Physics Update P. Emma FAC Meeting October 27, 2005 LCLS

No New Physics Surprises 1999: Surface roughness wakefield 2001: CSR micro-bunching instability 2002: Space-charge enhanced micro- bunching instability 2004: AC resistive-wall undulator wake 2005: no new set-backs? We must be too busy with construction? Thanks for past help from: K. Bane, Z. Huang, G. Stupakov, and Saldin, Schneidmiller, Yurkov

Normal Incidence Laser on Cathode Advantages No lossy, pulse distorting grating Non-dispersed beam – less $ Mirror change without gun vent Optics allows continuous variation of cathode beam size Disadvantages Mirror wakefield (solved) Mirror requires space (solved) e- beam laser beam previous grazing incidence Dowell, Gilevich, Limborg, White

Electron Trajectory Jitter Trajectory amplitude w.r.t. beam size Total amplitude2 for N uncorrelated kicks, <10% tolerance sensitivity Form budget with a few discreet tolerance levels, opening challenging tolerances but holding tight on more standard ones

Trajectory Stability – Sources of Jitter (f > 10 Hz) Expected Sources of Transverse Jitter Steering coil current regulation (120 x, 121 y) Bend magnet trim coil current reg. (13 x & 2 y) Misaligned quads/sol’s + current reg. (148 mag’s) Quad/solenoid mech. vibration (148 mag’s) CSR kicks with bunch length jitter (BC2, x only) Transverse wakes and charge jitter (X-band RF) Drive laser pointing stability

Trajectory Stability – Tol’s & Expectations System Stability Requirements at f > 10 Hz Steering coils (30-100 ppM  6% of beam size) Trim coils (30-100 ppM  2%) Misaligned quads (D  200 mm: 25-100 ppM  6%) Quad/solenoid vibration (0.05-1 mm required  10%) CSR kicks (1 nC, Dsz/sz  10%:  ~20%, x-only) Wakes (D  200 mm, DN/N  2%  2%) Drive laser pointing ( ~1%) 0.2 nC is more stable

Quadrupole Magnet Vibration Existing Linac ‘QE’ Quadrupole Magnets R. Stege, J. Turner, 1994 rubber boot on water pump 12 quads need rms 500 nm (most new injector quads) 101 magnets need rms 100 nm (existing linac quads) 35 quads need rms 50 nm (mostly new LTU quads)

CSR-Induced x-Trajectory Jitter 10% bunch length jitter  16% ‘core’ trajectory jitter 1-nC 22 mm 20 mm 18 mm core

Trajectory Feedback at Undulator Start undulator starts at Z = 0 5-mm BPM resolution of final 10 BPMs gives centroid stabilization to 5% of rms beam size at: f < 10 Hz (120 Hz rate)

Quad. Power Supply Regulation (Long-Term) Dz < 0.02 over all random quadrupole errors |Dk/k| = 1% to 0.01% rms over 24 hrs+ |Dk/k|

Magnet Polarities/Labeling Defined MMF will measure magnets and clearly label polarities

Commissioning – Tune-up ‘Stoppers’ Full set of beam diagnostics at each tune-up point 6 MeV Jan. through July ’07 135 MeV 250 MeV 4.3 GeV 13.6 GeV rf gun L0 TCAV0 TCAV3 e BC1 BC2 …linac L1 X L2 L3 undulator abort SLAC linac tunnel research yard

Commissioning Plans for each System

LCLS Feedback Performance (use CSR P/P) feedback off DIpk/Ipk0 (%) feedback on J. Wu at undulator entrance

CSR as Relative Bunch Length Monitor Red curve: Gaussian Black curve: Uniform Red dots: ‘Real’ J. Wu CSR detector is critical to LCLS stability (UCLA)

Relaxed Undulator Tolerances Full undulator error budget  0.5°C  1°F (H.-D. Nuhn) Beam-Finder Wire (BFW) to locate upstream end (D. Walters) Alignment drift tolerances loosened Correction strategy with target time-scales (FAC suggestion)

Undulator Alignment Drift – Long Term (24 hrs) 10 mm quad and BPM drift After beam-based alignment MICADO steering applied Tolerance set at 5 mm alignment drift over 24 hrs

Kem’s Correction Zones* Zone 1 (non-invasive correction) 120-Hz traj-feedback (LTU BPM’s) 0.1-Hz traj-feedback (und. BPM’s) Zone 2 (Dt > 1 hr, P/P0 > 90%, non-invasive) MICADO steering within undulator Zone 3 (Dt > 24 hr, P/P0 > 75%, invasive) Weighted steering of undulator traj. (1 min.) ... or quadrupole gradient scans - fast BBA (10 min.) Possible x-ray pointing (few min.) Zone 4 (Dt > 1 wk, P/P0 < 50%, machine time) One iteration of BBA (<1 hr) Zone 5 (Dt > 6 mo, shut-down) Tunnel survey with all movers set to zero (1 wk) Full 3 iterations of BBA (~3 hrs) * FAC suggestion, April ‘05

1-Å with Optical Klystron Enhancement Future? K = 2.7 E = 13.6 GeV ge = 1.2 mm Ipk = 3.4 kA b = 30 m sE/E = 0.005% Laser-Heater  1/2 -bunching issue? Shim gap  Dg = 2 mm SASE sim. ~longer Lsat 4 “OK” chicanes (long breaks) Yuantao Ding, Zhirong Huang

Summary Electron beam commissioning through BC1 starts Dec. ’06 ! Normal incidence simplifies drive laser (Gilevich) Trajectory stability expectations: 24% x & 14% y Quadrupole current regulation specified Magnet polarities defined Commissioning plans formed Feedback systems require CSR monitor (UCLA) Relaxed undulator tolerances (Milton, Nuhn) 1-Å future operation with “OK”? Electron beam commissioning through BC1 starts Dec. ’06 !