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Dec 1998

Volume 69, Issue 12, pp. 4027-4251

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Introductory overview of research instruments for recording the electrical activity of neurons in the human brain

P. C. Garell, M. A. Granner, M. D. Noh, M. A. Howard, I. O. Volkov, and G. T. Gillies

Rev. Sci. Instrum. 69, 4027 (1998); http://dx.doi.org/10.1063/1.1149245 (11 pages) | Cited 3 times

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Scientific advancement is often spurred by the development of new instruments for investigation. Over the last several decades, many new instruments have been produced to further our understanding of the physiology of the human brain. We present a partial overview of some of these instruments, paying particular attention to those which record the electrical activity of the human brain. We preface the review with a brief primer on neuroanatomy and physiology, followed by a discussion of the latest types of apparatus used to investigate various properties of the central nervous system. A special focus is on microelectrode investigations that employ both intracellular and extracellular methods of recording the electrical activity of single neurons; another is on the modern electroencephalographic, electrocorticographic, and magnetoencephalographic methods used to study the spontaneous and evoked field potentials of the brain. Some examples of clinical applications are included, where appropriate. © 1998 American Institute of Physics.
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01.30.Rr Surveys and tutorial papers; resource letters
87.63.-d Non-ionizing radiation equipment and techniques
87.63.Hg Thermography
87.19.-j Properties of higher organisms
87.80.-y Biophysical techniques (research methods)
87.50.C- Static and low-frequency electric and magnetic fields effects
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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Frequency stabilization of a radio frequency excited CO2 laser using the optogalvanic effect

Jong-Woon Choi, Young-Boong Chung, Marek Strzelec, and Mirek Kopica

Rev. Sci. Instrum. 69, 4038 (1998); http://dx.doi.org/10.1063/1.1149246 (3 pages) | Cited 1 time

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Frequency stabilization of a rf excited CO2 laser on the peak of the Doppler broadened gain curve using the optogalvanic effect generated from the laser itself is achieved. The optogalvanic signal is directly coupled from a rf discharge chamber via a capacitor into a detector and a lock-in stabilizer. The frequency stability is estimated to be better then 3×10−8. © 1998 American Institute of Physics.  
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Fc Modulation, tuning, and mode locking

Highly efficient optically pumped NH3 laser with near diffraction limited output

J. Makowe, O. V. Boyarkin, and T. R. Rizzo

Rev. Sci. Instrum. 69, 4041 (1998); http://dx.doi.org/10.1063/1.1149247 (3 pages) | Cited 2 times

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We present the design of a highly efficient, pulsed ammonia laser which is optically pumped by a commercial TEA CO2 laser and is line tunable in the spectral range of 780–930 cm−1. The power, spectral, and temporal characteristics of the laser have been investigated for different configurations of the optical cavity. Using a stable resonator, the laser operates with an efficiency of 24% (940 mJ) in a multiline configuration and 16.5% on a single line. Changing the resonator to an unstable configuration produces a diffraction limited output on a single line with an efficiency of 13%. These output characteristics make this laser suitable for experiments in the field of infrared multiphoton dissociation. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Calculation of Thomson scattering of intense lasers from electron beams at different interaction angles

Xiaochao Zheng, Cunjun Ruan, Rencheng Shang, and Jingkang Deng

Rev. Sci. Instrum. 69, 4044 (1998); http://dx.doi.org/10.1063/1.1149248 (5 pages)

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Recently there has been considerable interest in the Thomson scattering of intense laser from relativistic electron beams, and a new kind of x-ray source named laser synchrotron source (LSS) has been discussed based on this mechanism which is expected to have extremely good performances. In order to verify this theory, an experiment is going to be carried out by our group using a frequency-doubled yttrium–aluminum–garnet laser and a 25 MeV electron beam generated by the accelerator in the Applied Department of the Institute of High-Energy Physics. In this article some theoretical results have been calculated for this experiment, including the scattered x-ray’s wavelength and intensity distribution. The results at 180° and 90° have been given and the 180° result should be very close to the experimental geometry of 178.5°. In Sec. III, figures of the spatial distribution of x-ray are drawn. The future of LSS is prospected finally in Sec. IV. © 1998 American Institute of Physics.
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07.85.Qe Synchrotron radiation instrumentation
42.62.-b Laser applications
41.60.Ap Synchrotron radiation

High-resolution x-ray spectrometer based on spherically bent crystals for investigations of femtosecond laser plasmas

B. K. F. Young, A. L. Osterheld, D. F. Price, R. Shepherd, R. E. Stewart, A. Ya. Faenov, A. I. Magunov, T. A. Pikuz, I. Yu. Skobelev, F. Flora, S. Bollanti, P. Di Lazzaro, T. Letardi, A. Grilli, L. Palladino, et al.

