Volume 79, Issue 2, February 2008
- optics; atoms and molecules; spectroscopy; photon detectors
- particle sources, optics and acceleration; particle detectors
- nuclear physics, fusion and plasmas
- microscopy and imaging
- condensed matter; materials
- biology and medicine
- electronics; electromagnetic technology; microwaves
- thermometry; thermal diffusivity; acoustic; photothermal and photoacoustic
- general instruments
- proceedings of the 12th international conference on ion sources
Index of content:
- OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS
A proposed measurement method for void fraction in lubricant oil based on the image processing technique79(2008); http://dx.doi.org/10.1063/1.2839022View Description Hide Description
A new method for measuringvoid fraction in lubricating oils is presented based on the image processing technique. The problem here differs from the bubbles detection problem in two-phase fluids in that our interest lies in the gross amount of gas voids in oils. Our method is based on an observation that gas voids in oils change the color of the mixed gas-oil material. Therefore, a measurement technique was established based on the change in color. In particular, the relationship between the change in color and amount of voids was established experimentally. The experiment and testing were performed on a particular setup which consists of a pipe, oil, and air. The test result has shown that this method is effective. The method is the simplest and most accurate one among the existing methods.
An active-optic x-ray fluorescence analyzer with high energy resolution, large solid angle coverage, and a large tuning range79(2008); http://dx.doi.org/10.1063/1.2823527View Description Hide Description
A crystal-optic x-ray fluorescence energy analyzer has been designed and tested, which combines the features of electron-volt energy resolution, large solid angle coverage, and tunability over several kilo-electron-volts. The design is based upon the principle of active optics, with ten actuators available to optimally adjust the shape of a silicon crystal used in the Bragg geometry. In most applications the shape is that of a logarithmic spiral for high energy resolution with a spatially nonresolving detector, but a wide range of other shapes is also possible for applications such as imaging or single-shot spectroscopy in a spectral range of the operator’s choosing.
79(2008); http://dx.doi.org/10.1063/1.2839025View Description Hide Description
An x-ray streak camera with wide dynamic range and a large slit photocathode of length has been developed and calibrated. In order to achieve wide dynamic range, a conventional streak tube has been improved and the camerasystem has been designed without microchannel plate electron amplifier. As a result, a dynamic range of 922 is achieved in a single shot mode with laser pulse of (full width at half maximum) at time resolution of better than .
79(2008); http://dx.doi.org/10.1063/1.2844602View Description Hide Description
An instrument has been developed to avoid the rotation of large electron sources and detectors in quantum single particle scattering experiments. The rotation of an electron beam has been achieved by combining three small cylindrical electrostatic electron energy analyzers in series such that the first analyzer is fixed and the other two rotate together around the exit axis of the first; it is a development from an S-shaped deflector used by Hegemann et al. [J. Phys. B26, 4607 (1993)]. Novel design and construction, using copper, aluminum, and stainless steel parts mounted on polyvinyl printed circuit board, enabled an efficient, small-sized high vacuum compatible instrument. The characteristics and versatility of the instrument have been shown by measurements of angular and spin asymmetries of electron scattering phenomena.
Development of a vacuum ultraviolet laser-based angle-resolved photoemission system with a superhigh energy resolution better than79(2008); http://dx.doi.org/10.1063/1.2835901View Description Hide Description
The design and performance of the first vacuum ultraviolet (VUV) laser-based angle-resolved photoemission (ARPES) system are described. The VUV laser with a photon energy of and bandwidth of is achieved from the second harmonic generation using a novel nonlinear optical crystal . The new VUV laser-based ARPES system exhibits superior performance, including superhigh energy resolution better than , high momentum resolution, superhigh photon flux, and much enhanced bulk sensitivity, which are demonstrated from measurements on a typical high temperature superconductor. Issues and further development related to the VUV laser-based photoemission technique are discussed.
A versatile system for ultrahigh resolution, low temperature, and polarization dependent Laser-angle-resolved photoemission spectroscopy79(2008); http://dx.doi.org/10.1063/1.2839010View Description Hide Description
We have developed a low temperature ultrahigh resolution system for polarization dependent angle-resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet (vuv) laser as a photon source. With the aim of addressing low energy physics, we show the system performance with angle-integrated PES at the highest energy resolution of and the lowest temperature of . We describe the importance of a multiple-thermal-shield design for achieving the low temperature, which allows a clear measurement of the superconducting gap of tantalum metal with a . The unique specifications and quality of the laser source (narrow linewidth of , high photon flux), combined with a half-wave plate, facilitates ultrahigh energy and momentum resolution polarization dependent ARPES. We demonstrate the use of - and -polarized laser-ARPESs in studying the superconducting gap on bilayer-split bands of a high cuprate. The unique features of the quasi-continuous-wave vuv laser and low temperature enables ultrahigh-energy and -momentum resolution studies of the spectral function of a solid with large escape depth. We hope the present work helps in defining polarization dependent laser excited angle-resolved photoemission spectroscopy as a frontier tool for the study of electronic structure and properties of materials at the sub-meV energy scale.
