Rev. Sci. Instrum. - Review of Scientific Instruments

Select this Article

A high‐intensity, pulsed supersonic carbon source with C(³P_j) kinetic energies of 0.08–0.7 eV for crossed beam experiments

R. I. Kaiser and A. G. Suits

Rev. Sci. Instrum. 66, 5405 (1995); http://dx.doi.org/10.1063/1.1146061 (7 pages) | Cited 36 times

Full Text: | Download PDF

+

Show Abstract

An enhanced supersonic carbon source produces carbon atoms in their C(³P_j) electronic ground states via laser ablation of graphite at 266 nm. The 30 Hz (40±2) mJ output of a Nd‐YAG laser is focused onto a rotating graphite rod with a 1000 mm focal length UV‐grade fused silica plano‐convex lens to a spot of (0.5±0.05) mm diameter. Ablated carbon atoms are subsequently seeded into helium or neon carrier gas yielding intensities up to 10¹³ C atoms cm⁻³ in the interaction region of a universal crossed beam apparatus. The greatly enhanced number density and duty cycle shift the limit of feasible crossed beam experiments down to rate constants as low as 10⁻¹¹–10⁻¹² cm³ s⁻¹. Carbon beam velocities between 3300 and 1100 m s⁻¹, with speed ratios ranging from 2.8 to 7.2, are continuously tunable on‐line and in situ without changing carrier gases by varying the time delay between the laser pulse, the pulsed valve, and a chopper wheel located 40 mm after the laser ablation. Neither electronically excited carbon atoms nor ions could be detected within the error limits of a quadrupole‐mass spectrometric detector. Carbon clusters are restricted to ∼10% C₂ and C₃ in helium, minimized by multiphoton dissociation, and eliminating the postablation nozzle region. © 1995 American Institute of Physics.

+

Show PACS

34.50.Lf	Chemical reactions
37.20.+j	Atomic and molecular beam sources and techniques

Select this Article

Acceleration experiments for an intense H⁻ ion beam

A. Ando, Y. Takeiri, O. Kaneko, Y. Oka, K. Tsumori, E. Asano, T. Kawamoto, R. Akiyama, and T. Kuroda

Rev. Sci. Instrum. 66, 5412 (1995); http://dx.doi.org/10.1063/1.1146424 (7 pages) | Cited 3 times

Full Text: | Download PDF

+

Show Abstract

Intense H⁻ beams have been extracted from a large multicusp plasma source operated with cesium seeding. The H⁻ beams were accelerated up to 100 keV by a single‐stage or a two‐stage electrode system. Spatial profiles of the beams are measured calorimetrically and the beam divergence angle is obtained from half of the e‐folding width. A minimum beam divergence angle of 5 mrads is achieved at a H⁻ current density of 30 mA/cm² with a beam energy of 100 keV. The ratio of acceleration current to H⁻ current increases abruptly when a H⁻ current saturates in the space charge limited region. This enhancement is mainly due to secondary electrons caused by the intersection of H⁻ beams with an extraction grid. When the operating gas pressure decreases, the ratio of the acceleration current to the H⁻ current decreases. This is related to a stripping loss of H⁻ ions in the electrodes. A beam divergence angle reaches a minimum when a ratio of V_acc to V_ext is set at an optimum value of 1.6 in the single‐stage acceleration. This ratio is almost the same as that in the double‐stage acceleration, where the optimum ratio of E_accl/E_ext is 1.5. In the optimum E_accl/E_ext ratio the divergence angle is not affected by V_acc2. The divergence angle can be reduced by changing V_acc2 even if the ratio of E_accl/E_ext is not optimized. The beam steering effect by permanent magnets buried in an extraction grid is observed in nine beamlets experiments. A simple calculation of a single particle trajectory gives a good approximation of the beam deflection angle. © 1995 American Institute of Physics.

