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LCLS-IISC Parameters. Tor Raubenheimer 10/1/2013. LCLS-II - Linac and Compressor Layout for 4 GeV. L0 j  0 V 0  97 MV. L1 j = - 26° V 0 =235 MV. HL j = - 170 ° V 0 =40 MV. L2 j = - 28° V 0 = 1448 MV. L3 j = 0 V 0 = 2460 MV. CM01. CM2,3. CM15. CM35. CM04.

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lcls iisc parameters

LCLS-IISC Parameters

  • Tor Raubenheimer
  • 10/1/2013

LCLS-II - Linac and Compressor Layout for 4 GeV


j 0

V0 97 MV


j =-26°

V0=235 MV


j =-170°

V0 =40 MV


j = -28°

V0= 1448 MV


j = 0

V0= 2460 MV









4.0 GeV

R56 = 0

Ipk = 1000 A

Lb = 0.024 mm

sd 0.02 %


98 MeV

R56 = -5 mm

Ipk = 12 A

Lb = 2.0 mm

sd = 0.006 %


270 MeV

R56 = -65 mm

Ipk = 60 A

Lb = 0.40 mm

sd = 1.4 %


1550 MeV

R56 = -65 mm

Ipk = 1000 A

Lb = 0.024 mm

sd = 0.50 %


0.75 MeV

100 pC; Machine layout 26SEP2013; Bunch length Lb is FWHM

Start from 10A APEX beam

Includes 2-km RW wake

* L0 phases: (-40, -52, 0, 0, 0, 13, 33), with cav-2 at 20% of other L0 cav’s.

Paul Emma

operating modes
Operating modes

Concurrent operation of 1-5 keV and 5-18 keV is not possible

0.2-1.2 keV (100kHz)

4 GeV SC Linac

Cu Linac

1.0 - 18 keV (120 Hz)

1.0 - 5 keV (100 kHz)

  • Two sources: high rate SCRF linac and 120 Hz NCu LCLS-I linac
  • North and south undulators always operate simultaneously in any mode

LCLS-II Overview

high level schedule
High Level Schedule

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more immediate schedule
More Immediate Schedule

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Mid-October Workshop to review design, cost and schedule with collaborators

Late November FAC review of the draft CDR

Mid-December Director’s Review for CD1 Review

Early-February CD1 Lehman Review

assumed beam parameters
Assumed Beam Parameters

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The assumed emittance of 0.43 at 100 pC is roughly 25% larger than the LCLS-II baseline. It is more conservative than the NLS or the scaled NGLS values (the latter are consistent with the LCLS-II baseline) however a gun has not yet been demonstrated that achieves the desired emittances. Reduced emittances will decrease gain lengths.

Peak current is consistent with higher energy beams and BC’s

example of injector apex
Example of Injector: APEX

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example of litrack from apex simulation
Example of Litrack fromAPEX Simulation


20A peak current

Slice emittance0.2-0.25 um

Projected emittance ~ 0.35 um

  • better current/energy profile

Charge =100pC



L1 phase =-21.7 degree

L2 phase =-29.2 degree

L3 phase =-2 degree

3rd HC phase =-158 degree

L1voltage =211 MV

L2 voltage =1.54GV

3rdHC Voltage=47MV

Lanfa Wang

scrf linac
SCRF Linac

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Roughly 400 meters long including laser heater at ~100 MeV, BC1 at ~300 MeV and BC2 at 1000-2000 GeV. Long bypass line starting at Sector 10  BSY.

Based on 1.3 GHz TESLA 9-cell cavity with minor mods for cw operation

1 3 ghz 8 cavity cryomodule cm
1.3 GHz 8-cavity cryomodule (CM)
  • It is proposed to use an existing cryomodule design for the 4-GeV LCLS-II SRF linac.
  • CM is roughly 13 meters for 8 cavities plus a quadrupole package
  • The best-fit is the EU-XFEL cryomodule
    • Modifications are required for LCLS-II
    • (The CEBAF 12 GeV upgrade module must also be considered)
    • (The ILC CM is similar but has several important differences and is not as well suited for CW application)
  • 100 cryomodules of this design will be built and tested by the XFEL by 2016  Global industrial support for this task
    • One XFEL ~prototype CM was assembled and tested at Fermilab
    • (Fermilab assembled an ILC cryomodule and has parts for another)\
linac view in slac tunnel
Linac View in SLAC Tunnel