Rev. Sci. Instrum. 69, 4049 (1998); http://dx.doi.org/10.1063/1.1149249 (5 pages) | Cited 45 times

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Ultrashort-pulse, laser-produced plasmas have become very interesting laboratory sources to study spectroscopically due to their very high densities and temperatures, and the high laser-induced electromagnetic fields present. Typically, these plasmas are of very small volume and very low emissivity. Thus, studying these near point source plasmas requires advanced experimental techniques. We present a new spectrometer design called the focusing spectrometer with spatial resolution (FSSR-2D) based on a spherically bent crystal which provides simultaneous high spectral (λ/Δλ ≈ 104) and spatial resolution (≈10 μm) as well as high luminosity (high collection efficiency). We described in detail the FSSR-2D case in which a small, near point source plasma is investigated. An estimate for the spectral and spatial resolution for the spectrometer is outlined based on geometric considerations. Using the FSSR-2D instrument, experimental data measured from both a 100 fs and a nanosecond pulse laser-produced plasma are presented. © 1998 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.La X-ray and γ-ray measurements
07.85.Nc X-ray and γ-ray spectrometers

Characterization of an x-ray framing camera utilizing a charge coupled device or film as recording media

L. M. Logory, D. R. Farley, A. D. Conder, E. A. Belli, P. M. Bell, and P. L. Miller

Rev. Sci. Instrum. 69, 4054 (1998); http://dx.doi.org/10.1063/1.1149250 (7 pages) | Cited 5 times

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A compact charge coupled device (CCD) camera system has been designed and characterized for use in the six inch manipulator (SIM) at the Nova laser facility. The camera system has been designed to directly replace the 35 mm film packages currently used in SIM-based x-ray imaging diagnostics. The unit’s electronic package has been constructed for small size and high thermal conductivity which reduces the overall camera size and improves its performance when operated within the vacuum environment of the Nova target chamber. Measurements of the x-ray imager’s contrast transfer function (CTF) were made under a variety of operating conditions on a static x-ray Manson source using both the CCD and Kodak T-Max 3200 film as recording media. The CTF data were converted to an equivalent modulation transfer function (MTF). The MTF plots show that the microchannel plate has a uniform response within our measurement accuracy along its strips. In a direction normal to the strip, however, the MTF is reduced due to the slant angle of the pores in the MCP. The measurements show that the CCD camera has a lower MTF response than T-MAX film for all spatial frequencies and configurations measured. However, data obtained from the film exhibited reciprocity failure and border effects that are not observed in the CCD data. Measurements indicate that the signal-to-noise ratio for the CCD data is four to six times larger than that obtained with film and higher photon flux levels were recorded. The CCD-based diagnostic offers immediate access to the data, improved dynamic range, and reduced turnaround time, while eliminating the need for film development, digitization, equipment, and personnel. © 1998 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
52.57.-z Laser inertial confinement
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
28.52.Cx Fueling, heating and ignition

Microwave-submillimeter wave double-resonance spectrometer for the investigation of van der Waals complexes

Vladimir N. Markov, Yunjie Xu, and Wolfgang Jäger

Rev. Sci. Instrum. 69, 4061 (1998); http://dx.doi.org/10.1063/1.1149251 (7 pages) | Cited 27 times

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A double-resonance spectrometer, suitable for the investigation of low lying intermolecular vibrational modes and of tunneling transitions of van der Waals complexes, is described. The instrument utilizes a pulsed molecular beam Fourier transform microwave spectrometer (frequency range 4–26 GHz) for signal detection, and a high frequency, phase stabilized, backward wave oscillator (258–375 GHz), as well as a millimeter wave synthesizer (78–118 GHz), as pump radiation sources. A brief description of the Fourier transform microwave spectrometer and of the phase stabilization system of the backward wave oscillator is given. The experimental arrangement is such that the molecular ensemble travels through the submillimeter radiation field prior to the pulsed excitation microwave experiment, in which the resulting population changes are detected. The sensitivity and the resolution capabilities of the new technique are illustrated with double resonance spectra of the van der Waals complexes Ar–CO and CO–N2. © 1998 American Institute of Physics.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
33.20.Bx Radio-frequency and microwave spectra
34.20.Gj Intermolecular and atom-molecule potentials and forces

