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Nov 2002

Volume 73, Issue 11, pp. 3717-4039

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Space-based magnetometers

Mario H. Acuña

Rev. Sci. Instrum. 73, 3717 (2002); http://dx.doi.org/10.1063/1.1510570 (20 pages) | Cited 24 times

Online Publication Date: 25 October 2002

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The general characteristics and system level concepts for space-based magnetometers are presented to illustrate the instruments, principles, and tools involved in making accurate magnetic field measurements in space. Special consideration is given to the most important practical problems that need to be solved to ensure the accuracy of the measurements and their overall impact on system design and mission costs. Several types of instruments used to measure magnetic fields aboard spacecraft and their capabilities and limitations are described according to whether they measure scalar or vector fields. The very large dynamic range associated with magnetic fields of natural origin generally dictates the use of optimized designs for each particular space mission although some wide-range, multimission magnetometers have been developed and used. Earth-field magnetic mapping missions are the most demanding in terms of absolute accuracy and resolution, approaching <1 part in 100 000 in magnitude and a few arcsec in direction. The difficulties of performing sensitive measurements aboard spacecraft, which may not be magnetically clean, represent a fundamental problem which must be addressed immediately at the planning stages of any space mission that includes these measurements. The use of long, deployable booms to separate the sensors from the sources of magnetic contamination, and their impact on system design are discussed. The dual magnetometer technique, which allows the separation of fields of external and spacecraft origin, represents an important space magnetometry tool which can result in significant savings in complex contemporary spacecraft built with minimum magnetic constraints. Techniques for in-flight estimation of magnetometer biases and sensor alignment are discussed briefly, and highlight some basic considerations within the scope and complexity of magnetic field data processing and reduction. The emerging field of space weather is also discussed, including the essential role that space-based magnetic field measurements play in this complex science, which is just in its infancy. Finally, some considerations for the future of space-based magnetometers are presented. Miniature, mass produced sensors based on magnetoresistance effects and micromachined structures have made significant advances in sensitivity but have yet to reach the performance level required for accurate space measurements. The miniaturization of spacecraft and instruments to reduce launch costs usually results in significantly increased magnetic contamination problems and degraded instrument performance parameters, a challenge that has yet to be solved satisfactorily for “world-class” science missions. The rapidly disappearing manufacturing capabilities for high-grade, low noise, soft magnetic materials of the Permalloy family is a cause of concern for the development of high performance fluxgate magnetometers for future space missions.
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07.55.Ge Magnetometers for magnetic field measurements
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
01.30.Rr Surveys and tutorial papers; resource letters
91.25.-r Geomagnetism and paleomagnetism; geoelectricity
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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY; PHOTON DETECTORS

Design and implementation of a high-resolution, high-efficiency optical spectrometer

S. B. Utter, J. R. Crespo López-Urrutia, P. Beiersdorfer, and E. Träbert

Rev. Sci. Instrum. 73, 3737 (2002); http://dx.doi.org/10.1063/1.1510574 (5 pages) | Cited 7 times

Online Publication Date: 25 October 2002

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We present the design, implementation and testing of a high-efficiency, high-resolution transmission grating spectrometer for measurements of near-ultraviolet to visible-range spectra of light from an electron beam ion trap, where geometry is constrained. The system consists of two 5 in. diameter f/4.6 achromatic lenses, a 6 in. diameter transmission grating ion-beam etched in fused silica, and a thinned, backilluminated CCD detector. The simple design minimizes the number of optical components, each with optimal throughput and high efficiency. Using a 30 μm wide entrance slit, a resolving power (λ/Δλ) of 15 400 at λ ≈ 3850 Å has been demonstrated. The features and limitations of the instrument have been explored and an in situ calibration technique for use on the Livermore EBIT-II and SuperEBIT electron beam ion traps has been developed. © 2002 American Institute of Physics.
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07.60.Rd Visible and ultraviolet spectrometers
42.79.Bh Lenses, prisms and mirrors
42.79.Pw Imaging detectors and sensors
42.79.Dj Gratings
06.20.F- Units and standards
29.27.Fh Beam characteristics

Double subtractive spectrometer as a tunable high-resolution broad-bandpass optical filter

