No Arabic abstract
Electrical faults are in most cases dramatic events for magnets, due to the large stored energy which is potentially available to be dissipated at the fault location. After a reminder of the principles of electrostatics in Section 1, the basic mechanisms of conduction and breakdown in dielectrics are summarized in Section 2. Section 3 introduces the types and function of the electrical insulation in magnets, and Section 4 its relevant failure mechanisms. Section 5 deals with ageing and, finally, Section 6 gives some principles for testing. Though the School specifically dealt with warm magnets, for completeness some principles of dielectric insulation for superconducting accelerator magnets are briefly summarized in a dedicated appendix.
High pressure gas time projection chambers (HPGTPCs) are made with a variety of materials, many of which have not been well characterized in high pressure noble gas environments. As HPGTPCs are scaled up in size toward ton-scale detectors, assemblies become larger and more complex, creating a need for detailed understanding of how structural supports and high voltage insulators behave. This includes the identification of materials with predictable mechanical properties and without surface charge accumulation that may lead to field deformation or sparking. This paper explores the mechanical and electrical effects of high pressure gas environments on insulating polymers PTFE, HDPE, PEEK, POM and UHMW in Argon and Xenon, including studying absorption, swelling and high voltage insulation strength.
The next generation of accelerators for Megawatt proton and heavy-ion beams moves us into a completely new domain of extreme specific energies of up to 0.1 MJ/g (Megajoule/gram) and specific power up to 1 TW/g (Terawatt/gram) in beam interactions with matter. This paper is focused on deleterious effects of controlled and uncontrolled impacts of high-intensity beams on components of beam-lines, target stations, beam absorbers, shielding and environment. Two new experiments at Fermilab are taken as an example. The Long-Baseline Neutrino Experiment (LBNE) will explore the interactions and transformations of the worlds highest-intensity neutrino beam by sending it from Fermilab more than 1,000 kilometers through the Earths mantle to a large liquid argon detector. The Mu2e experiment is devoted to studies of the conversion of a negative muon to electron in the field of a nucleus without emission of neutrinos.
Laser powered dielectric structures achieve high-gradient particle acceleration by taking advantage of modern laser technology capable of producing electric fields in excess of 10GV/m. These fields can drive the bulk dielectric beyond its linear response, and break the phase synchronicity between the accelerating field and the electrons. We show how control of the pulse dispersion can be used to compensate the effect of self-phase modulation and maximize the energy gain in the laser accelerator.In our experiment, a high brightness 8MeV e-beam is used to probe accelerating fields of 1.8GV/m in a grating-reset dielectric structure illuminated by a 45fs laser pulse with a fluence of 0.7J/cm$^2$.
The ever increasing demands placed upon machine performance have resulted in the need for more comprehensive particle accelerator modeling. Computer simulations are key to the success of particle accelerators. Many aspects of particle accelerators rely on computer modeling at some point, sometimes requiring complex simulation tools and massively parallel supercomputing. Examples include the modeling of beams at extreme intensities and densities (toward the quantum degeneracy limit), and with ultra-fine control (down to the level of individual particles). In the future, adaptively tuned models might also be relied upon to provide beam measurements beyond the resolution of existing diagnostics. Much time and effort has been put into creating accelerator software tools, some of which are highly successful. However, there are also shortcomings such as the general inability of existing software to be easily modified to meet changing simulation needs. In this paper possible mitigating strategies are discussed for issues faced by the accelerator community as it endeavors to produce better and more comprehensive modeling tools. This includes lack of coordination between code developers, lack of standards to make codes portable and/or reusable, lack of documentation, among others.
Possible layouts of superconducting dipoles for the main injector of High Energy LHC (HE-LHC) are proposed on the basis of the experience matured with ongoing R&D activities at the Italian National Institute of Nuclear Physics (INFN), targeted at developing the technologies for high field fast cycled superconducting magnets for the SIS300 synchrotron of FAIR. Two different magnets are analysed: a) a 4 T dipole ramped up to 1.5 T/s, and b) a 6 T dipole to be operated at lower ramp rates.