P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Linac Commissioning P. Emma LCLS Commissioning Workshop, SLAC Sep , 2004 LCLS

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Linac Commissioning Document Available >23 page DRAFT document describing: initial checkout setup of linac how/where to measure beam what device to scan and by how much expected resolution how/where to correct beam etc… (not complete yet, but close)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Linac ‘Commissioning’ (Physics) Initial checkout (tunnel and beam-based) How to setup I pk = 3.4 kA,   1.2  m, etc. What to measure and what to adjust (simulations) Longitudinal phase space Bunch Length Energy Spread (proj. & slice) Transverse phase space Projected Emittance Slice Emittance

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Initial Machine Conditions Magnets warmed, standardized, and set properly Reasonable quality e  beam available: Rough beam steering established Rough RF phasing of each klystron (1 or 2 deg) Any beam obstruction and loss issues solved

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Initial Checkout - TUNNEL Power-on polarity checks of all “new” magnets Validate proper cabling connections (magnets, BPMs, diagnostics…) Rough alignment inspection (tape measure, eye) Verify all insertable devices move in and out, and are finally removed

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Initial Checkout - BEAM-BASED Take full set of x and y ‘oscillation’ data (checks optics and BPM scaling…) Verify all profile monitor scaling with known centroid shifts (wires, OTR, YAG, screens…) Repeat above at high dispersion points (DL1, BC1, BC2, DL2) using energy changes Calibrate all BPM-charge, and toroid readings based on one well established reference Document all the above for future scrutiny CHECKOUT MUST BE COMPLETE BEFORE MEASUREMENTS AND TUNING BEGIN!

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Location of Main Linac Diagnostics 5+ energy spread meas. stations (optimized with small  )...existing linac L0 rfgun L3L1 X L2  x,y EEEE EEEE EEEE EEEE 5+ emittance meas. stations designed into optics (  x,y ) BPMs at or near most quadrupoles and in each bend syst. RF deflectors for slice  and  E measurements (L0 & L3) EEEE EEEE EEEE EEEE EEEE EEEE T-cav. T-cav.

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Setup of Linac-0 RF RF-deflector at 1 MV Phasing L0-Linac RF-deflector  y  bunch length minimize energy spread with L0 RF phase Establish initial bunch length Phase linac-0

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Setup of Linac-1 RF Linac-1 RF phase scan (X-band off, BC1 bends at 295 MeV) Linac-X RF phase scan (BC1 bends at 250 MeV) set phase to  25˚  0.5˚ set phase to  160˚  0.5˚ 20-  m res. BC1 BPM L1 RF phase LX RF phase Turn on BC1 energy feedback Switch off BC2 chicane Use sec-25 RF-deflector to meas. bunch length (  z1 ) Adjust S-band RF phase (  0.5˚) to set  z1  195  10  m Linac-1 new rfgun 21-1b21-1d X

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Setup of Linac-2 RF Linac-2 RF phase scan (BC2 bends at 5.9 GeV, or…) set phase to  41˚  0.5˚ 40-  m res. BC2 BPM L2 RF phase Turn on BC2 energy feedback Use sec-25 RF-deflector to measure length (  z2 ) Adjust L2 RF phase (  0.5˚) to set  z2  20  2  m Linac-3 phasing is trivial (  5˚) 5-  m res. LTU BPM L2 phase Scan Linac-2 phase & use LTU BPM to find max. wake-induced energy loss across Linac-3 (NO CSR) L2L3

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Emittance Meas. Simulation in LCLS OTR1,2,3WS11,12,13 BC1 Multiple OTR screens Multiple wire-scanners Quad-scans on single OTR Quad-scans on OTR with RF-deflector

P. Emma, SLACLCLS Commissioning – Sep. 22, MeV OTR x -profiles from tracking  x = 0.75 ± 0.04  m  x  118  m  x  49  m  x  120  m non-Gaussian

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 x -Slice-Emittance Measurement RF-deflector at 1 MV slice OTR 10 times  y  bunch length “QE03” quad scanned

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 x -Slice-Emittance Measurement Simulation slice-5 Injector at 135 MeV with S-band RF-deflector at 1 MV = meas. sim. = calc. = y distribution = actual (same SLAC slice-  code used at BNL/SDL) DL1 slice-emit on WS02 “QE03” scanned  20% (centered on 106% of its nominal gradient)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 y -slice-Emittance Measurement in BC1 3.9 mm 0.1 mm “Q21201” scanned ±20%

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 y -slice-Emittance Measurement Simulation slice- y emittance in BC1 using x -chirp = meas. sim. = calc. = y distribution = actualslice-5 “Q21201” scanned  20% (centered on 92% of its nominal gradient)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Empirical BC1/BC2 Dispersion Correction Residual x -dispersion (and its angle) is precision minimized using ‘tweaker’ quads in the chicane actual data from SPPS chicane  x   /2 SPPS chicane with quads Correct  and (  ), orthogonally with 2 quads

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Transverse Wakefield Compensation trajectory after steering  x  2.1  m  y  5.2  m All quadrupoles, RF structures, and BPMs misaligned by 300  m rms steering coils  x  1.0  m  y  1.1  m Small ‘bumps’ added to correct emittance

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Repeat for 100 Different Seeds  /   20% (projected) M. Borland

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Energy Jitter Measurement (Feedback) undulator… relative energy centroid resolution: ~0.003% x1x1x1x1 x2x2x2x2 Two 5-  m BPMs: Difference of BPM x -readings is proportional to energy change, and insensitive to incoming trajectory jitter.  x  125 mm)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Slice-Emittance Configuration for LTU nominal optics (proj. emit.) WS31-34 undulator… slice-emit. meas. optics OTR33 stopperinserted

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Slice-Emittance Measurements in LTU = meas. sim. = calc. = y distribution = actualx x z y LTU at 14 GeV with S-band RF-deflector at 24 MV “QEM3” (or tweaker) scanned  3% (centered on its nominal gradient)

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Slice Energy Spread Measurements in LTU LTU at 14 GeV with S-band RF-deflector at 24 MV FEL goal  E /E  E /E  10  4  x  12  m

P. Emma, SLACLCLS Commissioning – Sep. 22, 2004 Summary Most diagnostics incorporated into design and simulated (1 st pass) Two RF-deflectors allow time resolved measurements at low and high energy Tune-up algorithms considered, but more refinement needed Feedback systems must maintain setup while tuning progresses (bunch length monitors?)