Fast photomultiplier tube gating system for photon counting applications

David J. Creasey, Peter A. Halford-Maw, Dwayne E. Heard, John E. Spence, and Benjamin J. Whitaker

Rev. Sci. Instrum. 69, 4068 (1998); http://dx.doi.org/10.1063/1.1149252 (6 pages) | Cited 14 times

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A normally “on” linear-focused 14-stage end-window photomultiplier tube (PMT) (Electron Tubes Limited 9893Q/100B), designed for fast photon counting, has been gated through control of the voltage applied to the first dynode. The gating circuit reduces the gain of the PMT during a laser pulse, in order to discriminate against the detection of scattered light, and then increases the gain promptly to observe extremely low levels of laser-induced fluorescence (LIF). An extinction factor for the laser scattered photons of >105 was observed, and has enabled count rates for photons due to LIF as low as 1 Hz to be measured for a laser pulse-repetition frequency of 7 kHz. The rise of the PMT gain is monitored directly by observation of the fluorescence using time-resolved photon counting, and the PMT turn-on time is 30 ns. No significant distortion of the temporal profile of the fluorescence was observed during PMT turn-on. The system, which can also be operated in ungated mode, is rugged and reliable, and has been employed outdoors during atmospheric field measurements of the hydroxyl radical using LIF. The gating circuit is suitable for the rejection of laser scattered light in applications with extremely low levels of fluorescence on the submicrosecond timescale. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Ha Photomultipliers; phototubes and photocathodes
42.79.Ls Scanners, image intensifiers, and image converters
84.30.Sk Pulse and digital circuits
07.60.Dq Photometers, radiometers, and colorimeters

Influence of the acousto-optic effect on laser Doppler anemometry signals

Susan H. Jack, David B. Hann, and Clive A. Greated

Rev. Sci. Instrum. 69, 4074 (1998); http://dx.doi.org/10.1063/1.1149253 (8 pages) | Cited 3 times

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When laser Doppler anemometry (LDA) is used to measure sound fields in water it is important to take into account the refractive index variations in the water due to the sound wave. These have the effect of creating a phase difference between the two laser beams in the LDA setup so that when they intersect they create moving fringes. In some situations this acousto-optic effect can dominate over the movement of the particles due to the sound wave, thereby influencing the Doppler signal. This article determines in which situations the acousto-optic effect can be ignored and in which situations it has a dominant effect. Theoretical expressions are derived for the magnitude of the acousto-optic effect on the LDA signal in terms of the distance of the laser beam propagation and acoustic wave number. The results show that varying the value of the wave number, the distance the laser beams have traveled in the direction perpendicular to the optical axis, or the angle of the sound wave, has an effect on the amplitude, yamp, of the fringe movement. For low wave number values, an angle of 0, ±π from the optic axis (y direction) corresponds to the situation in which the laser beams have been affected to the same degree by refractive index changes in the water and thus the path difference is zero and the value of yamp is a minimum. A maximum value of yamp is obtained for an angle of ±π/2 from the y direction for low wave number values. It is shown that the ratio of the acousto-optic effect to the amplitude of the particle movement due to the sound wave varies as the square of both the acoustic wave number and the distance of the laser beam propagation for low wave number values. An equation for the apparent motion of the particles in the fringes is determined and is used to show that the acousto-optic effect dominates as the value of the wave number and the distance of propagation of the beams increases. Also, for very low wave numbers and short distances, the acousto-optic effect is negligible. This is because at low wave numbers, corresponding to low sound frequencies, the refractive index gradients, and hence the phase changes along the lengths of the laser beams, are small. © 1998 American Institute of Physics.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
06.30.Gv Velocity, acceleration, and rotation
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
back to top CHARGED PARTICLE SOURCES, OPTICS and ACCELERATION

Summary of the performances of the superconducting electron cyclotron resonance ion source at 14 GHz

