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The development of peptide-based drugs, which are usually synthetic analogues of endogenous peptides, is currently one of the most topical directions in drug development. Among them, antitumor peptide-based drugs are of great interest. Anticancer peptides can be classified into three main groups based on their mechanism of action: inhibitory, necrosis-inducing and pro-apoptotic peptides. As an antitumor...
NRL large signal design codes have been developed recently to be suitable for accurate simulations of multiple beam traveling wave tubes (MB-TWT). MB-TWTs are attractive novel devices with enhanced power-bandwidth characteristics. However, they are more vulnerable to spurious oscillations than single beam TWTs. The results of performance and stability analysis of MB-TWTs with 3D EM codes, NRL 3D PIC...
Recent advances in the development of millimeter wave vacuum electronic devices have been made possible by powerful, specialized design tools. We summarize them here and point out areas where improved models and codes will be needed.
In any TWT design, understanding of potential spurious oscillation characteristics is critical to achieve optimal amplifier performance and, more importantly, to avoid the unpleasant surprise of discovering problems after the fact. This paper serves to illustrate these oscillation characteristics and to discuss potential mitigation approaches with special emphasis on serpentine/folded-waveguide TWTs...
Serpentine or, its cousin, the folded waveguide (FW) traveling-wave tubes (TWTs) are a class of vacuum electronic devices capable of wideband, high-power performance. This was first demonstrated in [1] with several Q-band 2-stage TWTs that produced 135 W of average power and saturated gains of ∼30 dB over an impressive 25% instantaneous bandwidth. More recently, a 60 W broadband 220-GHz (G-band) serpentine...
Simulations of modern, high current electron beam lithography devices may require modeling of optical components and multiple electron sources that are positioned in an oblique fashion with respect to the main device axis and include counter streaming regions, where two beams are co-located in space while propagating in opposite directions. Modeling such complex multi-beam systems presents different...
Progress on the demonstration of a high power broadband three-beam Ka-band cascaded traveling-wave tube (TWT) prototype is presented. The amplifier will be driven by an electron gun (0.6 A × 3, 20 kV) adapted from our 18-beam multiple-beam klystron gun design. Both serpentine and folded-waveguide versions of the cascaded-TWT have been evaluated. The expected peak RF output power is 4.5 kW with 100...
The design of a W-band serpentine TWT with >200 W of power over a 4 GHz bandwidth (>100 W over 7 GHz) is presented. The amplifier is driven by a 122mA, 20 kV electron beam generated by a slightly modified version of the demonstrated 670 GHz beamstick at a reduced magnetic field. The design was performed by both the established MAGIC-3D and the recently validated NRL code Neptune, with good agreement...
We are developing a wideband 95-GHz, 200-W TWT powered by a 20-kV, 122-mA electron beam. The serpentine waveguide circuit is fabricated by UV-LIGA using an embedded monofilament, which produces an all-copper structure with beam tunnel. Simulations predict 37 dB small-signal gain and 245 W maximum output power.
Simulation of counter streaming charged particle beams, where two beams are co-located in space while propagating in opposite directions, has many applications ranging from the lower current electron beam lithography regime to the higher current Free Electron Laser (FEL) regime. Modeling such counter streaming beams presents different computational challenges depending on the specific device being...
A simple model for the dispersive properties of a folded waveguide slow wave structure is presented. The model, with a small number of fitting parameters, reproduces well the dispersion relation and Kino impedance of a structure as calculated using a computational electromagnetics code. The model allows for the inclusion of asymmetric beam tunnel fields and the stop bands introduced when the beam...
We present results of an electromagnetic cold-test of an all-copper, microfabricated 220 GHz serpentine waveguide amplifier circuit. Transmission/reflection measurements are used to determine the ohmic loss, pass band, and cutoff frequency. We observe the effects of fabrication accuracy, including circuit depth and beam tunnel alignment, on the measured electromagnetic properties.
We present a new MICHELLE software module (eBEAM) that is capable of high accuracy simulations of electron beams with stochastic space charge effects. In modeling low current electron beam systems such as electron beam lithography, nanolithography and electron microscopy, it is necessary to simulate ensembles of individual electrons to account correctly for the statistical effects of inter-particle...
Modeling low current electron beams with high accuracy presents a number of novel challenges to existing simulation tools. For applications that use currents of the order of microamperes, such as electron beam lithography, nanolithography, electron microscopy and quality inspection, it is necessary to simulate ensembles of individual electrons to account correctly for the statistical effects of inter-particle...
We undertook a qualitative exploration of police perspectives on injecting drug use and needle and syringe access among injecting drug users (IDUs) in a Russian city which has witnessed explosive spread of HIV associated with drug injecting. Twenty-seven in-depth qualitative interviews were conducted in May 2002 with police officers of varying rank who reported having regular contact with IDUs. All...
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