Design of an electron-beam ion trap to be situated at Queen's University, Belfast

An electron-beam ion trap (EBIT) has been designed for atomic physics experiments at the Queen's University of Belfast. A pair of permanent magnets will be used to produce an axial magnetic field to compress an electron beam, whereas pairs of superconducting magnets have been used for traditional EBITs. The design of the new EBIT is detailed and possible experiments are explained to show the feasibility of the EBIT. (C) 2004 American Institute of Physics.

Thomson scattering system at the Tokyo electron beam ion trap

A Thomson scattering system has been installed at the Tokyo electron beam ion trap for probing characteristics of the electron beam. A YVO4 green laser beam was injected antiparallel to the electron beam. The image of the Thomson scattering light from the electron beam has been observed using a charged-coupled device camera. By using a combination of interference filters, the spectral distribution of the Thomson scattering light has been measured. The Doppler shift observed for the scattered light is consistent with the beam energy. The beam radius dependence was investigated as a function of the beam energy, the beam current, and the magnetic field at the trap region. The variation of the measured beam radius against the beam current and the magnetic field were similar to those in Herrmann's prediction. The beam radius as a function of the beam energy was also similar to Herrmann's prediction but seemed to become larger at low energy. (C) 2002 American Institute of Physics.

Prism coupler with variable coupling gap

The construction and operation of a prism/variable-gap/sample system (or variable-gap Otto coupler) for the excitation of surface electromagnetic modes is reported. This system has been used for the observation and characterization of surface plasmon polaritons on thin film structures. The initial alignment of prism and sample is performed under gravity and the subsequent gap variation is performed by means of a single actuator operating a flexure stage on which the prism is mounted. The flexure stage ensures the maintenance of good parallelism between sample and prism as the gap dimension is varied. The coupler has also served as a prototype, in terms of design principle, for the construction of a more sophisticated, variable-gap Otto coupler that can operate in vacuum at temperatures from ambient to 85 K. (C) 2000 American Institute of Physics. [S0034-6748(00)02311-X].

Variable temperature, variable-gap Otto prism coupler for use in a vacuum environment

The field of surface polariton physics really took off with the prism coupling techniques developed by Kretschmann and Raether, and by Otto. This article reports on the construction and operation of a rotatable, in vacuo, variable temperature, Otto coupler with a coupling gap that can be varied by remote control. The specific design attributes of the system offer additional advantages to those of standard Otto systems of (i) temperature variation (ambient to 85 K), and (ii) the use of a valuable, additional reference point, namely the gap-independent reflectance at the Brewster angle at any given, fixed temperature. The instrument is placed firmly in a historical context of developments in the field. The efficacy of the coupler is demonstrated by sample attenuated total reflectance results on films of platinum, niobium, and yttrium barium copper oxide and on aluminum/gallium arsenide (Al/GaAs) Schottky diode structures. (C) 2000 American Institute of Physics. [S0034-6748(00)02411-4].

Characterization of a picosecond laser generated 4.5 keV TiK-alpha source for pulsed radiography

K alpha radiation generated by interaction of an ultrashort (1 ps) laser with thin (25 mu m) Ti foils at high intensity (2x10(16) W/cm(2)) is analyzed using data from a spherical Bragg crystal imager and a single hit charge-coupled device spectrometer together with Monte Carlo simulations of K alpha brightness. Laser to K alpha and electron conversion efficiencies have been determined. We have also measured an effective crystal reflectivity of 3.75 +/- 2%. Comparison of imager data with data from the relatively broadband single hit spectrometer has revealed a reduction in crystal collection efficiency for high K alpha yield. This is attributed to a shift in the K-shell spectrum due to Ti ionization. (c) 2005 American Institute of Physics.

The Langmuir probe as a diagnostic of the electron component within low temperature laser ablated plasma plumes

A Langmuir probe has been used as a diagnostic of the temporally evolving electron component within a laser ablated Cu plasma expanding into vacuum, for an incident laser power density on target similar to that used for the pulsed laser deposition of thin films. Electron temperature data were obtained from the retarding region of the probe current/voltage (I/V) characteristic, which was also used to calculate an associated electron number density. Additionally, electron number density data were obtained from the saturation electron current region of the probe (I/V) characteristic. Electron number density data, extracted by the two different techniques, were observed to show the same temporal form, with measured absolute values agreeing to within a factor of 2. The Langmuir probe, in the saturation current region, has been shown for the first time to be a convenient diagnostic of the electron component within relatively low temperature laser ablated plasma plumes. (C) 1999 American Institute of Physics. [S0034-6748(99)01503-8].

Use of a random phase plate as a KrF laser beam homogenizer for thin film deposition applications

Fabrication of devices based on thin film structures deposited using the pulsed laser deposition technique relies on reproducibility and control of deposition rates over substrate areas as large as possible. Here we present an application of the random phase plate technique to smooth and homogenize the intensity distribution of a KrF laser footprint on the surface of a target which is to be ablated. It is demonstrated that intensity distributions over millimeter-sized spots on the target can be made insensitive to the typical changes that occur in the near-field intensity distribution of the ultraviolet output from a KrF laser. (C) 1999 American Institute of Physics. [S0034-6748(99)02504-6].

A technique for mapping three-dimensional number densities of species in laser produced plumes

The potential of a diagnostic technique to provide quantitative three-dimensional (3D) density distributions of species in a low temperature laser-produced plume is shown. An expanded, short pulse, tunable dye laser is used to probe the plume at a set time during the expansion. Simultaneous recording of two-dimensional in-line absorbance maps and orthogonal recording of laser induced fluorescence permits the 3D density mapping by scanning the dye laser frequency. Preliminary data, supported by a simple model, is presented for the case of Ba II ions in a YBCO plume heated by a KrF laser. (C) 1996 American Institute of Physics.

The plasma mirror - A subpicosecond optical switch for ultrahigh power lasers

Plasma mirrors are devices capable of switching very high laser powers on subpicosecond time scales with a dynamic range of 20–30 dB. A detailed study of their performance in the near-field of the laser beam is presented, a setup relevant to improving the pulse contrast of modern ultrahigh power lasers ~TW–PW!. The conditions under which high reflectivity can be achieved and focusability of the reflected beam retained are identified. At higher intensities a region of high specular reflectivity with rapidly decreasing focusability was observed, suggesting that specular reflectivity alone is not an adequate guide to the ideal range of plasma mirror operation. It was found that to achieve high reflectivity with negligible phasefront distortion of the reflected beam the inequality csDt,lLaser must be met (cs : sound speed, Dt: time from plasma formation to the peak of the pulse!. The achievable contrast enhancement is given by the ratio of plasma mirror reflectivity to cold reflectivity.

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

A method of measuring the temperature of the fast electrons produced in ultraintense laser-plasma interactions is described by inducing photonuclear reactions, in particular (gamma,n) and (gamma,3n) reactions in tantalum. Analysis of the gamma rays emitted by the daughter nuclei of these reactions using a germanium counter enables a relatively straightforward near real-time temperature measurement to be made. This is especially important for high temperature plasmas where alternative diagnostic techniques are usually difficult and time consuming. This technique can be used while other experiments are being conducted. (C) 2002 American Institute of Physics.