1. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy A 10 kW IRFEL Design for Jefferson Lab S. Benson, G. Biallas, J. Boyce, D. Douglas, H. F. Dylla, R. Evans, A. Grippo, J. Gubeli, K. Jordan, G. A. Krafft, R. Li, J. Mammosser, L. Merminga, G. Neil, L. Phillips, J. Preble, M. Shinn, T. Siggins, R. Walker, B. Yunn Thomas Jefferson National Accelerator Facility

2. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy IR Demo FEL Wiggler assembly Routine operation since July 1999 Regularly generate > 1 kW IR power Energy recover ~ 200 kW RF power

3. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy 10 kW Upgrade Success of the IR Demo has motivated funding by USN, USAF, DOE, Commonwealth of Virginia, & various industrial partners to apply lessons learned to extend output power to 10 kW Upgrade Path: Output power = P FEL = E e- beam *I e- beam *  FEL o Demo: E = ~ 40 MeV, I = 5 mA,  FEL = 0.5%  P FEL = 1 kW o Upgrade: ~ quintuple beam power & double extraction efficiency E > 100 MeV, I = 10 mA,  FEL >1%  P FEL > 10 kW

4. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Lessons Learned from IR Demo (1) Source DC photocathode gun performance fully adequate for high repetition rate/high power FEL applications o good beam quality/brightness Demo nominal  N : 10 mm-mrad @ 60 pC/bunch Upgrade  N : 30 mm-mrad @ 135 pC/bunch (achieved) o excellent cathode lifetimes (3.5 kC to date on present cathode; contrast to “traditional” Coulomb-scale lifetimes)* Halo generated in injector – if limited there, it is controlled everywhere

5. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy *Cathode Lifetime

6. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Lessons Learned from IR Demo (2) Driver Accelerator longitudinal phase space management allows efficient generation of FEL power while limiting RF power requirement (*, **) o bunch length compression for high peak current o energy recovery with energy compression (compensate lattice & RF nonlinearity) beam quality degradation & collective effects manageable o space charge, BBU, CSR, HOM power deposition, FEL/RF interaction,… TOAA012: High Average Current Effects in Energy Recovery Linacs, L. Merminga et al RPAH049: Simulation of the CSR Induced Emittance Growth Measured at CTF II, R. Li

7. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy *Efficiency of Energy Recovery

8. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy **Longitudinal Matching Scenario. Requirements on phase space:. high peak current (short bunch) at FEL. bunch length compression at wiggler. “small” energy spread at dump. energy compress while energy recovering. “short” RF wavelength/long bunch  get slope and curvature right E  E  E  E  E  E 

9. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Lessons Learned from IR Demo (3) FEL Wiggler-driven near-concentric optical cavity resonator supports high power lasing (at 2 nd, 3 rd, and 5 th harmonics as well) Modeling in agreement with observed performance Mirror radius of curvature stability & coatings adequate for 4 kW @ 3  m; implementation of active control of radius of curvature and improved coatings will extend power limit…

10. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Modeling of IR Demo Now Agrees Well With Experimental Performance

11. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Application of Demo Experience to Upgrade 80-210 MeV SRF energy recovering linac accelerating 10 mA o compaction management for high peak current at wiggler, energy compression during energy recovery o large acceptance transport allows use of higher extraction efficiency Near-concentric optical cavity resonator driven by optical klystron, operating at 1+% extraction efficiency o active control of mirror radius of curvature, high quality coatings, high output coupling will allow output powers as high as 25 kW Wiggler 210 MeV Linac

12. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Expected Performance of the IR Upgrade with a Near Concentric Cavity

13. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Beyond 10 kW IR… Funding awarded for 1 kW UV construction Ongoing study of IR transport system suggests acceptance may be as high as 15%  higher FEL extraction efficiencies tolerable   FEL ~1% generates ~ 5 - 6%  p/p (Demo, modeling);   FEL ~2.5% generates ~ 15%  p/p & gives 50 kW at full linac power (200 MeV/10 mA) o injector upgrade to 100 mA could give MW class performance

14. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Energy Recovery Transport Acceptance;  p/p initial = 15%  p/p = 15% wide initial distribution

15. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Conclusions & Project Status JLab IR Demo serves as basis for upgrade to higher (>>1 kW) power Design & construction of CW 10 kW IR FEL possible using system paradigm of energy recovering SRF linac-driven optical cavity resonator Status: o USN funded IR construction underway o USAF funding for UV construction starting o IR Demo decommissioning Dec 2001 o Upgrade component installation starts at Demo decommissioning o 1 st beam operations expected in fall of 2002

16. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy System Parameters (IR&UV) DemoIR UpgradeUV UpgradeAchieved Energy (MeV)35-4880-21020020-48 I ave (mA)51055 Beam Power (kW)20020001000240 Charge/bunch (pC)60135 Rep. Rate (MHz)18.75-754.7-752.3-7518.75-75 Bunch Length (psec)1½½1 (60 pC) Peak Current (A)60270 >60 A  p/p (full) 2% ½%<1%  N (mm-mrad) <13<30<115-10 FEL ext. efficiency½%1%¼%¼%>¾%>¾% FEL power (kW)1>10>11.72 Induced energy spread5%10%5%6-8%

17. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Use Optical Klystron for Flexibility Wigglers Wavelength20 cm K 2 1–16 Number of periods12 ea. Gap26 mm Polarizationvertical Phase error<5 deg. Dispersion section Length58 cm Dispersion>40 periods for K 2 =16 Gap26 mm For highest power operation we will operate with the dispersion section set to phase match between the two wigglers so it looks like one 26 period wiggler.

18. svb[General files ‘01/Presentations]PAC 10 kW laser input.ppt Operated by the Southeastern Universities Research Association for the U.S. Dept. of Energy Raising the Bar for Near Concentric Resonator Performance IR Demo resonator power limit is 4 kW at 3 µm. By using radius of curvature control on the high reflector mirror, we gain a factor of 1.75 in optical power. User of better coatings gains and more output coupling gives us a factor of 3.6. Numbers below are for 25 kW: Shift in waist from cold cavity52 cm Mirror aberration0.043 waves Wavefront distortion0.2 waves Circulating Intensity83 kW/cm 2