviolet-visible spectrophotometers
Authors: Castiglioni E. , Grilli E. , Sanguinetti S.
Published: July 2002

A very simple but effective accessory, based on a couple of large area silicon photodiodes, is presented. It allows the analysis, by a conventional double-beam ultraviolet-visible spectro- photometer, of scattering samples. The accessory, very low in cost, can be installed and removed quickly and can be easily constructed by the users to match different commercial models. The layout and the wiring diagram of the unit are described and the performances are tested.
An automated susceptometer for the measurement of linear and nonlinear magnetic ac susceptibility
Authors: Bajpai A. , Banerjee A.
Published: July 2002

A completely automated ac susceptometer is constructed to measure phase resolved linear and nonlinear ac susceptibility. Measurements over a wide range of experimental variables, such as ac and superimposed dc fields up to 300 Oe, frequency from 1 Hz to 100 kHz, and temperature from 77 to 300 K are made using only a lock-in amplifier (LIA), a PC, and some simple electronic circuits. A temperature-measurement and control unit is built utilizing the analog–digital input and digital–analog output of the LIA. Using a proportional and integral algorithm, a control accuracy better than 50 mK is achieved. The overall sensitivity of the setup is better than 10−7 emu and a reproducibility better than 0.1% is achieved in the system.
Tapping mode imaging with an interfacial force microscope
Authors: Warren O. L. , Graham J. F. , Norton P. R.
Published: July 2002

In their present embodiment, sensors used in interfacial force microscopy do not have the necessary mechanical bandwidth to be employed as free-running tapping mode devices. We describe an extremely stable method of obtaining tapping mode images using feedback on the sensor. Our method is immune to small dc drifts in the force signal, and the prospect of diminishing the risk of damaging fragile samples is realized. The feasibility of the technique is demonstrated by our imaging work on a Kevlar fiber-epoxy composite. We also present a model which accounts for the frequency dependence of the sensor in air when operating under closed loop control. A simplified force modulation model is investigated to explore the effect of contact on the closed loop response of the sensor.
A new design for a versatile Fabry-Pérot interferometer for Brillouin spectroscopy
Authors: Weishaupt Klaus , Anders Stefan H. , Eberle Reinhold G. , Pietralla Martin
Published: July 2002

We present a new design of a Fabry-Pérot interferometer for Brillouin spectroscopy. Emphasis is placed on a quick change of the free spectral range without losing alignment, the possibility of switching the multipass arrangement from 3 to 5 pass and back, and finally on a simple and inexpensive construction. Besides this the new interferometer shows very good long term stability and is easy to handle. These features were not available before in this combination. The performance of the instrument will be demonstrated.
Instrumentation for charged particle traps
Authors: Rajput S. S. , Garg S. C.
Published: July 2002

This article reports the design and its special features for various grid biases for a retarding potential analyzer instrument aboard Indian satellite SROSS-C2 to ensure trouble free functioning of electron and ion traps. The polarities of the various grid biases, identify the difference between ion traps and electron traps. A new concept of generating bias sweeps on line for future missions has been proposed.
Development of a calorimetric technique for measuring absorption cross section of rigid bodies—Case study: carbon fiber
Authors: Gurton Kristan P. , Bruce Charles W.
Published: July 2002

A balanced calorimetric device has been developed to measure the absorption cross section of a single macroscopic sized particle (in this case a carbon fiber) at a microwave frequency of 35 GHz, as a function of size and orientation with respect to the electric field. The technique used is based on simple thermodynamic principles that relate the electromagnetic absorption of a particle to its thermal response. A single particle is irradiated in a fixed volume of gas by an approximate plane wave. Absorption by the particle results in a change in the ambient pressure that is proportional to the absorption cross section of the particle. Comparison of measured quantities with recently developed theory agree well.
Toward a realistic and tractable model for negative-ion extraction from volume sources
Authors: Whealton J. H. , Olsen D. K. , Raridon R. J.
Published: July 2002

A negative-ion source extraction model has been formulated and implemented that explicitly considers the motion of positive ions and the volume generation of negative ions. It is found that (1) for high-beam currents, the beam current is limited by a transverse space-charge limit, meaning that an increase in negative-ion density at the extraction sheath will result in a lower-beam current (this result is universally observed at high-beam current); (2) there is a saddle point with a potential barrier preventing most volume-produced negative ions from being extracted [the combination of (1) and (2) indicates that most of the negative ions being created do not find their way into the beam]; (3) the introduction of cesium may cause an increase in the transverse space-charge limit; (4) cesium also results in an increase in the fraction of volume-produced negative ions that are extracted; (5) cesium may also result in reduction of extracted electrons by producing a less negative bias on the plasma electrode with respect to the plasma, thus allowing the transverse space-charge limit budget to be taken up virtually totally by the ions. [The combination of (3)–(5) represents the way an actual increase in the beam current can be achieved]; (6) a strong ion time scale sheath instability due to violation of the Bohm criteria produces an anomalous ion temperature, which increases with the beam current, as routinely seen in measurements; and (7) the introduction of cesium may result in a reduction in this instability. These insights may lead to improvements in volume negative-ion sources.
Neutron spectrum measurements in DT discharges using activation techniques
Authors: Esposito B. , Bertalot L. , Loughlin M. , Roquemore A. L.
Published: July 2002

