1 ERL MainLinac Cryomodule Why and What CLASSE

1 ERL Main-Linac Cryomodule Why ? and What ? CLASSE CW linac R&D DC-gun R&D SRF injector R&D Undulator R&D Georg H. Hoffstaetter MLC review 03 October 2012

2 Cornell history: The ERL principle CLASSE Energy recovery needs continuously fields in the RF structure Ø Normal conducting high field cavities can get too hot. Ø Superconducting cavities used to have too low fields. Georg H. Hoffstaetter MLC review 03 October 2012

3 ERL on Cornell’s campus as extension of CHESS CLASSE ERL@CESR, Cornell Georg H. Hoffstaetter MLC review 03 October 2012

4 Parameters CLASSE Required beam parameters drive MLC choices l 5 Ge. V, 100 m. A, 8 pm emittances, 2 ps bunch length Georg H. Hoffstaetter MLC review 03 October 2012

5 From beam parameters to MLC CLASSE l 5 Ge. V, 100 m. A, 8 pm emittances, 2 ps bunch length l 8 pm: requires small bunch charge and therefore high repetition rate – results in 1. 3 GHz l Cost optimization: Construction (favors high gradients and small length) + 10 year operation (favors low gradient and small cooling needs) - results in 15 MV/m < Eacc < 20 MV/m l 100 m. A: By far the largest current in an SRF linac, produces strong Higher Order Modes. To damp these modes, cavities cannot be too long - results in 7 -cell cavities with a beam-pipe HOM absorber each. l 5 Ge. V and 15 MV/m, i. e 312 m of acceleration, 7 -cells for 1. 3 GHz – results in 384 cavities l ERL: Optics for two beam requires regular focusing – results in a quadrupole every 10 m, and therefore a 10 m long cryomodule. l 10 m MLC for cavities with HOM absorbers – results in 6 cavities per MLC Georg H. Hoffstaetter MLC review 03 October 2012

6 Cornell Energy Recovery Linac Project Design Definition Report (PDDR) CLASSE 530 pages between conceptual design and engineering design. Contains considerations for MLC. Georg H. Hoffstaetter MLC review 03 October 2012

7 Beam parameter input to MLC requirements CLASSE 8 pm: Stringent alignment tolerances, obtained by orbit correction simulations small coupler kick limits obtained by RF and beam dynamics simulations 16 MV/m High Q requirements and suitable cryogenic design 100 m. A: Strong HOM damping requirements, obtained by BBU simulations b) Georg H. Hoffstaetter MLC review 03 October 2012

8 The right time for an ERL MLC ! CLASSE Peak DC-gun voltage: 440 k. V (of 500 k. V required with beam) Peak bunched-beam current: 52 m. A with Ga. As / 35 m. A with Cs. K 2 Sb for 8 h Typical bunch length: 2 ps (up to spec) Smallest normalized thermal emittance: 0. 25 mm mrad/mm radius Smallest normalized emittance after injector at 80 p. C: 0. 7 mm mrad with normalized bunch core emittance : 0. 3 mm mrad For this gun, 0. 5 mm mrad is theoretical limit ! This bunch in a 5 Ge. V ERL would produce X-rays brighter than any ring today. (a 50 pm. X 50 pm ERL/USR or a 0. 6 nm. X 6 pm storage ring) Cathode research: reduction of thermal emittance by 2 SRF-cavity: Q of 3. 5 E 10 at 16 MV/m without ERL couplers The injector prototype has already achieved ERL-quality beams. Now the rest of the accelerator, particularly the MLC has to be prototyped ! Georg H. Hoffstaetter MLC review 03 October 2012

9 Charge to the MLC review committee CLASSE (1) Review the ERL’s MLC and evaluate whether it’s design is suitable for the ERL’s parameters. Consider the cryogenic and mechanical. (2) Review the prototype MLC that will be tested individually, and evaluate whether its design and its planned tests will yield sufficient insight of the ERLs MLC. (3) Write a short report of your findings, if possible before October 14, 2012. Georg H. Hoffstaetter MLC review 03 October 2012

10 CLASSE Start of MLC review Georg H. Hoffstaetter MLC review 03 October 2012