SLAC Linac

(11 wide x 10 feet high)

(3.35 x 3.05 m)


first 800 m of slac linac 1964
First 800 m of SLAC linac (1964):

350 m

Injector Length

Cryoplant placement and construction

g eometry downstream of sc linac
Geometry downstream of SC linac

Plan view

old LCLS2 linac

120 Hz

LCLS2SC bypass

100 kHz

fast kicker

Elevation view

100 kHz

LCLS2SC bypass


old LCLS2 linac

lcls2sc bypass from sec 21 to dump
LCLS2SC bypass (from sec-21) to dump




LTU dogleg + V-bend



assumed fel configuration
Assumed FEL Configuration

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  • High rep rate beam could be directed to either of two undulators HXR or SXR bunch-by-bunch
  • 120 Hz beam could be directed to the HXR at separate times
  • The SC linac would be located in Sectors 0-10 and would be transported to BSY in the 2km long Bypass Line. It would use a dual stage bunch compressor.
  • A dechirper might be used to further cancel energy spread for greater flexibility in beam parameters
  • The high rep rate beam energy would be 4 GeV and the HXR would fill the LCLS hall with ~144 m while the SXR would be <75 m so that it could be fit into ESA
  • Both undulators would need to support self-seeding as well as other seeding upgrades
undulator requirements
Undulator Requirements

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SXR self-seeding operation between 0.2 and 1.3 keV in ESA tunnel (<75 meters) with 2.5 to 4 GeV beam

HXR self-seeding operation between 1.3 and 4 keV in LCLS tunnel (~144 meters) with 4 GeV beam

HXR SASE operation up to 5 keV with 4 GeV beam

Primary operation of SXR and TXR at constant beam energy  large K variation

HXR operation comparable to present LCLS with 2 to 15 GeV beam

baseline tuning range
Baseline Tuning Range

With overhead

LCLS-IISC Undulator Options

x ray pulse energy at high rate
X-ray pulse energy at High Rate

Results assume full beam and are somewhat optimistic

LCLS-IISC Undulator Options

comparison of hxr with lcls performance at 120 hz 1
Comparison of HXR with LCLS performance at 120 Hz (1)

26 mm HXR covers 0.5 keV at ~2.5 GeV to ~30 keV at 15 GeV

LCLS-IISC Undulator Options

comparison of hxr with lcls performance at 120 hz 2
Comparison of HXR with LCLS performance at 120 Hz (2)

26 mm HXR provides lower pulse energy than 30 mm LCLS but much shorter l

LCLS-IISC Undulator Options

options for hxr scu or 30 mm period 2
Options for HXR: SCU or 30 mm period (2)

Example of a 30 mm period hybrid undulator below. Nearly recovers LCLS performance (reduction due to slightly larger gap with VG undulator) however the maximum photon energy at high rate, i.e., 4 GeV is now 4.3 keV not5 keVas with 26 mm period and 5 keV would require 4.4 GeV beams.

LCLS-IISC Undulator Options

superrconducting undulator options
SuperrConducting Undulator options

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  • An SCU has a number of benefits:
    • Would attain comparable performance as LCLS even while achieving 5 keV at 4 GeV at high rate by operating with high K
    • Would allow shorter SXR period to reduce SXR beam energy and gain length to ensure space in ESA while still covering full wavelength range at constant energy.
points of contact
Points of Contact

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cdr writing
CDR Writing

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  • Must keep the document concise – it is a conceptual design
  • Executive Summary (Galayda)
  • Scientific Objectives (TBD)
  • Machine Performance and Parameters (Raubenheimer)
  • Project Overview (Galayda)
  • Electron Injector (Schmerge)
  • Superconducting Linac Technologies (Ross,Corlett)
  • Electron Bunch Compression and Transport (Raubenheimer, Emma)
  • FEL Systems (Nuhn)
  • Electron Beam Diagnostics (Frisch, Smith)
  • Start-to-End Tracking Simulations (Emma)
  • Photon Transport and Diagnostics (Rowen)
  • Experimental End-Stations (Schlotter)
  • Timing and Synchronization (Frisch)
  • Controls and Machine Protection (Shoaee, Welch)
  • Conventional Facilities (Law)
  • Environment, Safety and Health (Healy)
  • Radiological Issues (Rokni)
  • Future Upgrade Options (Galayda)