Guoxing Xia Kieran Hanahoe Oznur Mete Tom Pacey University of Manchester and the Cockcroft Institute 11102016 CALIFES Workshop 2016CERN 1 Outline Conventional beam dump ID: 1011816
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1. Compact plasma based beam dumpGuoxing Xia, Kieran Hanahoe, Oznur Mete, Tom PaceyUniversity of Manchester and the Cockcroft Institute11/10/2016CALIFES Workshop 2016-CERN1
2. OutlineConventional beam dumpPlasma beam dumpSimulation of plasma beam dumpExperiment test at CALIFESConclusion11/10/2016CALIFES Workshop 2016-CERN2
3. Conventional beam dump11/10/2016CALIFES Workshop 2016-CERN3ILC TDR
4. Noble gas beam dumpPlasma beam dumpVery long length, but low power density.Reduced radionuclide production.No hydrogen/oxygen gas production.A. Leuschner, LC-ABD dump meetings, Sept. 2005High decelerating gradients with low density dump medium.Effectiveness depends on bunch parameters.Possibility for electrical energy recovery.Cannot decelerate bunch head.H.C. Wu, T. Tajima et al. PR-STAB 13, 101303 (2010)Conventional beam dumps use high density materials – metal, water etc.They require high power density cooling, can produce radionuclides and (for water) explosive gasses through decomposition.Stopping a beam with a low density material could have advantages.Plasma beam dump-a comparison11/10/2016CALIFES Workshop 2016-CERN4
5. Passive plasma beam dump11/10/2016CALIFES Workshop 2016-CERN5
6. 11/10/2016CALIFES Workshop 2016-CERN6Passive plasma beam dump
7. 11/10/2016CALIFES Workshop 2016-CERN7Passive plasma beam dump
8. 11/10/2016CALIFES Workshop 2016-CERN8Passive plasma beam dump
9. Passive plasma beam dump11/10/2016CALIFES Workshop 2016-CERN9
10. 11/10/2016CALIFES Workshop 2016-CERN10Passive plasma beam dump
11. Decelerating gradient saturates after some distance as a portion of the bunch is re-accelerated.The low energy particles need to be removed.Wu et al. proposed using a series of foils after the saturation length.Re-accelerated portion of bunchLongitudinal phase space of plasma decelerated bunchTrajectory of decelerated particlesH.C. Wu, T. Tajima et al. PR-STAB 13, 101303 (2010)Plasma beam dump11/10/2016CALIFES Workshop 2016-CERN11
12. When the density increases, the decelerated portion of the bunch passes into a defocusing region.Stepped profile gives instant shift in wavelength while gradient shifts wavelength gradually.An alternative to absorbing the low energy particles is to move them into a defocusing region of the wakefield by reducing the plasma wavelength.Modified plasma density11/10/2016CALIFES Workshop 2016-CERN12
13. Longitudinal phase space for uniform (L) and stepped (R) plasma.Left: Energy loss for different plasma profilesRight: Initial and final energy spectra for gradient plasma.Simulations carried out for an ultrashort bunch: 7.5 µm rms bunch length, 100 pC, 250 MeV.Initial decelerating gradient 4.5 GV/m (peak), 1.5 GeV/m (average).Simulation of plasma beam dump11/10/2016CALIFES Workshop 2016-CERN13
14. Experimental test at CALIFES11/10/2016CALIFES Workshop 2016-CERN14After compressionCourtesy of Jürgen Pfingstner
15. Longitudinal electric field and on-axis line out for hollow plasma Peak accelerating/decelerating field:Uniform plasma: 1 GV/mLongitudinal phase space at z=20 cm for uniform plasma.2D PIC simulations of CALIFES beam using uniform plasma, assuming rms radius of 50 µm. Plasma density 2×1020 m–3.CALIFES simulation11/10/2016CALIFES Workshop 2016-CERN15
16. ConclusionPlasma based beam dump is much compact than conventional beam dump and produce less radiation hazardsThe plasma density step up/gradually increase could be used to damp the whole beam more effectivelyPlasma based beam dump can be tested at CALIFES, with decelerating gradient ~1GV/m for uncompressed bunch. Much higher decelerating field can be expected if short bunch is usedThis plasma dump will enables the compactness of the overall scale for future machines11/10/2016CALIFES Workshop 2016-CERN16
17. Thanks for your attention!11/10/2016CALIFES Workshop 2016-CERN17