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Tungsten (W) is a principal candidate as target material because of its high density and extremely high melting point. W inherently has a critical disadvantage of its brittleness at around room temperature (low temperature brittleness), recrystallization embrittlement, and irradiation embrittlement. TFGR (Toughened, Fine Grained, Recrystallized) W-1.1%TiC has been considered as a realized solution to the embrittlement problems. We started to fabricate TFGR W-1.1%TiC in 2016 under collaboration between KEK and Metal Technology Co. LTD (MTC). The TFGR W-1.1%TiC samples were successfully fabricated in June, 2018. As a result, the specimen showed slight bend ductility and 2.6 GPa of fracture strength.

Hot isostatic pressing (HIP) processes are widely used for removing inner defects, densifying sintered components, consolidating particles and powders, and interfacial diffusion bonding. However, microscopic views of the phenomena have not been fully understood. X-ray absorption fine structure (XAFS) experiments were performed to study the interfacial region of the HIP bonded Fe–Cu sample. XAFS analyses clearly show that the bond distance around Cu is extraordinarily short compared with the bulk fcc Cu. The Cu species in the Fe–Cu HIP bonded sample takes a bcc structure even in the Cu-rich phase at room temperature. This anomalous bcc phase of Cu may derive from the HIP diffusion bonding process, which is performed below the melting points of both the elements. Cu atoms can diffuse into Fe with the bcc structure and settle in the bcc sites.

Tungsten (W) is a principal candidate as target material because of its high density and extremely high melting point. W inherently has a critical disadvantage of its brittleness at around room temperature (low temperature brittleness), recrystallization embrittlement, and irradiation embrittlement. TFGR (Toughened, Fine Grained, Recrystallized) W-1.1%TiC has been considered as a realized solution to the embrittlement problems. We started to fabricate TFGR W-1.1%TiC in 2016 under collaboration between KEK and Metal Technology Co., LTD (MTC). The TFGR W-1.1%TiC samples were successfully fabricated in June, 2018. As a result, the specimen showed slight bend ductility and 2.6 GPa of fracture strength. The TFGR W-1.1%TiC was included in the HRMT-48 PROTAD experiment on September 28th, 2018. After cooling, the post-irradiation-examination will be conducted for the irradiated TFGR W-1.1%TiC.

The spectrum of optical emission from the plasma of hydrocarbon gases was measured with a photomultiplier and an optical multichannel analyzer in PBIID (plasma-based ion implantation and deposition) system. When negative pulsed voltage was applied to a sample, a strong optical emission was observed. It is important to know a contribution of negative pulsed voltage discharge on DLC (diamond-like carbon) synthesis. Spectra of CH (431 nm), H α (656 nm), H β (486 nm) and H γ (434 nm) were observed. Deposition rate of DLC film using acetylene gas was almost proportional to intensity of CH spectrum.

Optical emission from plasmas of hydrocarbon gases was measured with a photomultiplier and an optical multichannel analyzer in a hybrid system of plasma-based ion implantation and deposition (PBII&D). In the PBII&D system, a RF pulse for plasma generation was applied to a substrate of trench structure together with a negative high-voltage (HV) pulse for ion implantation. The negative HV pulse with a voltage of −20 kV and the pulse width of 5 μs was applied at 50 μs after turning off of the RF pulse. The strong optical emission from the hydrocarbon plasma in the rectangular trench was observed at the same time as the application of the negative HV pulse. Intensity of optical emission from the HV pulsed plasma became stronger in a deeper trench, indicating the plasma generation in the trench by a hollow cathode effect. The optical spectra from CH (430.0 nm), H α (656.2 nm) and H β (486.1 nm) were dominant in the HV pulsed plasma of methane, acetylene and toluene gases.

A virtual cathode oscillator with a stainless-steel mesh anode of various transparencies and wire diameters was studied experimentally for the enhancement of microwave power and its repetitive operations. The maximum microwave power observed was about 20 MW at 12 GHz for a diode voltage of 250 kV and an electron beam current of 39 kA using an anode mesh with wire diameter of 0.22 mm and a transparency of 67%. The microwave emission was enhanced by decreasing the mean angle of beam scattering when a mesh of smaller wire diameters was used in the anode. The increased transparency of the fine mesh also contributed to the enhancement of the microwave emission. Use of the mesh anode afforded the operation in several repetitive shots. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 1–10, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10259

A new method of repetitive operation of a virtual cathode oscillator was performed using a carbon plate anode with a hole in the center, a knife-edged annular cathode and an external axial magnetic field. Repetitive microwave radiations more than 450 were observed. Almost all microwave frequency of each operation was contained in 11.8 to 12.8 GHz, while the microwave emission was varied widely. The maximum microwave peak power and pulse duration were 14 MW and 16 ns, respectively, for the diode voltage of 460 kV, the electron beam current of 12.8 kA at the upstream. The dominant radiation pattern of microwave was found to be TE01 mode.

