mad deck updates tor raubenheimer october 15, 2014

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

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)


1011 photons at 5 keV is ~80 uJ

(or 40 uJ if looking at spectral flux - SASE BW is 0.5x10-3)


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


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


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


• 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


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


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]


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]


Not Optimized


18

Option 2: Impact of increased Beam Energy


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]




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]




1.000 2.000 3.000 4.000 5.000 6.0000.200

2.000

20.000

200.000

2000.000

Average Power [W]





41 uW

150 uW

67 uJ @ 4.0 GeV180 uJ @ 4.2 GeV

20

Option 3: Effect of reduced Undulator Period


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


1.000 2.000 3.000 4.000 5.000 6.0000.001

0.010

0.100

1.000

10.000

Peak Energy [mJ]



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]



1.000 2.000 3.000 4.000 5.000 6.0000.200

2.000

20.000

200.000

2000.000

Average Power [W]



22

Tuning Ranges from SCRF for 26 and 24 mm period HXR


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


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


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


24 mm offers greater energy reach than 26 mm (38 versus

35 keV) but reduces pulse energy in mid-energy range


HD Nuhn

25

Pulse Energy from CuRF for 26 and 24 mm period HXR


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


HD Nuhn

26

Summary


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

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.


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.


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.


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.