bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital electron beam induced current imaging: Apparatus and analysis
Authors: Sawyer William D. , Bell Richard O.
Published: July 2002

The electron beam induced current (EBIC) method is a well known technique for studying charge carrier recombination at extended defects in semiconductors. In this work a new electron beam induced current apparatus is described. It employs computer automated measurement and control equipment to acquire high resolution beam induced current images using a conventional secondary electron microscope. The electron beam induced current images typically contain a matrix of 512×512 digitally measured points. They can be displayed on a workstation monitor and imaging processing can be performed. The increased current resolution of the apparatus necessitated the modification of traditional quantitative EBIC analysis methods. The modified quantitative analysis method is presented and applied to the problem of precipitates contained in a Czochralski silicon solar cell. It results in a characterization of the amount of charge carrier recombination at the defects and a calculation of the depth of the defects below the sample surface.
Supersonic cluster beam source using a differential cryopumping system
Authors: Hirayama Takato , Kanehira Atsuko , Arakawa Ichiro
Published: July 2002

We have developed a supersonic cluster beam source for the use of an electron-cluster crossed-beam experiment to study the electronic excitation processes in rare gas clusters. A cryopump is used for the differential pumping system instead of a diffusion pump, which is used in conventional cluster beam sources. The performance of this differential pumping system is examined. The size distribution in the cluster beam is estimated by measuring the kinetic energy and velocity distribution as a function of the stagnation pressure.
A voltage control unit for ion scattering spectroscopy analyzers
Authors: Roos W. D. , Henson R. P. , van Wyk G. N.
Published: July 2002

A voltage control unit for a spherical sector analyzer used in the energy analysis of scattered ions is described. Three modes of operation, namely, automatic, manual, and computer control is possible. The unit is directly calibrated in terms of the scattered energies which is displayed on a liquid crystal unit. The scanning time in the auto mode is adjustable from 1 to 999 s in 1-s steps for any selected energy range. A 0–10-V recorder output is available regardless of the energy window selected. The basic operation and the functioning of the various components are explained with the help of block diagrams and a final evaluation of the system is given. Complete circuit diagrams are available from the Physics Auxiliary Publication Service (PAPS) of the American Institute of Physics.
Capacitive angle sensor with infinite range
Authors: Peters Randall D.
Published: July 2002

A variant of the linear rotary differential capacitance transducer has been used to build an angle sensor which is essentially linear over an infinite range, while maintaining microradian resolution. This capability is realized by ganging two of the transducers on a common axle, in quadrature. By sequentially monitoring the output from the pair of transducers with a personal computer, estimates of axle position are obtained through a switching algorithm.
Ultrahigh vacuum/transfer system for electrochemical studies
Authors: Wang Kuilong , Eppell Steve , Chottiner Gary S. , Scherson Daniel A.
Published: July 2002

An ultrahigh vacuum/transfer system has been designed and constructed to investigate the electrochemical properties of surfaces prepared and characterized in ultrahigh vacuum (UHV). One of the unique features of this system is a self-contained electrochemical cell with a built-in dynamic hydrogen reference electrode which can be charged and tested in situ. The capabilities of the apparatus were demonstrated by examining the cyclic voltammetry of c(4×2)CO/Ni(111) surfaces (formed in UHV) in 0.1 M KOH electrolytes. The first linear scan in the positive direction revealed characteristic features associated with the quantitative electrooxidation of the adsorbed CO not observed in specimens exposed to an oxygen containing atmosphere.
Tip alignment system in a sextupole-corrected scanning transmission electron microscope
Authors: Ruan Shengyang , Kapp Oscar H.
Published: July 2002

Tip alignment and replacement in ultrahigh vacuum field-emission electron microscopes is traditionally a time-consuming endeavor. A convenient autodrive system for the 200 kV scanning transmission electron microscope was developed to facilitate the alignment of field-emission tips, thus saving a great deal of experimenter time. Under computer control, a series of automatic electrical and mechanical processes are initiated to systematically adjust various parameters to effect passage of the electron beam through the various apertures of the microscope column. The task of ‘‘finding the beam’’ is thus performed automatically. In this process the tip holder is moved in a raster parallel to the first anode. Feedback from various detectors placed throughout the column direct the positioning of the tip for optimal alignment. This process is routinely performed in about 45 min.
In situ calibration of a streak camera in nanosecond region with a sequenced multispark switch
Authors: Tou T. Y.
Published: July 2002

This article presents an in situ calibration of a streak camera from 500 ps/mm to 20 ns/mm of streak speeds with an adjustable time-sequenced multispark switch. This switch is comprised of a trigatron which drives two other secondary sparks separated in time from several nanoseconds to almost 1 μs by simply varying their respective breakdown gaps. The spark light sources of ≤7-ns rise time from these two secondary breakdowns are coupled into the streak camera using optical fibers and the null streak span separating two parallel streak images corresponding to the time delay between their measured spark currents, thus allowing a streak speed to be calibrated. The main advantage of this calibration technique, besides simplicity and cost effectiveness of the multispark switch, is that the streak camera is easily synchronized without using any electronic delay unit.
High-pressure cell for oxygen annealing at elevated temperatures
Authors: Mihaly L. , Kendziora C. , Hartge J. , Mandrus D. , Forro L.
Published: July 2002