D. J. Dunstan and M. D. Frogley

Rev. Sci. Instrum. 73, 3742 (2002); http://dx.doi.org/10.1063/1.1512338 (5 pages) | Cited 1 time

Online Publication Date: 25 October 2002

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In the optical part of the electromagnetic spectrum, technologies such as dielectric and holographic filters provide a broad-bandpass function with poor resolution between fully blocking and fully transmitting and with almost no tunability. Standard double subtractive spectrometers provide a high-resolution filter function that is tunable over a wide range, but because of the placing of the dispersive element relative to the collimating optics, these instruments are intrinsically narrow-bandpass. A double subtractive spectrometer in which the resolution and tunability are not compromised, yet the bandpass may be as broad as may be desired, can be achieved by placing the dispersive element at twice the focal length from the collimating optics. Such an instrument is described and demonstrated in low-wave-number Raman spectroscopy. With a 0.2 m focal length, it achieves better than 1 cm−1 resolution and can work to 5 cm−1 of the laser line. Throughput is up to 35%, and a bandpass of 1000 cm−1 is demonstrated. Combined with a final stage spectrograph, the laser rejection is 10−13 at 50 cm−1. © 2002 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.62.Fi Laser spectroscopy
42.79.Ci Filters, zone plates, and polarizers
42.79.Ag Apertures, collimators

A calcium vapor cell for atomic spectroscopy

Mao-Sheng Huang, Mao-Hong Lu, and Jow-Tsong Shy

Rev. Sci. Instrum. 73, 3747 (2002); http://dx.doi.org/10.1063/1.1511800 (3 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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A calcium vapor cell used in laser spectroscopy usually suffers from calcium coating on the cell windows. To solve the problem, we add two mirrors in the cell to reflect the laser beam, then the calcium will coat on these mirrors instead of on the windows. Calcium coating degrades the reflectivity of the mirrors at the beginning, but the mirrors become calcium mirrors after a certain period of coating and their reflectivity will not change by further calcium coating. Using this cell in a conventional saturated-absorption spectroscopy, the observed saturated-absorption peak at 657 nm is about 2.4% of the probe beam power and its linewidth is below 300 kHz. Therefore, a portable secondary calcium-wavelength standard at 657 nm having an accuracy better than 1×10−11 is possible. In addition, our cell has a continuous working time longer than 3 d and it can be easily extended to 10 d. © 2002 American Institute of Physics.
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42.62.Fi Laser spectroscopy
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.60.Rd Visible and ultraviolet spectrometers
06.20.F- Units and standards
42.79.Bh Lenses, prisms and mirrors
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

He discharge lamp for photoemission experiments with radioactive materials

Tomasz Durakiewicz, Al Arko, John J. Joyce, David P. Moore, and Kevin Graham

Rev. Sci. Instrum. 73, 3750 (2002); http://dx.doi.org/10.1063/1.1510551 (4 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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A simple He discharge lamp is described. The lamp is designed specially for photoemission measurements performed on radioactive materials, mainly Pu and Pu compounds. The lamp construction allows easy single-use assembly/disassembly of the discharge tube with minimum risk of radiological contamination, minimum amount of waste generated, air cooling capability, very good He II/He I ratio at low He pressures, and stable operation for at least 200 h. Thanks to the high brightness in the He II range we were able to observe the He IIβ, He IIγ, and even He IIε features in the PuIn3 photoemission spectrum. Total cost of parts used to produce the discharge tube is less than $300, so that the cost of operation is less than $1.5/h. © 2002 American Institute of Physics.
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42.72.-g Optical sources and standards
84.47.+w Vacuum tubes
79.60.-i Photoemission and photoelectron spectra

A fast position sensitive microstrip-gas-chamber detector at high count rate operation

I. P. Dolbnya, H. Alberda, F. G. Hartjes, F. Udo, R. E. Bakker, M. Konijnenburg, E. Homan, I. Cerjak, P. Goedtkindt, and W. Bras

