NLC Reliability Analysis Notes : Klystron - Modulator System By :

This paper address the reliability and availability issues to be faced in deploying and operating the klystronmodulator assemblies proposed for the Next Linear Collider (NLC). The rf power sources are a major system of the NLC and require a high uptime in order to reach the goal of 0.85 availability. Since the NLC is made up of several systems, not just klystron-modulator assemblies, the availability goal for the assemblies must be higher than 0.85. Currently this goal is at least 0.95. This short paper summarizes the analysis currently under way to determine whether the design of the rf power system will meet the design availability goal. NLC Reliability Analysis Notes: Klystron-Modulator System By: Zane Wilson , Stanford Linear Accelerator Center, Stanford University US Department of Energy This paper addresses the reliability and availability issues facing the deployment and operation of the klystron-modulator assemblies proposed for the Next Linear Collider (NLC). The rf power sources are a major system of the NLC and require a high uptime in order to reach the goal of 0.85 availability. Since the NLC is made up several systems in addition to klystron-modulator assemblies the availability goal for the assemblies must be higher than 0.85. Currently this goal is at least 0.95. This short paper summarizes the analysis currently being conducted to see if the design of the system will meet the design availability goal. It deals primarily with the issue of using a solid-state modulator to drive 8 klystrons (or 4 pairs). This configuration is known as the Solid State 8-pack. The analysis was done using the following models/tools: 1. A review of the klystron-modulator design that will be used to develop a reliability block diagram (RBD). The components were grouped in the 8-pack configuration for analysis. 2. Since availability is the driving factor for the accelerator a Logistic Support Analysis Report (LSAR). was generated. This report will allow us to see the operational effects on the klystron availability. 3. Knowing the LSAR and other parameters a discrete time model was created using the software packages Extend and MathCAD. The results of this model and the availability numbers generated will be shown. The solid state klystron-modulator assembly used in the analysis is based on the design by Dick Cassel and company. The model of the system is made up of: eight 75-MW klystrons and one modulator power supply using a solid state switch known as an IGBT. This model differs from the other proposed system, a traditional line-type modulator. The conventional klystron-modulator system was our starting point and impacted the way the modeling of the solid-state modulator was done. In order to show this impact we will outline the conventional system. The conventional system model consisted of five major components that contribute most to the reliability of the system. They are: Two 75-MW klystrons, a thyratron, a pulse forming network (PFN), and an end of line clipper (EOLC). As you can see, the number of klystrons is different from the solid state system and the reason for that is the tubes are put in pairs on the assembly and then four pairs are joined together. The differences are also evident in the RBD’s of each system shown below: Klystron Klystron Thratron PFN EOLC Klystron Klystron Thratron PFN EOLC Klystron Klystron Thratron PFN EOLC Klystron Klystron Thratron PFN EOLC Conventional Line-Type Klystron-Modulator “8-Pack” Each of the components for the proposed systems was then assigned a projected mean time between failure (MTBF) to be used for the model. The mission time, the time the components are expected to operate without failure, was set to 9 months. The MTBFs for each component are shown next. The MTBF of 6000 hours shown is for one pair a “2-pack” of the conventional system. For an “8-pack” of the conventional system the MTBF would be: Klystron Klystron Klystron Klystron Klystron Klystron Klystron Klystron