We have designed and tested a pressure cell for oxygen treatment of small samples. Using this cell, oxygen pressure up to 4 kbar can be applied at temperatures up to 600 °C in a simple, cost effective, and reliable way. We have applied this method to O2 doping of high-temperature superconductors.
Direct measurement of plasma flow velocity using a Langmuir probe
Authors: Lee S.-G. , Diebold D. , Hershkowitz N. , Intrator T. , Wang X. , Kim G.-H.
Published: July 2002

Plasma flow velocity was determined experimentally from the time delay between fluctuations measured by two spatially separated Langmuir probes in both subsonic and supersonic, steady-state, unmagnetized plasma flows.
A PC-based system for studying current-controlled electrical switching in solids
Authors: Chatterjee R. , Acharya K. V. , Asokan S. , Titus S. S. K.
Published: July 2002

A simple PC-based system has been developed for studying the current-controlled electrical switching in solids, in particular amorphous semiconductors. The system has provisions for investigating the switching behavior in the continuous current mode or in the pulse mode and for resetting memory-switched samples. It also has facilities for studying the switching behavior under controlled heating.
A fast multi-time-interval analyzer with real-time processing capability
Authors: Höbel M. , Wüthrich M. , Ricka J. , Binkert T.
Published: July 2002

We report on the prototype of a new digital multi-time-interval analyzer (MTIA-1) based on a counter/memory architecture. The occurrence of multiple events with respect to a common start can be determined with a timing resolution of 4 ns. Incoming standard TTL or ECL pulses are processed and stored immediately after their detection in a 4096×16 Bit RAM. By virtue of this real-time histogramming concept, data acquisition does not have to be interrupted during signal processing. The maximum repetition rate of events to be processed in real time can be in excess of 20 MHz. The MTIA-1 is designed for repetitive timing applications where multiple time intervals have to be processed with very high speed. The analyzer accepts standard TTL or ECL pulses and has a maximum measurement range of 4096 channels. After the end of an individual multi time interval measurement no additional time consuming postprocessing is needed for data transfer or data analysis. The article gives an overview of the structure of the analyzer and its principle of operation. We further present an example for an application where the MTIA-1 is used in fiberoptic distributed temperature sensing.
A double-crystal (n,−n) x-ray monochromator with sagittally bent second crystal for arbitrarily divergent radiation
Authors: Hrdý J.
Published: July 2002

The maximum transmitted intensity through a (n,−n) double-crystal x-ray monochromator with sagittally (cylindrically) bent second crystal takes place when the virtual source lies on the surface of the cylinder. In this case all beams diffracted from the first flat crystal are also diffracted from the second cylindrically bent crystal. The magnification in this case is exactly 1/3 independently of Bragg angle.
Novel magnetic-spiker sustainer excitation circuit for a multijoule TE CO2 laser
Authors: Bhadani P. K. , Tang Y. X. , Harrison R. G.
Published: July 2002

Successful operation of a multijoule output TE CO2 laser using a new magnetic-spiker sustainer excitation circuit is reported. The use of the new excitation circuit has resulted in a significant reduction (∼90%) in the amount of sustainer pulse energy that has to pass through the magnetic switch. In addition, the new circuit technique allows operation of the discharge at reduced voltage (∼50%) and extends the range of excitation current pulse durations (up to ∼7 μs) over which arc-free discharges can be formed. The laser has produced a typical output of 5 J at an overall efficiency of ∼13% from a helium-free gas mixture at a pressure of 400 mbar.
New time-of-flight electronics for atom-probe field-ion microscopy
Authors: Chan D. K. , Davis B. M. , Seidman D. N.
Published: July 2002

We present new time-of-flight electronics for atom-probe field-ion microscopy that is based on the LeCroy 2277/EXP2 time-to-digital converter (TDC) and is significantly superior to the commonly used LeCroy 4208 TDC. The maximum number of ions detected for each cycle is increased, the electronics dead time is decreased, and the pulse width from the Phillips Scientific 6904 discriminator is measured. The LeCroy 2277/EXP2 TDC records up to 128 ions per field evaporation pulse as opposed to a maximum of eight ions for a single LeCroy 4208 TDC. The dead time is reduced by increasing the pulse pair resolution, in the multihit mode of the TDC, from 7.3 to 3.3 ns. The LeCroy 2277/EXP2 TDC has both leading and trailing edge detection capability, allowing us to measure the pulse width generated by the Phillips Scientific 6904 discriminator. Combining the pulse width measurement capability with the updating capability of the Phillips Scientific 6904 discriminator, in which the discriminator extends the output pulse width by the time difference between two closely spaced (<2 ns) pulses, we resolve two ions arriving within 2 ns of each other. With these improvements, we find that 66% of the total number of multiply field-evaporated ions arriving with a pulse separation of up to 8 ns are incorrectly counted as a single ion. The percentage of multiply field-evaporated ions occurring with a pulse separation of 2 ns is 6%.
Design features of a high-intensity, cesium-sputter/plasma-sputter negative ion sourcea)
Authors: Alton G. D. , Mills G. D. , Dellwo J.
Published: July 2002

