<P class=abstract>This paper describes and quantifies the role of group facilitation in an experiential, real-time, online, university level credit course entitled eAHSC/230 Interpersonal Communications and Relations. A new and unique group interaction pattern called parallel communication, as well as classical elements of group interaction are described and quantified. New measures of online group facilitation attributes with analogous face-to-face (F2F) counterparts are presented. Specifically, the impact of effective group facilitation on Attentiveness, on Interaction, on Involvement, and on Participation is explored. The paper also examines the eClassrom’s potential effectiveness as a real time teaching and training laboratory which also functions as a process observation tool that collects and feeds back interaction data, providing teachers and trainers immediate and ongoing measures of facilitation effectiveness.</P>
We describe the fabrication and testing of the RF windows designed to transmit power to the PEP-II 476 MHz cavities. Design choices to maximize the reliability of the window are discussed.Fabrication technologies for the window are described and finite-element analysis of the assembly process is presented. Conditioning and high-power testing of the window are discussed. Design of the coupler assembly including the integration of the window and other components is reported.
SLAC is developing sheet beam klystron technology for narrow bandwidth, high peak and average power applications from L-band to W-band. Sheet beam devices are advantageous for several reasons. The primary advantage is the increased surface area in the RF circuit which significantly increases the dissipated heat that can be transferred through the circuit. The reduced charge density in the beam decreases the magnetic field required for beam transport and increases the achievable efficiency compared to a pencil-beam tube with the same beam voltage and current. Finally, both the RF circuit and the magnetic focusing system are simpler and less expensive to fabricate. The combination of features provided by a sheet beam klystron make it an ideal source for linear accelerator and high average power applications.SLAC designed, built and tested a proof of principle, W-band sheet beam klystron (WSBK). The goal of the design was to answer several basic questions regarding sheet beam klystron operation. First, does the cylindrical cathode produce an acceptable, elliptic cross Figure 2 One half of 7 cavity, single-gap, WSBK circuit.section beam. Second, can this beam be transported over the 9 cm. of RF circuit. Third, given that the rectangular drift tube is not cut off to TE modes, will the device be free of oscillations and spurious modes. Finally, does the measured performance of the device agree with the modeling codes used in its design. The test results for the WSBK answered all of the above questions. The 74 kV, 3.6 A beam produced 91% transmission with a 1.1 kG PPM field. There was no evidence of oscillation or beam breakup from TE modes in the circuit. The small signal RF performance agreed well with two different simulation programs. Full power output requires a multigap output cavity to achieve the required impedance. A multi-cell cavity is currently being designed. Progress on the design and fabrication of the 100 kW peak power, 2 kW average power WSBK will also be reported.
To reduce the impedance of the cavity higher order modes, (HOM's), a compact broad-band, low-reflection, waveguide load is required with a VSWR less than 2:1 in the frequency range 714 MHz to 2500 MHz. The load must also work in the high vacuum of the cavity, and be capable of dissipating up to 10 kW of power which is generated by the the interaction of the beam with the cavity HOM's and which is directed to each load assembly. A prototype load assembly is being fabricated which uses the lossy ceramic Al-N with 7% by weight glassy carbon to absorb the microwave power.
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