MAD Deck UpdatesTor Raubenheimer
October 15, 2014
2
MAD Deck Status
LCLS-II MAD Decks, Sept. 26, 2014
March 2014 deck was costed in June meanwhile decks
continued to evolve including updated diagnostics,
interference fixed and correction of physics limitations
June costing led to significant component reduction. The
August MAD decks were a starting point to reconcile
differences.
Estimated that there is an 8M$ discrepancy between P6
and August MAD deck. Developing October MAD deck that
will be roughly cost-neutral with P6.
3
Modifications in August 2014 From March 2014
LCLS-II MAD Decks, Sept. 26, 2014
Added space for cryo-distribution, endcaps, differential pumping
Lengthened laser heater to deal with uBI
Shortened 3.9 GHz cryomodules
Removed matching for Post-BC1 Diagnostic line and diagnostic
lines DIAG1, DIAG2, DIAGB, DIAGH and DIAGS
Removed collimators Post BC1
Reversed sign of BC2 bends into aisle
Removed 5 quads in EXT
Removed BC3
Updated collimation, stoppers & dumps in Bypass and LTU’s
Spreader as magnetic kicker and two 2-hole septa
Added missing diagnostics throughout
Fixed interferences throughout
Modifications for October MAD Release
Aiming to develop cost-neutral deck to allow reconciliation with P6
Compactifying LH/BC1 cryo-distribution for savings
Removing correctors with less than 90 deg phase advance
Removing 4 collimators
Including critical magnets for matching and transport
Adding new BSY1 beamline from S-30 BSY for Cu-linac
Still missing critical components for CD4 Threshold: buncher, laser
heater, some diagnostics as well as component for CD4 Objective
Will include new deferment level @0 = required for CD4 threshold
End
Options for Robust Lasing at 5 keVTor Raubenheimer
October 15, 2014
Outline
Concern was expressed at DOE Status review about LCLS-II
performance at 5 keV as expressed in the recommendation:
“The project team should work with the program management to bring
the 5-keV high repetition rate performance of the FEL in line with the
BESAC recommendation. Due by March 2015.”
Outline:
1. Review 100 pC operation
2. Operation across parameter range (300 pC – 10 pC)
3. Performance with increased beam energy
4. Performance with reduce undulator period
Other options could be considered using new technology (SCU’s)
Options for 5 keV, October 15, 20147
8
LCLS-II KPP (from LCLS-II GDR)
Options for 5 keV, October 15, 2014
1011 photons at 5 keV is ~80 uJ
(or 40 uJ if looking at spectral flux - SASE BW is 0.5x10-3)
Options for 5 keV, October 15, 2014
FEL X-ray Power at High rate (slide #9 from my review talk)
SCRF linac can deliver ~1 MHz beam to either undulator
• Goal is to provide >20 Watts over wavelength range- Easily met except at 5 keV where limited by energy and e
• Simulated performance is better
than analytic curve shown
• XTES is designed to
handle up to 200 Watts- Studying methods
of turning down FEL
power other than rep.
rate
0 1 2 3 4 5 6 72
20
200
Photon Energy [keV]
X-R
ay
Po
wer
[W
atts
]
X-ray Power using 4 GeV SCRF Linac
8 SXR SASE8 HXR SASE8 SXR Seeded
XTES limit
X-ray power goal
Power estimated for 100 pC and 300 kHz
See LCLSII-1.1-PR-0133, LCLS-II Parameters
9
10
100 pC, 1 kA: HXR SASE simulation results @ Eγ = 5.0 keV (slide #6 from Gabe Marcus review talk)
0 20 40 60 80 100 120 14010
-3
10-2
10-1
100
101
102
z [m]
E [ J
]
Energy gain curve
ΔEFWHM ~ 2.8 eVΔEFWHM/E0 ~ 5.6 x 10-4
E ~ 10.3 μJ
0 10 20 30 40 50 600
0.5
1Power (blue), Current (green)
s [m]
P [G
W]
0 10 20 30 40 50 600
1
2
I [k
A]
4980 4985 4990 4995 50000
0.5
1
1.5
2
2.5
3
3.5 x 1011 Spectrum
E [eV]
P(
) [a
.u.]