A versatile, high-intensity, negative ion source has been designed and is now under construction which can be operated in either the cesium-sputter or plasma-sputter mode. The cesium-sputter mode can be effected by installation of a newly designed conical-geometry cesium-surface ionizer; for operation in the plasma-sputter mode, the surface ionizer is removed and either a hot filament or rf antenna plasma-discharge igniter is installed. A multicusp magnetic field is specifically provided confining the plasma in the radial direction when the plasma-sputter mode is selected. This arrangement allows comparison of the two modes of operation. Brief descriptions of the design features, ion optics, and anticipated performances of the two source geometries will be presented in this report.
Displacement sensor using a hollow metal optical waveguide
Authors: Branzalov P. P. , Ivanov L. M. , Pavlov L. I.
Published: July 2002

A displacement sensor utilizing a light mode attenuation principle in a hollow metal waveguide is investigated. This sensor can be used to control and measure displacements up to 20 cm. The sensor characteristics are studied both experimentally and theoretically. The sensor design allows a variation of its specified characteristics in a broad range making it suitable for every practical application. A very simple and cheap design has been obtained.
A system for in-situ pressure and ac susceptibility measurements using the diamond anvil cell: T
c(P) for HgBa2CuO4+δ
Authors: Kim Charles C. , Reeves M. E. , Osofsky M. S. , Skelton E. F. , Liebenberg D. H.
Published: July 2002

Substantial improvements have been made in the sensitivity of an ac susceptibility measurement system which determines the pressure dependence of the superconducting transition temperature, Tc(P). The pressure, P, is determined near Tc from the position of the R1 and R2 fluorescence peaks from ruby chips. The system was used to determine Tc(P) for several high Tc single crystals, but was not sufficiently sensitive to determine Tc(P) of polycrystalline samples for HgBa2CuO4+δ. This motivated us to improve the sensitivity of our system. Other parts of the system and the data analysis procedures also have been improved. As a demonstration, Tc(P) of HgBa2CuO4+δ polycrystal to 4 GPa is presented. The improvement of the system using the diamond anvil cell opens the possibility of measuring Tc above 10 GPa and on smaller samples.
Methods of temperature stabilization of light-emitting diode radiation
Authors: Mroczka Janusz , Parol Marian
Published: July 2002

Some problems of temperature stabilization of light-emitting diode (LED) radiation have been discussed in the paper. Temperature–electrical characteristics of LED have been discussed and a way has been suggested to use them for the improvement of techniques for the temperature stabilization of their radiation power. There exists a possibility of developing one common monolithic LED-compensation system, and at the same time, a thermally compensated electroluminescence diode. The compensation system presented in the paper, in which an LED is a source of radiation and a temperature sensor, is not complicated and is practical in measurements where thermal conditions undergo fast changes. The presented system for the thermal stabilization can be adapted for impulse work, which allows for a considerable increase of LED radiation power. It has been proved in the paper that LED is an original source of radiation which can be applied to a construction of photometers of different kinds, working in real field conditions.
New setup for a position-sensitive γ-ray detector
Authors: Aspacher B. , Maier K.
Published: July 2002

We present experimental results about a position-sensitive γ detector with a diameter of 75 mm, a position resolution of 3.5 mm, and a good linearity for 662 keV γ rays using a NaI or plastic scintillator. The detector is designed to solve some of the Anger camera’s readout problems and to be as close as possible to the sample in a 90° perturbed angular correlation experiment. It might substitute up to 100 smaller detectors with the same angular resolution or could cover 70% of the 4π geometry in crystal ball experiments. The setup allows easy and fast signal processing in angular correlation experiments due to the use of point symmetry in the experiment as well as in data analysis.
Fiber-optic proton beam intensity monitor
Authors: Bernini U. , Campajola L. , Conti M. , Del Guerra A. , Di Fiore L. , Grado A. , Roca V. , Russo P.
Published: July 2002

The thermally induced change of the birefringence of a high-birefringence fused-silica optical fiber, when exposed to a proton beam (2 MeV, 0.5–44 nA, 5-mm spot diameter), was measured with a fiber-optic polarimetric sensor. A short length (5 cm) of 125-μ-diam, single-mode, polarization-maintaining optical fiber was put orthogonally to the beam in vacuo and the linear polarization of a HeNe laser beam launched into the fiber was analyzed by a polarizer and recorded by a photodetector. The response of the sensor both to a continuous and to a modulated proton beam was studied. The photodetector output, which varies with the cosine of the induced relative phase retardance between the fiber eigenmodes, provides a dc or an ac (10 Hz test modulation frequency) measurement of the beam current. This device acts as a proton beam intensity monitor, with minimum beam perturbation and a sensitivity of 0.1 nA. Its possible use also as a beam position monitor or as a wire-scanner beam profiler is suggested.
Efficient low-energy beam transport for intense, high-brightness H− beams in high energy accelerators: Perspectives and a solution using ESQ lenses (abstract)a)
Authors: Guharay S. K. , Allen C. K. , Reiser M. , Saadatmand K. , Chang C. R.
Published: July 2002

