SCU Motivation-Emma

Superconducting Undulator R&D
Proposal for LCLS-II
Paul Emma (SLAC)
Superconducting Undulator R&D
Jan. 31, 2014
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Outline of Presentation
Meeting Agenda
LCLS-II Performance Requirements and Issues
Superconducting Undulators (SCU’s) compared with
permanent magnet undulators
SCU impact on LCLS-II Hard X-Ray (HXR) FEL performance
SCU impact on LCLS-I performance (using Cu linac)
Brief SCU R&D Plan (more from other speakers)
Review Charge and Committee
This is a review of the R&D Proposal which leads up to a possible
design baseline change in 2015, and not an evaluation of that
SCU R&D Review, Jan. 31, 2014
DRAFT Agenda for Jan. 31 Review* (2014)
Meeting Site at (no password needed):
Review Agenda (all times Pacific/SLAC):
07:00 AM (5 min)
07:05 AM (30 min)
07:35 AM (20 min)
07:55 AM (50 min)
08:45 AM (10 min)
08:55 AM (50 min)
09:45 AM (20 min)
10:05 AM (25 min)
10:30 AM
Welcome and Charge
SCU Advantages in LCLS-II
Undulator Tolerance Estimates
SCU Development at ANL
SCU Development at LBNL
SCU Field Measurements
(executive session)
Norbert Holtkamp (SLAC)
Paul Emma (SLAC)
Heinz-Dieter Nuhn (SLAC)
Efim Gluskin (ANL)
Soren Prestemon (LBNL)
Diego Arbelaez (LBNL)
Committee Only
Chairman assembles committee response in writing within 2 weeks (Feb. 14, 2014)
* Carried out by teleconference to save travel.
SCU R&D Review, Jan. 31, 2014
LCLS-II Design Summary
New 4-GeV CW linac (1 MHz) and 2 new FELs (~2020)
2 New Permanent Magnet (PM) adjustable gap undulators
0.2 - 1.3 keV (SASE and self-seeded)
1.2 - 5.0 keV (SASE and self-seeded?)
PM for HXR undulator barely allows 5.0 keV in SASE (no selfseeding unless 4 keV or less) – existing und. hall is 150 m
Will also replace existing LCLS-I und. with adj.-gap PMU (HXR)
Radiation damage to PM’s is a major issue at 1 MHz (gap?)
HXR FEL based on 150-m long PM-undulator at 4 GeV is very
sensitive to e- emittance when tuned above 3.5 keV (risk)
Schematic of the LCLS-II facility with the new SCRF linac and two new undulators, along with the existing copper (Cu) linac,
and experimental
The “Cu Linac” is in the 3rd km of the SLAC tunnel.
Jan. 31,
Superconducting Undulator Motivation
Using an SCU for the LCLS-II HXR undulator…
…allows full LCLS-II performance to 5 keV (SASE & selfseeded) and with 50-70 m less undulator (or more taper)
…has orders of mag. less sensitivity to rad. dose
…is much less sensitive to e- emittance (new high-rate gun)
…produces very low pressure in a small vacuum chamber
(gas scattering at 1 MHz)
…enhances LCLS-I FEL power, whereas a new PM degrades it.
SCU R&D Review, Jan. 31, 2014
SCU’s Provide Real Performance Enhancement
Much higher fields for a given period and gap
(planar undulators)
SCU (Nb3Sn)
SCU (NbTi)
PM (in-vac)
PM (NdFeB)
gap = 7.5 mm (5.7 mm for in-vac  same stay-clear)
SCU R&D Review, Jan. 31, 2014
lu = 26 mm
Bpk = 1.0 T
gap = 7.2 mm
Examine Field’s Impact on LCLS-II Undulator Length
The next 2 slides assume the following:
4-GeV electron energy (1 kA, ge = 0.45 mm, sE = 500 keV, etc.)