+

Show PACS

28.52.Cx	Fueling, heating and ignition
29.25.Ni	Ion sources: positive and negative

Select this Article

Beam diagnostic techniques for a small‐size high‐efficiency radio‐frequency ion source

S. G. Zakhary

Rev. Sci. Instrum. 66, 5419 (1995); http://dx.doi.org/10.1063/1.1146062 (4 pages) | Cited 3 times

Full Text: | Download PDF

+

Show Abstract

The use of both a small discharge volume and magnetic mirror fields allow sequential ionization and an increased efficiency of this ion source. The extracted ion current can reach 12 mA at an extraction voltage=3 kV and discharge pressure=20 mTorr. In this paper a description of the techniques which are used for measuring the important parameters to evaluate this ion source is presented. These parameters are: beam profile, beam emittance, energy spread, and charge spectra of the beam. The source is found to have a beam emittance of 150 mm m rad, and energy spread of 30–60 eV, and a content of Ar⁺⁴ reaching ≂20% of the total extracted ion current. © 1995 American Institute of Physics.

+

Show PACS

29.25.Ni	Ion sources: positive and negative
29.27.Fh	Beam characteristics

Select this Article

Production of a large diameter electron cyclotron resonance plasma using a multislot antenna for plasma application

Yoko Ueda, Masayoshi Tanaka, Shunjiro Shinohara, and Yoshinobu Kawai

Rev. Sci. Instrum. 66, 5423 (1995); http://dx.doi.org/10.1063/1.1146063 (5 pages) | Cited 10 times

Full Text: | Download PDF

+

Show Abstract

An electron cyclotron resonance plasma with large diameter, uniform, and high electron density is produced using a multislot antenna. The uniformity of the plasma is within 5% over 20 cm in diameter. The electron density of the helium plasma in front of a substrate is 7×10¹⁰ cm⁻³, while the electron density without the substrate is higher than the cutoff density for 2.45 GHz. The effect of the magnetic field configuration on plasma uniformity is investigated. Both of the R wave (electron cyclotron wave) and L wave are found to be excited in the plasma. © 1995 American Institute of Physics.

+

Show PACS

52.50.Gj	Plasma heating by particle beams
52.77.Bn	Etching and cleaning
52.77.Dq	Plasma-based ion implantation and deposition

Select this Article

Fast reciprocating probe system for local scrape‐off layer measurements in front of the lower hybrid launcher on JT‐60U

N. Asakura, S. Tsuji‐Iio, Y. Ikeda, Y. Neyatani, and M. Seki

Rev. Sci. Instrum. 66, 5428 (1995); http://dx.doi.org/10.1063/1.1146064 (5 pages) | Cited 11 times

Full Text: | Download PDF

+

Show Abstract

A fast reciprocating probe system with a long drive shaft was incorporated into a multi‐junction lower hybrid (LH) wave launcher on JT‐60U in order to investigate an improved coupling mechanism of the radio frequency wave to the core plasma. The system has been operated reliably over a horizontal scan of 25 cm in 1.5 s using a compact pneumatic cylinder drive and springs. A double probe measurement provided the scrape‐off layer plasma profile between the last closed flux surface and the first wall with the spatial resolution of 1−2 mm measured with a laser displacement gauge. The profiles of the electron density n_e and temperature T_e were in good agreement with those obtained with a triple probe method. During the LH wave injection with good coupling to the core plasma, an increase in the local T_e was observed in front of the LH launcher mouth. The local n_e was (7−10)×10¹⁶ m⁻³, consistent values needed for the good coupling. © 1995 American Institute of Physics.

+

Show PACS

52.55.Fa	Tokamaks, spherical tokamaks
52.70.Ds	Electric and magnetic measurements

Select this Article

A spatially scanning vacuum ultraviolet and visible range spectrometer for spectroscopy of tokamak plasmas in ASDEX‐Upgrade

A. R. Field, J. Fink, R. Dux, G. Fussmann, U. Wenzel, and U. Schumacher

Rev. Sci. Instrum. 66, 5433 (1995); http://dx.doi.org/10.1063/1.1146065 (9 pages) | Cited 18 times

Full Text: | Download PDF

+

Show Abstract

A spatially scanning, combined vacuum‐ultraviolet (VUV) and visible range spectrometer system for the spectroscopy of tokamak plasmas in the ASDEX‐Upgrade experiment is described. This system is designed to allow flexible observation of about 2/3 of the boundary plasma using VUV (30–200 nm) and visible range spectrometers viewing along a common line of sight which can be scanned during the plasma discharge by means of a rotatable mirror. From successive spectra recorded using intensified, multichannel photodiode detectors and the recorded position data, spatial profiles of the plasma emission can be reconstructed. Because radiation losses from the boundary plasma can largely be attributed to line emission in the VUV spectral region, this instrument finds application in quantitative studies of radiation loss processes as well as to studies of impurity production and transport. Simultaneous observation in the visible spectral range facilitates an in situ absolute calibration of the VUV instrument by means of the ‘‘branching‐ratios’’ technique. © 1995 American Institute of Physics.