The characteristics of a 30 mA, 35 kV H− beam from a volume source have been determined using emittance measurements. A low energy-beam transport (LEBT) system consisting of six electrostatic quadrupole lenses and a short (about 5 cm long) single-stage einzel lens is designed with the aim of transporting the beam over a distance of about 30 cm and focusing a clean, matched beam into a radio-frequency quadrupole accelerator of the Superconducting Super Collider. The system parameters are chosen on the basis of simulation of beam dynamics. The emittance growth in the LEBT section is within a factor of about 1.5 and this satisfies the requirement of the emittance budget. The LEBT system is designed to be mechanically rugged.
The calculations of low-energy beam transport
Authors: Jian-Qin Lu
Published: July 2002

After the ion beams are extracted from ion sources, it is necessary to transport the beams to the experimental areas or to the accelerating installations. Low-energy beam transport systems usually consist of some axially symmetrical electrostatic focusing and accelerating lenses as well as quadrupoles and dipoles. Here, we discuss the calculation methods for the beam transport in electrostatic lens systems and describe a computer program for this use.
Physical images of extraction systems with four and five electrodes (abstract)
Authors: Wang G.
Published: July 2002

Some expressions of the variation of the beam divergence caused by apertures in each electrode versus the electric field intensity ratio for the extraction system with four and five electrodes are given. When the electric field intensity ratio is changed from 0.8 to 3.2 for a four-electrode system, the divergence caused by an aperture in the third electrode is always divergent and slightly increases with the electric field intensity ratio. The divergence caused by an aperture in the second electrode increases linearly with the electric field intensity ratio and varies from divergence through the zero point to convergence. When the beam perveance is matched, the beam divergence formed by the ion emission boundary will cancel out the role of the second and third electrodes. Thus, the beam divergence caused by the ion emission boundary decreases with increases in the electric field intensity ratio and varies from convergence through the zero point to divergence. On one hand, the perveance ratio increases as the electric field intensity ratio increases, and on the other hand, the perveance of the plane diode, at a certain beam energy, will evidently decrease as the electric field intensity ratio increases. Therefore, the beam current only falls slightly with an increase in the electric field intensity ratio at a certain beam energy. When the beam divergence in each electrode aperture is smaller, the optimum electric field intensity ratio only decreases from 1.76 to 1.47. For an extraction system with five electrodes, the beam current is changed by changing the voltage across the extraction gap, and then the beam is accelerated to the given energy by the voltage across the third gap. Moreover, the beam current can be kept constant by adjusting the voltage across the extraction gap; in this case, the beam energy is changed by changing the voltage across the third gap.
Electrostatic low-energy beam transport systems for the SSC linac (abstract)a)
Authors: Raparia D. , Guy F. , Saadatmand K. , Funk W.
Published: July 2002

This paper provides arguments to choose electrostatic low-energy beam transport (LEBT) over the magnetic LEBT for the SSC linac. We will outline the rules to design the electrostatic LEBTs with examples of SSC LEBTs.
Theory of abnormal desorption
Authors: Ptitsin V. E.
Published: July 2002

A phenomenological model is offered for the mechanism of a drastic increase in the desorption flow density of the native metal atoms under the influence of a high-power density (∼107 W/cm2) electron flux incident on the metal surface. The possibility is discussed of building an electron-optical system capable of producing a submicron probe of a ∼107 W/cm2 power density.
Model of the mechanism of liquid metal ion source emission
Authors: Ptitsin V. E.
Published: July 2002

The results of calculations of the liquid metal subsurface layer atom binding energy and temperature under operating conditions of a Ga liquid metal ion source (LMIS) are given. The concepts developed in this article can help to explain the presence of excited neutral atoms of the LMIS substance in the desorption flux.
Ion cyclotron resonance in a magnetized sheet plasma
Authors: Nanri K. , Matsumura M. , Homma M. , Kinoshita N. , Yabe E. , Kawamura K. , Takayama K.
Published: July 2002

Separation of ionic or isotopic species in a magnetized sheet plasma has been studied by using the ion cyclotron resonance method. The sheet plasma was used instead of a cylindrical plasma in which many unfavorable collisions take place. An rf electric field is applied to the plasma by two parallel plate electrodes. It is shown that a resonance is strongly dependent on the plasma space potential across the sheet plasma. The resonance spectra of argon, neon, and nitrogen ions in the low dense sheet plasma with a shallow potential well are clearly observed, while the resonances in high dense plasma with a deep potential well are not observed. It is also found that the resonance frequency for a corresponding ion is proportional to the magnetic field strength.
Helicon ion source for plasma processing
Authors: Katyukha V. P. , Kirichenko G. S. , Rusavskii A. V. , Taranov V. B. , Shamrai K. P.
Published: July 2002

The results of theoretical and experimental investigations of dense plasma source resonantly excited by helicon wave are presented. Driven by a single-loop low-voltage (≂300 V) antenna, a source generates a plasma of density up to 5×1011 cm−3 at gas pressures 0.5–20 mTorr, operates at magnetic fields <100 Gs, and produces low-energy ion fluxes (<60 eV) with current densities up to 7 mA/cm2 and 3.5% nonuniformity within a diameter 10 cm. A high-efficiency helicon source originates in a special kind of ‘‘resonance’’ wave discharge, where a sharp increase of plasma resistance occurs near the helicon wave dispersion branches.
Low energy broad beam multipole ion source
Authors: Lu D. L. , Yang J. F. , Jiang S. F.
Published: July 2002