At 300 kHz (120 kW) 3 W x-ray power
Options for 5 keV, October 15, 2014
11
100 pC, 1 kA: HXR SASE simulation results @ Eγ = 5.0 keV
0 20 40 60 80 100 120 14010
-3
10-2
10-1
100
101
102
z [m]
E [ J
]
Energy gain curve
ΔEFWHM ~ 2.8 eVΔEFWHM/E0 ~ 5.6 x 10-4
E ~ 10.3 μJ
0 10 20 30 40 50 600
0.5
1Power (blue), Current (green)
s [m]
P [G
W]
0 10 20 30 40 50 600
1
2
I [k
A]
4980 4985 4990 4995 50000
0.5
1
1.5
2
2.5
3
3.5 x 1011 Spectrum
E [eV]
P(
) [a
.u.]
At 300 kHz (120 kW) 3 W x-ray power
Performance @ 100 pC can probably be improved factors of ~2 using chirps etc.
12
Summary of 100 pC Operation at 5 keV
Options for 5 keV, October 15, 2014
1. LCLS-II operation at 5 keV is limited by emittance leading to
an increase in the gain length – saturation length is close to
(or beyond) undulator len.
2. 100 pC operation at 5 keV is not robust
• Solutions include decreasing the beam emittance, increasing
the beam energy, or decreasing the undulator period.
LCLS-II (SCRF) Baseline Parameters (slide 13 of review talk)
Parameter symbol nominal range unitsElectron Energy Ef 4.0 2.0 - 4.14 GeV
Bunch Charge Qb 100 10 - 300 pC
Bunch Repetition Rate in Linac fb 0.62 0 - 0.93 MHz
Average e- current in linac Iavg 0.062 0.0 - 0.3 mA
Avg. e- beam power at linac end Pav 0.25 0 - 1.2 MW
Norm. rms slice emittance at undulator ge-s 0.45 0.2 - 0.7 m
Final peak current (at undulator) Ipk 1000 500 - 1500 A
Final slice E-spread (rms, w/heater) Es 500 125 - 1500 keV
RF frequency fRF 1.3 - GHz
Avg. CW RF gradient (powered cavities) Eacc 16 - MV/m
Avg. Cavity Q0 Q0 2.7e10 1.5 - 5e10 -
Photon energy range of SXR (SCRF) Ephot - 0.2 - 1.3 keV
Photon energy range of HXR (SCRF) Ephot - 1 - 5 keV
Photon energy range of HXR (Cu-RF) Ephot - 1 - 25 keV
See LCLSII-1.1-PR-0133, LCLS-II Parameters
13
14
LCLS-II Parameter Ranges
Options for 5 keV, October 15, 2014
• LCLS-II is being designed to operate over a large range
of bunch charges, peak currents, and beam emittances
• Beam emittance decrease roughly as sqrt of bunch charge
as supported by simulations of injector• More challenging to achieve high peak current with lower
bunch charge – CSR and longitudinal space charge have
greater impact• Current simulations generate ~600 A peak current at 20 pC
and <500 A peak current at 10 pC but simulated emittance
at 10 pC is almost 4x lower than at 100 pC
15
Injector Performance
Options for 5 keV, October 15, 2014
From the Injector PRD:
ASTRA simulations are significantly better (~30%) than PRD
spec using thermal emittance of 1 um. APEX measurements
of thermal emittance are 0.7~0.8 um. High charge emittance
measurements will be made at APEX and Cornell in FY15.
Speced slice e in coreat injector & undulator
16
Option 1: Optimized Performance using Parameter Range
Options for 5 keV, October 15, 2014
Optimize bunch charge, repetition rate, and undulator
focusing across parameter range limited by 4T
quadrupoles, 300 – 10 pC, and 120 kW beam power
Use full undulator length with post-saturation taper
• Consider 3 separate goals:
• Peak pulse energy, Peak power, Average power
• Peak power will optimize towards lower bunch charge,
peak pulse energy will optimize towards higher bunch
charge, and average power will maximize repetition rate
Optimized Charge versus 100 pC Fixed ChargeUse full HXR Undulator length of 32 segments
Compare 100 pC fixed charge
versus charge optimized for
Peak pulse energy, Peak
power, and Max. average
power up to 5.5 keV.
