The growing interest in wireless high data rate communications at millimeter waves both for terrestrial networks and satellite communications is stimulating novel solutions to overcome the strong atmosphere attenuation. In particular, the development of high throughput satellite communication systems for internet distribution is fundamental to complement the terrestrial networks and to cover regions not connected to terrestrial backbones, such as sea or remote areas. Ku-band and Ka-band satellite systems are presently available. Recently, the Wband (71-76 GHz, 81-86 GHz) has been allocated for multigigabit transmissions, providing 5 GHz bandwidth both for uplink and downlink. However, it has been estimated that for enabling high throughput W-band satellite communication systems, transmission power higher than 50 W is needed. In this paper, a 71-76 GHz double corrugated waveguide (DCW) traveling wave tube (TWT) is designed as amplifier for high-data rate satellite downlink, with about 70 W output power. The dispersion characteristic of the designed DCW is experimentally validated by cold test. The proposed TWT is also a test vehicle, scaled in frequency, for a future novel 220 GHz DCW TWT for terrestrial wireless networks.

No abstract

A microfabrication process has been developed by using ultraviolet photolithography (UV-LIGA) with multi-layer SU-8 photoresist to create high aspect ratio Slow Wave Structures (SWS) for millimeter waves and THz vacuum electron devices. The main steps of the process will be described, applied to the fabrication of a double corrugated waveguide at 300 GHz.

Electrons are emerging as a strong complement to X-rays for diffraction based studies. In this paper we investigate the performance of a JUNGFRAU detector with 320 um thick silicon sensor at a pulsed electron source. Originally developed for X-ray detection at free electron lasers, JUNGFRAU features a dynamic range of 120 MeV/pixel (implemented with in-pixel gain switching) which translated to about 1200 incident electrons per pixel and frame in the MeV region. We preset basic characteristics such as energy deposited per incident particle, resulting cluster size and spatial resolution along with dynamic (intensity) range scans. Measurements were performed at 4, 10 and 20 MeV/c. We compare the measurements with GEANT4 based simulations and extrapolate the results to different sensor thicknesses using these simulations.

The pBR322 plasmid DNA was irradiated with 35 MeV electrons, 228 MeV protons and 300 kVp X-rays to quantify DNA damage and make comparisons of DNA damage between radiation modalities. Plasmid was irradiated in a medium containing hydroxyl radical scavengers in varying concentrations. This altered the amount of indirect hydroxyl-mediated DNA damage, to create an environment that is more closely associated with a biological cell. We show that increasing hydroxyl scavenger concentration significantly reduced post-irradiation DNA damage to pBR322 plasmid DNA consistently and equally with three radiation modalities. At low scavenging capacities, irradiation with both 35 MeV electrons and 228 MeV protons resulted in increased DNA damage per dose compared with 300 kVp X-rays. We quantify both single-strand break (SSB) and double-strand break (DSB) induction between the modalities as a ratio of yields relative to X-rays, referred to as relative biological effectiveness (RBE). RBESSB values of 1.16 ± 0.15 and 1.18 ± 0.08 were calculated for protons and electrons, respectively, in a low hydroxyl scavenging environment containing 1 mM Tris–HCl for SSB induction. In higher hydroxyl scavenging capacity environments (above 1.1 × 106 s−1), no significant differences in DNA damage induction were found between radiation modalities when using SSB induction as a measure of RBE. Considering DSB induction, significant differences were only found between X-rays and 35 MeV electrons, with an RBEDSB of 1.72 ± 0.91 for 35 MeV electrons, indicating that electrons result in significantly more SSBs and DSBs per unit of dose than 300 kVp X-rays.