A low energy broad beam multipole ion source has been successfully developed at the Southwestern Institute of Physics, which can be used for both sputtering deposition and direct ion beam deposition. The extracted A+r beam current is 30–250 mA at a beam energy of 200–6000 eV. It has been used for sputtering deposition at the three beam synchronously mixing machine in Dalian University of Technology.
High-energy intense beam current focusing ion source (abstract)
Authors: Yucai Feng , Baomin Zheng
Published: July 2002

This paper describes a special designed 8-cm-diam broad beam ion source. Special cusp magnetic fields are used to control the beam spot area by magnetic convergence, so that a focusing beam can be extracted from a simple two-grid accelerator system without using dished grids. A beam current over 350 mA can be extracted from this source for argon gas, and the maximum of beam current density is over 20 mA/cm2 at a location 40 cm downstream of the source. The highest energy of the extracted ions is about 10 keV and the maximum of sputter coating rate from high to low sputter yield of target material is 15 Å/s for aluminum, 7.5 Å/s for titanium and 2.5 Å/s for graphite, respectively.
High current O+ ion source
Authors: Chen Y. G. , Zhou D. Q. , Luo Z. X.
Published: July 2002

A high current O+ ion source is desirable for applications to SIMOX and materials modification. To meet the requirements of this field, a new type of nonfilament high current O+ ion source has been developed successfully in our institute. Using O2 as discharge material, the typical extraction characteristics are as follows: The total oxygen ions current is 100 mA, of which the content of O+ is 80%, beam current density is larger than 200 mA/cm2 when the power consumption is 100 W; therefore the economic property is 1 mA/W. Feeding N2, the total extraction beam current is 100 mA of which 70% is N+ while the power consumption is 135 W.
Development of a new-type full-ion source
Authors: Biehe Sun , Qin Chen , Bin Liu , Shangbin Hu
Published: July 2002

This article gives the physical thinking and technical design for studying a new-type full-ion source. An optimum configuration of the source, the optimum distribution of electric field and magnetic field in the discharge chamber, and the operation parameters are given by theoretical calculations. The source has features as follows: It has a microwave plasma cathode; in principle, it may produce the ions of all elements in the periodic table and provide high current ion beams; the sputtering mechanism for the production of metal ions has been adopted; the configuration of the source and the distribution of the electric field and magnetic field in the discharge chamber contribute more to producing high-concentrated plasma; ions of multiple charge state may be obtained.
Experimental test of H− volume production process in a hydrogen discharge
Authors: Fukumasa Osamu , Iwasaki Toshio , Naitou Hiroshi , Sakiyama Satoshi
Published: July 2002

To investigate electron energy dependence of pure H− volume production, we have recently designed a double-plasma-type negative ion source. In this source, both energy and density of fast electrons are well controlled. With the use of this source, the effect of fast electrons on H− production, i.e., the so-called two-step process of H− production, is discussed.
Various ways of cathode plasma formation to produce up to 200 A/cm2 of H− and 0.1–1 A/cm2 of C−, F−, I−, and Pb− ions
Authors: Mozgovoy A. G. , Papadichev V. A.
Published: July 2002

Various ways of initiating cathode plasma for producing high-current densities of negative ions were tried at the P. N. Lebedev Physical Institute. The first was prepulse induced electrical breakdown on the surface of a dielectric inserted between two metallic parts of a cathode. A second method was surface discharge of a perforated dielectric sleeve on a metallic cathode rod, which yielded acceptable plasma parameters for larger prepulse voltages than in the first case. A circuit was developed and tested to supply an externally applied prepulse with changeable parameters. The third method employed laser illumination of a cathode dielectric surface to initiate cathode plasma. No prepulse was used in this case and nearly the same current densities of negative hydrogen ions were obtained as with the first method of plasma initiation. A new more widely applicable way of cathode plasma initiation was proposed recently and studied experimentally. This method allows one to produce negative ions of various chemical elements in high-current pulsed diodes. It utilizes cathode bombardment by positive ions extracted from near-anode plasma injected at the outer surface of the anode and which penetrates partially through anode holes into the diode. Plasma parameters can be easily varied by changing plasma gun voltage and time delay between plasma gun pulse and diode voltage pulse. Current densities of up to 30 A/cm2 of H− and about 1 A/cm2 of C−, 0.3 A/cm2 of F− and 0.1 A/cm2 of I− and Pb− were recorded using this last method of cathode plasma production. The merits and disadvantages of all methods of cathode plasma production are discussed.
Ion beam noise reduction method for the MEVVA ion source (abstract)a)
Authors: Oks E. , Spädtke P. , Emig H. , Wolf B. H.
Published: July 2002

The beam extracted from the MEVVA ion source tends to be of a relatively high-noise level, particularly for the higher charge states, making beam transport difficult in accelerator applications. This paper presents experimental results which show that the use of grids within the ion source in combination with a solenoidal magnetic field can decrease the noise of the extracted beam considerably. The noise reduction can be explained by an increase in plasma density due to the applied magnetic field and space charge limitation of the extracted ion beam current.
Vacuum separation of the ionization volume from the cryostat insulating volume in the Stockholm cryogenic electron-beam ion source
Authors: Pikin A. I. , Liljeby L. , Beebe E. N. , Björkhage M. , Engström Å. , Paal A.
Published: July 2002

