High-Power High-Efficiency L-band Multiple-Beam Klystron Development at CPI
Communications and Power Industries, Inc., has designed and manufactured two versions of a 10-MW-peak high-efficiency multiple-beam klystron (MBK) operating at 1300 MHz. This type of klystron is favored for large particle accelerator projects such as the European X-ray Free-Electron Laser at the Deutsches Elektronen Synchrotron (DESY). Two klystrons have been made for DESY. The first-generation MBK was a vertically oriented prototype using a six-cavity design with higher order mode input and output cavities and conventional intermediate cavities. For cost and performance reasons, the second-generation MBK, designated VKL-8301B, utilized seven coaxial fundamental-mode cavities and is an “industrialized” horizontally oriented klystron. The klystron was designed and optimized using state-of-the-art multidimensional design codes to ensure that all performance requirements are exceeded. Agreement between the simulated and measured performances is good. The VKL-8301B prototype achieved a peak saturated RF output power of 10.4 MW and 67.8% efficiency. The data were measured at the full 1.5% duty and with 1.5-ms pulse width. The klystron satisfied all required operating conditions, including stable operation into an output mismatch of 1.2:1 voltage standing wave ratio at various phases. The prototype has been shipped to DESY and has been successfully tested by a customer.
Development of a 1.3 GHz, 10 MW, 65% efficiency multi-beam klystron for XFEL
CPI's second generation, 10 MW, 1300 MHz multiple beam klystron (MBK), designated the VKL-8301B, has been developed and is being built for the European X-ray free electron laser (XFEL), which is under construction at DESY in Hamburg (Germany). At 10 MW peak rf output the MBK is required to provide at least 65% efficiency and more than 3 MHz instantaneous -1 dB bandwidth. Average power and rf pulse length are 150 kW and 1.5 ms, respectively. MBKs have the advantage of generating high rf output powers at moderate electron beam energies. For our design, six off-axis electron beams enable low cathode current density for longer cathode life. Compared to our first- generation design, where higher-order-mode cylindrical cavities were used, we are utilizing ring resonators operating in the fundamental-mode. This ensures sufficient beam separation while still keeping the overall diameter of the device small in order to reduce cost. Our in-house 1D large-signal rf code (LSCEX) was used to come up with the initial rf design. The 2.5D rf code TESLA enabled us to verify and refine the design. For the cavity design we utilized the commercially available 3D codes MAFIA and HFSS. The baseline beam optics design was created using our in-house 2.5D code XGun. With state-of- the-art 3D modeling software for beam optics (MICHELLE) and magnetics (MagNet) we then validated and optimized the design. Most of the mechanical design is completed. Material for the prototype is currently being procured and we will start building the klystron by the end of February 2008. We are going to present simulated data showing the expected performance of the device. The simulations exceed the requirements by a healthy margin. Measured data will be presented as they become available throughout the assembly process.
Pharmacokinetics of amikacin and chloramphenicol in the aqueous humor of rabbits
Composite data describing ocular pharmacokinetics are unreliable because of intersubject variation. To address this problem, an animal model was developed in which multiple aqueous samples from single subjects were obtained. Following direct anterior chamber or intravenous administration of amikacin or chloramphenicol, pharmacokinetic analysis of drug concentrations in the serum and anterior chamber was performed by using a nonlinear least-squares regression program. The number of anterior chamber paracenteses performed did not alter the beta elimination rates or percent penetration into the anterior chamber. The aqueous humor and peripheral-compartment terminal slopes were identical. These data indicate that complete ocular concentration-time curves can be obtained without altering antibiotic pharmacokinetics. Following direct injection into the anterior chamber, the elimination rates for both antibiotics followed a one-compartment model, whereas those following intravenous administration best fit an open, first-order, two-compartment model. Following intravenous administration, the anterior chamber elimination rate constants for both drugs were equal to that of the serum and significantly longer than that following direct injection. The elimination rates of both drugs following direct injection were similar. Systemic administration resulted in drug levels in aqueous humor that persisted longer than those following direct injection. Chloramphenicol, a lipophilic compound, gave higher mean concentrations in aqueous humor than did amikacin. Our model provides a new approach which rigorously examines ocular pharmacokinetics and provides data which suggest that for selected compounds the parenteral route of administration is preferable.