Juhao Wu Juhao Wu LCLS FAC LCLS FAC [email protected][email protected]u 7 Apr. 2005 7 Apr. 2005 Dark Current, Beam Loss, Dark Current, Beam Loss, and Collimation in the and Collimation in the LCLS LCLS J. Wu , J. Wu , D. Dowell, P. Emma, C. Limborg, J. D. Dowell, P. Emma, C. Limborg, J. Schmerge, H. Vincke Schmerge, H. Vincke LCLS LCLS FAC Meeting FAC Meeting April 7, 2005 April 7, 2005 Thanks to M. Borland for Thanks to M. Borland for Elegant Elegant code changes in support of code changes in support of these studies these studies LCLS LCLS
20
Embed
Dark Current, Beam Loss, and Collimation in the LCLS
LCLS. Dark Current, Beam Loss, and Collimation in the LCLS J. Wu , D. Dowell, P. Emma, C. Limborg, J. Schmerge, H. Vincke LCLS FAC Meeting April 7, 2005. Thanks to M. Borland for Elegant code changes in support of these studies. Description of the Study. - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Juhao WuJuhao Wu
LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu7 Apr. 20057 Apr. 2005
Dark Current, Beam Loss, Dark Current, Beam Loss, and Collimation in the and Collimation in the LCLSLCLSJ. Wu ,J. Wu , D. Dowell, P. Emma, C. Limborg, J. Schmerge, H. VinckeD. Dowell, P. Emma, C. Limborg, J. Schmerge, H. Vincke
LCLSLCLS FAC Meeting FAC Meeting April 7, 2005April 7, 2005
Thanks to M. Borland for Thanks to M. Borland for ElegantElegant code changes in support of these studies code changes in support of these studies
LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu7 Apr. 20057 Apr. 2005
Model dark current from cathode using Model dark current from cathode using Fowler-NordheimFowler-Nordheim and and ParmelaParmela, but scaling charge from , but scaling charge from GTFGTF measurements measurementsAdd dark current in critical RF structures along linac, Add dark current in critical RF structures along linac, based on K. Bane work in NLC (not significant)based on K. Bane work in NLC (not significant)Track dark current through entire linac up to and through Track dark current through entire linac up to and through undulator, using symplectic integration for every bend and undulator, using symplectic integration for every bend and quadrupole in quadrupole in ElegantElegant (M. Borland, (M. Borland, ANLANL))Include aperture restrictions and collimatorsInclude aperture restrictions and collimatorsAssess collimation scheme in terms of undulator Assess collimation scheme in terms of undulator protection and average power loss on each collimatorprotection and average power loss on each collimatorEvaluate wakefield effect of each collimatorEvaluate wakefield effect of each collimator
LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu7 Apr. 20057 Apr. 2005
Structure dark currentStructure dark currentStudy approach:Study approach:• Use Use MafiaMafia to get field map to get field map• Use Use MathematicaMathematica (K. Bane’s code) to track through 3-m structure (K. Bane’s code) to track through 3-m structure • Normalized according to measurement: Normalized according to measurement: 15 pC in 2 15 pC in 2 s pulse for 3 meter s pulse for 3 meter
structure at 26 MV/mstructure at 26 MV/m (J. Schmerge) --- fit (J. Schmerge) --- fit ~ 120 ~ 120, and , and AAe e ~ 350 ~ 350 mm22
• Most capture in down streamMost capture in down stream
Examples of K. Bane’s study for X-band. We then compute for S-band and X-band
LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu7 Apr. 20057 Apr. 2005
Structure dark currentStructure dark currentContribution of structure dark current:Contribution of structure dark current:• X-bandX-band gives the largest contribution, however, deflected gives the largest contribution, however, deflected• Structures withStructures with E~24 MV/mE~24 MV/m will give additional particle loss will give additional particle loss
LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu7 Apr. 20057 Apr. 2005
SummarySummaryUndulator is protected from gun and structure Undulator is protected from gun and structure dark currentdark currentMaximum collimated beam power in above-Maximum collimated beam power in above-ground section is 0.2 Wground section is 0.2 WResults still look safe even for 10-times more Results still look safe even for 10-times more dark current (but already used worst-case dark current (but already used worst-case GTFGTF))Collimator wakefields should not be an issue Collimator wakefields should not be an issue (~0.5-mm alignment tolerances)(~0.5-mm alignment tolerances)Shower calculations were done (20 W/coll. was Shower calculations were done (20 W/coll. was assumed, now ~100-times smaller)assumed, now ~100-times smaller)