1. Proton Driver Main Linac Parameter Optimization G. W. Foster Proton Driver General Meeting Jan 19, 2005

2. OPTIMIZATION The Proton driver is mainly eight repetitions of the TESLA RF unit: –One Klystron –36 Cavites ~ 1 GeV of Beam Energy Optimization of the main linac means mainly optimization of this basic RF unit, subject to the constraints of the Proton Driver

3. Nov 18, 2004G.W.Foster - Proton Driver 0.5 MW with TESLA Frequencies & SCRF F.E.

4. SRF Linac Parameters

5. Proton Driver Beam Power Upgrade Scenario Initial scenario with 0.5 MW Stand-alone 8 GeV Beam Power and 12 Klystrons (looks a lot like TESLA…) Ultimate scenario with 2 MW Stand-alone 8 GeV Beam Power and 36 Klystrons (looks a lot like the SNS…) Both scenarios support 2 MW of 120 GeV Beam Power out of the Main Injector

6. Proton Driver Upgrade Scenario The attempt to display a CAD-rendered movie of the PD Linac Upgrade Scenario was a fiasco, with the best result being the laptop displaying the movie on it’s local screen, while the projector simultaneously displayed the Windows Media Player outline and controls on the big screen except the media player frame was blank… sigh. However, these movies and others are available at: http://protondriver.fnal.gov

7. What are the Input Parameters ? Particle TypeH- Linac Energy8 GeV (kinetic) Charge per pulse1.5E14 PPP (25uC) Beam Pulse Width3 msec * Linac Rep Rate2.5 Hz * Operating Frequencies1300 MHz / 325 MHz Accelerating Gradient25 MV/m Copper  SCRF transition15-85 MeV * for the PD linac with 0.5 MW 8 GeV Beam Power

8. Why is this an H- Linac? H- stripping foil injection allows: – cheating Liouville with multi-turn injection (~100) – spreading out the energy-per-pulse over a longer time interval In principle, you could do one-turn injection of Protons –The Booster was originally run this way –The linac beam current would be 2 Amps and the peak RF power (=Klystron power) required would be (2 amps) x (8 GeV) = 16 GigaWatts

9. What are the Derived Parameters ? 1.Beam Energy Per Pulse 2.Average Beam Power 3.Peak Beam Current 4.Average Beam Current 5.Peak RF Power 6.Number of Klystrons 7.RF Coupler Power 8.Cavities Per Klystron 9.Average RF Power 10.Klystron Duty Factor 11.Modulator Charging Supply Power 12.Number of Cavities 13.Cryogenic Operating Power 14.AC Wall Power 15.Number of turns of H- Injection 16.Circulating Current in Main Injector 17.RF Power in Main Injector Technological Limitations must be Respected on both Input and Derived Parameters!

10. Examples of Derived Parameters Energy Per Pulse = Charge * Beam Energy = 25 uC * 8 GeV = 200kJ Average Power= (Rep Rate) *(E/pulse) = 2.5 Hz * 200kJ = 0.5MW Beam Current= Charge / Pulse Length = 25uC / 3 msec = 8.5 mA

11. More Derived Parameters Peak RF Power= Beam Energy * Current = 8 GeV * 8.3 mA = 67MW Naïve Klystron Count: (10 MW TESLA MBK’s) = 67 MW / 10 MW/klystron = 6.7 Klystrons Actual Klystron Count = 12 (reflects overheads, waveguide losses, etc)

12. Some Parameters non-Negotiable Modulator Capacitor Bank Size x Fractional Discharge of Cap Bank (~40%) x Efficiency of Klystron (~60%) x Efficiency of RF Distribution (80%) x (1-fraction of energy left in cavity) (70%) = Linac Energy Per Pulse But you still get to chose how often to recharge the capacitor bank and re-fire the linac

13. Reconfigurable Klystron Modulators Pulse Transformer & Oil Tank IGBT Switch & Bouncer CAP BANK 10 kV 115 kV Charging Supply 300kW 4.5 msec x 2.5 Hz x 12 Stations 0.5 MW Beam Power Klystron 1300 MHz TESLA MBK or 325MHz JPARC 10kV Pulse Transformer & Oil Tank IGBT Switch & Bouncer CAP BANK 10 kV 115 kV Charging Supply 300kW Klystron 1300 MHz TESLA MBK or 325MHz JPARC 10kV Pulse Transformer & Oil Tank IGBT Switch & Bouncer CAP BANK 10 kV 115 kV Charging Supply 300kW Klystron 1300 MHz TESLA MBK or 325MHz JPARC 10kV 3 msec x 5 Hz x 24 Stations 1MW Beam Power 1.5 msec x 10 Hz x 36 Stations 2 MW Reconfigure & add new modulators for 3, 2, or 1 msec beam pulse widths for upgrade scenarios Modulators can be reconfigured & parts re-used for RF power upgrade scenarios

14. Technological Limitation: Klystron Duty Factor The Klystron (and other RF components) have Duty Factor Limitiations from average heating: ~1.5% for TESLA RF The prohibits, for example, just turning up the Repetition rate for the (long 3 msec pulse) initial scenario to obtain 2MW No substitute for Average klystron power!

15. Technological Limitation: Coupler Power & Gradient If we are aggressive simultaneously on both beam current (25 mA) and SCRF gradient (40 MV/m) then we can get into trouble on RF coupler power: (40 MV/m)*(1m cavity)*(25 mA) = 1 MW/cavity This is at or beyond the present state of the art for reliable power couplers. ILC faces same problem when considering superstructures (~2m cavities)

16. Long or Short Pulse Length (from Ch 4 of 2003 PD Linac Design Report)

17. Conclusions 1.This subject is longer than a half-hour talk 2.The SNS and TESLA linacs are reasonably optimized point designs, and the Proton Driver is operating in an intermediate parameter space where it does not appear we get into trouble.