+

Show PACS

52.55.Fa	Tokamaks, spherical tokamaks
52.70.Kz	Optical (ultraviolet, visible, infrared) measurements

Select this Article

One‐dimensional position‐sensitive superheated‐liquid‐droplet in‐phantom neutron dosimeter

W. Lim and C. K. Wang

Rev. Sci. Instrum. 66, 5442 (1995); http://dx.doi.org/10.1063/1.1146066 (8 pages) | Cited 1 time

Full Text: | Download PDF

+

Show Abstract

The one‐dimensional (1D) position‐sensitive superheated‐liquid‐droplet in‐phantom neutron dosimeter incorporating a sensitive volume emulsion has been fabricated, prepared, and tested. The 1D position‐sensitive superheated‐liquid‐droplet dosimeter (SLDD) is fabricated from a 3/8‐in.‐o.d., 1/4‐in.‐i.d., 20‐cm‐long, Plexiglas^T^M‐walled tube filled with a mixture of superheated‐liquid Freon^T^M droplets and host medium glycerol solution. Washer‐shaped piezoelectric acoustic transducers are positioned at both ends of the tube; they determine the number and positions of the acoustic events when the superheated‐liquid droplets evaporate upon neutron irradiation. The SLDD is sensitive to a wide range of neutron energy, from thermal (0.0253 eV) up to 10 MeV and higher. The SLDD is irradiated with the ¹³⁷Cs and ⁶⁰Co γ sources, as well as a ²⁵²Cf neutron source to test for its radiation response and spatial resolution. The SLDD based on the Freon‐134a superheated‐liquid droplets operating at 20 °C and 1 atm is found to be ideal for measuring neutron depth dose and relative biological effectiveness dose. This study also proves that the position of the radiation‐induced nucleation acoustic events can be linearly determined from the differences in the transmission times received by the acoustic transducers on the 1D SLDD. The spatial resolution of the neutron depth dose is 1 mm due to the finite response time (1 μs) of the piezoelectric acoustic transducers. © 1995 American Institute of Physics.

+

Show PACS

87.53.Bn	Dosimetry/exposure assessment
87.56.Da	Ancillary equipment

Select this Article

Measurement of hydrogen radical concentration for a hydrogen pressure range from 0.01 to 30 Torr

N. Tsuji, Tomoo Akiyama, and Hiroshi Komiyama

Rev. Sci. Instrum. 66, 5450 (1995); http://dx.doi.org/10.1063/1.1146067 (5 pages) | Cited 5 times

Full Text: | Download PDF

+

Show Abstract

A thermocouple method was used to measure the concentration of hydrogen radicals at hydrogen pressures from 0.01 to 30 Torr. The concentration can be calculated from a heat balance at the thermocouple. Under low hydrogen concentration conditions, all terms in the heat balance equation must be estimated accurately. Our results for the measured absolute concentration of the hydrogen radicals at pressures below 1 Torr agreed well with the calculated concentration predicted by a model that is based on the surface dissociation probability at the hot filament and the simulation of diffusion from the filament. With increasing pressure, the hydrogen radical concentration shifted from the surface‐dissociation‐rate‐controlled regime to the diffusion‐controlled regime at the hot filament. The agreement between the heat balance at the thermocouple and that at the hot filament shows that the measurement of the hydrogen radical concentration is of the correct order. Our results show that this measurement technique could be used in studying the growth mechanisms in various deposition processes where hydrogen is a main species. © 1995 American Institute of Physics.

