CW Energy Recovery Linac for Next Generation of XFELs General Thoughts based on TESLA XFEL-TDR TJNAF: A. Bogacz INFN: M. Ferrario, L. Serafini DESY: D. Proch, J. Sekutowicz, S. Simrock BNL: I. Ben-Zvi LANL: P. Colestock UCLA: J. B. Rosenzweig TESLA_TTF Meeting Frascati, May 26-28, 2003 TTF Meeting , May 26-28, 2003
Motivation XFEL pulsed linac, present layout: Emax = 20 GeV L = 1.4 km 78 Cryomodules each housing 12 sc cavities 936 cavities at Eacc = 23.5 MV/m Cryoplant 1.2 kW at 2 K (safety margin ~50%) capital cost: 336 M€ includes 1000 m of active length ~ 0.34 M€/m TTF Meeting , May 26-28, 2003
What do we buy for this money ? up to 40000 @ 1 nC bunches /s at 20 GeV up to 120000 @ 1 nC bunches /s at 10 GeV (add. costs) The questions are: can we buy much more in the future after pulsed XFEL ? and is there a major change in the technology needed ? TTF Meeting , May 26-28, 2003
An alternative possible future layout of the linac driving XFEL Technical assumptions, towards cw operation : I. 1284 cavities @ Qo ~ 2E10 @ Eacc 15 MV/m II. 46 kW @ 2K cryoplant III. energy recovery Are these assumptions very challenging ? TTF Meeting , May 26-28, 2003
• cavities : • cryoplant = ~45÷55 M€ • energy recovery 95 %: we have good chance after experiment at CEBAF : 1 GeV 20 MeV (98 %) with 320 sc cavities TTF Meeting , May 26-28, 2003
Possible layout can be very similar to the present pulsed linac 1.8 km ~3 km Dump (0.5 MW) 3xSASE 2xUndulators RF-Gun ? BC I : 0.14 GeV BC II : 0.50 GeV En = 10÷20 GeV R~150 m BC III : 2.50 GeV TTF Meeting , May 26-28, 2003
A very preliminary and not optimized list of parameters TTF Meeting , May 26-28, 2003
Example: 1 mA= 1 nC @ spacing 1 µs Any combination of the bunch charge and the spacing of bunches giving nominal current is OK Example: 1 mA= 1 nC @ spacing 1 µs TTF Meeting , May 26-28, 2003
Length of the pulse and power/FPC vs. En 25 000 bunches/s But this requires additional RF TTF Meeting , May 26-28, 2003
How much does the RF cost ? We have here practically 2 solutions: Solid state amplifiers ~ 5 kW/FPC 6 M€ (Simrock) 16 kW klystrons (CEBAF 12 GeV upgrade) 16 M€ TTF Meeting , May 26-28, 2003
• suppression of microphonics Conclusion Needed R&D : • cw RF gun • suppression of microphonics • more experience with the energy recovery Total cost without experiments should be < 400 M€ Total AC power for Cryoplant + RF < 10 MW But we will have : 6 x more bunches /s very flexible time structure of the beam. TTF Meeting , May 26-28, 2003