Rev. Sci. Instrum. 73, 3754 (2002); http://dx.doi.org/10.1063/1.1510572 (5 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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Testing of a newly developed position sensitive high count rate microstrip gas chamber (MSGC) detector at high count rate operation has been carried out at the Dutch–Belgian x-ray scattering beamline at the European Synchrotron Radiation Facility (Grenoble, France) with a high intensity x-ray beam. The measurements show local count rate capabilities up to ∼ 4.5×105 counts/s/channel. Experimental data taken with this detector are also shown. These tests show that both time resolution down to 1.5 ms/frame and a reliable operation at high counting rates can be achieved. © 2002 American Institute of Physics.
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29.40.Gx Tracking and position-sensitive detectors
84.40.Az Waveguides, transmission lines, striplines
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
back to top PARTICLE SOURCES, OPTICS and ACCELERATION; PARTICLE DETECTORS

On line multitarget selection device with multiple facilities

Subir Roy, Avijit Das, N. Ibomcha, and R. K. Bhandari

Rev. Sci. Instrum. 73, 3759 (2002); http://dx.doi.org/10.1063/1.1510577 (5 pages)

Online Publication Date: 25 October 2002

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We have developed a multitarget holding device as a subsystem for atomic or nuclear physics experiments. A permanent magnet stepper motor rotates the device for target selection without breaking the vacuum. The target holder is potentially isolated from the rest of the system with the help of a Teflon block. The device and its controlled circuits are described below. © 2002 American Institute of Physics.
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29.25.Pj Polarized and other targets
84.50.+d Electric motors
37.20.+j Atomic and molecular beam sources and techniques

New type audio frequency ion source

M. S. Ragheb and S. G. Zakhary

Rev. Sci. Instrum. 73, 3764 (2002); http://dx.doi.org/10.1063/1.1510575 (4 pages) | Cited 3 times

Online Publication Date: 25 October 2002

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In this work, a new miniature type audio frequency (AF) (10 up to 100 kHz) of capacitive discharge type ion source has been constructed. The source is featured with its high output intensity and its small size. The optimized working condition of the source is defined at certain discharge pressure (0.2 Torr) and certain frequency (15 kc/s) of the audio power supply. At this optimum operating condition of pressure and frequency of the AF supply, the source yields an ion current up to 25 mA and electron current up to 60 mA at low extraction voltage (V=50 up to 150 V). The extracted ion current is found to mainly depend on the discharge pressure and frequency of the audio supply. © 2002 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors

Magnetic fluctuation probe design and capacitive pickup rejection

Christian M. Franck, Olaf Grulke, and Thomas Klinger

Rev. Sci. Instrum. 73, 3768 (2002); http://dx.doi.org/10.1063/1.1512341 (4 pages) | Cited 18 times

Online Publication Date: 25 October 2002

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In this article the capacitive pickup of magnetic fluctuation probes for plasma applications is studied. The nine most commonly used probe designs are compared with respect to their capacitive pickup rejection, magnetic sensitivity, and minimum plasma disturbance. For absolute calibration, well defined electric and magnetic field fluctuations are produced separately in a Faraday cup and in a Helmholtz magnetic field coil configuration, respectively. A sample measurement in a radio frequency helicon plasma demonstrates that the optimum probe design is well suited for measuring magnetic fluctuations in a plasma environment. © 2002 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
06.20.F- Units and standards
07.55.Ge Magnetometers for magnetic field measurements

Deconvolving long-pulse electron-beam centroid data from resistive wall-current monitors

Bruce E. Carlsten

Rev. Sci. Instrum. 73, 3772 (2002); http://dx.doi.org/10.1063/1.1515763 (6 pages)

Online Publication Date: 25 October 2002

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A technique is described to deconvolve long-pulse electron-beam centroid data from resistive wall-current monitors. These monitors are typically capable of accurately measuring total current for tens of microseconds, but, due to magnetic diffusion, tend to give direct centroid measurements only up to hundreds of nanoseconds. As a result, resistive wall-current monitors are usually not considered reliable for long-pulse operation. However, the voltage signals azimuthally around the monitor still contains that information, and the information can be easily deconvolved by differentiating the signals. In this article, the diffusive part of Maxwell's equations is used to find an expression for the time response of a resistive wall-current monitor for a beam of arbitrary current and centroid evolution. A simple way of inverting this response is shown to find the beam centroid as a function of time within the electron pulse. © 2002 American Institute of Physics.
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29.27.Fh Beam characteristics
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Performance of a Mott detector for undulator-based spin-resolved spectroscopy