+

Show PACS

81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.80.Yc	Rutherford backscattering (RBS), and other methods of chemical analysis

Select this Article

Long‐pulsed Nd:YAG frequency‐doubled laser for optical measurements of high‐velocity phenomena

Masakazu Uchino, Gang Yuan, and Tsutomu Mashimo

Rev. Sci. Instrum. 66, 5455 (1995); http://dx.doi.org/10.1063/1.1146068 (4 pages) | Cited 1 time

Full Text: | Download PDF

+

Show Abstract

A long‐pulsed neodymium‐doped yttrium aluminum garnet (Nd:YAG) frequency‐doubled laser with no Q‐switch was constructed for optical measurements of high‐velocity phenomena. The laser consists of a doubled‐elliptical pump cavity with a Nd:YAG rod and two xenon flash lamps, an intracavity potassium titanyl phosphate crystal, and a high‐voltage electrical‐pulse source. A narrow‐band‐stimulated emission at the frequency‐doubled 532‐nm wavelength was confirmed by a spectrometer. The delay time from a trigger signal and the effective pulse duration were approximately 40 and 65 μs, respectively. The laser average output power was measured to be larger than 6 kW by a pyroelectric joulemeter. This laser may be used as a flash monowavelength light source, and also as a long‐pulsed single‐mode laser in the visible wavelength region using for example, an intracavity étalon and/or a brewster plate. © 1995 American Institute of Physics.

+

Show PACS

42.55.Rz	Doped-insulator lasers and other solid state lasers
42.62.-b	Laser applications

Select this Article

Phase‐sensitive interferometry with ultrashort optical pulses

Rik H. J. Kop and Rudolf Sprik

Rev. Sci. Instrum. 66, 5459 (1995); http://dx.doi.org/10.1063/1.1146069 (5 pages) | Cited 13 times

Full Text: | Download PDF

+

Show Abstract

Reliable phase‐sensitive time‐resolved interferometry with ultrashort pulsed lasers is performed with the use of a closed scanning Michelson interferometer in combination with a fixed Mach–Zehnder interferometer at the front end. The technique is based on measuring the full phase and frequency properties of the pulse distortion of an ultrashort optical pulse introduced by linear or nonlinear interaction with a sample. The necessary stability and reproducibility to perform an interferometric measurement is provided by a commercially available Fourier transform spectrometer enabling time‐resolved measurements from the IR well into the visible part of the optical spectrum. The feasibility of the technique is demonstrated by measuring the distortion introduced by an etalon and a surface‐plasmon polariton. © 1995 American Institute of Physics.

+

Show PACS

07.57.-c	Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.Ly	Interferometers

Select this Article

A low coherence ‘‘white light’’ interferometric sensor for eye length measurement

D. N. Wang, S. Chen, K. T. V. Grattan, and A. W. Palmer

Rev. Sci. Instrum. 66, 5464 (1995); http://dx.doi.org/10.1063/1.1146070 (5 pages) | Cited 1 time

Full Text: | Download PDF

+

Show Abstract

This article discusses the use of low coherence interferometric techniques, employing the so‐called ‘‘white light interferometer,’’ for axial eye length measurement. This system utilizes two Michelson interferometers, each of which locates one of the surfaces of the eye, the cornea and the retina, respectively, and thus a simultaneous determination of the two surface positions of the eye gives the value of eye length. The experimental results carried out on a simulated eye are presented, showing that the proposed system is simple, easy to align, suitable for measuring different kinds of eyes, tolerant to transverse eye movement, and worth further exploration. © 1995 American Institute of Physics.

+

Show PACS

07.60.Ly	Interferometers
87.63.-d	Non-ionizing radiation equipment and techniques

Select this Article

Light emitting diode‐based nanosecond ultraviolet light source for fluorescence lifetime measurements

Tsutomu Araki and Hiroaki Misawa

Rev. Sci. Instrum. 66, 5469 (1995); http://dx.doi.org/10.1063/1.1146519 (4 pages) | Cited 29 times

Full Text: | Download PDF

+

Show Abstract

A compact pulsed‐light source is devised from an InGaN/AlGaN double heterostructure light‐emitting diode (LED). The LED emits a 450‐nm (blue) light under conventional dc operation below 30 mA. When a current larger than 50 mA is applied, the intensity of the 450‐nm light saturates, but that of the 380‐nm light due to the InGaN component continues to increase. This phenomenon is utilized to realize a nanosecond ultraviolet (UV) light source. Under repetitive, large current pulsing (frequency=10 kHz, pulse width=4 ns, peak current=2 A), the peak LED emission shifts from 450 to 380 nm. Intense light pulses (peak value=40 mW) of 4‐ns duration were generated. To evaluate the potential of the pulsed LED as an excitation source, the fluorescence lifetime of a quinine‐sulfate solution was measured. The observed lifetime characteristics agreed well with the generally accepted behavior. © 1995 American Institute of Physics.

