High Reliability Prototype Quadrupole for the Next Linear Collider

Abstract-- The Next Linear Collider (NLC) will require over 5600 magnets, each of which must be highly reliable and/or quickly repairable in order that the NLC reach its 85 % overall availability goal. A multidiscipline engineering team was assembled at SLAC to develop a more reliable electromagnet design than historically had been achieved at SLAC. This team carried out a Failure Mode and Effects Analysis (FMEA) on a standard SLAC quadrupole magnet system. They overcame a number of longstanding design prejudices, producing 10 major design changes. This paper describes how a prototype magnet was constructed and the extensive testing carried out on it to prove full functionality with an improvement in reliability. The magnet’s fabrication cost will be compared to the cost of a magnet with the same requirements made in the historic SLAC way. The NLC will use over 1600 of these 12.7 mm bor

A novel approach to increasing the reliability of accelerator magnets

Abstract — When a very large particle accelerator with about 8000 electromagnets, such as the proposed Next Linear Collider (NLC), has an 85 % overall availability goal, then all these magnets and their power supplies must be highly reliable and/or quickly repairable. An interdisciplinary reliability engineering approach, more commonly applied to aircraft and space vehicles, has been taken to design maximum reliability in the NLC main linac quadrupoles, while maintaining magnetic field performance and reducing cost. A specially assembled team of engineers with a variety of experiences with magnets carried out a Failure Mode and Effects Analysis (FMEA) on a standard SLAC quadrupole magnet system. This process helped them identify which components were less reliable. Then they redesigned the quadrupole to avoid all the potential problems. A prototype magnet will be made and tested to ensure that functionality has not been lost. Index Terms—Magnet, reliability, FMEA. I

Life Cost Based FMEA Manual: A Step by Step Guide to Carrying Out a Cost-based Failure Modes and Effects Analysis

Failure occurs when one or more of the intended functions of a product are no longer fulfilled to the customer's satisfaction. The most critical product failures are those that escape design reviews and in-house quality inspection and are found by the customer. The product may work for a while until its performance degrades to an unacceptable level or it may have not worked even before customer took possession of the product. The end results of failures which may lead to unsafe conditions or major losses of the main function are rated high in severity. Failure Modes and Effects Analysis (FMEA) is a tool widely used in the automotive, aerospace, and electronics industries to identify, prioritize, and eliminate known potential failures, problems, and errors from systems under design, before the product is released (Stamatis, 1997). Several industrial FMEA standards such as those published by the Society of Automotive Engineers, US Department of Defense, and the Automotive Industry Action Group employ the Risk Priority Number (RPN) to measure risk and severity of failures. The Risk Priority Number (RPN) is a product of 3 indices: Occurrence (O), Severity (S), and Detection (D). In a traditional FMEA process design engineers typically analyze the 'root cause' and 'end-effects' of potential failures in a sub-system or component and assign penalty points through the O, S, D values to each failure. The analysis is organized around categories called failure modes, which link the causes and effects of failures. A few actions are taken upon completing the FMEA worksheet. The RPN column generally will identify the high-risk areas. The idea of performing FMEA is to eliminate or reduce known and potential failures before they reach the customers. Thus, a plan of action must be in place for the next task. Not all failures can be resolved during the product development cycle, thus prioritization of actions must be made within the design group. One definition of detection difficulty (D) is how well the organization controls the development process. Another definition relates to the detectability of a particular failure in the product when it is in the hands of the customer. The former asks 'What is the chance of catching the problem before we give it to the customer'? The latter asks 'What is the chance of the customer catching the problem before the problem results in a catastrophic failure?' (Palady, 1995) These differing definitions confuse the FMEA users when one tries to determine detection difficulty. Are we trying to measure how easy it is to detect where a failure has occurred or when it has occurred? Or are we trying to measure how easy or difficult it is to prevent failures? Ordinal scale variables are used to rank-order industries such as, hotels, restaurants, and movies (Note that a 4 star hotel is not necessarily twice as good as a 2 star hotel). Ordinal values preserve rank in a group of items, but the distance between the values cannot be measured since a distance function does not exist. Thus, the product or sum of ordinal variables loses its rank since each parameter has different scales. The RPN is a product of 3 independent ordinal variables, it can indicate that some failure types are 'worse' than others, but give no quantitative indication of their relative effects. To resolve the ambiguity of measuring detection difficulty and the irrational logic of multiplying 3 ordinal indices, a new methodology was created to overcome these shortcomings, Life Cost-Based FMEA. Life Cost-Based FMEA measures failure/risk in terms of monetary cost. Cost is a universal parameter that can be easily related to severity by engineers and others. Thus, failure cost can be estimated using the following simplest form: Expected Failure Cost = {sup n}{Sigma}{sub i=1}p{sub i}c{sub i}, p: Probability of a particular failure occurring; c: Monetary cost associated with that particular failure; and n: Total number of failure scenarios. FMEA is most effective when there are inputs into it from all concerned disciplines of the product development team. However, FMEA is a long process and can become tedious and won't be effective if too many people participate. An ideal team should have 3 to 4 people from: design, manufacturing, and service departments if possible. Depending on how complex the system is, the entire process can take anywhere from one to four weeks working full time. Thus, it is important to agree to the time commitment before starting the analysis else, anxious managers might stop the procedure before it is completed

Women in physics in the United States: Recruitment and retention

Initiatives to increase the number, persistence, and success of women in physics in the United States reach preteen girls through senior women. Programs exist at both the local and national levels. In addition, researchers have investigated issues related to gender equity in physics and physics education. Anecdotal evidence suggests increased media coverage of the underrepresentation of women in science. All of these efforts are motivated and made more effective by the continued collection and presentation of data on the presence, persistence, and promise of women in physics

Observation of Magnetic Resonances in Electron Clouds in a Positron Storage Ring

The first experimental observation of magnetic resonances in electron clouds is reported. The resonance was observed as a modulation in cloud intensity for uncoated as well as TiN-coated aluminum surfaces in the positron storage ring of the PEP-II collider at SLAC. Electron clouds frequently arise in accelerators of positively charged particles, and severely impact the machines performance. The TiN coating was found to be an effective remedy, reducing the cloud intensity by three orders of magnitude

Modification and Measurement of the Adjustable Permanent Magnet Quadrupole for the Final Focus in a Linear Collider

An adjustable permanent magnet quadrupole has been developed for the final focus (FF) in a linear collider. Recent activities include a newly fabricated inner ring to demonstrate the strongest field gradient at a smaller bore diameter of 15mm and a magnetic field measurement system with a new rotating coil. The prospects of the R&D will be discussed

(A) Fabrication of a Prototype Dipole for the SSC Low Energy Booster

Super Collider (SSC) will be a synchrotron containing 96 dipoles operating between 0.13T and 1.35T at 10 Hz. Each dipole’s 1.865 m-long core is made from ~2900 steel laminations (lams), each 52x 66 cm and 0.635 mm thick. A n=d to minimize power supply costs and stringent field specifications led to a straight core with very tight mechanical tolerances of the order of 0.05 mm. To satisfy these tolerances, we decided to stack the core in a vertical posit io ~ i.e., with the Iaminat iom laid horizontally. We designed and built an unusual vert ical stacking fixture that pivots into a horizontal position after all the laminations have been stacked and compressed and four support angles welded onto the laminations. The stacking fixture, our experience using it, and conclusions as to the merits of stacking such a long core vertically will be described. The methods of insulating and potting the pancake coib and their installation into”the unsplittable core is abo described