Neon Source Research Articles

The neon gas field ion source—a first characterization of neon nanomachining properties

At the Charged Particle Optics Conference (CPO7) in 2006, a novel trimer based helium gas field ion source (GFIS) was introduced for use in a new helium ion microscope (HIM), demonstrating the novel source performance attributes and unique imaging applications of the HIM (Hill et al., 2008 [1]; Livengood et al., 2008 [2]). Since that time there have been numerous enhancements to the HIM source and platform demonstrating resolution scaling into the sub 0.5nm regime (Scipioni et al., 2009 [3]; Pickard et al., 2010 [4]). At this Charged Particle Optics Conference (CPO8) we will be introducing a neon version of the trimer-GFIS co-developed by Carl Zeiss SMT and Intel Corporation. The neon source was developed as a possible supplement to the gallium liquid metal ion source (LMIS) used today in most focused ion beam (FIB) systems (Abramo et al., 1994 [5]; Young et al.,1998 [6]). The neon GFIS source has low energy spread (∼1eV) and a small virtual source size (sub-nanometer), similar to that of the helium GFIS. However neon does differ from the helium GFIS in two significant ways: neon ions have high sputtering yields (e.g. 1 Si atom per incident ion at 20keV); and have relatively shallow implant depth (e.g. 46nm in silicon at 20keV). Both of these are limiting factors for helium in many nanomachining applications. In this paper we will present both simulation and experimental results of the neon GFIS used for imaging and nanomachining applications.

Kinetics of acrylamide photopolymerization as investigated by capillary zone electrophoresis

Riboflavin-mediated photopolymerization of acrylamide had been investigated earlier and found to give a poor conversion of the monomer into the polymeric phase (barely 60% with standard 1-h light exposure at room temperature with a 12-W neon source). The kinetics of such process were re-examined by using capillary zone electrophoresis and it was found that the efficiency could be augmented to > 95% (even higher than in peroxodisulphate polymerization) under the following conditions: by conducting the photopolymerization process at 70°C 1 h, instead of at room temperature, alterantively, by using a 105-W UV-A lamp, having a radiation spectrum extending also in the UV region, instead of the standard 12-W neon bulbs, and by increasing the amount of catalyst (riboflavin 5′-phosphate) from 6 to 12 ppm. In all instances, it was found that atmospheric oxygen would act as a retarder, the lag time being ca. 17 min at an oxygen partial pressure of 35 mmHg and increasing progressively to > 70min at > 200 mmHg. However, even at a partial pressure as high as 900 mmHg (as obtained by oxygen insufflation from a tank), once the retarder had been consumed a conversion of monomers into the polymer chains of > 92% was still obtained. In contrast, oxygen acts as an inhibitor in peroxidisulphate polymerization: from an incorporation efficiency of ca. 92% at 25 mmHg oxygen partial O 2 pressure, the conversion is lowered to only 40% at 900 mmHg.

Impurity transport studies in ASDEX by means of neon-seeded pellets

Neon-seeded deuterium pellets, containing 1% neon, were successfully produced and injected into ASDEX divertor discharges. The behaviour of the deposited neon ions was studied by VUV spectroscopy, using a special version of the ASDEX/JET impurity transport code for interpretation. The neutral neon source was tailored so as to resemble theoretical ablation curves. Estimates of time-scales for ionization and toroidal spreading of neon ions show that toroidal symmetry is established before ionization to Ne X takes place; however, the results for Ne VIII burnthrough must be treated with caution in a one-dimensional model. Some ionization and recombination rate coefficients were verified experimentally by investigation of the time delays between pellet entry and maximum line intensities, and of the low remaining level of Ne VIII radiation after its ionization peak. The anomalous neon diffusion coefficient was derived from the final decay of the Ne X line intensity, which was observed to be exponential, down to the 5% level. Below this level, recycling via the divertor chambers became important. A value of D ≈ 0.4 m2·s−1 was found under the assumption of an associated drift velocity vD = −2D r/a2; this is in good agreement with the results of other transport studies of ASDEX OH plasmas and similar values have been reported from other tokamaks. No apparent dependence of the diffusion coefficient on electron density was observed.

Compression Measurements of Neon-Seeded Glass Microballoons Irradiated by CO2-Laser Light

Compression of DT-neon-seeded, glass microballoons has been observed in CO/sub 2/-laser experiments at Los Alamos Scientific Laboratory. DT densities of the order of 20% of liquid density have been attained. Detailed comparisons of the neon densities determined from the measured neon source size and from the fit of observed spectra by Stark-broadening calculations have been made. The excellent agreement obtained with these methods indicates that the extrapolation of the microfield effects used in Stark-broadening calculations to high densities is reasonable.

The spatial and frequency distributions of the intensity of pulsed amplified spontaneous emission

A single pulse of amplified spontaneous emission (ASE) from a neon source at 540 nm is studied and an explanation presented of the granular structure of its output intensity. The explanation accounts quantitatively for the size and shape of the granules and for the degree of coherence observed in sources of pulsed ASE. The same approach is extended to account for the spectral structure observed in certain ASE sources. A preliminary attempt has been made of study the effect of nonuniform amplification and wall reflections in the ASE source.

Comparison of satellite self‐contamination experiments and scattering return flux calculations

Gaseous emissions from a spacecraft modify the orbital environment and degrade the observations of distant radiation sources. These emissions also provide contamination fluxes induced by self‐scattering and scattering with ambient particles. Experiments were carried out on the orbiting Atmosphere Explorer D satellite (AE‐D) to verify the calculated return fluxes of a neon source. Known rates of neon were emitted in the direction of the velocity vector on command from the MRMU (molecular return measurement unit). At 250 km the neutral mass spectrometer indicated a total neon return flux of 2.46 × 10−2 times the emitted flux. The calculated fraction was 1.23 × 10−2, including 9.14 × 10−3 for the ambient scatter and 3.54 × 10−3 for the altitude‐independent self‐scatter. The pressure gages indicated pressures less than 7 × 10−6 torr at altitudes from 161 to 210 km. The maximum pressure for 161‐km orbit was calculated as 7.4 × 10−7 torr.

Camera Timing Marker with Dual Spark and Neon Light Sources

Efficient camera timing marker blocks with dual light sources, one spark and one neon lamp, for installation in 16 and 35mm high-speed cameras have been designed and produced. These timing-light sources can be operated continuously in short bursts or pulsed at cycling times of 1,000 to 50,000 cps. They are positioned to produce intense timing marks with sharp leading edges outside and between the perforations on either side of 16mm and 35mm film. They are designed with small dimensions for fitting into most high-speed cameras. — The rear source consists of a small spark-gap assembly designed to fire from a 5,000- to 10,000-v d-c pulse. This spark gap produces an intense spot of light at pulse frequencies of from 1,000 to 10,000 cps with the pulse duration of 12 to 30μsec. The resulting high-contrast image is readily observable and measurable on medium-speed black-and-white and color films, with the cameras operating at at 16mm frame rates of 8,000 frames/sec (200 ft/sec) and higher. — The neon source utilizes the NE2J or BA1C neon lamps which, when pulsed with short-duration pulses at input voltages of 200 to 300 v, produce bright images at frequencies of 1,000 to 50,000 cps. Extremely sharp edges and light intensities of an order of magnitude over conventional systems are obtained with a special f/1.3 illuminating and projection lens system designed to collect the light from the neon electrode and produce a bright image of a slit on the film.