D. J. Huang, W. P. Wu, J. Chen, C. F. Chang, S. C. Chung, M. Yuri, H.-J. Lin, P. D. Johnson, and C. T. Chen

Rev. Sci. Instrum. 73, 3778 (2002); http://dx.doi.org/10.1063/1.1510552 (6 pages) | Cited 5 times

Online Publication Date: 25 October 2002

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To measure spin-polarized core-level electron spectra, a spectrometer equipped with a highly efficient retarding-potential Mott spin polarimeter using undulator-based soft-x-ray beamlines has been set up. With a thin film of Au as a target this polarimeter has an efficiency estimated to be ∼ 2×10−4. The performance of this system for spin-polarized spectroscopy has been tested using core-level spin-polarized photoemission of magnetic and nonmagnetic thin films excited with linearly and circularly polarized light, respectively. Measurements using a new spin-resolved absorption technique are also discussed. © 2002 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
07.85.Qe Synchrotron radiation instrumentation
79.60.-i Photoemission and photoelectron spectra
73.20.-r Electron states at surfaces and interfaces
41.60.-m Radiation by moving charges
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

The use of a Shack–Hartmann wave front sensor for electron density characterization of high density plasmas

K. L. Baker, J. Brase, M. Kartz, S. S. Olivier, B. Sawvel, and J. Tucker

Rev. Sci. Instrum. 73, 3784 (2002); http://dx.doi.org/10.1063/1.1510546 (5 pages) | Cited 8 times

Online Publication Date: 25 October 2002

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This article examines the use of a Shack–Hartmann wave front sensor to accurately measure the line-integrated electron density gradient formed in laser-produced and Z-pinch plasma experiments. The minimum discernable line-integrated density gradient is derived for the Shack–Hartmann wave front sensor, as well as its range of applicability. A laboratory comparison between a Shack–Hartmann wave front sensor and a Twyman–Green interferometer is also presented. For this comparison, a liquid-crystal spatial-light modulator is used to introduce a spatially varying phase onto both of the wave front sensors, simulating a phase profile that could occur when a probe passes through a plasma. The phase change measured by the Shack–Hartmann sensor is then compared directly with the Twyman–Green interferometer. In this article, the merits associated with the use of a Shack–Hartmann sensor are discussed. These include a wide dynamic range, high optical efficiency, broadband or low coherence length light capability, experimental simplicity, two-dimensional gradient determination, and multiplexing capability. © 2002 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties
07.60.Ly Interferometers
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
52.58.Lq Z-pinches, plasma focus, and other pinch devices

Large field double Kirkpatrick–Baez microscope with nonperiodic multilayers for laser plasma imaging

F. Bridou, R. Mercier, A. Raynal, J. Y Clotaire, C. Colas, P. Fournet, M. Idir, G. Soullié, C. Remond, and P. Troussel

Rev. Sci. Instrum. 73, 3789 (2002); http://dx.doi.org/10.1063/1.1512334 (7 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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The double Kirkpatrick–Baez (DBA) microscope is derived from the grazing x-ray Kirkpatrick–Baez (KB) microscope. The KB is compound of two concave spherical mirrors working at grazing incidence and in an energy range about 100 eV–10 keV. The combination of two similar mirrors in the DKB increases the useful field. This device only requires spherical mirrors, more easy to manufacture (precision and roughness) than aspherical ones. In order to image a laser plasma source in a large field of view and within a bandpass of 0.6 keV around 3.4 keV, a KB optic covered with multilayers is developed. In fact, a compromise has to be found between the resolution of the optic (better with a less grazing angle), and the reflectivity (better with more grazing angle). We have chosen to keep the average grazing incidence on the four mirrors around 2°–3° just as for a first uncoated DKB made in our laboratory. This allows us to keep the same radius of curvature for the mirrors. At this energy multilayers are needed, due to the required reflectivity of better than 7% for each mirror. A difficulty appears concerning the energy and angular acceptance of multilayers. It is shown that a nonperiodic multilayer structure can be calculated to solve this problem, in spite of the absorption of the layers at the low energy of our application. The variation of periods is not continuous as in known classical supermirrors, and all the experimental parameters such as complex index of refraction and roughness have to be known. Thicknesses can then be optimized individually. The multilayers were deposited, tested, and the defects identified and corrected. Final experimental results of such stacks are given. © 2002 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
41.50.+h X-ray beams and x-ray optics
07.85.Tt X-ray microscopes