+

Show PACS

33.50.-j	Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
42.72.Bj	Visible and ultraviolet sources
85.60.Jb	Light-emitting devices

Select this Article

An accurate technique to record the angular distribution of backscattered light

D. S. Wiersma, Meint P. van Albada, and Ad Lagendijk

Rev. Sci. Instrum. 66, 5473 (1995); http://dx.doi.org/10.1063/1.1146071 (4 pages) | Cited 20 times

Full Text: | Download PDF

+

Show Abstract

We report on a new technique to record the angular distribution of light which is scattered from a (disordered) material around the backscattering direction. The technique is accurate over a large scanning range (500 mrad) which includes the exact backscattering direction, and the angular resolution is high (100 μrad). The technique is particularly suitable for the study of coherent backscattering from very strongly scattering random media, but it can be applied in any situation where the angular distribution of backscattered light is studied. It allowed us to measure for the first time the theoretical value of two of the enhancement factor in coherent backscattering. © 1995 American Institute of Physics.

+

Show PACS

78.20.Ci

Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Select this Article

A new apparatus for surface x‐ray absorption and diffraction studies using synchrotron radiation

H. Oyanagi, I. Owen, M. Grimshaw, P. Head, M. Martini, and M. Saito

Rev. Sci. Instrum. 66, 5477 (1995); http://dx.doi.org/10.1063/1.1146072 (9 pages) | Cited 4 times

Full Text: | Download PDF

+

Show Abstract

A new apparatus for structural studies of surfaces and buried interfaces using synchrotron radiation was built and tested at the 27‐pole wiggler station BL13B of the Photon Factory. The apparatus was designed to combine x‐ray absorption fine structure (XAFS), x‐ray standing wave (XSW), and surface x‐ray diffraction techniques in the same ultrahigh vacuum (UHV) chamber. The apparatus features a seven‐element Si(Li) solid‐state detector array for a fluorescence yield measurement and a high precision eight‐axis goniometer in the UHV chamber with a base pressure of 1×10⁻¹⁰ Torr. For the same sample mounted on the in‐vacuum goniometer, vertically or horizontally polarized surface‐sensitive XAFS, surface x‐ray diffraction, and XSW can be measured. As a performance test, the structure of Ge overlayers on Si(001) was studied by polarized surface‐sensitive XAFS. The results show that the apparatus can probe the local structure of adatoms with ∼0.1 monolayer sensitivity. © 1995 American Institute of Physics.

+

Show PACS

07.85.Qe	Synchrotron radiation instrumentation
61.05.cf	X-ray scattering (including small-angle scattering)
61.05.cj	X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
78.70.Dm	X-ray absorption spectra

Select this Article

On the possibilities of x‐ray phase contrast microimaging by coherent high‐energy synchrotron radiation

A. Snigirev, I. Snigireva, V. Kohn, S. Kuznetsov, and I. Schelokov

Rev. Sci. Instrum. 66, 5486 (1995); http://dx.doi.org/10.1063/1.1146073 (7 pages) | Cited 394 times

Full Text: | Download PDF

+

Show Abstract

Coherent properties of the x‐ray beam delivered at the ESRF allow the observation of very weak perturbations of the wave front, resulting in the phase contrast. A straightforward experimental setup for phase contrast imaging is proposed and used to record holographic images from organic samples of 10–100 μm at energy 10–50 keV with the contrast up to 50%–100%. The theory of phase contrast imaging is considered and some theoretical estimations are made to reveal the performance of the proposed technique in terms of resolution, sensitivity, geometrical requirements, and energy range applicability. It is found that for carbon‐based fibers a detectable size with 2% contrast is 0.1 μm for 10 keV and −1 μm for 100 keV. It is demonstrated that the fine interference structure of the image is very sensitive to the shape, density variation, and internal structure of the sample. Some prospects for the practical use and future development of the new coherent techniques such as phase contrast microscopy, microtomography, holography, and interferometry at high energies are also discussed. © 1995 American Institute of Physics.