A new technique for time-resolved daughter ion mass spectrometry on the microsecond to millisecond time scale using an electrostatic ion storage ring79(2008); http://dx.doi.org/10.1063/1.2884121View Description Hide Description
A new method for time-resolved daughter ion mass spectrometry is presented, based on the electrostatic ion storage ring in Aarhus, ELISA. Ions with high internal energy, e.g., as a result of photoexcitation, dissociate and the yield of neutrals is monitored as a function of time. This gives information on lifetimes in the microsecond to millisecond time range but no information on the fragment masses. To determine the dissociation channels, we have introduced pulsed supplies with switching times of a few microseconds. This allows rapid switching from storage of parent ions to storage of daughter ions, which are dumped into a detector after a number of revolutions in the ring. A fragment mass spectrum is obtained by monitoring the daughter ion signal as a function of the ring voltages. This technique allows identification of the dissociation channels and determination of the time dependent competition between these channels.
79(2008); http://dx.doi.org/10.1063/1.2839918View Description Hide Description
Several computational methods are presented for the rapid extraction of decay time constants from discrete exponential data. Two methods are found to be comparably fast and highly accurate. They are corrected successive integration and a method involving the Fourier transform (FT) of the data and the application of an expression that does not assume continuous data. FT methods in the literature are found to introduce significant systematic error owing to the assumption that data are continuous. Corrected successive integration methods in the literature are correct, but we offer a more direct way of applying them which we call linear regression of the sum. We recommend the use of the latter over FT-based methods, as the FT methods are more affected by noise in the original data.
Actively stabilized optical fiber interferometry technique for online/in-process surface measurement79(2008); http://dx.doi.org/10.1063/1.2870085View Description Hide Description
In this paper, we report the recent progress in optical-beam scanning fiber interferometry for potential online nanoscale surface measurement based on the previous research. It attempts to generate a robust and miniature measurement device for future development into a multiprobe array measurement system. In this research, both fiber-optic-interferometry and the wavelength-division-multiplexing techniques have been used, so that the optical probe and the optical interferometer are well spaced and fast surface scanning can be carried out, allowing flexibility for online measurement. In addition, this system provides a self-reference signal to stabilize the optical detection with high common-mode noise suppression by adopting an active phase tracking and stabilization technique. Low-frequency noise was significantly reduced compared with unstabilized result. The measurement of a sample surface shows an attained repeatability of .
79(2008); http://dx.doi.org/10.1063/1.2888527View Description Hide Description
The analytical performance of surface plasmon resonance imaging with charge coupled device detection can be improved significantly by splitting a macroscopic sensing surface into multiple microscopic neighboring sensing and referencing subareas. It is shown that such a multiple referencing reduces intensity fluctuations across the total sensing area and, therefore, improves the signal/noise (S/N) ratio proportional to the splitting factor. The approach is demonstrated by detection of biotin binding to a monolayer of streptavidin. An effective variation of the reflected intensity of about , which corresponds to the refraction index variation of , was detected with a S/N ratio about 10 without any temperature stabilization of the sensing area.
- PARTICLE SOURCES, OPTICS AND ACCELERATION; PARTICLE DETECTORS
79(2008); http://dx.doi.org/10.1063/1.2835717View Description Hide Description
The construction and testing of a portable energy-sensitive neutron instrument are described. This instrument has been designed and constructed for the primary purpose of characterizing cosmic-ray neutron fields in the upper atmosphere and in cosmic reference field facilities. The instrument comprises a helium-3 proportional counter surrounded by of lead and of polyethylene creating a spherical structure with a diameter of . The instrument also incorporates 12 boron-coated diodes, six on the outside of the polyethylene layer with six placed within the structure. The dimensions, materials, and arrangement of these in the instrument have previously been optimized with the MCNPXMonte Carlo simulation software to provide a compromise between the requirements of portability and spectral response. Testing took place at several locations and experimental data from the instrument’s operation at the high-altitude Jungfraujoch laboratory in the Swiss alps are presented.
79(2008); http://dx.doi.org/10.1063/1.2839583View Description Hide Description
A new beam-charge interlock system is under development for radiation safety and machine protection at the KEKB injector linac. A hardware-based interlock system is required instead of the present software-based interlock system in order to boost its reliability. This system restricts the integrated amount of beamcharges delivered to four different storage rings. The beamcharges are measured using wall-current monitors and detection electronics at six locations along the linac. The detection electronics independently transmits a beam-abort request through a twisted hardwire cable directly to the safetycontrol system of the linac, when the integrated amount of beamcharges exceeds a certain threshold level prescribed for each location. We describe the characteristics and performance of the new beam-charge interlock system along with the details of the experimental tests.
79(2008); http://dx.doi.org/10.1063/1.2832638View Description Hide Description
A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel ( divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with protons proved true with a deflection angle of with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam.