Wide-dynamic-range “neutron bang time” detector on OMEGA

C. Stoeckl, V. Yu. Glebov, J. D. Zuegel, D. D. Meyerhofer, and R. A. Lerche

Rev. Sci. Instrum. 73, 3796 (2002); http://dx.doi.org/10.1063/1.1511804 (5 pages) | Cited 7 times

Online Publication Date: 25 October 2002

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A simple, low-cost “neutron bang time” detector has been implemented on the OMEGA laser system to measure the average time of neutron emission from inertial confinement fusion targets. This detector uses fast plastic scintillators coupled to photomultiplier tubes. A fast digital real-time oscilloscope records the signals. Absolute timing accuracies of better than 100 ps are achieved over a wide dynamic range (107<YN<1011) for both D2 (2.45 MeV) and DT (14 MeV) neutrons using a two-channel setup. Instrument characterization and comparison of the timing accuracy with a streak camera-based neutron burn history diagnostic are presented. © 2002 American Institute of Physics.
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28.52.Lf Components and instrumentation
29.40.Mc Scintillation detectors
85.60.Ha Photomultipliers; phototubes and photocathodes
52.70.Nc Particle measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
28.20.Gd Neutron transport: diffusion and moderation

A nearly real-time high temperature laser–plasma diagnostic using photonuclear reactions in tantalum

I. Spencer, K. W. D. Ledingham, R. P. Singhal, T. McCanny, P. McKenna, E. L. Clark, K. Krushelnick, M. Zepf, F. N. Beg, M. Tatarakis, A. E. Dangor, R. D. Edwards, M. A. Sinclair, P. A. Norreys, R. J. Clarke, et al.

Rev. Sci. Instrum. 73, 3801 (2002); http://dx.doi.org/10.1063/1.1511802 (5 pages) | Cited 15 times

Online Publication Date: 25 October 2002

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A method of measuring the temperature of the fast electrons produced in ultraintense laser–plasma interactions is described by inducing photonuclear reactions, in particular (γ,n) and (γ,3n) reactions in tantalum. Analysis of the γ rays emitted by the daughter nuclei of these reactions using a germanium counter enables a relatively straightforward near real-time temperature measurement to be made. This is especially important for high temperature plasmas where alternative diagnostic techniques are usually difficult and time consuming. This technique can be used while other experiments are being conducted. © 2002 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
27.70.+q 150 ≤ A ≤ 189
25.20.Lj Photoproduction reactions

A gold film detector for radial profile measurement of plasma density by using a gold neutral beam probe

K. Ishii, Y. Takemura, A. Fueki, K. Hagisawa, A. Kojima, A. Itakura, M. Yoshikawa, I. Katanuma, and K. Yatsu

Rev. Sci. Instrum. 73, 3806 (2002); http://dx.doi.org/10.1063/1.1510553 (7 pages) | Cited 4 times

Online Publication Date: 25 October 2002

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A gold film detector was developed in order to measure the plasma density profile by use of the gold neutral beam probe. The detector is a kind of neutral beam detector composed of a rectangular entrance collimator, two sets of grid plates, a gold thin film, a quartz backing, and a microcarbon coated copper plate. The secondary electrons emitted from the gold film were utilized for the neutral beam detection. The yield curves of the secondary electrons were measured as a function of the incident angle and electron energy in both cases of the gold neutral probing beam and ultraviolet ray injection. Time evolution of the plasma line density was measured by adjusting the incident angle and adding a beam chopping method. The result was in good agreement with the line density measured by a microwave interferometer. It was found that this film detector was quite useful in the viewpoint of simultaneous measurements of the electrostatic potential and plasma density profiles. © 2002 American Institute of Physics.
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52.70.Nc Particle measurements
52.25.Kn Thermodynamics of plasmas
52.40.Mj Particle beam interactions in plasmas