5 keV operation reasonable1.000 2.000 3.000 4.000 5.000 6.000
0.001
0.010
0.100
1.000
10.000
Peak Energy [mJ]
4.0 GeV 26 mm 32 Und
Not Optimized
1.000 2.000 3.000 4.000 5.000 6.000 0.0100
0.1000
1.0000
10.0000
100.0000
Peak Power [GW]
4.0 GeV 26 mm 32 Und
Not Optimized
1.000 2.000 3.000 4.000 5.000 6.0000.200
2.000
20.000
200.000
2000.000
Average Power [W]
4.0 GeV 26 mm 32 Und
Not Optimized
Options for 5 keV, October 15, 201417
18
Option 2: Impact of increased Beam Energy
Options for 5 keV, October 15, 2014
At 4 GeV, 100pC, the beam emittance is >3x the 5 keV photon
emittance. Increasing the beam energy decreases the 3D gain
length rapidly:
• 4.0 4.2 GeV yields a 20% reduction in gain length• 4.0 4.5 GeV yields a 30% reduction in gain length• Allows for higher saturation power and longer post-saturation
taper• Performance similar at 4.0 GeV/4.5 keV as 4.2 GeV/5.0 keV as
4.5 GeV/5.5 keV
Increasing the energy can be done by adding CM. Roughly 130
MeV per CM but adds to heat load.
Constant heat load CM number scales as:
3 CM for 4.2 GeV or 8 CM for 4.5 GeV
Comparing different beam energies – charge optimizedUse 80% of HXR Undulator length (26 segments)
All cases use optimized bunch
charge and rep rate for 120 kW
and 26 undulator segments.
3~4x more power at 5.0 keV
with 4.2 GeV than 4.0 GeV
1.000 2.000 3.000 4.000 5.000 6.0000.001
0.010
0.100
1.000
10.000
Peak Energy [mJ]
4.0 GeV 26 mm 26 Und
4.2 GeV 26 mm 26 Und
4.5 GeV 26 mm 26 Und
1.000 2.000 3.000 4.000 5.000 6.000 0.0100
0.1000
1.0000
10.0000
100.0000
Peak Power [GW]
4.0 GeV 26 mm 26 Und
4.2 GeV 26 mm 26 Und
4.5 GeV 26 mm 26 Und
1.000 2.000 3.000 4.000 5.000 6.0000.200
2.000
20.000
200.000
2000.000
Average Power [W]
4.0 GeV 26 mm 26 Und
4.2 GeV 26 mm 26 Und
4.5 GeV 26 mm 26 Und
Options for 5 keV, October 15, 201419
41 uW
150 uW
67 uJ @ 4.0 GeV180 uJ @ 4.2 GeV
20
Option 3: Effect of reduced Undulator Period
Options for 5 keV, October 15, 2014
Decreasing the undulator period will increase energy reach
from SCRF and CuRF (performance similar to 4.2 GeV)
BUT it will also reduce overlap between HXR and SXR at
nominal SCRF energy (4.0 GeV) and will reduce pulse
energy at modest wavelengths from SCRF and CuRF
Comparing different undulator l – charge optimizedUse 80% of HXR Undulator length (26 segments)
All cases use optimized bunch
charge and rep rate for 120 kW
and 26 undulator segments.
