High Current Density Electron Beam Research Articles

Study of raman spectroscopy on carbon materials irradiated with a high current density electron beam

Micro Raman spectroscopy analysis has been performed on the eroded surfaces of Isotropie graphite and C/C composite materials irradiated with a high current density electron beam (HCDE). The results show that no amorphous structure has been produced in either materials by HCDE beam irradiation, and the growth of graphite microcrystallites is due to annealing induced by electron beam heating. Furthermore, irradiation has induced no great change in the spectrum of carbon fibers in the C/C composite. The shift of the peaks in Raman spectra has also been reported and discussed.

New compensation method for avoiding proximity resist heating in variably shaped electron beam lithography

A horizontal-mode resist heating is proposed and a suitable method for avoiding it in variably shaped electron beam lithography is described. The horizontal thermal diffusion through a top layer resist between electron beam shots cannot be neglected when using a high current density electron beam, a high speed deflector amplifier, and a multiple layer resist because these cause a horizontal-mode resist heating (labeled ‘‘proximity resist heating’’) which depends on the pattern size and on the time interval between shots. A method, suitable to avoid this resist heating, is proposed where the pattern size dependent optimum repetition number of exposures for each pattern is used. There is a slight throughput degradation of typically 10%–20% increase.

Spectral characteristics of an injection-controlled XeF(C→A) excimer laser

The spectral output characteristics of an injection-controlled XeF(C→A) excimer laser pumped by a short pulse (10 ns), high current density (250 A/cm2) electron beam are reported. A tuning bandwidth of 50 nm full width half maximum, centered at 490 nm, with a peak specific energy density of 1.3 J/ℓ was measured using an injection laser intensity of ∼2 MW/cm2. Continuously tuned output across the entire blue-green region (450–530 nm) with an energy density exceeding 0.2 J/ℓ was achieved. Injection beam spectral linewidths as narrow as 0.001 nm were shown to be preserved in the XeF(C→A) laser output.

Scaling of an injection-controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam

This letter reports the design and performance of a scaled, injection-controlled XeF(C→A) laser pumped by a repetitively pulsed, high current density electron beam with a temporal duration of 10 ns full width at half maximum. Injection of a 2 mJ pulse at 486.8 nm having a spectral width of <0.005 nm resulted in an amplified output of 0.7 J corresponding to energy density and efficiency values of 1.5 J/ℓ and 1.2%.

High Current Density Electron Beam Induced Desorption

ABSTRACTHigh current density electron beam irradiation with a small probe can lead to the production of holes in a variety of inorganic materials. We review some of the experimental observations of the hole formation process and compare these to the predictions of a simple model.

Nonlinear photoemission from organic cathodes excited by a pulsed near-ultraviolet laser

High current density electron beams with fast modulation capability can be generated using laser-driven photoemission. Organic film cathodes having a real intermediate energy level can work in a poor vacuum environment and with near ultraviolet (∼ 350 nm) illumination where temporal formats from CW to picosecond pulse are available. Measured nonlinear photoemission characteristics of several organic films are presented and compared to the response of a rate equation model. Pulse distortions for 5 ns and 5 ps pulses also have been computed. Current densitities above 30 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for 5 ns, 337 nm pulses have been measured: an increase up to 3 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> for 5 ps pulses is predicted by the model.

Emission of electron and ion pulses from porous tungsten partially covered with cesium

Cesiated tungsten at about 1700 K provides a low work function (∼ 2 eV) surface for the emission of high current density electron beams as well as for the generation of cesium ions by contact ionization at 1300 K. Tungsten with porosities up to 35% has been investigated, supplying the cesium coverage by diffusion through the body from a heated reservoir. A test diode has been designed by computer simulation, achieving extremely high current densities by a convex emission surface. In dc mode of operation, the obtained ion current density of 8 mA/cm 2 compares well with data from literature, whereas the electron emission was negligible. In pulsed operation, however, electron densities of up to 512 A/cm 2 have been obtained for pulses as long as 100 μs. Even more surprising is an increase of the emitted ion current density to 200 mA/cm 2 for up to 0.8 ms.

In-situ electron-beam-induced reduction of CuO: A study of phase transformations in cupric oxide

The reduction of CuO to Cu has been studied using high resolution electron microscopy and electron energy loss spectroscopy. The reduction proceeds via at least two intermediate phases - Cu 4O 3 and Cu 2O. This is the first experimental observation and the first successful synthesis of the rare Cu 4O 3 phase. The CuO particles were observed to reduce via these two phases with a continuous refinement of particle size and a redistribution of material over the support film (carbon). In the case of large CuO crystals, the entire particle transformed to Cu 4O 3 before further reduction or decrease in particle size occurred. This is the first direct observation of the mechanism involved in the formation of the very small metallic Cu particles normally observed in reduced supported CuO. The reduction was effected by a high current density electron beam in the residual gas atmosphere of an electron microscope. The similarity between this technique and the normal hydrogen reduction at high temperatures is discussed. The presence of the Cu 2O and Cu 4O 3 was determined by application of the optical diffraction method to small regions of a high resolution electron micrograph. This enabled the measurement of both interplanar spacings and interplanar angles, which combine together to allow an unambiguous identification of the phases present.

LEED-Auger study of the interaction of ethylene and hydrogen with Al(100)

AES, LEED, ELS and work function determination were used in order to study H 2 and C 2H 4 adsorption on Al(100). Results indicate that C 2H 4 and H 2 adsorb dissociatively at room temperature. The adsorbed species are incorporated into ordered islands at intermediate exposures. At high exposures the adsorbed species are probably deposited on the surface. Present results indicate that incorporation is randomlike for C 2H 4 adsorption at -80°C. Conversion to an ordered structure results from heating at -30°C. At high current density electron beam stimulates hydrocarbon desorption upon C 2h 4 adsorption and leads to a random incorporation of hydrogen, probably in the form of an amorphous hydride.

Internally Coated Cathodes

RECENT publications1 have indicated that internally coated cathodes would be useful as sources of annular, high current-density electron beams in millimetre wave-length klystrons. For this application their behaviour in magnetic confining fields and their life are important. To study these factors, the cathode shown in Fig. 1 was used; in the first set of experiments, cathodes were made from ‘O’ nickel and coated with a standard triple-carbonate mixture. Cathode temperatures were measured with 0.005 in. diameter platinum–platinum 13 per cent rhodium thermocouples.