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Accelerator Seminars


Accelerator Seminar Committee:
  Chair: Carlos Hernandez- Garcia
    Members: Steve Benson, Gianluigi Ciovati, Vasiliy Morozov and Kevin Jordan


 Accelerator Seminars are scheduled weekly on Thursday's from 11:00 a.m. - 12:00 p.m.
If you would like to schedule a seminar, please contact Carlos Hernandez-Garcia for approval.

 

DATE: December 8, 2016

TIME: 11:00 a.m.

LOCATION: ARC, Room 231

TITLE: High Quality Factors and Large Gradients in Superconducting Niobium Resonators

SPEAKER: Mattia Checchin, Illinois Institute of Technology

ABSTRACT: Very high quality factors in superconduciting niobium resonators can be successfully achieved by implementing the nitrogen-doping technique. Many studies proved that such a treatment decreases tremendously the temperature-dependent part of the surface resistance, but, on the other hand, it increases the surface resistance per amount of trapped magnetic field. Such a contribution to the surface resistance as a function of the mean-free-path can be described as the interplay of two different regimes: pinning and flux-flow regimes, for low and large values of mean-free-path respectively. The experimental data acquisition and the model to describe the trapped flux surface resistance as a function of the mean-free-path will be presented.

A new thermal treatment, nitrogen-infusion, suggests that low temperature nitrogen-doping can provide both high gradients and high quality factors, allowing low dissipation at gradients larger than 35 MV/m. Such high accelerating gradients can be reached because the nitrogen-infusion generates a dirty/doped layer at the rf surface, with thickness lower than the penetration depth. By means of numerical solutions of the Ginzburg-Landau equations, the energetics of the vortex penetration for a superconductor with a dirty layer at the surface is studied in detail. Such a calculation suggests that the dirty layer at the rf surface promotes a higher energy barrier to the vortex penetration, and an enhanced lower critical field that delays the vortex penetration increasing the accelerating gradient. By cleverly tuning the superficial layer dirtiness, the beneficial effect of nitrogen-doping on the quality factor can also be exploited, allowing for low dissipation at high accelerating gradients.

 

DATE: December 15, 2016

TIME: 11:00 a.m.

LOCATION: CEBAF Center, Room F113

TITLE: Crab Cavity Efforts at CERN

SPEAKER: Alejandro Castilla, University of Guanajuato, Guanajuato, Mexico

ABSTRACT:This talk will present a general overview of the concepts of luminosity, crossing angle and crabbing correction schemes in colliders, as a preamble to compare the needs for high luminosity between Jefferson Lab's Electron-Ion Collider (JEIC) and the High Luminosity Upgrade of the LHC at CERN (HL-LHC). In this talk we will also highlight some of the activities planned at CERN, foreseen for the installation and implementation of crab cavity systems in the HL-LHC. This includes cavity validation, cryostat assembly, evaluation of the cavity performance with the proton beam of the CERN- SPS and machine protection aspects.

 

DATE: January 12, 2017

TIME: 11:00 a.m.

LOCATION: CEBAF Center, Room L102

TITLE: ER @ CEBAF - A Proposed High Energy, Multi-pass Energy Recovery Experiment at CEBAF

SPEAKER: Todd Satogata

ABSTRACT: A high-energy, multiple-pass energy recovery (ER) experiment proposal, using CEBAF, has been proposed by a collaboration between Jefferson Lab and BNL. This new capability of CEBAF extends the 2003, 1-pass, 1 GeV CEBAF-ER demonstration into a unprecedented range of energy and recirculation passes. Beam physics issues associated with this new regime of energy recovery include recirculating beam dynamics in the presence of disruptive synchrotron radiation, and control and scaling
of beam breakup instabilities to a large-scale superconducting RF facility. Multiple-beam diagnostics also would need to be developed to support this capability. This talk provides an overview of the ER@CEBAF project, its context, and current design status.

 

Seminar Archives: [2016]  [2015]  [2014]  [2013]  [2012]  [2011]  [2010]  [2009]  [2008]  [2007]  [2006]  [2005]  [2004]  [2003]  [2002]  [2001]