Cyclic plasma shearing interferometry for temporal characterization of a laser-produced plasma

J. A. Cobble, R. P. Johnson, N. A. Kurnit, D. S. Montgomery, and J. C. Fernández

Rev. Sci. Instrum. 73, 3813 (2002); http://dx.doi.org/10.1063/1.1512339 (5 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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A cyclic shearing interferometer has been employed to characterize a laser-produced plasma with 180 ps resolution. Counterpropagation maintains an equal path length for the probe and reference beams, and the shear is provided solely by the plasma, which appears within the circuit after the reference beam has passed the laser focal spot. The background is virtually fringe free because of the overlapping of the reference and probe beams so that analysis is simplified. The plasma, which is formed by a line focus, is seen to expand in a cylindrical manner away from the line focus with an exponential density profile. In addition, the interferometer shows evidence of a bow shock when an interaction beam is introduced into the plasma parallel to the direction of the line focus. © 2002 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.-b Plasma properties
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.60.Ly Interferometers
52.35.Tc Shock waves and discontinuities

Ultrasonic frequency driven long plasma column

M. S. Ragheb

Rev. Sci. Instrum. 73, 3818 (2002); http://dx.doi.org/10.1063/1.1512333 (7 pages)

Online Publication Date: 25 October 2002

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A study of argon gas stimulated at ultrasonic frequencies reveals different characteristic aspects. The plasma is created in a 50 cm tube with an effective work length of 25 cm. In order to initialize and maintain the process, plasma discharge parameters, namely, current, voltage, power, pressure, and frequency are studied and optimized. The data obtained show that in order to maintain a plasma discharge specific current, it would be sufficient to apply a higher frequency and lower voltage, whereas the current, at higher frequency and higher voltage, would be higher. Moreover the increase of the discharge voltage, frequency, and pressure increases the discharge current and consequently the discharge power. On the other hand along the half length of the tube, the plasma parameters; temperature, density, mean electron energy, and Debye length are studied and evaluated by means of a floating double Langmuir probe system. Moving from the hot electrode towards the grounded one, the electron temperature increases while the electron density decreases. The plasma temperature measured is 3–20 eV and the average plasma density is on the order 1011 cm−3, according to the pressure, the frequency, and the discharge voltage applied. The plasma source has low power consumption where, for normal operation of 25 W, the discharge voltage VD is 300 V, and the discharge current Ip is 80 mA. Away from gas breakdown, the maximum power absorbed is found to be 60 W, where VD = 500 V and Ip = 120 mA. A plasma phenomenon of alternatively dark and bright regions appear in the vessel, and are easily seen along the plasma tube, denoting the response of both the electron temperature and the electron density to an oscillatory behavior. The range of the applied pressure, discharge voltage, frequency, current, and power consumed inside the vessel are, respectively, 0.01–0.25 Torr, 50–500 V, 10–100 kHz, 1.5–160 mA, and 5–60 W. The formed plasma is durable, until it would be discarded. Physically it has a pale pink color that becomes brighter by increasing the discharge voltage. © 2002 American Institute of Physics.
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52.80.-s Electric discharges
52.25.Fi Transport properties
52.70.Ds Electric and magnetic measurements
back to top MICROSCOPY and IMAGING

Scanning μ-superconduction quantum interference device force microscope

C. Veauvy, K. Hasselbach, and D. Mailly

Rev. Sci. Instrum. 73, 3825 (2002); http://dx.doi.org/10.1063/1.1515384 (6 pages) | Cited 20 times