The main goal of this project was to increase the reliability of CRYSIS by separating the ionization region from the insulating volume which contains vacuum seals at the cryostat. These volumes are separated with two bellow units installed between the cryostat and both ends of the vacuum vessel. The bellow units contain drift tubes with different fixed temperatures, heat shields, feedthroughs for drift tubes, and a gas delivery tube for gas injection. Preliminary results of tests after CRYSIS vacuum separation are presented.
MIDAS, a high efficiency microwave discharge ion source for the EXCYT facility
Authors: Ciavola G. , Gammino S. , Raia G. , Sura J.
Published: July 2002

A microwave discharge ion source has been designed in order to obtain high efficiencies for positive ionization of the recoils to be produced at the exotics at the cyclotron Tandem facility. After a charge exchange process the negative ions will be injected into the 15-MV Tandem, already working at the Laboratorio Nazionale del Sud. The short ionization time and the fast wall recycling make this source very well suited for the purpose of high efficiency ionization of the recoils. The operational principle and the design are described in the following.
A simple liquid nitrogen gas-flow cryostat for variable temperature laser luminescence studies
Authors: Fairman Richard A. , Spence Kirk V. N. , Kahwa Ishenkumba A.
Published: July 2002

A liquid nitrogen gas-flow cryostat is described which provides steady temperatures between 77 K and room temperature for variable temperature laser luminescence studies. The cryostat is constructed from common laboratory apparatus and requires no quartz glassware. Liquid nitrogen is consumed by the cryostat at a rate of 1 ℓ per hour.
Reliable high-pressure seal for multiple applications
Authors: Gorbaty Yu. E.
Published: July 2002

A simple steel-to-steel packing for sealing details of high-pressure, high-temperature vessels is described. Being self-sealing, the packing is fairly reliable and can be used repeatedly. In addition, it allows one to avoid damage of the valuable parts of the apparatus.
Analytical tool to study beam optics (abstract)
Authors: Elsamman A.-R. A. , Abdelaziz M. E. , Zakhary S. G.
Published: July 2002

The influence of beam perveance, emittance on a beam propagating in the axial direction, has been studied. The beam envelope equation has been solved in order to find the variation of both beam radius and slope during beam transport.
An analytical model for scanning electron microscope Type I magnetic contrast with energy filtering
Authors: Chim W. K.
Published: July 2002

In this article, a theoretical model for type I magnetic contrast calculations in the scanning electron microscope with energy filtering is presented. This model uses an approximate form of the secondary electron (SE) energy distribution by Chung and Everhart [M. S. Chung and T. E. Everhart, J. Appl. Phys. 45, 707 (1974). Closed form analytical expressions for the contrast and quality factors, which take into consideration the work function and field-distance integral of the material being studied, are obtained. This analytical model is compared with that of a more accurate numerical model. Results showed that the contrast and quality factors for the analytical model differed by not more than 20% from the numerical model, with the actual difference depending on the range of filtered SE energies considered. This model has also been extended to the situation of a two-detector (i.e., detector A and B) configuration, in which enhanced magnetic contrast and quality factor can be obtained by operating in the ‘‘A–B’’ mode.
Radio-frequency hollow cathode etching reactor with multipolar confinement
Authors: Kessi O. , Djahièche-Nencib S.
Published: July 2002

A magnetically enhanced radio-frequency (13.56 MHz) triode plasma reactor with ‘‘multitubes hollow’’ cathode is characterized by measuring the self-bias potential Vdc and the saturation ion current density Js as a function of SF6 pressure and incident power. The cathode shape allows a decreasing of Vdc and an increasing of Js. For a power of 600 W and a pressure of 15 mTorr, Vdc does not exceed 200 V and Js is about 0.6 mA cm−2.
Measurement of low energy ion tracks in CR-39 plastic with an atomic force microscope
Authors: He Y. D. , Hancox C. I.
Published: July 2002

We demonstrate that an atomic force microscope allows one to measure the detailed geometry of etch pits due to heavy ions with kinetic energies of 1−10 keV/amu at small distance scales registered in the nuclear track detector CR-39 plastic. With a typical range of a few hundred nm and an etch pit depth on the order of a few tens of nm, these ion tracks cannot be measured using conventional methods. With the technique developed in this work one is able to study the response of CR-39 plastic to particles at low ionization rates by precise measurements of low energy ion tracks. Among other applications, of particular interest is to explore the response of CR-39 in the regime in which nuclear stopping is comparable to electronic stopping.
Viscosity measurement with double-wire torsion pendulum
Authors: Hong Xinguo , Lu Kunquan
Published: July 2002