Application of a low power atmospheric pressure plasma jet for surface modifications of acrylic, aluminum, and highly crystalline graphite has been carried out experimentally. The plasma jet was generated with batteries‐driven high voltage modulator. The power consumed for the plasma generation was estimated to be 0.12 W. The plasma had hydroxyl radicals, which is known as a strong oxider from an observation of optical emission spectrum. After the irradiation of the plasma, the surfaces of acrylic and aluminum became to be hydrophilic from the compartment of contact angle of water on these surfaces. The surface of highly crystalline graphite irradiated by the plasma jet had oxygen‐rich functional groups such as C‐O, C = O, and O = C‐O.

Summary form only given. A new method for repetitive operation of a virtual cathode oscillator is presented. In this scheme, a virtual cathode diode in an external axial magnetic field consists of an anode (1 mm in thickness) with a hole in the center and a knife-edged annular cathode. The diameter of anode hole is typically 32 mm that is slightly larger than the cathode diameter of 30 mm. The gap between the anode and the cathode is typically 38 mm. The concept is similar to the reditron except no center part of anode. The radiated microwave travels along a circular waveguide (45 mm in diameter and 2 m in length) and is emitted into free space through a conical horn. An open-ended rectangular waveguide antenna detects microwave signals. The total microwave power is determined by integrating the radiation pattern. The microwave frequency is determined with a long waveguide dispersive delay line. With the axial magnetic field of 0.74 T, we have observed repetitive microwave radiations more than thirty times. The microwave peak power and the pulse duration is typically several MW and 20 ns, respectively, for the diode voltage of 500 kV, the electron beam current of 8 kA at the upstream and 4 kA at the downstream. The microwave frequency of each shot is almost constant, that is, 12.5/spl plusmn/1 GHz. The radiation power of microwave reduces rapidly after 30 operations.

The temporal and spatial evolution of gas discharge induced by a high-power, short-pulsed microwave (HPM) was observed using a high-speed image converter camera. The HPM with the peak power of 20 MW, frequency of 13 GHz, and pulse duration of 14 ns was irradiated uniformly into a gap between two spherical electrodes biased to a DC voltage less than the gap breakdown voltage. The streak images show two different breakdown mechanisms depending on air pressure. In the high-pressure region above about 300 Torr, the microwave-induced discharge begins at several points on the gap axis. When these local discharges increase sufficiently to link together with each other, the gap breakdown occurs. The gap breakdown is delayed by 30–300 ns depending on gas pressures and applied DC voltages. In the low-pressure region less than 300 Torr, on the other hand, a two-stage breakdown occurs. In the first stage, a single large discharge luminescence appears in the gap center at the time of the microwave injection and is followed by another discharge between the first discharge and two electrodes. After approximately 0.1–20 microseconds of the first stage discharge, the second-stage discharge appears followed by the gap breakdown.

Summary form only given. High-power, short-pulse microwave with the peak power of 20 MW, frequency of 13 GHz and pulse duration of 14 ns, which is generated from a virtual cathode oscillator, is irradiated on a gap space between a spherical and a spherical electrodes to induce gas discharge. The electrode is being biased at a constant dc voltage less than that for breakdown at the moment of microwave pulse injection. The gap separation is 15 mm. Gas pressure is changed from 760 Torr to 50 Torr. A high-speed image converter camera observes temporal and spatial evolutions of gas discharge luminescence.

Summary form only given. High power microwave (HPM) with the peak power of 20 MW, pulse width of 14 ns and frequency of 13 GHz generated by a virtual cathode oscillator was irradiated uniformly into a gap with a DC voltage less than the gap-breakdown voltage. The gap consists of two spherical stainless electrodes of 4.1 cm in a diameter. The gap distance is 15 mm. The air pressure was varied from 50 to 760 Torr. Gas discharge luminescence was observed with a high-speed image converter camera. The time history of the applied voltage, the discharge current and the microwave was observed with a digital oscilloscope.