Online Publication Date: 25 October 2002

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A scanning probe technique is presented: Scanning μ-superconducting quantum interference device (SQUID) force microscopy (SSFM). The instrument features independent topographic and magnetic imaging. The force microscope uses a piezoelectric quartz tuning fork as the detector and magnetic imaging is obtained by scanning μ-SQUID microscopy. The μ-SQUID is placed at the edge of a silicon chip attached to the tuning fork. A topographic vertical resolution of 0.02 μm is demonstrated and magnetic flux as weak as 10−3 Φ0 is resolved with a 1 μm diameter μ-SQUID loop. The SSFM operates in a dilution refrigerator in a cryogenic vacuum. Sample and probe can be cooled to 0.45 K. © 2002 American Institute of Physics.
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07.79.Pk Magnetic force microscopes
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Use of biaxially oriented polypropylene film for evaluating and cleaning contaminated atomic force microscopy probe tips: An application to blind tip reconstruction

H.-Y. Nie, M. J. Walzak, and N. S. McIntyre

Rev. Sci. Instrum. 73, 3831 (2002); http://dx.doi.org/10.1063/1.1510554 (6 pages) | Cited 6 times

Online Publication Date: 25 October 2002

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An atomic force microscopy (AFM) image of a surface is basically a convolution of the probe tip geometry and the surface features; it is important to know this tip effect to ensure that an image truly reflects the surface features. We have found that a biaxially oriented polypropylene (BOPP) film is suitable for checking tip performance and for cleaning contaminated tips, thus making it possible to collect images of the same area of a BOPP film surface before and after the tip was cleaned. Therefore, the difference between the two different images is solely due to the contamination of the tip. We took advantage of our ability to collect AFM images of the same area using the same tip, in one instance, contaminated and, in the other, after being cleaned. First we used blind reconstruction on the image collected using the contaminated tip. Blind tip reconstruction allows one to extract the geometry of the tip from a given image. Once we had estimated the geometry of the contaminated tip, we used it to simulate the tip effect using the image collected using the cleaned tip. By comparing the simulation result with the image collected using the contaminated tip we showed that the blind reconstruction routine works well. Prior to this, there was no de facto method for testing blind reconstruction algorithms. © 2002 American Institute of Physics.
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07.79.Lh Atomic force microscopes
81.65.Cf Surface cleaning, etching, patterning

High frequency-bandwidth optical technique to measure thermal elongation time responses of near-field scanning optical microscopy probes

B. Biehler and A. H. La Rosa

Rev. Sci. Instrum. 73, 3837 (2002); http://dx.doi.org/10.1063/1.1510548 (4 pages) | Cited 2 times

Online Publication Date: 25 October 2002

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A near-field scanning optical microscopy (NSOM) probe elongates when light is coupled into it. The time response of this thermal process is measured here by a new optical technique that exploits the typical flat-apex morphology of the probe as a mirror in a Fabry–Perot type cavity. Pulsed laser light is coupled into the probe to heat up the tip, while another continuous wave laser serves to monitor the elongation from the interference pattern established by the reflections from the flat-apex probe and a semitransparent metal-coated flat sample. A quarter wave plate is introduced into the interferometer optical path in order to maximize the signal to noise level, thus allowing the elongation of the tip to be monitored in real time. This optical technique, unlike other methods based on electronic feedback response, avoids limited frequency bandwidth restrictions. We have measured response time constants of 500 and 40 μs. The technique presented here will help determine the power levels, operating probe-sample distance, and pulse repetition rate requirements for safe operation of NSOM instrumentation. In addition to NSOM, the instrumentation described in this article could also impact other areas that require large working range, accuracy, and high-speed response. © 2002 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Ly Interferometers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Reactive sputter deposition of alumina thin films using a hollow cathode sputtering source

Anshu A. Pradhan, S. Ismat Shah, and Karl M. Unruh

Rev. Sci. Instrum. 73, 3841 (2002); http://dx.doi.org/10.1063/1.1512340 (5 pages) | Cited 3 times

Online Publication Date: 25 October 2002

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Reactive sputtering allows deposition of insulating compounds that cannot be easily prepared using conventional dc sputtering methods. However, this technique suffers from problems related to the poisoning of the target and associated hysteresis effects. In addition, the operating conditions that yield the highest growth rate are unstable, and feedback control is required to maintain the system at the optimal operating point. In order to address some of these issues, we have developed a new hollow cathode sputtering (HCS) source. In addition to the inherent advantages of high deposition rates and the capability for coating complex surfaces, we have found that the hollow cathode sputtering source does not exhibit the hysteresis behavior generally observed in planar reactive sputtering systems and is stable at all operating points without feedback control. We have characterized a HCS source for reactively depositing alumina thin films. The deposition rate increases on increasing the oxygen concentration. Pure alumina thin films can be deposited with high growth rates at very low-power densities. © 2002 American Institute of Physics.
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81.15.Cd Deposition by sputtering
85.40.Sz Deposition technology