A new method of measuring the viscosity of liquid, which is named the double-wire torsion pendulum method in contrast to the conventional torsion pendulum method, is described in this paper. It was found that the damping factor αl changes nearly linearly with the kinematical viscosity η/ρ of the standard oil in the range from 1.55 to 1.15×104 cp. An empirical formula is derived for the damping factor αl and the viscosity η/ρ, and which factors can influence this empirical formula are also presented. The apparatus as constructed is capable of measuring the viscosity and its activation energy over a wide range of temperatures, and is especially suitable for melts at high temperatures with a wide, accurate, dynamic viscosity range. Applying this method, we have observed that the viscous activation energy of a supercooled Li2B8O13 melt is obviously different from that of the normal melt.
High-pressure high-temperature Raman cell for corrosive liquids
Authors: Gorbaty Yu. E. , Bondarenko G. V.
Published: July 2002

A high-pressure high-temperature cell for Raman studies of fluids at pressures of up to 1000 bar and temperatures up to 800 K is described. An uncommon feature of the cell is the internal vessel assembled of sapphire and gold details so that a liquid under study can come in contact only with these materials. An original technique for filling the internal vessel with a liquid to be studied is also presented.
Development and application of stagnation pressure probe for dusty gas measurements
Authors: Batt R. G. , Petach M. B. , Peabody S. A. , Castleberry P. J. , Gallaway C. R.
Published: July 2002

The design, development and application of a fast response probe for measuring gas phase pressures under dusty flow conditions are described. Measured results for this probe, historically designated as the ‘‘Snob’’ probe, demonstrate satisfactory resolution of past limitations on output performance. The present vented Snob probe incorporates three transducers in a single probe body to measure static, total, and total-static differential pressures. The vented nozzle design allows for long duration testing without cavity plugging difficulties while measuring total pressures to within 1% accuracy. Measured data obtained to date demonstrate that the current ‘‘tri sensor Snob’’ performs satisfactorily over a range in a dusty flow environment (ρdust/ρair≤3) extending from high shock overpressure conditions (ΔP∼100 psi) to low velocity flows (2–5 fps). Performance validation results are presented herein as obtained from a series of dusty flow experiments performed in a high pressure shock tube and a low speed wind tunnel designed to investigate dust sweep-up phenomena.
Flexure-mounted external cavity for single-mode operation of semiconductor diode lasers
Authors: Nguyen An , Cassidy Daniel T.
Published: July 2002

The construction of a short external cavity (SXC) module based on the flexure mount concept for semiconductor lasers is presented. The SXC system is an inexpensive and simple means to achieve single-mode operation from normally multimode lasers. The SXC assembly is a flexure mount designed to hold an external cavity mirror and a laser in alignment. The flexure mount permits easy and precise angular positioning of the external mirror. With InGaAsP lasers, side mode suppression ratio as high as 300 can easily be obtained.
A directly water-cooled silicon crystal for high power insertion devices
Authors: Oyanagi H. , Kuwahara Y. , Yamaguchi H.
Published: July 2002

Directly water-cooled silicon crystals with various types of water channels and cooling fins were fabricated and tested at the 27-pole wiggler beamline BL13 of the Photon Factory. Double-crystal rocking curves for a Si(111) reflection indicated that the performance of a grooved silicon crystal in cooling efficiency is significantly improved by replacing conventional semicircular water channels and cooling fins with flat ones with optimum dimensions. For this design, the width of a Si(111) rocking curve was independent of a wiggler power within 2/3 of the full power. In this power range, a highly stable monochromatized beam with an energy resolution required in x-ray absorption near-edge structure experiments (ΔE/E∼2×10−4) was obtained.
Simple techniques for the generation of ultrashort, synchronized electrical pulses
Authors: Lindenberger F. , Ritter G. , Thurn W.
Published: July 2002

Two simple devices based on Auston switches are described for optoelectronic pulse generation. The first technique uses a partially illuminated gap and produces variable pulse durations ≤21 ps and amplitudes in the 5 V range. The second device benefits from the carrier lifetime shortening of proton-implanted GaAs yielding pulses of 12 ps and 500 mV.
A VME timing system for the tokamak ISTTOK
Authors: Varandas C. A. F. , Carvalho B. , Fernandes H. , Sousa J. , Cabral J. A. C. , Correia C. , Morgado M.
Published: July 2002

This paper describes the ISTTOK timing system, which was built under a centralized philosophy based on a locally developed 16 channel, 1 μs maximum resolution, VME unit. The trigger options for each channel are provided, following an innovatory approach, by a programmable pulse multiplexer.
Suppressing oscillations of Zener diode in an ultrahigh-voltage electron microscope
Authors: Zhang Haibo , Takaoka Akio , Ura Katsumi
Published: July 2002

Even in the low-current region of some high-voltage applications, e.g., in electron microscopes, a Zener diode may cause unwanted oscillations due to negative resistance. An effective method to suppress the oscillations is presented. In this method a series resistor and a parallel capacitor are connected with the Zener diode. The former can eliminate relaxation oscillation due to external capacitance and the latter can smooth parasitic oscillations.
Multiple detector triple coincidence spectrometer for (e,3e) electron impact double-ionization measurements
Authors: Ford M. J. , Doering J. P. , Moore J. H. , Coplan M. A.
Published: July 2002

