Driver Accelerator Physics and Design D. Douglas, S. Benson, G. Krafft, R. Li, L. Merminga, B. Yunn

18 October “The WBS 3 Talk” Scope of work: beam physics support for –injector –IR Demo analysis for upgrade guidance –upgrade design and analysis (specification & performance) –system integration

18 October System Parameters (IR&UV) DemoIR UpgradeUV UpgradeAchieved Energy (MeV) I ave (mA)51055 Beam Power (kW) Charge/bunch (pC)60135 Rep. Rate (MHz) Bunch Length (psec)1½½1 (60 pC) Peak Current (A)60270 >60 A  p/p (full) 2% ½%>1%  N (mm-mrad) <13<30< FEL ext. efficiency½%1%¼%¼%>¾%>¾% FEL power (kW)1>10>11.72 Induced energy spread5%10%5%6-8%

18 October Design Issues/Requirements Source/Injector Performance Delivery of appropriate beam to FEL; beam quality preservation –Beam internal self-interaction - space charge –Beam external self-interaction - CSR –Beam environmental interaction - wakefields, HOMs Machine Performance & Energy Recovery –Space charge, ions, BBU, FEL/RF interaction Geometric, schedule constraints –Must meet cost & schedule, fit in vault, avoid interference with Demo ops as long as possible

18 October WBS 3 Status IR Driver Design Revision 1.0 released –design concept frozen –details to be finalized (Revision 1.1): integrate final optical cavity design(s), resolve minor mechnical interferences & perform parametric optimizations (improve chromatics by pushing quads around) change request for UV compatibility UV Driver Design Revision 1.0 ready for release; –UV Revision 1.1 to follow on heels of IR Revision 1.1 Machine performance/beam physics studies started

18 October Demo in Vault - Before

18 October Upgrade

18 October Upgrade Layout

18 October UV Integration

18 October Common Dipole Geometry Reduce bend field/angle, increase bend radius

18 October Large dispersion slope requires dispersion management; use final backleg dipoles run at half field to reduce angle, quads to dispersion suppress Requires slightly wider pole

18 October

18 October

18 October UV Compatibility Change Request Corner dipoles  common dipoles Minor modification to rectangular dipole to utilize common design for IR chicane & UV bypass reverse bends (IR Revision 1.1)

18 October Status –Beam Physics Tasks TaskIRUV Machine top-level designRev 1.0 completeRev 1.0 underway “Engineering” design (Rev 1.1)underway Baseline injector designcomplete Space-charge analysisunderway CSR certificationcommencing BBU, HOM analysisunderway Impedance stewardshipunderway RF dynamics analysisunderway Machine model Commissioning planning

18 October Performance Analyses Starting beam/machine performance studies Longitudinal phase space management, octupole correction; ultrashort bunches Accelerator error effects & specifications –HOM driven skew quad effects –Alignment, magnet field quality/excitation errors, etc

18 October Longitudinal Phase Space Management Requirements: –short bunch (high peak current) at wiggler –small momentum spread at dump E  E  E  E  E  longitudinal phase space through acceleration cycle

18 October Longitudinal Matching - cont. E  E  longitudinal phase space during energy recovery

18 October

18 October Performance Analyses – cont. Injector design & performance, space charge (bunch “internal” self-interactions) CSR (bunch external self-interactions) BBU/HOM/other wakefield effects (beam/environmental interactions) RF system dynamics

18 October Upgrade Injector Design Space Charge analysis ongoing Support for gun design work (POISSON)

18 October CSR Analysis Ongoing refinement of model IR Rev 1.0 subjected to rudimentary check

18 October

18 October Beam/Environmental Interactions, RF System Dynamics RF system issues –7-cell control module FEL/RF interaction analysis ion trapping BBU –Thresholds –TDBBU benchmarks HOM power dissipation other wakefield effects

18 October “Publish or Perish” PAC99 : –L. Merminga, I. E. Campisi, D. Douglas, C. Hovater, G. A. Krafft,, B. C. Yunn, “Beam Current Limitations in the Jefferson Lab FEL: Simulations and Analysis of Proposed Beam Breakup Experiments,” –L. Merminga, I. Campisi, D. Douglas, B. Yunn, “Beam Breakup Simulations for the Jefferson Lab FEL Upgrade” –R. Li, “The Impact of Coherent Synchrotron Radiation on the Beam Transport of Short Bunches” –L. Merminga with the Jefferson Lab FEL Team, “First Results on Energy Recovery in the Jefferson Lab IRFEL,” FEL99 –R. Li, “Improvement of the Self-Consistent CSR Simulation” –L. Merminga, P. Alexeev, S. Benson, L. Doolittle, G. Neil, “FEL-RF Instabilities in Recirculating, Energy-Recovering Linacs with an FEL” EPAC2000 : –R. Li, “Sensitivity of the CSR Self-Interaction to the Local Longitudinal Charge Concentration of an Electron Bunch”

18 October “Publish or Perish” FEL2000: –L. Merminga and B. Yunn, “Collective Effects in the Jefferson Lab FEL Upgrade” –R. Li, “Sensitivity of the CSR Self-Interaction to the Local Longitudinal Charge Concentration of an Electron Bunch” Linac2000 : –R. Li, “Analysis and Simulation on the Enhancement of CSR Effects –L. Merminga, G. Krafft, C. Leemann, R. Sundelin, B. Yunn, J. Bisognano, “Specifying HOM Power Extraction Efficiency In a High Average Current, Short Bunch Length SRF Environment” –D. Douglas, S. Benson, G. Krafft, R. Li, L. Merminga, B. Yunn, “Driver Accelerator Design for the 10 kW Upgrade of the Jefferson Lab IR FEL” APS Division of Plasma Physics Meeting: –R. Li, “Bunch Self-interaction via Coherent Synchrotron Radiation: Theory, Simulation, and Experiment” PRL submissions: –R. Li, “Sensitivity of the CSR Self-Interaction to the Local Longitudinal Charge Concentration of an Electron Bunch”

18 October “Publish or Perish” JLab TNs: –CEBAF-TN : Design Considerations for the IR FEL Upgrade –JLAB-TN : “RF Requirements for the IRFEL Upgrade Project,'' –JLAB-TN : A Driver Accelerator for an FEL Upgrade –JLAB-TN : FEL Upgrade Scenarios –JLAB-TN : A 75% solution for the FEL Upgrade –JLAB-TN : IR/UV FEL Upgrade Project Accelerator Physics Plan –JLAB-TN : Aperture Considerations for the FEL Upgrade –JLAB-TN : WBS 3.0: Beam Physics Requirements for IR Upgrade Driver Accelerator –JLAB-TN : IR FEL Upgrade Driver Accelerator Design, Revision 1.0 –JLAB-TN : Preliminary Estimates of CSR Effects in the IR Upgrade FEL Driver –JLAB-TN : Longitudinal Phase Space Management in the IR Upgrade FEL Driver

18 October Schedule

18 October