P. Ludwig, F. Bourg, P. Briand, A. Girard, G. Melin, D. Guillaume, P. Seyfert, A. La Grassa, G. Ciavola, S. Gammino, M. Castro, F. Chines, and S. Marletta

Rev. Sci. Instrum. 69, 4082 (1998); http://dx.doi.org/10.1063/1.1149254 (4 pages) | Cited 8 times

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This article deals with the most recent performance of the superconducting electron cyclotron resonance ion source (SERSE) working at 14 GHz with high magnetic fields after the required conditioning and optimization of several operating parameters. SERSE has now achieved an outstanding level of performance in delivering highly charged ion beams in argon and oxygen gases: the results obtained while operating in a stainless steel chamber and with an aluminum liner are shown and discussed. © 1998 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative
84.71.Ba Superconducting magnets; magnetic levitation devices
52.50.Gj Plasma heating by particle beams
52.50.Dg Plasma sources

Electrostatic cage “Stark barrel” for rapidly switching a uniform electric field through arbitrary angles

J. L. Horn, D. M. Homan, C. S. Hwang, W. L. Fuqua, and K. B. MacAdam

Rev. Sci. Instrum. 69, 4086 (1998); http://dx.doi.org/10.1063/1.1149268 (8 pages) | Cited 6 times

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A cylindrical arrangement of electrodes, together with control electronics, is described that provides uniform electric fields over cm3 volumes in a vacuum, whose angle and magnitude can be switched on a μs time scale. Full 360° field rotation is achieved, and the device allows access for particle or light beams from all sides. Both numerical and analytic descriptions of the general fields are given. Extension to full three-dimensional field control and other variations are described. The device, which was originally designed for crossed-beam collision experiments with keV energy ions and laser-excited Rydberg atoms in field-directed Stark states or coherent-elliptic states, may be more generally useful in atom trapping and cold collisions or in materials and surface science. © 1998 American Institute of Physics.
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41.90.+e Other topics in electromagnetism; electron and ion optics (restricted to new topics in section 41)
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
32.60.+i Zeeman and Stark effects
02.60.Lj Ordinary and partial differential equations; boundary value problems
07.77.-n Atomic, molecular, and charged-particle sources and detectors
81.00.00 Materials science
31.50.Df Potential energy surfaces for excited electronic states

Mass spectrometric characterization of a high-field asymmetric waveform ion mobility spectrometer

Randy W. Purves, Roger Guevremont, Stephen Day, Charles W. Pipich, and Matthew S. Matyjaszczyk

Rev. Sci. Instrum. 69, 4094 (1998); http://dx.doi.org/10.1063/1.1149255 (12 pages) | Cited 93 times

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Ion mobility spectrometry (IMS) has become an important method for the detection of many compounds because of its high sensitivity and amenability to miniaturization for field-portable monitoring; applications include detection of narcotics, explosives, and chemical warfare agents. High-field asymmetric waveform ion mobility spectrometry (FAIMS) differs from IMS in that the electric fields are applied using a high-frequency periodic asymmetric waveform, rather than a dc voltage. Furthermore, in FAIMS the compounds are separated by the difference in the mobility of ions at high electric field relative to low field, rather than by compound to compound differences in mobility at low electric field (IMS). We report here the first cylindrical-geometry-FAIMS interface with mass spectrometry (FAIMS-MS) and the MS identification of the peaks observed in a FAIMS compensation voltage (CV) spectrum. Using both an electrometer-based-FAIMS (FAIMS-E) and FAIMS-MS, several variables that affect the sensitivity of ion detection were examined for two (polarity reversed) asymmetric waveforms (modes 1 and 2) each of which yields a unique spectrum. An increase in the dispersion voltage (DV) was found to improve the sensitivity and separation observed in the FAIMS CV spectrum. This increase in sensitivity and the unexpected dissimilarity in modes 1 and 2 suggest that atmospheric pressure ion focusing is occurring in the FAIMS analyzer. The sensitivity and peak locations in the CV spectra were affected by temperature, gas flow rates, operating pressure, and analyte concentration. © 1998 American Institute of Physics.
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07.75.+h Mass spectrometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

A phase-space-compressing, mass-selecting beamline for hyperthermal, focused ion beam deposition

Kevin J. Boyd, Adam Łapicki, Masato Aizawa, and Scott L. Anderson

Rev. Sci. Instrum. 69, 4106 (1998); http://dx.doi.org/10.1063/1.1149242 (10 pages) | Cited 13 times