+

Show PACS

07.85.Qe	Synchrotron radiation instrumentation
41.50.+h	X-ray beams and x-ray optics

Select this Article

Development of a chamber for in situ polarized total‐reflection fluorescence x‐ray absorption fine structure spectroscopy

Masayuki Shirai, Masaharu Nomura, Kiyotaka Asakura, and Yasuhiro Iwasawa

Rev. Sci. Instrum. 66, 5493 (1995); http://dx.doi.org/10.1063/1.1146074 (6 pages) | Cited 4 times

Full Text: | Download PDF

+

Show Abstract

We have constructed a chamber for the in situ structural study of metals and metal oxides supported on single‐crystal surfaces by polarized total‐reflection fluorescence x‐ray absorption fine structure (PTRF‐XAFS) spectroscopy. This chamber makes it possible to measure in situ PTRF‐XAFS spectra under a variety of conditions; from high vacuum (1×10⁻⁹ Pa) to high pressure (1×10⁵ Pa) and from low temperature (100 K) to high temperature (800 K). A wide degree (100°) of rotation of the sample along the x‐ray light axis can be attained in order to measure the asymmetric or anisotropic structure of active sites on the single‐crystal substrates in two different directions—parallel and perpendicular to the surface. The chamber is mounted on XYZ and rotation tables to achieve total‐reflection conditions of the incident x ray to the sample. The advantage of this in situ PTRF‐XAFS technique has been demonstrated by measuring extended x‐ray absorption fine structure spectra of Pt/α‐Al₂O₃(0001) and x‐ray absorption near‐edge structure spectra of vanadium oxide on ZrO₂(100) under reaction conditions © 1995 American Institute of Physics.

+

Show PACS

07.30.Kf	Vacuum chambers, auxiliary apparatus, and materials
07.85.Nc	X-ray and γ-ray spectrometers
61.05.cf	X-ray scattering (including small-angle scattering)
61.05.cj	X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
73.20.Mf	Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Select this Article

A simple and compact synchrotron radiation x‐ray exposure system in a vacuum for ultrafine pattern fabrication

T. Horiuchi, K. Deguchi, T. Ishiyama, and M. Oda

Rev. Sci. Instrum. 66, 5499 (1995); http://dx.doi.org/10.1063/1.1146520 (8 pages)

Full Text: | Download PDF

+

Show Abstract

This paper describes a simple and compact manual synchrotron radiation x‐ray exposure system for fundamental research on ultrafine pattern fabrication with x‐ray lithography. Special requirements for printing ultrafine patterns are investigated, and a step‐and‐repeat exposure system that includes a new gap‐setting, a soft‐contact mechanism in a vacuum, and a rough alignment mechanism is developed. All the mechanisms are neatly packed into a small vacuum chamber and are manually remote controlled. The system can be used for various fundamental studies. It is especially useful for experiments to print ultrafine patterns using x‐ray cross‐sectioned and phase‐shifting masks. The success of a variety of experiments verifies the good performance and usefulness of this system. © 1995 American Institute of Physics.

+

Show PACS

07.85.Qe	Synchrotron radiation instrumentation
81.07.-b	Nanoscale materials and structures: fabrication and characterization
81.16.-c	Methods of micro- and nanofabrication and processing
85.35.-p	Nanoelectronic devices

Select this Article

Fast‐ion‐beam photoelectron spectrometer

K. A. Hanold, C. R. Sherwood, M. C. Garner, and R. E. Continetti

Rev. Sci. Instrum. 66, 5507 (1995); http://dx.doi.org/10.1063/1.1146075 (5 pages) | Cited 12 times

Full Text: | Download PDF

+

Show Abstract

A high‐collection‐efficiency fast‐ion‐beam photoelectron spectrometer is described. In a straight time‐of‐flight mode, the spectrometer collects ∼1% of the photoelectrons and achieves an energy resolution of ΔE/E of ∼5%. For coincidence experiments requiring greater collection efficiency, a paraboloidal electrostatic mirror is used. The mirror collects ∼40% of the photoelectrons while maintaining ΔE/E≤35%. In both modes of operation, a time‐ and position‐sensitive electron detector allows conversion of the photoelectron laboratory energy to center‐of‐mass energy. The fast‐ion‐beam photoelectron spectrometer is used to prepare mass‐ and energy‐selected neutral molecules which are used in molecular dissociation studies. © 1995 American Institute of Physics.

