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H. P. Johnson

Bio: H. P. Johnson is an academic researcher from Los Alamos National Laboratory. The author has contributed to research in topics: Linear particle accelerator & Particle accelerator. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the phase and amplitude control of the EIMAC 8973 tetrode was evaluated for the deuteron beam at the FMIT facility and it was shown that it is the most suitable final amplifier tube for each of a series of 15 amplifier chains operating at 0.5-MW output.
Abstract: Preliminary rf system design for the accelerator portion of the Fusion Materials Irradiation Test (FMIT) Facility is in progress. The 35-MeV, 100-mA, cw deuteron beam will require 6.3 MW rf power at 80 MHz. Initial testing indicates the EIMAC 8973 tetrode is the most suitable final amplifier tube for each of a series of 15 amplifier chains operating at 0.5-MW output. To satisfy the beam dynamics requirements for particle acceleration and to minimize beam spill, each amplifier output must be controlled to ±1° in phase and the field amplitude in the tanks must be held within a 1% tolerance. These tolerances put stringent demands on the rf phase and amplitude control system.

6 citations


Cited by
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Journal ArticleDOI
TL;DR: The results suggest that the microbiota of Ae.
Abstract: Since it has been understood that gut microbiota of vector mosquitoes can influence their vector competence, efforts have been undertaken to develop new control strategies based on host microbiota manipulation, and aimed at suppressing the vector population or replacing it with a less competent one. For the proper design of such control strategies it is necessary to know the microbiota composition of the target vector species, how it is acquired, and how it changes throughout the host’s life cycle. In this study, 16S rRNA amplicon high-throughput sequencing was used to characterize the changes in microbiota from the aquatic environment (larval breeding sites) to the different developmental stages of field-collected Aedes koreicus in Italy, an emerging invasive mosquito species in Europe and a potential vector of several pathogens. The bacterial communities of the aquatic breeding sites, larvae, pupae and adults showed distinctive structures to one another. Indeed, 84% of community members were unique to a given sample type. Nevertheless, almost 40% of the sequences generated were assigned to bacteria detected in all sample types, suggesting the importance of bacteria transstadially transmitted from water to the adult stage in constituting mosquito microbiota. Among these, genus C39 largely constituted water microbiota, family Burkholderiaceae was the most abundant in larvae and pupae, and genus Asaia dominated adult communities. In addition, Asaia consitituted a core microbiota across all sample types. Our results suggest that the microbiota of Ae. koreicus mosquitoes is composed by a community which derives from the aquatic bacteria of the larval breeding sites, is then filtered by the larval gut, where only certain members are able to persist, rearranged by metamorphosis and finally modified by the change in diet at the adult stage. Understanding how the microbiota of Ae. koreicus changes through the mosquito life cycle represents a first step in selecting bacterial candidates for use in microbiota-based intervention measures for this species. The properties which Asaia exhibits in this species, such as dominance, high prevalence and transstadial transmission, prevent the use of Wolbachia but make Asaia an ideal candidate for paratransgenesis.

34 citations

Journal ArticleDOI
TL;DR: The Fusion Materials Irradiation Test (FMIT) Facility at the Hanford Engineering Development Laboratory (HEDL), Richland, Washington, was designed to provide a high neutron flux and a neutron energy spectrum representative of fusion reactor conditions in volumes adequate to screen and qualify samples of candidate fusion reactor materials as mentioned in this paper.
Abstract: For fusion reactors to become operational, one of the many problems to be solved is to find materials able to withstand the intense bombardment of 14-MeV neutrons released by the fusion process The development of alloys less likely to become damaged by this neutron bombardment will require years of work, making it desirable to begin studies in parallel with other aspects of fusion power generators The Fusion Materials Irradiation Test (FMIT) Facility, to be built at the Hanford Engineering Development Laboratory (HEDL), Richland, Washington, will provide a high neutron flux and a neutron energy spectrum representative of fusion reactor conditions in volumes adequate to screen and qualify samples of candidate fusion reactor materials FMIT's design goal is to provide an irradiation test volume of 10 cm3 at a neutron flux of 1015 n/cm2-s, and 500 cm3 at a flux of 1014 n/cm2-s This will not allow testing of actual components, but samples in the most intense flux region can be subjected to accelerated life testing, accumulating in one year the total number of neutrons seen by a fusion reactor in 10-20 years of operation To produce the neutrons, a 100-mA, 35-MeV deuteron beam will be directed onto a 2-cm-thick, 600-gpm curtain of liquid lithium metal, which strips the deuterons and allows the remaining neutrons to continue on to the test samples The deuterons will be produced by the largest component of the facility, a high-intensity, continuously operating linear accelerator (Linac)

13 citations

Journal ArticleDOI
TL;DR: A 35-MeV 100-mA cw linear accelerator is being designed by Los Alamos for use in the Fusion Materials Irradiation Test (FMIT) Facility as mentioned in this paper.
Abstract: A 35-MeV 100-mA cw linear accelerator is being designed by Los Alamos for use in the Fusion Materials Irradiation Test (FMIT) Facility. Essential to this program is the design, construction, and evaluation of performance of the accelerator's injector, low-energy beam transport, and radio-frequency quadrupole sections before they are shipped to the facility site. The installation and testing of some of these sections have begun as well as the testing of the rf, noninterceptive beam diagnostics, computer control, dc power, and vacuum systems. An overview of the accelerator systems and the performance to date is given.

10 citations

Patent
08 Dec 1994
TL;DR: An electron acceleration device uses thermionic fission cells, an electromagnetic scoop coil, and/or microwaves for power as discussed by the authors, where a power control junction and electron injector control and feed free electrons in packets into the acceleration components that consist of a series of either induction module units, or radio-frequency linacs module units.
Abstract: An electron acceleration device uses thermionic fission cells, an electromagnetic scoop coil, and/or microwaves for power. A power control junction and electron injector control and feed free electrons in packets into the acceleration components that consist of a series of either induction module units, or radio-frequency linacs module units, having quadrapole magnet units in series between the induction module units or RF linac units. The RF linac and quadrapole series are surrounded by a Klystron series. At the high speed electron exit from the device, deflector plates control the exit path of the electrons to direct the course of a craft or electrons to a work area.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the high frequency operation of linacs is discussed and several trial designs for fusion material irradiction test facility in Japan are given, where the size of linac namely the construction cost may be reduced by using 1 MW CW klystrons with the frequency of about 1 GHz.
Abstract: The high frequency operation of linacs is discussed and several trial designs for fusion material irradiction test facility in Japan are given. The size of linac namely the construction cost may be reduced by using 1 MW CW klystrons with the frequency of about 1 GHz. Preliminary results of the fabrication technique for the linac drift tube by copper coating are shown.

1 citations