3~4x more power at 5.0 keV
with 24 mm than 26 mm
Options for 5 keV, October 15, 201421
1.000 2.000 3.000 4.000 5.000 6.0000.001
0.010
0.100
1.000
10.000
Peak Energy [mJ]
4.0 GeV 26 mm 26 Und
4.0 GeV 24 mm 26 Und
1.000 2.000 3.000 4.000 5.000 6.000 0.0100
0.1000
1.0000
10.0000
100.0000
Peak Power [GW]
4.0 GeV 26 mm 26 Und
4.0 GeV 24 mm 26 Und
1.000 2.000 3.000 4.000 5.000 6.0000.200
2.000
20.000
200.000
2000.000
Average Power [W]
4.0 GeV 26 mm 26 Und
4.0 GeV 24 mm 26 Und
22
Tuning Ranges from SCRF for 26 and 24 mm period HXR
Options for 5 keV, October 15, 2014
24 mm offers greater energy reach but reduces overlap at 4
GeV and requires reducing beam energy to <3 .0 GeV to
access 1 GeV from HXR
26 mm HXR period 24 mm HXR period
HD Nuhn
23
Pulse Energy from SCRF for 26 and 24 mm period HXR
Options for 5 keV, October 15, 2014
24 mm offers greater energy reach with ~300 uJ at 100 pC
versus few uJ but reduces reduces pulse energy in mid-
energy range from 2.2 mJ to 2.0 mJ
26 mm HXR period 24 mm HXR period
HD Nuhn
With 26 undulators at 5 keVget roughly ½ pulse energy
With 100 pC get ~8uJ at 5 keV
24
Tuning Ranges from CuRF for 26 and 24 mm period HXR
Options for 5 keV, October 15, 2014
24 mm offers greater energy reach than 26 mm (38 versus
35 keV) but reduces pulse energy in mid-energy range
26 mm HXR period 24 mm HXR period
HD Nuhn
25
Pulse Energy from CuRF for 26 and 24 mm period HXR
Options for 5 keV, October 15, 2014
24 mm offers greater energy reach than 26 mm (38 versus
35 keV) but reduces pulse energy in mid-energy range from
4.2 mJ to 3.5 mJ
26 mm HXR period 24 mm HXR period
HD Nuhn
26
Summary
Options for 5 keV, October 15, 2014
1. Baseline design (when charge is optimized) provides
>100 W (or >100 uJ) at 5 keV using full undulator
• Clearly meets the Objective KPP requirements• Provides >60uJ when using only 80% of full undulator and
meets spectral flux Objective KPP
2. Increasing beam energy to 4.2 GeV or shortening
undulator period to 24 mm provides >100 W (or uJ) with
80% of planned undulator (doubles margin in design)
• Decreasing undulator period degrades performance at
longer wavelengths
3. Increasing beam energy to 4.5 GeV increases energy
reach out to >5.5 keV (with >100 W in 80% of undulator)
• Performance at 5.5 keV similar to 5.0 keV with 4.2 GeV
End
Recommendations from DOE Status ReviewTor Raubenheimer
October 15, 2014
DOE Status Review (Sect 30 – Oct 2)
Accelerator Physics Recommendations (Stephen Milton & Bruce
Carlsten)
1. The project team should work with the program management to bring the 5-
keV high repetition rate performance of the FEL in line with the BESAC
recommendation. Due by March 2015.
2. The project team should develop a table of nominal operating conditions
consisting of [X-ray energy; electron bunch charge and length; peak photon
flux; photon flux/electron bunch; time-averaged photon power] spanning the
SXR and HXR X-ray ranges, backed up by a set of high-fidelity S2E
simulations which includes all the relevant accelerator physics. Due by March
2015.
DOE Status Review (Sect 30 – Oct 2)
Injector/Linac Recommendations (D.C. Nguyen & P. Piot)
1. Complete full 6-D beam characterization at APEX and Cornell facilities in
support to selected gun by end of Q4FY15 -- use conservative parameters for the
VHF gun (e.g., lower gradients) to mitigate dark current + avoid another incident
2. Consider early commissioning of the LCLS-II VHF gun at SLAC:
• installation of the photocathode laser system as early as possible• and alternate injector “layout 2” would allow for (i) a diagnostics section and (ii)
full characterization of the emittance-compensated beam at ~10 MeV (one
“capture cavity” is easy to cool without the CHL)
3. Explore the effect of laser-bandwidth on laser-heater trickle effect.
DOE Status Review (Sect 30 – Oct 2)
RF System Recommendations (Ali Nassiri/ Alessandro Fabris)
1. Finalize Engineering Specifications and Engineering Interface Documents
for the LLRF Controllers system. Produce a technical note that captures
engineering design performance specifications including phase and amplitude
tolerances with assigned bandwidths, due by March 2015.
2. Develop a preliminary design of the LLRF Controllers system. Hold a peer-
review of the system due by December 2015.
3. Complete cavity simulator. Focus on understanding off-line
calibration/simulations that will influence system design choices ( e.g.,
reference line drift compensation scheme) due by December 2015.
DOE Status Review (Sect 30 – Oct 2)
Undulator Recommendations (Toshi Tanabe & Joachim Pflueger)
1. Make a decision on the type of XHR undulator soon. If there is no clear
decision towards VPU from the user side soon, the decision should be based
on minimizing risks for the project. The LBL design is close to production
readiness and is in full compliance with the LCLS II schedule.
2. Continue working on the collimator system and provide more detailed
information.
End