+

Show PACS

33.60.+q	Photoelectron spectra
33.80.Eh	Autoionization, photoionization, and photodetachment
07.77.-n	Atomic, molecular, and charged-particle sources and detectors

Select this Article

An ellipsoidal mirror time‐of‐flight photoelectron energy analyzer

P. Hansch, J. R. Norby, S. H. Evans, and L. D. Van Woerkom

Rev. Sci. Instrum. 66, 5512 (1995); http://dx.doi.org/10.1063/1.1146076 (4 pages) | Cited 2 times

Full Text: | Download PDF

+

Show Abstract

A novel time‐of‐flight photoelectron energy analyzer that uses an electrostatic field to reflect and focus electrons has been designed and built. By means of high quality ellipsoidal grids, photoelectrons can be collected at high efficiency and focused onto a detector. The problems of space charge and extended electron sources are addressed in the context of the ellipsoidal mirror analyzer. This versatile spectrometer analyzes single and multiphoton ionization processes and operates over a wide energy range. The experimental data demonstrate the high collection efficiency. We have obtained good spectra at target densities of less than 10⁻⁷ Torr. For six‐photon ionization of xenon a gain of 36 has been achieved. © 1995 American Institute of Physics.

+

Show PACS

07.81.+a	Electron and ion spectrometers
32.80.Rm	Multiphoton ionization and excitation to highly excited states
41.85.Qg	Particle beam analyzers, beam monitors, and Faraday cups

Select this Article

Chemical vapor deposited diamond radiation detectors for ultrahigh radiation dose‐rate measurements: Response to subnanosecond, 16‐MeV electron pulses

S. Han, R. S. Wagner, J. Joseph, M. A. Plano, and M. Dale Moyer

Rev. Sci. Instrum. 66, 5516 (1995); http://dx.doi.org/10.1063/1.1146077 (6 pages) | Cited 5 times

Full Text: | Download PDF

+

Show Abstract

Conductivity modulated devices, similar to photoconductors in operation, for use as radiation detectors were fabricated from polycrystalline chemical vapor deposited diamond films. These detectors were designed to operate under extremely high radiation fields with a large dynamic range in both response and speed. Two types of detectors were studied: a parallel‐plate device and a surface device (SDT). The radiation used to excite these detectors was minimum ionizing electrons with an energy of 16 MeV and a nominal pulse width of less than 25 ps. The response time of all detectors was less than 45 ps. The sensitivity of the detectors was in the range 10⁻⁵–10⁻⁶ A/W. Over the operating range of the detectors, signal saturation was not observed because to the signal size was small in comparison to the applied bias voltage. The detectors appeared to be linear with dose and dose rate over two orders of magnitude, and for dose rates up to 10¹³ rad/s. Long‐lived signal decay tails contributed to much less than 1% of the signal. The response of a SDT detector appeared to be independent of the orientation of the detector to the incident beam direction when the excitation source is minimum ionizing. It appears that the dose‐rate linearity may be extended to a range greater than 10¹³ rad/s. © 1995 American Institute of Physics.

+

Show PACS

29.40.Wk	Solid-state detectors
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Select this Article

Double‐bracelet resonator Helmholtz probe for NMR experiments

Stephane Serfaty, Luc Darrasse, and Siew Kan

Rev. Sci. Instrum. 66, 5522 (1995); http://dx.doi.org/10.1063/1.1146078 (5 pages) | Cited 3 times

Full Text: | Download PDF

+

Show Abstract

A Helmholtz probe made from two parallel‐plate bracelet resonators for nuclear magnetic resonance imaging experiments possesses a number of advantages such as high unloaded quality factor, absence of tuning capacitors, low cost, accessibility, easy to design, patient comfort, etc. Energy transfer to and from the probe is assured by a one‐turn loop magnetically coupled to the coils, disposing the pair of current feed lines needed for conventional Helmholtz coils. Design procedure and a practical example are given, showing good agreement between calculated and experimental results. © 1995 American Institute of Physics.