The JET activation system has eight irradiation ends where samples may be irradiated in the neutron flux from the plasma. There is one end, re-entrant into the top of the vessel, for which there is little intervening material between it and the plasma; the other ends, including two beneath the divertor coils, have increasingly larger amounts of intervening structure. The local neutron spectrum at each irradiation end was measured by simultaneously activating several elemental foils (Al, Au, Co, Fe, In, Mg, Nb, Ni, Ti, Zr). There were 15 activation reactions in the energy range of 0.5–16 MeV which were used as input to the SNL-SAND-II code to determine the neutron energy spectrum. The results are compared with neutron transport calculations both from the MCNP and FURNACE codes: the average standard deviation between measured to SNL-SAND-II calculated activity ratios was as low as 5%. The results demonstrate the reliability of the neutronics calculations and have implications for the design of diagnostics and blankets for the next generation of large tokamaks such as ITER. The 377.9 keV line of the Fe54(n,2n)Fe53 reaction (threshold ∼13.9 MeV, not a dosimetric standard) has also been measured in different plasma conditions. The ratio of the saturated activity from this reaction to that from the Fe56(n,p)Mn54 reaction (threshold ∼4.5 MeV) provides information on the broadening of the 14 MeV fusion peak.
A 14 MeV neutron spectrometer for the Joint European Torus deuterium-tritium experiments
Authors: Hawkes N. P. , van Belle P. , Bond D. S. , Croft S. , Jarvis O. N.
Published: July 2002

A 14 MeV neutron spectrometer, based on the principle of the proton recoil telescope, has been installed as a deuterium–tritium (DT) plasma diagnostic at the Joint European Torus. The device comprises three identical telescope modules arranged one behind the other, to increase efficiency without worsening resolution. It views the plasma along a horizontal line of sight. The total efficiency is 7.05×10−5 counts per (neutron per cm2), and the calculated response function has a full width at half maximum of 2.2% at an incident neutron energy of 14.1 MeV. The spectrometer was operational throughout the recent DT experiment No. 1, and selected neutron spectra have been analyzed in terms of the contributions from the various neutron production mechanisms.
Investigation of plasma fluctuation coherence by backscattering of ordinary and extraordinary waves (abstract)
Authors: Skibenko A. I. , Berezhnyj V. L. , Pavlichenko O. S. , Ocheretenko V. L. , Pinos, I. B. , Fomin I. P. , Voitsenya V. S.
Published: July 2002

A modified method of dual polarization single line microwave backscattering is proposed for correlation and spectral studies of density fluctuations in plasma with known geometry of magnetic field (stellarator with low β plasma, reflex discharge). Simultaneous launching of microwaves of both ordinary (O) and extraordinary (X) polarization via the same antenna has an advantage for correlation measurements of fluctuations in adjacent plasma layers because a procedure of separation of reflected waves is simplified.
Turbulence and beam size effects on profile reflectometry (abstract)
Authors: Estrada T. , Sánchez J. , de la Luna E. , Zhuravlev V.
Published: July 2002

A two-dimensional code based on the Wentzel–Kramers–Brillouin approximation is used to simulate the ability of reflectometry techniques to reproduce the average density profile in an ignition device to test engineering concept (ITER) size plasma with density turbulence. Analysis is mainly performed for frequency modulation [(FM) swept frequency] systems, with some comparison with the amplitude modulation techniques. The effects of turbulence with nonperpendicular reflection and plasma rotation are analyzed. Perturbation effects seem to appear for the FM technique, although the real impact for reflectometry in ITER will strongly depend on the parameters of turbulence and rotation. The influence of the turbulence level, fluctuation wavelengths, and antenna beam size on the density profile determination has been studied in a static plasma with perpendicular launching. The vector average of the reflected e field improves the resultant profiles in turbulent plasmas, while an inappropriate choice of the antenna beam size may cause additional errors. The code has also been used to simulate correlation measurements. The results show the correlation of the reflectometry signals for different turbulence parameters. Errors in the correlation length increase when two-dimensional effects become important, although the homodyne signal works better than the phase. Along with the use of these studies for turbulence analysis and code validation, the correlation measurements can be used as a robust method for the determination of the signal time delay and therefore of the density profile in highly turbulent plasmas with parasitic reflections.