1.2 - 4.0 keV photon tuning range (SASE & self-seeded)
Full-height magnetic gap of 7.5 mm (chamber gap is 5.7 mm)
Und. period set by lower-limit photon energy (1.2 keV) for FEL
resonance at highest field possible for this gap and technology
Und. length set by max. photon energy (4 keV), assuming 18LG
(based on beam brightness), plus 50% longer for self-seeding
Compare in-vacuum and out-of-vacuum Permanent Magnets
(NdFeB), and SCUs (NbTi & Nb3Sn) – all with same chamber gap
Und. length includes 1.15-m breaks, 3.4-m segments, +20% for
margin, and 4-m extra space for self-seeding monochromator
Examine total length sensitivity to main parameters (see next)…
SCU R&D Review, Jan. 31, 2014
Undulator Length vs. e- Energy for LCLS-II HXR
1.2 - 4.0 keV
Self-Seeded (SS)
lu = 27.5 mm, 24.8 mm, 20.3 mm, 18.7 mm (4 GeV)
SCU R&D Review, Jan. 31, 2014
lu = 20.3 mm
lu = 18.7 mm
g = 7.5 mm
ge = 0.45 mm
Ipk = 1 kA
sE = 500 keV
b = 15 m
lu = 16.3 mm
Period varies
with energy
to maintain
tuning range
(1.2 keV)
Und. Length Comparison for LCLS-II HXR
Self-Seeded + 20%
stay-clear = 5.7 mm
PM sensitive to gex,y
m-bunching not incl.
lu defined by this
lu = 27.5 mm, 24.8 mm, 20.3 mm, 18.7 mm
SCU R&D Review, Jan. 31, 2014
5 keV SS not possible
Compare Baseline LCLS-II with LCLS-I (Cu linac)
LCLS-I FEL Performance Compromised with new PMU
PM, lu = 26 mm (project baseline)
H.-D. Nuhn
SCU R&D Review, Jan. 31, 2014
Compare Nb3Sn (lu = 20 mm) LCLS-II with LCLS-I
LCLS-I FEL Further Enhanced with 20-mm SCU
Nb3Sn, lu = 20 mm
H.-D. Nuhn
SCU R&D Review, Jan. 31, 2014
SCU R&D Plan in Brief
Builds 2-m test cryostat (based on existing design at APS)
Build & test 1.5-m long NbTi prototype planar undulator (lu  21.0 mm)
Build & test 1.5-m long Nb3Sn prototype planar undulator (lu  18.5 mm)
Develop and tune each of the NbTi and Nb3Sn undulators
Both Labs…
Develop field measurement and field correction techniques
Demonstrate predicted field, field quality, end-field corrections, field
measurement and tuning, cold mass fiducialization, and integration of
cold mass into cryostat
Goal: Within 18 months deliver 2 fully functional, 1.5-m long,
SC prototype undulators which meet LCLS-II specifications
SCU R&D Review, Jan. 31, 2014
SCU R&D and LCLS-II Construction Time-Line
17-Month SCU R&D (to ~May 2015)
3-Year production cycle for 33 SCU segments (~3 m/ea)
Installation of LCLS-II undulator starts mid-2018
Start SCU
End R&D
Start Und.
SCU R&D Review, Jan. 31, 2014
Start Und.
Linac and Cryo
Install Complete
Review Committee and Charge
Review Committee:
Mikael Eriksson, chair
Sara Casalbuoni
David Larbalestier
Joachim Pflueger
Johannes Bahrdt
Max Lab
E-Mail Address
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Yes – 12/18/13
Yes – 12/18/13
Yes – 12/17/13
Yes – 12/18/13
Yes – 01/08/14
Charge to the Committee:
1. Is the SCU R&D plan technically sound, and is it well enough defined in scope,
schedule, and cost so as to produce definitive results that can support a baseline
design change to the hard x-ray LCLS-II undulator, by May 2015?
2. If the plan appears insufficient, what recommendations can the committee make
to improve the chances for supporting a baseline change within 18 months?
3. What further alterations might be made to solidify the plan and move it forward in
time or reduce costs?
SCU R&D Review, Jan. 31, 2014
SCU R&D Review, Jan. 31, 2014
Compare Nb3Sn (lu = 18.5 mm) LCLS-II with LCLS-I
LCLS-I FEL Performance Enhanced with New SCU
Nb3Sn, lu = 18.5 mm
H.-D. Nuhn
SCU R&D Review, Jan. 31, 2014
Und. Length with 4-mm Stay Clear (5.8 mm gap)
stay-clear = 4.0 mm
lu = 25.0 mm, 22.0 mm, 18.6 mm, 17.0 mm
SCU R&D Review, Jan. 31, 2014
Prototype Undulator Parameters
SCU R&D Review, Jan. 31, 2014

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