79(2008); http://dx.doi.org/10.1063/1.2840756View Description Hide Description
The design of a compact multiangle electron analyzer array for simultaneous detection of scattered and ejected electrons at nine different angles is described. It consists of eight slim “simulated” cylindrical mirroranalyzers (CMAs) providing electron detection for scattering/ejected angles of 14° apart from each other. A ninth analyzer is arranged to a scattering angle on the opposite side. A single analyzer has cylindrical symmetry equipotential lines in the region of the beam trajectories, whereas its electrodes are noncylindrical, except for the inner cylinder. The new spectrometer is easy to build because only a few electrodes of simple shape are needed for each of the analyzers. The electron optical properties of the new device are very close to those of a true CMA. Its geometric width, however, is only less than one-fifth of that of a conventional CMA, which allows one to arrange several analyzers close to each other. Example results with the new device are presented.
79(2008); http://dx.doi.org/10.1063/1.2841694View Description Hide Description
A set of measurements with the CAPRICE ion source at the GSI test bench has been carried out to investigate its behavior in terms of intensity and shape of the extracted beam when the microwaves generating the plasma sweep in a narrow range of frequency around the klystron center frequency . Remarkable variations have been observed depending on the source and the beamline operating parameters, confirming that a frequency dependent electromagnetic distribution is preserved even in the presence of plasma inside the source. Moreover, these observations confirm that the frequency tuning is a powerful method to optimize the electron cyclotron resonance ion source performances. A description of the experimental setup and of the obtained results is given in the following.
Fourth-generation plasma immersion ion implantation and deposition facility for hybrid surface modification layer fabrication79(2008); http://dx.doi.org/10.1063/1.2870088View Description Hide Description
The fourth-generation plasma immersion ion implantation and deposition (PIIID) facility for hybrid and batch treatment was built in our laboratory recently. Comparing with our previous PIIID facilities, several novel designs are utilized. Two multicathode pulsed cathodic arc plasma sources are fixed on the chamber wall symmetrically, which can increase the steady working time from (the single cathodesource in our previous facilities) to about . Meanwhile, the inner diameter of the pulsed cathodic arc plasma source is increased from the previous , thus, large area metal plasma can be obtained by the source. Instead of the simple sample holder in our previous facility, a complex revolution-rotation sample holder composed of 24 shafts, which can rotate around its axis and adjust its position through revolving around the center axis of the vacuum chamber, is fixed in the center of the vacuum chamber. In addition, one magnetron sputteringsource is set on the chamber wall instead of the top cover in the previous facility. Because of the above characteristic, the PIIID hybrid process involving ion implantation, vacuum arc, and magnetron sputteringdeposition can be acquired without breaking vacuum. In addition, the PIIID batch treatment of cylinderlike components can be finished by installing these components on the rotating shafts on the sample holder.
- NUCLEAR PHYSICS, FUSION AND PLASMAS
79(2008); http://dx.doi.org/10.1063/1.2839023View Description Hide Description
Neutron-imaging systems are being considered as an ignition diagnostic for the National Ignition Facility (NIF) [Hogan et al., Nucl. Fusion41, 567 (2001)]. Given the importance of these systems, a neutron-imaging design tool is being used to quantify the effects of aperture fabrication and alignment tolerances on reconstructedneutronimages for inertial confinement fusion. The simulations indicate that alignment tolerances of more than would introduce measurable features in a reconstructed image for both pinholes and penumbral aperturesystems. These simulations further show that penumbral apertures are several times less sensitive to fabrication errors than pinhole apertures.
79(2008); http://dx.doi.org/10.1063/1.2827514View Description Hide Description
A scintillator based energetic ion loss detector has been built and installed on the National Spherical Torus Experiment (NSTX) [Synakowski et al., Nucl. Fusion43, 1653 (2000)] to measure the loss of neutral beam ions. The detector is able to resolve the pitch angle and gyroradius of the lost energetic ions. It has a wide acceptance range in pitch angle and energy, and is able to resolve the full, one-half, and one-third energy components of the D neutral beams up to the maximum toroidalmagnetic field of NSTX. Multiple Faraday cups have been embedded behind the scintillator to allow easy absolute calibration of the diagnostic and to measure the energetic ion loss in several ranges of pitch angle with good time resolution. Several small, vacuum compatible lamps allow simple calibration of the scintillator position within the field of view of the diagnostic’s video camera.
79(2008); http://dx.doi.org/10.1063/1.2839587View Description Hide Description
Measuringmagnetic fields near the edge of a plasma device can be complicated by the geometric effects of the ports through which such measurements are made. The primary effect is an attenuation of the magnetic field at the probe coil due to the field expanding into the finite sized conducting well of the port. In addition, it is possible to determine the correspondence between the location of a field line as it intersects the probe coil inside the well, with its location far from the perturbation of the well. Here we explore several methods of experimentally characterizing the magnetic fields in the vicinity of the magnetic probe ports of a vacuum vessel, with the aim of improving the interpretation of magnetic measurements needed for experiments in plasma physics.