1. LCLS-II will use sectors 11-20 (2 nd kilometer of SLAC linac) + a bypass line FACET has already removed all RF from sector 20 LCLS-II will re-install RF in the first half of 20 (20-1, 2, 3, 4) Bypass line will start at 20-5 and needs to level out before the FACET wall This is 4 RF stations fewer than LCLS-I so we need to be efficient: 1.Assume 225 MeV per RF station (18.5 MV/m over a 12-m section) 2.Place the new BC1 at 250 MeV in 11-2, as in LCLS-I (21-2) 3.Keep BC2 at similar energy (~4 GeV) so new CSR issues, but move as needed 4.Assume L2 is at a worst case RF phase of  2   40° (user chirp option) 5.Always provide  3 spare tubes in L2, plus 2 BC2-energy-feedback stations 6.Typically provide  3 spare tubes in L3, plus 8 final energy-feedback stations 7.Set L3 on crest and find acomfortable top-end energy for LCLS-II… 20-1, 2, 3, 4 FACETFACET ~50 m ? bypass line LCLS-II Linac Layout Issues

2. 11 BC2BC1 78234561786782345617823456178234561782345612341 78234561782345612317834561 121314 2 151617181920  2   40°   =    = 250 MeV   = 4.0 GeV   = 13.6 GeV TCAV3? (klys. 14-5) 11 n n n n Standard station (klys & ~12 m RF) Feedback station (klys & ~12 m RF) Spare Feedback station (ditto) Spare RF station (ditto) Proposed Layout of LCLS-II High Power RF Stations BC2 will displace the 14-4 & 14-5 stations (14-4 is gone) 14-5 station will power a new TCAV3 at 14-7 Presently there is no RF in 11-3 (very old e + system – re-install b,c,d) Should we locate BC1 at 11-3 (~450 MeV) to save money? Presently there is no RF in 19-7 (SLC e + system – re-install? – no e + ?) Presently there is no RF in 20-1 (historical? – re-install) Presently there is one missing section at 19-8d (re-install)

3. 11 BC2BC1 78234561786782345617823456178234561782345612341 7823456178234561231784561 121314 2 151617181920  2   40°   =    = 450 MeV   = 4.0 GeV   = 13.2 GeV TCAV3? (klys. 14-5) 11 n n n n Standard station (klys & ~12 m RF) Feedback station (klys & ~12 m RF) Spare Feedback station (ditto) Spare RF station (ditto) Leave 11-2 unchanged (12 m) and locate BC1 at 11-3, 450 MeV (save money) Then how to power L1X? Provide only two L2 spares at  2 =  40° (i.e., 4 spares at  2 =  32° nom.) Leave no RF in 19-7 (e + system remains) Leave no RF in 20-1 (save money) Final maximum comfortable energy is 13.2 GeV (|  3f | = 30° ) Alternate (cheaper) Layout of LCLS-II High Power RF Stations

4. LiTrack Study in LCLS-II (Heater at 16 keV rms) 13.6 GeV at undulator 135 MeV after injector 250 MeV after BC1 4.0 GeV after BC2 0.62 mm 0.13 mm 7.1  m 1.1% 0.07% 0.41% 0.01%

5. LCLS-II Accelerator for 14 GeV, 120 Hz, 250 pC

6. LCLS-I Injector Layout LCLS-II Phase-I Injector Layout LCLS-II Phase-II Injector Layout Use BXS magnet and short spectrometer beamline in these temporary positions