An (e,3e) spectrometer for the study of double ionization of magnesium by electron impact is described. With the spectrometer the angular and energy distributions of the ejected electrons can be measured over a range of incident-electron energies. The spectrometer incorporates two ejected-electron electrostatic energy analyzers and a tandem electrostatic analyzer for the scattered electrons. Up to eight detectors can be placed at the focal planes of each of the ejected analyzers. This increases the data rate by a factor of 64 over arrangements with two ejected-electron detectors. In order to reduce noise and establish the energy of the final state of the doubly charged residual magnesium ion, triple-coincidence electronics are used with a preprocessing circuit to reduce dead time. The first double-ionization study with the instrument was the ejection of a 2p inner valence electron by a 3.5 keV incident electron accompanied by the subsequent filling of the 2p hole and the emission of a 35 eV Auger electron.
Use of primary electron counting for detection of ultrasoft x-rays with a low-pressure multistep gaseous detector
Authors: Milne J. Christopher , Johnson Erik D. , Smith G. C.
Published: July 2002

The use of primary electron counting techniques as an alternative to the more usual parallel plate avalanche chamber that has been employed in soft x-ray scattering experiments is being investigated at the National Synchrotron Light Source. The theoretical aspects of primary electron counting and motivation behind building a primary electron counting detector are described, as well as characteristics and future improvements of the device constructed at the NSLS. The detector consists of a low electric field drift region and a low pressure multistep avalanche region which can be operated with two or three stages of electron multiplication. The device has worked well in extensive tests as a simple parallel plate avalanche chamber, providing energy resolutions of 58% and 43% at 277 and 500 eV, respectively. Operated as a primary electron counter, preliminary results show an energy resolution of 38% at 500 eV.
Gas proportional detectors: Comments on present and future capabilities (invited) (abstract)
Authors: Smith G. C.
Published: July 2002

A brief description of the most common encoding methods, and their relative merits, used with position sensitive proportional detectors at synchrotron facilities will be made. While some of these systems are reaching maturity, continued development is resulting in further improvements, especially in terms of linearity and resolution. The use of detectors with special geometries for specific experiments will be described. The microstrip gas chamber will be addressed, with particular emphasis on a comparison of its capabilities with those of the multiwire proportional chamber. The development of proportional detectors intended for dynamic studies at second- and third-generation sources, with counting rate capabilities well in excess of these generally available at present, will be described. The use of gas based detectors, albeit with modest energy resolution, for photon detection in the energy regime of a few hundred electron volts will be mentioned.
Applications of the superconducting compact ring AURORA
Authors: Masui Shin , Amano Daizo , Katoh Takanori , Zhang Yanping , Yamada Hironari
Published: July 2002

The compact ring AURORA has exhibited excellent performance since 1989. Other than x-ray lithography for semiconductor device fabrication, research activities ranged from infrared to hard x-rays. Especially, the usefulness of the x-rays from AURORA could be verified in several experiments underway. Short beam lines and increased stored beam current made it possible to utilize the hard x-rays and currently a double-crystal monochromator for XAFS experiments is being installed.
Status of the UVSOR facility—1994
Authors: Kamada M. , Hama H.
Published: July 2002

The 10th anniversary of UVSOR was celebrated on December 3, 1993. During the past 10 years the number of users has been increasing and is now at about 600, including scientists from foreign countries. The stability and the lifetime of the SR light were improved by introducing a double rf cavity system. The free-electron laser experiment in the short-wavelength region has been carried out and the UV lasing at 300 nm was successfully obtained in July 1993. Eighteen experimental stations are now operational, which cover the wide energy range from far infrared to soft x rays. Two new beamlines are now under construction, which are expected to be useful in the extreme ultraviolet region.
Summary of the workshop on the applications of x-ray standing waves in studies of surfaces, films, and bulk materials
Authors: Heskett D. , Berman L.
Published: July 2002

Highlights of the satellite workshop on the technique of x-ray standing waves which preceded the 5th International Conference on Synchrotron Radiation Instrumentation held at the State University of New York at Stony Brook, USA are presented. At the workshop, many applications of the x-ray standing-wave technique were described in both invited and contributed talks. While the predominant use of the XSW technique was to analyze the structure of adsorbates on surfaces, applications in the characterization of thin films, interfaces, clean surfaces, and bulk materials were also presented. Most of the talks concentrated on experimental results, but some theory was also featured.
Multiwavelength excitation by vacuum-ultraviolet beams coupled with fourth harmonics of a Q-switched Nd:YAG laser for high-quality ablation of fused quartz
Authors: Sugioka K. , Wada S. , Tashiro H. , Toyoda K. , Ohnuma Y. , Nakamura A.
Published: July 2002

Simultaneous irradiation of multiwavelength beams emitted from a vacuum-ultraviolet (VUV) Raman laser offers great potential for high-quality microfabrication of fused quartz by ablation. In this process, short wavelength components of the beam play two roles, that is, stationary effect and transitional effect. The stationary effect means photodissociation of Si–O bonds and formation of metastable absorption sites to the longer wavelength beam components. The transitional effect increases the absorption to the fundamental beam with a 266 nm wavelength from 0% to more than 60%. This phenomenon may be explained as the excited-state absorption (ESA) due to the coupling of the VUV laser beams with the fundamental beam. The mechanism of the high-quality ablation is discussed by making a comparison between these two effects.