+

Show PACS

07.57.Pt	Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
87.63.-d	Non-ionizing radiation equipment and techniques

Select this Article

Semi‐automatic atomic force microscope for imaging in solution

Jianxun Mou, Gang Huang, and Zhifeng Shao

Rev. Sci. Instrum. 66, 5527 (1995); http://dx.doi.org/10.1063/1.1146079 (5 pages) | Cited 2 times

Full Text: | Download PDF

+

Show Abstract

A semiautomatic atomic force microscope for imaging in solution is described. With this new design, the laser beam is focused into a fine line, and a rotating mirror is used to deflect the optical signal onto a fixed photodetector. The alignment is now operated with stepper motors. Combined with a three stepper motor sequential advancement for tip engagement, the operation of the atomic force microscope for imaging in solution is much simplified, and the crashing of the tip is largely avoided. Since all controls are now coupled with stepper motors, this system is fully compatible with automation and operation in a self sealed temperature controlled chamber. The design and the construction of this system is relatively simple and can be fitted into any existing system. © 1995 American Institute of Physics.

+

Show PACS

07.79.Lh	Atomic force microscopes
87.80.-y	Biophysical techniques (research methods)

Select this Article

Force‐balancing force sensor with an optical lever

Nobuhiro Kato, Ippei Suzuki, Hisao Kikuta, and Koichi Iwata

Rev. Sci. Instrum. 66, 5532 (1995); http://dx.doi.org/10.1063/1.1146080 (5 pages) | Cited 7 times

Full Text: | Download PDF

+

Show Abstract

Scanning force microscopes (SFMs) are sometimes used to obtain a force curve, which shows the force variation as a function of tip–sample distance. In the force curve measurement, if the spring constant of the force detecting lever is small, the measured force curve has discontinuity and is different from the true force curve. In this paper, we present a new type of force balancing force sensor built in SFM. This force sensor employs an optical lever for detecting the rotation of the lever and two electrostatic force actuators with transparent electrodes. This sensor has two operating modes; with and without feedback. In the feedback mode, the force detecting lever is balanced with the electrostatic force. This system has the effect of enlarging the effective spring constant of the whole sensor. In the nonfeedback mode, this sensor acts as an ordinary force sensor. By using this sensor in both modes we will show the effectiveness of the force feedback in force curve measurements. © 1995 American Institute of Physics.

+

Show PACS

07.10.Pz	Instruments for strain, force, and torque
07.79.-v	Scanning probe microscopes and components

Select this Article

A spin rotator for detecting all three magnetization vector components by spin‐polarized scanning electron microscopy

Teruo Kohashi, Hideo Matsuyama, and Kazuyuki Koike

Rev. Sci. Instrum. 66, 5537 (1995); http://dx.doi.org/10.1063/1.1146081 (7 pages) | Cited 6 times

Full Text: | Download PDF

+

Show Abstract

A spin rotator for observing magnetic domains with all three magnetization components of a sample surface by spin‐polarized scanning electron microscopy (spin SEM) has been developed. The spin rotator is placed between the sample and the spin detector in a spin SEM, and can rotate the polarization vector of secondary electrons by π/2. Although the spin detector itself can detect only two independent polarization components, the rotation of polarization makes third‐component detection possible. The conventional spin rotator, which is a well‐known energy filter named a Wien filter, has been much improved to have a large focusing area by using hyperbolic cylindrical pole pieces as a magnet and several auxiliary electrodes. As a result, all the secondary electrons emitted from the area of a surface as large as 1 mm in diameter can pass the spin rotator with uniform spin rotation, and the distribution of all three magnetization components can be imaged successfully by spin SEM. © 1995 American Institute of Physics.

+

Show PACS

07.78.+s	Electron, positron, and ion microscopes; electron diffractometers
75.70.Rf	Surface magnetism

Select this Article

Improved Kelvin method for measuring contact potential differences between stepped gold surfaces in ultrahigh vacuum

J. P. Bellier, J. Lecoeur, and C. Koehler

Rev. Sci. Instrum. 66, 5544 (1995); http://dx.doi.org/10.1063/1.1146082 (4 pages) | Cited 1 time

Full Text: | Download PDF

+

Show Abstract

A new mechanical system and a convenient piezoelectric driven Kelvin probe for the measurement of the contact potential difference (CPD) under ultrahigh vacuum are described. Charging effects on CPD measures are discussed. The probe is small (2.2 mm diam) and allows cartography of the surface. The mechanical system is frictionless so the distance between the sample and the probe can be maintained constant and at a low value (≊20 μm). By elimination of charging effects, reliable and reproducible results can be obtained within ±10 mV. The system is tested on gold vicinal surfaces. © 1995 American Institute of Physics.

+

Show PACS