Field Measurements of Magnets for Modern SR Sources and FEL
Magnets for modern accelerators and storage rings may have a rather complex field distribution and strict quality requirements. The Budker Institute of Nuclear Physics (Novosibirsk, Russia) is a well-known producer of magnets for various accelerator projects worldwide. This paper describes our magnet measurement facility with examples of NSLS-II booster magnets, small-aperture X-FEL quadrupoles, and PETRA-III dipoles. NSLS-II booster dipoles have quadrupole and sextupole components with a rather high field quality of 1 · 10-3 in the good field region of ±2 cm, providing booster operation at energy from 170 MeV to 3.15 GeV with a 2-Hz repetition rate. We designed a special bench with a ceramic rotation coil to measure X-FEL quadrupoles. The equipment provided measurements of the magnetic axis with accuracy better than 5 μm. We used the system of three temperature-stabilized Hall sensor arrays distributed vertically to obtain a three-dimensional field map from a single measurement of PETRA-III dipole magnets.
MAGNETIC MEASUREMENT OF THE NSLS-II BOOSTER DIPOLE WITH COMBINE FUNCTIONS*
The magnetic system of NSLS II Booster is designed, manufactured and tested in BINP, Russia. The booster dipole incorporates quadrupole and sextupole components and has rather tight requirement for the field quality ±2·10 -4 in the good field region ±2 cm. The magnets provide the booster operation in the energy range from 170 MeV to 3.15 GeV with 2 Hz repetition frequency. This report contains description of the magnetic measurement bench and the results achieved for the DC case; AC magnet test including vacuum chamber influence is described in [1]. INTRODUTION The NSLS II is a third generation light source under construction at Brookhaven National Laboratory [2]. The project includes a highly optimized 3 GeV electron storage ring, linac pre-injector and full-energy boostersynchrotron. Budker Institute of Nuclear Physics (BINP) builds booster for NSLS-II. The booster should accelerate the electron beam continuously and reliably from minimum injection energy of 170 MeV to maximum extraction energy of 3.15 GeV with average beam current of 20 mA. The booster shall be capable of multi-bunch and single bunch operation. The booster BF (BD) dipoles contains focusing (defocusing) quadrupole and sextupole components but should provide rather high field quality ±2·10 -4 in the good field region ±2 cm in the whole energy range Dipole parameters are listed in Table 1.
Pedagogy of the “Not”: Negation, Exodus, and Postdigital Temporal Regimes
Postdigital capitalist time is an incessant acceleration that acts to homogenize time and wed us to the present, to which we have to constantly catch up. While the impulse of this is no doubt economic (the realization of value), it is crucially undergirded by a pedagogical logic wherein we have to perpetually learn and re-learn the latest apps, social media configurations, operating systems, and so on. Political strategies of resistance thus need to be bolstered by an alternative mode of educational life, and I propose a pedagogy of the “not” as one possibility. Such a pedagogy is an act of suspension that sustains a detachment from the present, clearing out oppositions and thereby exposing us to a radical indeterminacy and potentiality that is always untimely. Suspension is the praxis of negation, which means that negation operates by keeping sense indeterminate to meaning and signification. Rather than suppressing, disavowing, or annihilating the stated content, negation retains even that which is negated. While this would appear as a form of exopedagogy, which withdraws from the dialectic of the private/public, I instead argue that it redefines the terms of any dialectic, redefining the very categories exopedagogy withdraws from. Before concluding, I spend some time with Sandy Grande’s important critiques of Eurocentrism and progress in Western critical education, demonstrating how negation as suspension circumvents these errors through its accommodation of—or, better, insistence on—variegated temporalities and forms of life.