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We have developed an ion beamline for hyperthermal ion-surface collisions that incorporates a phase-space compressor to improve the focusability/current density of the ion beam in the 1–10 eV deposition energy range. In essence, collisional damping is used to substantially improve the brightness of the ion source. In addition to the focusing behavior, the beamline also accomplishes mass selection, source-target pressure reduction of >1010, confinement of the beam to avoid space charge spreading, and hyperthermal energy beam transport. For our application the requirement is moderately tight (100 s of microns) focusing at hyperthermal energies (1–100 eV), but the principle should also be applicable to improving spot sizes/current densities at higher energies. © 1998 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
41.85.Ja Particle beam transport
29.25.Ni Ion sources: positive and negative
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Low aberration focusing system for a proton nanoprobe

H. Wollnik, M. I. Yavor, and A. G. Kalimov

Rev. Sci. Instrum. 69, 4116 (1998); http://dx.doi.org/10.1063/1.1149256 (4 pages) | Cited 1 time

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Based on detailed numerical calculations, an ion-optical scheme is proposed for a low aberration proton nanoprobe system that includes four electrostatic quadrupoles arranged like a “Russian Quadruplet” and a magnetic solenoid lens with a flux density of 2 T. The sensitivity of the system to misalignments of the lenses is investigated. © 1998 American Institute of Physics.
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41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
41.75.Ak Positive-ion beams
41.85.Ne Electrostatic lenses, septa
07.77.Ka Charged-particle beam sources and detectors
82.80.-d Chemical analysis and related physical methods of analysis
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Spins and parities of levels in fission fragments

M. A. Jones, W. Urban, and W. R. Phillips

Rev. Sci. Instrum. 69, 4120 (1998); http://dx.doi.org/10.1063/1.1149257 (10 pages) | Cited 17 times

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Efficient methods for using triple and fourfold γ-ray coincidence data to give information on spins and parities of levels in secondary fission fragments are described. Triple-γ angular correlations and double-γ angular correlations culled from triple coincidences with one γ ray observed isotropically for selectivity have been used to give information on the multipole nature of transitions; directional linear polarization data culled from fourfold coincidences with one isotropically observed γ ray have been used to provide parity information. Results for known cascades agree with predicted correlation and polarization patterns. Examples of the techniques applied to transitions in 106Mo produced in the decay of 248Cm are given. © 1998 American Institute of Physics.
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21.10.Hw Spin, parity, and isobaric spin
25.85.Ca Spontaneous fission
23.20.Lv γ transitions and level energies
29.40.Wk Solid-state detectors
27.90.+b A ≥ 220
27.60.+j 90 ≤ A ≤ 149

Real time measurement of plasma position in the SINP tokamak

S. K. Saha, A. Bal, and R. Kumar

Rev. Sci. Instrum. 69, 4130 (1998); http://dx.doi.org/10.1063/1.1149258 (6 pages) | Cited 3 times

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An electronic hardware has been developed for the real time determination of the position of the plasma column in the SINP tokamak. The method is based on the Fourier integration of the poloidal magnetic field using cos θ and sin θ coils. The spurious pickups in these coils due to time varying magnetic fields have been explained by a model as being due to eddy currents in the vacuum vessel and the conducting shell. These pickups have been compensated in the hardware by simulating the effects of the eddy currents by linear networks. This diagnostic provides outputs proportional to the horizontal and vertical displacements of the plasma column at three toroidal locations simultaneously. An output proportional to the plasma current is also available. Performance evaluation shows that for both plasma current and displacements, the hardware outputs are in good agreement with the values computed by software. © 1998 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Gj Fluctuation and chaos phenomena

Development of a high performance core snubber for high power neutral beam injectors

Kazuhiro Watanabe, Makoto Mizuno, Shin Nakajima, Tsutomu Iimura, and Yuzo Miyai

Rev. Sci. Instrum. 69, 4136 (1998); http://dx.doi.org/10.1063/1.1149259 (6 pages) | Cited 8 times