Hyperthermal ion beam system optimized for studying the effects of kinetic energy on thin-film growth

J. M. Pomeroy, A. J. Couture, M. V. R. Murty, E. N. Butler, and B. H. Cooper

Rev. Sci. Instrum. 73, 3846 (2002); http://dx.doi.org/10.1063/1.1512337 (7 pages) | Cited 3 times

Online Publication Date: 25 October 2002

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A hyperthermal and low-energy ion beam (10–1000 eV) optimized for studying morphological trends in epitaxial metal thin films as a function of atomic kinetic energy has been built and characterized. The ion beam line produces metal and inert gas ions and is specially designed to produce up to 2.9 μA of highly collimated ions with single amu mass resolution while precisely controlling the ion’s energy, achieving a ΔE/E ∼ 0.1. Energy resolution can be enhanced further at the expense of flux. Varying the focal length of the final electrostatic lens allows the flux density to be adjusted from 10 to 500 nA/mm2. The beam line has been coupled to an ultra-high-vacuum deposition chamber with a versatile sample manipulator, an electron beam deposition source, residual gas analysis, and real-time reflection high-energy electron diffraction (RHEED). Once prepared, the sample can be moved in situ to perform Auger electron spectroscopy (AES), and scanning tunneling microscopy (STM). The high fluxes with narrow energy distributions this apparatus produces allows the poorly understood hyperthermal energy regime to be probed with RHEED, AES, and STM. The atomic kinetic energy can be varied to measure effects on nuclei densities, growth mode, and surface morphology. STM images of copper films deposited under a variety of conditions illustrate the diverse range of possible results. © 2002 American Institute of Physics.
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41.75.-i Charged-particle beams
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.77.Ka Charged-particle beam sources and detectors
41.85.Ne Electrostatic lenses, septa
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
79.20.Fv Electron impact: Auger emission

An evaporation source for ion beam assisted deposition in ultrahigh vacuum

J. Kirschner, H. Engelhard, and D. Hartung

Rev. Sci. Instrum. 73, 3853 (2002); http://dx.doi.org/10.1063/1.1511791 (8 pages) | Cited 11 times

Online Publication Date: 25 October 2002

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We describe the design, construction, and operation of an ion beam assisted deposition source for molecular beam epitaxy in ultrahigh vacuum. At a typical deposition rate of a monolayer per minute, the source may be operated in each of five modes: using self-ions from the vapor, self-ion plus noble gas ions from an additional gas inlet, both pulsed or continuous, or with complete suppression of ions. The source is based on electron bombardment heating of a metal rod or a crucible while the ions generated from the vapor are focused electrostatically onto the sample. Additional ions may be extracted from a noble gas stream injected into the ionization region. Examples for each of the different modes are given for Co deposition onto Cu(111), a system known to resist layer-by-layer growth. © 2002 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
07.77.Ka Charged-particle beam sources and detectors

Electrostatic electron analyzer with 90° deflection angle

L. Vattuone and M. Rocca

Rev. Sci. Instrum. 73, 3861 (2002); http://dx.doi.org/10.1063/1.1510555 (6 pages) | Cited 1 time

Online Publication Date: 25 October 2002

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We demonstrate the feasibility of a new type of electrostatic cylindrical analyzer terminated with plates with focus at 90° also in the presence of significant space charge. The transmission function is determined by numerical simulation of the trajectories after a full three-dimensional solution of the Poisson problem with boundary condition by an iterative finite difference algorithm. This device may allow a new generation of spin polarized electron energy loss spectroscopy experiments. © 2002 American Institute of Physics.
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41.85.Qg Particle beam analyzers, beam monitors, and Faraday cups
07.81.+a Electron and ion spectrometers
79.20.Uv Electron energy loss spectroscopy
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
02.70.Bf Finite-difference methods
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