A fifty megawatt klystron for the Stanford Linear Collider
The proposed Stanford Linear Collider (SLC) has been designed to provide 50 on 50 GeV electron-positron collisions. The performance of the 240 klystrons driving the two-mile long linac must be upgraded to achieve at least 50 Megawatts of peak power output at a pulse width of 5 µsec and a pulse repetition frequency of 180 pulses per second. The operating frequency of the upgraded linac will continue to be 2856 MHz. A klystron amplifier meeting these new requirements has been designed to operate at 315 KV, µk = 2, with a computed efficiency of slightly greater than 50%. Initial tests indicate the achievement of the basic power objectives; however, observed parasitic instabilities make beam focusing, RF drive frequency and drive level extremely critical. High electric fields in the electron gun, output gap and output window are all potential problems. Steps taken in the design to overcome these problems are discussed and test results are presented.
An impedance measurement method for double-gap klystron cavity
A new method has been developed for measuring the impedance of a two-gap cavity used in high-power klystrons. The principle is based on network analysis. The cavity under test is considered as a microwave network. The two gaps of the cavity and its output terminal are referred to as three ports. We then can use an impedance matrix to characterize this system, and the six independent impedance parameters can be found by measuring the input impedance seen from the output waveguide when the gaps are in different conditions; viz., either open, shorted, or perturbed. The gap impedance then can be deduced therefrom. It is shown that there are three impedances for a double-gap cavity instead of one for a single-gap cavity. Another problem dealt with here is how to evaluate the capacitance introduced by the perturbation. A few typical experimental results are presented.
The contribution of charcoal production to rural livelihoods in a semi-arid area in Kenya
Forest incomes in the form of both timber and non-timber forest products are an important source of livelihood for many communities in Africa. A major forest resource is charcoal, which contributes to the livelihoods of millions across the region. While incomes from charcoal are used to meet a wide spectrum of needs within rural livelihoods, the role of charcoal production on livelihoods of small-scale producers is not well understood. Therefore, we provide an example on the importance of charcoal on livelihoods in an agropastoralist community in a semi-arid region in Kenya. Based on a household questionnaire targeting 150 charcoal and 150 non-charcoal makers, as well as focus group discussions, we assessed the determinants for participation in charcoal production and developed a household typology based on charcoal income dependence. We also determined the role of charcoal in income equalization and poverty reduction. Our study shows that charcoal contributes about 20% of the household income in the study area. Gender, land size and the number of food-scarce months are the key determinants of participation in charcoal production. Based on the poverty analysis, we conclude that even though charcoal income does not lift the producers out of poverty, it can mitigate the impacts of poverty by reducing the poverty gap and poverty severity. Based on our findings, we recommend a multipronged approach to address sustainable rural livelihoods including a more explicit acknowledgement of charcoal production as a source of rural income. We also recommend broadening of the local livelihood base and a more active management of the woodland to ensure the sustainability of the income.