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E200 PWFA Collaboration Meeting TCAV April 12, 2013 M. Litos. Study of TCAV profile monitor location for new FACET optics. Sector 20 vertical (y) beta function for new optics provided by Glen White on 1/28/13. s TCAV = 39.93m s USTHz = 54.50m s DSTHz = 55.30m s min = 56.19cm.
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E200 PWFA Collaboration Meeting TCAV April 12, 2013 M. Litos
Sector 20 vertical (y) beta function for new optics provided by Glen White on 1/28/13 sTCAV= 39.93m sUSTHz = 54.50m sDSTHz= 55.30m smin= 56.19cm by,TCAV= 53.09m by,USTHz = 14.94m by,DSTHz= 3.78m by,min= 23cm TCAV USTHz DSTHz
Sector 20 vertical (y) phase advance for new optics provided by Glen White on 1/28/13 sTCAV= 39.93m sUSTHz = 54.50m sDSTHz= 55.30m smin= 56.19cm yy,TCAV= 0.703p yy,USTHz = 0.995p yy,DSTHz= 0.960p yy,min= 1.593p Min b DSTHz USTHz TCAV
sin(yy– yy,TCAV) DSTHz sinDyy,TCAV= 0 sinDyy,USTHz = 0.73 sinDyy,DSTHz= 0.80 sinDyy,min= 0.33 USTHz Min b TCAV
sin(yy– yy,TCAV) Zoomed View DSTHz sinDyy,TCAV= 0 sinDyy,USTHz = 0.73 sinDyy,DSTHz= 0.80 sinDyy,min= 0.33 USTHz Min b TCAV Conclusion:DSTHz is better location for TCAV profile monitor than USTHz with new FACET optics
More important conclusion: monitoring the beam at the waist decreases the streaking strength to ONE THIRD of the nominal max strength! The betatron phase advances very quickly just before and after the waist, and can blow right past the 90 degree point from the TCAV, significantly reducing the resolution of the measurement. This is possibly the reason we saw a factor of ~2 or so reduction in streaking strength during the 2012 run when going from E200 config to “TCAV optimized” config.
June 5, 2012 R56 = 10mm Note: Axis labels are flipped and calibration is unreliable, but image is in correct orientation. Beam is streaked in vertical direction. Longitudinal bunch separation measured to be ~150um.
March 24, 2013 Pencil Beam – No Compression Note: Axis labels are correct and calibration is good. Beam is streaked in vertical direction. Longitudinal bunch separation measured to be ~1200um.
March 24, 2013 Pencil Beam – Compressed Note: Axis labels are correct and calibration is good. Beam is streaked in vertical direction. Horizontal dispersion present. Longitudinal bunch separation measured to be ~200um.
Summary • TCAV is kicking ass this year! • Addition of YAG to prof. mon. gives good photon yield even when streaked • Using DSTHz window gives clear line of sight, better magnification and resolution • Lower beta function optics = more stable beam w/ lower chromatics • Careful examination of phase advance to guide desired beta func., which happens to be nominal value • Improved calibration of RF equipment in control system • RF controls feedbacks to stabilize phase & amp • GUI for fast bunch length measurement • WIP: integrate profile measurement with sYAG online beam characterization tool