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A high performance core snubber using Fe-based soft magnetic alloys composed of ultrafine grain structure cores has been developed to protect an ion source accelerator from electrical breakdowns. Dimension of each core is 900 mm in outer diameter, 400 mm in inner diameter, and 25.4 mm in thickness. Basic characteristics of the core has been investigated and confirmed that the core has a saturation magnetic flux density of 1.35 T with a high relative permeability of about 3500 for a high frequency pulse of 1 MHz. A total magnetic flux of the core snubber is 0.15 Wb with 13 cores and a biasing current. The size of the core snubber could be reduced to about 1/3 from the conventional one composed of Ni–Zn ferrite cores. © 1998 American Institute of Physics.  
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28.52.Cx Fueling, heating and ignition
52.50.Gj Plasma heating by particle beams
07.55.Db Generation of magnetic fields; magnets
84.30.Jc Power electronics; power supply circuits
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

The optimum dynamics of preset count digital rate meter algorithms

V. Dj. Arandjelović and A. M. Koturović

Rev. Sci. Instrum. 69, 4142 (1998); http://dx.doi.org/10.1063/1.1149260 (4 pages) | Cited 1 time

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The concept of “quality of measurement,” Q, of the count rate digital measurement algorithm has been applied to the class of preset count digital rate meter algorithms. The best quality corresponds to the minimum of (τ×ϵ) product, where τ is the response time of the algorithm to a sudden change in the average count rate and ϵ is the fractional standard deviation of the steady-state measurement of a constant average count-rate pulse stream. Analytical expressions for τ and ϵ of digital rate meter algorithms are used to calculate maximum values of Q for both weighted moving average and exponential algorithms. The values of the basic algorithm parameters, k for the moving average, and a for the exponential algorithm to achieve these maximum values of Q are derived for both algorithms. A comparison of the present results with the corresponding results obtained for preset time algorithms of these types has been carried out.© 1998 American Institute of Physics.
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06.20.Dk Measurement and error theory
07.05.Kf Data analysis: algorithms and implementation; data management
back to top BASIC PHENOMENA

Methodology and instrumentation for testing the weak equivalence principle in stratospheric free fall

V. Iafolla, S. Nozzoli, E. C. Lorenzini, and V. Milyukov

Rev. Sci. Instrum. 69, 4146 (1998); http://dx.doi.org/10.1063/1.1149261 (6 pages) | Cited 9 times

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The use of the GiZero free-fall facility for testing the weak equivalence principle is discussed in this article. GiZero consists of a vacuum capsule, released from a balloon at an altitude of 40 km, which shields an experimental apparatus free falling inside the capsule itself. The expected residual acceleration external to the detector is 10−12 g (with g the Earth’s gravitational acceleration) for the 30 s free fall. A common-mode rejection factor of about 10−4 reduces the residual noise differential output to only 10−16 g. The gravity detector is a differential accelerometer with two test masses with coincident center of masses (i.e., zero baseline) with capacitive pick ups. Preparatory experiments have been conducted in the laboratory with a precursor detector by measuring controlled gravity signals, at low frequency, and by observing the Luni-Solar tides. The estimated accuracy in testing the weak equivalence principle, with a 95% confidence level, is 5×10−15 in a 30 s free fall. When compared to orbital free-fall experiments, the GiZero experiment can be considered as a valid compromise which is able to satisfy the requirement for improving significantly the experimental accuracy in testing the equivalence principle with a substantial lower cost, the ability to recover the detector and to repeat the experiment at relatively short time intervals. © 1998 American Institute of Physics.
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04.80.Cc Experimental tests of gravitational theories

Optical pumping magnetic resonance in Cs atoms for use in precise low-field magnetometry

Cheol Gi Kim and Ho Seong Lee

Rev. Sci. Instrum. 69, 4152 (1998); http://dx.doi.org/10.1063/1.1149262 (4 pages) | Cited 2 times

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Magnetic resonance experiments were conducted on optically pumped Cs to investigate the use of atomic magnetic resonance in Cs atoms for precision magnetometry. The resonance frequencies agreed within 4 ppm with the theoretically calculated ones. The different amplitudes of the separate signals were ascribed to differences in the population densities in the sublevels. The noise level for low-field measurements was 10 pT/math. © 1998 American Institute of Physics.
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32.30.Dx Magnetic resonance spectra
32.80.Xx Level crossing and optical pumping
07.55.Ge Magnetometers for magnetic field measurements

Variable path cryogenic acoustic interferometer

D. M. Kucera and J. B. Ketterson

Rev. Sci. Instrum. 69, 4156 (1998); http://dx.doi.org/10.1063/1.1149263 (4 pages)

