CW Energy Recovery Linac for Next Genera of

CW Energy Recovery Linac for Next Genera of XFELs General Thoughts based on TESLA XFEL-TDR TJNAF: INFN: DESY: BNL: LANL: UCLA: A. Bogacz M. Ferrario, L. Serafini D. Proch. J. Sekutowicz, S. Simrock , I. Ben-Zvi P. Colestock J. B. Rosenzweig TESLA_TTF Meeting Frascati, May 26 -28, 2003 TTF Meeting , May 26 -28, 2003 1

Motivation XFEL pulsed linac, present layout: Emax = 20 Ge. V L = 1. 4 km 78 Cryomodules each housing 12 sc cavities 936 cavities at acc= 23. 5 MV/m E Cryoplant 1. 2 k. W 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 2

What do we buy for this money ? up to 40000 @ 1 n. C bunches /s at 20 Ge. V up to 120000 @ 1 n. C bunches /s at 10 Ge. V (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 3

An alternative possible future layout of the linac. XFEL driving Technical assumptions, towards cw operation : I. 1284 cavities@ Qo ~ 2 E 10 @ Eacc 15 MV/m II. 4 6 k. W @ 2 K cryoplant III. energy recovery Are these assumptions very challenging ? TTF Meeting , May 26 -28, 2003 4

• cavities : • cryoplant = ~45÷ 55 M€ • energy recovery 95 %: we have good chance after experiment at CEBAF : 1 Ge. V 20 Me. V (98 %) with 320 sc cavities TTF Meeting , May 26 -28, 2003 5

Possible layout can be very similar to the present pulsed lina 1. 8 km ~3 km En = 10÷ 20 Ge. V BC III : 2. 50 Ge. V BC II : 0. 50 Ge. V BC I : 0. 14 Ge. V RF-Gun ? R~150 m 3 x. SASE 2 x. Undulators Dump (0. 5 MW) TTF Meeting , May 26 -28, 2003 6

A very preliminary and not optimized list of parameters TTF Meeting , May 26 -28, 2003 7

Any combination of the bunch charge and the spacing of bunches nominal current is OK Example: 1 m. A= 1 n. C @ spacing 1 µs TTF Meeting , May 26 -28, 2003 8

Length of the pulse and power/FPC vs. En 25 000 bunches/s But this requires additional RF TTF Meeting , May 26 -28, 2003 9

How much does the RF cost ? We have here practically 2 solutions: Solid state amplifiers ~ 5 k. W/FPC 6 M€ (Simrock) 16 k. W klystrons (CEBAF 12 Ge. V upgrade) 16 M€ TTF Meeting , May 26 -28, 2003 10

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 11