Computer-Automated Linac Diagnostics and Data Acquisition
Computer interactive diagnostics have been developed and tested for measuring RF Linac electron beam position and emittance. Electron beam position is measured with ferrite-loaded stripline monitors. The measured signals are processed by an APPLE-II computer, displayed and updated (at the Linac repetition rate) on a monitor. Data to determine emittance is collected by measuring electron beam spot size (using the wire scanner technique) as the focal strength of a quadrupole triplet is adjusted around the focus at the scanner. The emittance is calculated by the APPLE-II making a hyperbolic curve fit to these data.
Beam measurements on Argonne linac for collider injector design
The 20 MeV electron linac at Argonne produces 5 × 1010 electrons in a single bunch. This amount of charge per bunch is required for the proposed single pass collider at SLAC. For this reason the characteristics of the beam from this machine are of interest. The longitudinal charge distribution has been measured by a new technique. The technique is a variation on the deduction of bunch shape from a spectrum measurement. Under favorable conditions a resolution of about 1° of phase is possible, which is considerably better than can be achieved with streak cameras. The bunch length at 4.5 × 1010e− per bunch was measured to be 15° FWHM. The transverse emittance has also been measured using standard techniques. The emittance is 16 mm-mrad at 17. 2 MeV.
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.