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We describe a variable path acoustic interferometer for use at cryogenic temperatures. Movement is enabled without mechanical coupling via two piezoelectric bimorphs wired and mounted in a manner that preserves the parallelism of two ultrasonic transducers that define the acoustic path. A certain degree of in situ alignment can also be accomplished. Path length sweeps from 0 to 180 μm have been made at cryogenic temperatures and preliminary sound velocity measurements in liquid 4He and gaseous 3He near 4 K are presented which agree well with past measurements. © 1998 American Institute of Physics.
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43.58.Dj Sound velocity
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.64.+z Acoustic instruments and equipment

High frequency ultrasonic transducers with near optimal efficiency

M. Lippert, C. Bruneel, and F. Bruneel

Rev. Sci. Instrum. 69, 4160 (1998); http://dx.doi.org/10.1063/1.1149264 (6 pages)

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We present a technique for indium bonding lithium niobate single crystal (LiNbO3) on a substrate using a vacuum evaporation. This bonding is realized at room temperature and under atmospheric pressure. We also present a technique of characterization based on the measurement of the electric impedance of these transducers and we show that with this bonding we obtain good piezoelectric transducers, with an electromechanical coupling coefficient of about 98% of theoretical value. © 1998 American Institute of Physics.
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43.38.Fx Piezoelectric and ferroelectric transducers
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Coulomb blockade thermometer: Tests and instrumentation

J. P. Kauppinen, K. T. Loberg, A. J. Manninen, J. P. Pekola, and R. A. Voutilainen

Rev. Sci. Instrum. 69, 4166 (1998); http://dx.doi.org/10.1063/1.1149265 (10 pages) | Cited 12 times

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Coulomb blockade thermometry (CBT) provides a simple method for absolute thermometry in every day laboratory use at cryogenic temperatures. CBT has been found insensitive to even high magnetic fields. We review the principles and the operation of CBT and the fabrication of the sensors, and present new data on radiation hardness and stability of the sensors. We describe the instrumentation of CBT in detail. We have developed two signal conditioning units for CBT measurements. One is a modified alternating current resistance bridge, a versatile laboratory instrument operating with a PC computer, and the other one is a simple stand-alone instrument for direct temperature reading. Test results on their performance are also presented. Both prototypes have a short-term reproducibility of 0.3% or better in temperature measurement. © 1998 American Institute of Physics.
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07.20.Dt Thermometers
85.35.Ds Quantum interference devices
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Reduction of vibrational noise from continuously filled 1 K pots

G. Lawes, G. M. Zassenhaus, S. Koch, E. N. Smith, J. D. Reppy, and J. M. Parpia

Rev. Sci. Instrum. 69, 4176 (1998); http://dx.doi.org/10.1063/1.1149266 (3 pages) | Cited 3 times

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We have examined the vibrational noise originating from 1.3 K pumped helium chambers (1 K pots) that are continuously filled from the 4.2 K bath through an impedance. The noise can be largely eliminated by either heating the pot or by heating the impedance directly. Noise in 1 K pots has detrimental consequences for the operation of audio frequency torsional oscillators and for high precision thermometry. © 1998 American Institute of Physics.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.07.Tw Servo and control equipment; robots

Ytterbium-based fluorescence decay time fiber optic temperature sensor systems

T. Sun, Z. Y. Zhang, K. T. V. Grattan, and A. W. Palmer

Rev. Sci. Instrum. 69, 4179 (1998); http://dx.doi.org/10.1063/1.1149267 (7 pages) | Cited 10 times

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A series of different Yb-doped fibers has been investigated to determine their potential for use as the active elements in fluorescence–lifetime based thermometry, over a wide range from room temperature to 700 °C. Heat treatment (“annealing”) has been shown to be necessary in practical applications to achieve consistent and reproducible calibration curves, each of which is consistent with the results of a simple two level model. Each sample studied was found to possess unique sensitivity characteristics, enabling an optimized selection for specific applications. The response of the thermometer and the error in the measurement was found to be, at <±5 °C, consistent with the stability of the calibrated oven used. © 1998 American Institute of Physics.
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42.81.Pa Sensors, gyros
07.20.Dt Thermometers
07.60.Vg Fiber-optic instruments
06.20.F- Units and standards
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