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There are many ways that a resistive particle accelerator electromagnet can fail, and most failure modes and their root causes are well known to more experienced magnet engineers. There are thousands of new electromagnets being fabricated every year and tens of thousands already operating in institutions worldwide. Yet some magnet engineers designing a new-style magnet still do not make the design choices that will lead to fewer failing magnets; fabricators still make errors as they assemble magnets and magnets still operate, for example, with low conductivity water (LCW) that corrodes or erodes the coils' conductor. One reason for these continuing problems is the lack of readily available information on the most reliable materials, fabrication techniques, and operating parameters. In order to learn from the experiences of other institutions running accelerators regarding their magnets' failure modes and how they have dealt with them, a web-based survey was created with 64 detailed questions. The survey was completed by 28 designers and operators of accelerator magnets worldwide covering conventional magnets 5 to 55 years old, being used in all kinds of accelerators, in dc, ramping, and pulsed modes. A detailed analysis of the survey's responses was carried out to find, for example, correlations between materials used and frequencies of related failure types. This paper describes the results of the survey analysis, leading to some more reliable design values, materials, fabrication techniques, and operating conditions, especially the properties of the LCW, and thus provides advice on how to improve the reliability of accelerator electromagnets.

The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2 K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2?) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.

The international linear collider has about 80 km of beamlines which require over 13,000 magnets for focusing and steering the beams. Approximately 18% are superconducting magnets and the rest "conventional" warm iron-dominated magnets with copper coils, totaling about 135 styles. Superconducting technology is primarily used for the magnets located in the linacs' RF cryomodules, but it is also required for the spin rotation solenoids, damping ring wigglers, positron source undulator and beam delivery octupoles, sextupoles and final doublet quadrupoles. A major criterion for ILC magnet design is to achieve very high availability in spite of the very large number of magnets. The "availability" goal of the ILC is 85% (or better) and the magnets have been budgeted to cause no more than 0.75% down time. Alignment and mechanical stability requirements in many areas are very challenging. In the Beam delivery system, beam positions must be maintained at sub-micron levels to collide the beams at the interaction point. The ILC has 11 styles of kicker, pulsed or septum magnets. Some kickers need rise and fall times of a few ns and will require very powerful pulsers. Strategies for dealing with the major challenges confronting the ILC magnets will be described.

A rotating double coil apparatus has been designed and built so that the relative magnetic center change of a quadrupole is measured to an uncertainty smaller than 0.02 micrometers (=micron, mum) for a single measurement. Furthermore, repeated measurements over about an hour vary by less than 0.1 mum and by less than 1 mum for periods of 24 hrs or longer. Correlation analyses of long data runs show that the magnet center measurement is sensitive to mechanical effects, such as vibration and rotating part wear, as well as to environmental effects, such as temperature and relative humidity. Evolving apparatus design has minimized mechanical noise and environmental isolation has reduced the effects of the surrounding environment so that sub-micron level measurement uncertainties and micron level stability have been achieved for multi-day measurement periods. Apparatus design evolution will be described in detail and correlation data taken on water-cooled electromagnet and adjustable permanent quadrupoles, which are about 350 mm in overall length, will be shown. These quads were prototypes for the linac quads of the Next Linear Collider (NLC) that had to meet the requirement that their magnetic centers change less than 1 micron during a 20% change in field strength. Thus it was necessary to develop an apparatus that could track the magnetic center with a fraction of a micron uncertainty

The proposed Next Linear Collider (NLC) will require over 1400 adjustable quadrupoles between the main linacs' accelerator structures. These 12.7 mm bore quadrupoles will have a range of integrated strength from 0.6 to 132 Tesla, with a maximum gradient of 135 Tesla per meter, an adjustment range of +0 -20% and effective lengths from 324 mm to 972 mm. The magnetic center must remain stable to within I micrometer during the 20% adjustment. In an effort to reduce estimated costs and increase reliability, several designs using hybrid permanent magnets have been developed. All magnets have iron poles and use either Samarium Cobalt or Neodymium Iron to provide the magnetic fields. Two prototypes use rotating rods containing permanent magnetic material to vary the gradient. Gradient changes of 20% and center shifts of less than 20 microns have been measured. These data are compared to an equivalent electromagnet prototype.

In order to achieve the high luminosity required at the proposed International Linear Collider (ILC), it is critical to focus the beams to nanometer size with the ILC Beam Delivery System, and to maintain the beams' collisions with a nanometer-scale stability. To establish the technologies associated with this ultra-high precision beam handling, a special beamline has been designed and built as an extension of the existing extraction beamline of the Accelerator Test Facility at KEK, Japan. The ATF provides an adequate ultra-low emittance electron beam that is comparable to the ILC requirements; the ATF2 mimics the ILC final focus system to create a tightly focused, stable beam. There are 37 magnets in the ATF2, 29 quadrupoles, 5 sextupoles and 3 bends. These magnets had to be acquired in a short time and at minimum cost, which led to various acquisition strategies; but nevertheless they had to meet strict requirements on integrated strength, physical dimensions, compatibility with existing magnet movers and beam position monitors, mechanical stability and field stability and quality. This paper will describe how 2 styles of quadrupoles, 2 styles of sextupoles, one dipole style and their supports were designed, fabricated, refurbished or modified, measured and aligned by a small team of engineers from 3 continents.