Upgrades of beam diagnostics in support of emittance-exchange experiments at the Fermilab A0 photoinjector

The possibility of using electron beam phase space manipulations to support a free-electron laser accelerator design optimization has motivated our research. An on-going program demonstrating the exchange of transverse horizontal and longitudinal emittances at the Fermilab A0 photoinjector has benefited recently from the upgrade of several of the key diagnostics stations. Accurate measurements of these properties upstream and downstream of the exchanger beamline are needed. Improvements in the screen resolution term and reduced impact of the optical system's depth-of-focus by using YAG:Ce single crystals normal to the beam direction will be described. The requirement to measure small energy spreads (<10 keV) in the spectrometer and the exchange process which resulted in bunch lengths less than 500 fs led to other diagnostics performance adjustments and upgrades as well. A longitudinal to transverse exchange example is also reported.Comment: 16 p

Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train

We experimentally demonstrate the production of narrow-band ($\delta f/f \simeq20$% at $f\simeq 0.5$ THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.Comment: 3 pages, 6 figure

Tunable subpicosecond electron bunch train generation using a transverse-to-longitudinal phase space exchange technique

We report on the experimental generation of a train of subpicosecond electron bunches. The bunch train generation is accomplished using a beamline capable of exchanging the coordinates between the horizontal and longitudinal degrees of freedom. An initial beam consisting of a set of horizontally-separated beamlets is converted into a train of bunches temporally separated with tunable bunch duration and separation. The experiment reported in this Letter unambiguously demonstrates the conversion process and its versatility.Comment: 4 pages, 5 figures, 1 table; accepted for publication in PR

First observation of the exchange of transverse and longitudinal emittances

An experimental program to demonstrate a novel phase space manipulation in which the horizontal and longitudinal emittances of a particle beam are exchanged has been completed at the Fermilab A0 Photoinjector. A new beamline, consisting of a TM110 deflecting mode cavity flanked by two horizontally dispersive doglegs has been installed. We report on the first direct observation of transverse and longitudinal emittance exchange

Obsessive passion: a dependency associated with injury-related risky behaviour in dancers

Grounded in self-determination theory, obsessive passion for an activity has been associated with increased risky behaviour and rigid persistence, both symptomatic of dependence. However, it is unknown whether obsessive passion may predict the development of dependence, and furthermore, theoretically important relationships between basic need satisfaction, passion, exercise dependence and subsequent risky behaviour have not been fully explored. A sample of 100 professional dancers (50fs; 50ms; Mage = 20.88; SD = 2.69) completed self-ratings of risk-related behaviours (doctor visits; following treatment, and warming up), passion for dance and dance dependence. Findings supported the maladaptive nature of obsessive passion in relation to risky behaviour and as predicted dance dependence mediated this relationship. Interestingly, need satisfaction was positively related to both obsessive passion and harmonious passion. Results are discussed in the light of self-determination theory and dysfunctions of obsessive passion, suggesting that professional dancers are at risk of employing maladaptive behaviours if high in obsessive passion, which may be detectable via symptoms of dance dependence

Essential nonlinearities in hearing

Our hearing organ, the cochlea, evidently poises itself at a Hopf bifurcation to maximize tuning and amplification. We show that in this condition several effects are expected to be generic: compression of the dynamic range, infinitely shrap tuning at zero input, and generation of combination tones. These effects are "essentially" nonlinear in that they become more marked the smaller the forcing: there is no audible sound soft enough not to evoke them. All the well-documented nonlinear aspects of hearing therefore appear to be consequences of the same underlying mechanism.Comment: 4 pages, 3 figure

The scientific and societal uses of global measurements of subsurface velocity

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Szuts, Z. B., Bower, A. S., Donohue, K. A., Girton, J. B., Hummon, J. M., Katsumata, K., Lumpkin, R., Ortner, P. B., Phillips, H. E., Rossby, H. T., Shay, L. K., Sun, C., & Todd, R. E. The scientific and societal uses of global measurements of subsurface velocity. Frontiers in Marine Science, 6, (2019): 358, doi:10.3389/fmars.2019.00358.Ocean velocity defines ocean circulation, yet the available observations of subsurface velocity are under-utilized by society. The first step to address these concerns is to improve visibility of and access to existing measurements, which include acoustic sampling from ships, subsurface float drifts, and measurements from autonomous vehicles. While multiple programs provide data publicly, the present difficulty in finding, understanding, and using these data hinder broader use by managers, the public, and other scientists. Creating links from centralized national archives to project specific websites is an easy but important way to improve data discoverability and access. A further step is to archive data in centralized databases, which increases usage by providing a common framework for disparate measurements. This requires consistent data standards and processing protocols for all types of velocity measurements. Central dissemination will also simplify the creation of derived products tailored to end user goals. Eventually, this common framework will aid managers and scientists in identifying regions that need more sampling and in identifying methods to fulfill those demands. Existing technologies are capable of improving spatial and temporal sampling, such as using ships of opportunity or from autonomous platforms like gliders, profiling floats, or Lagrangian floats. Future technological advances are needed to fill sampling gaps and increase data coverage.This work was supported by the National Science Foundation, United States, Grant Numbers 1356383 to ZBS, OCE 1756361 to ASB at the Woods Hole Oceanographic Institution, and 1536851 to KAD and HTR; the National Oceanographic and Atmospheric Administration, United States, Ocean Observations and Monitoring Division and Atlantic Oceanographic and Meteorological Laboratory to RL; Royal Caribbean Cruise Ltd., to PBO; the Australian Government Department of the Environment and Energy National Environmental Science Programme and Australian Research Council Centre of Excellence for Climate Extremes to HEP; and the Gulf of Mexico Research Initiative Grant V-487 to LS

Overview of charged-particle beam diagnostics for the Advanced Photon Source (APS)

Plans, prototypes, and initial test results for the charged-particle beam (e[sup [minus]],e[sup +]) diagnostic systems on the injector rings, their transport lines, and the storage ring for the Advanced Photon Source (APS) are presented. The APS will be a synchrotron radiation user facility with one of the world's brightest x-ray sources in the 10-keV to 100-keV regime. Its 200-MeV electron linac, 450-MeV positron linac, positron accumulator ring, 7-GeV booster synchrotron, 7-GeV storage ring, and undulator test lines will also demand the development and demonstration of key particle-beam characterization techniques over a wide range of parameter space. Some of these parameter values overlap or approach those projected for fourth generation light sources (linac-driven FELs and high brightness storage rings) as described at a recent workshop. Initial results from the diagnostics prototypes on the linac test stand operating at 45-MeV include current monitor data, beam loss monitor data, and video digitization using VME architecture