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MAD Deck Updates

MAD Deck Updates. Tor Raubenheimer October 15, 2014. MAD Deck Status. March 2014 deck was costed in June meanwhile decks continued to evolve including updated diagnostics, interference fixed and correction of physics limitations

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MAD Deck Updates

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  1. MAD Deck Updates Tor Raubenheimer October 15, 2014

  2. MAD Deck Status 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. LCLS-II MAD Decks, Sept. 26, 2014

  3. Modifications in August 2014 From March 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 LCLS-II MAD Decks, Sept. 26, 2014

  4. 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

  5. End

  6. Options for Robust Lasing at 5 keV Tor Raubenheimer October 15, 2014

  7. 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: • Review 100 pC operation • Operation across parameter range (300 pC – 10 pC) • Performance with increased beam energy • Performance with reduce undulator period • Other options could be considered using new technology (SCU’s) Options for 5 keV, October 15, 2014

  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) Options for 5 keV, October 15, 2014

  9. FEL X-ray Power at High rate (slide #9 from my review talk) See LCLSII-1.1-PR-0133, LCLS-II Parameters X-ray Power using 4 GeV SCRF Linac ̶ SXR SASE ̶ HXR SASE ̶ SXR Seeded XTES limit X-ray power goal Power estimated for 100 pC and 300 kHz • 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 betterthan analytic curve shown • XTES is designed to handle up to 200 Watts • Studying methodsof turning down FELpower other than rep.rate Options for 5 keV, October 15, 2014

  10. 100 pC, 1 kA: HXR SASE simulation results @ Eγ = 5.0 keV (slide #6 from Gabe Marcus review talk) E ~ 10.3 μJ At 300 kHz (120 kW)  3 W x-ray power ΔEFWHM~ 2.8 eV ΔEFWHM/E0 ~ 5.6 x 10-4 Options for 5 keV, October 15, 2014

  11. 100 pC, 1 kA: HXR SASE simulation results @ Eγ = 5.0 keV E ~ 10.3 μJ At 300 kHz (120 kW) 3 W x-ray power ΔEFWHM~ 2.8 eV ΔEFWHM/E0 ~ 5.6 x 10-4 Performance @ 100 pC can probably be improved factors of ~2 using chirps etc.

  12. Summary of 100 pC Operation at 5 keV • 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. • 100 pC operation at 5 keV is not robust • Solutions include decreasing the beam emittance, increasing the beam energy, or decreasing the undulator period. Options for 5 keV, October 15, 2014

  13. LCLS-II (SCRF) Baseline Parameters (slide 13 of review talk) See LCLSII-1.1-PR-0133, LCLS-II Parameters

  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 Options for 5 keV, October 15, 2014

  15. Injector Performance Speced slice e in coreat injector & undulator 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. Options for 5 keV, October 15, 2014

  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 Options for 5 keV, October 15, 2014

  17. Optimized Charge versus 100 pC Fixed ChargeUse full HXR Undulator length of 32 segments Compare 100 pC fixed chargeversus charge optimized forPeak pulse energy, Peak power, and Max. averagepower up to 5.5 keV. 5 keV operation reasonable Options for 5 keV, October 15, 2014

  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 Options for 5 keV, October 15, 2014

  19. Comparing different beam energies – charge optimizedUse 80% of HXR Undulator length (26 segments) 67 uJ@ 4.0 GeV180 uJ @ 4.2 GeV 150 uW 41 uW All cases use optimized bunch charge and rep rate for 120 kWand 26 undulator segments.3~4x more power at 5.0 keVwith 4.2 GeV than 4.0 GeV Options for 5 keV, October 15, 2014

  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 Options for 5 keV, October 15, 2014

  21. Comparing different undulator l – charge optimizedUse 80% of HXR Undulator length (26 segments) All cases use optimized bunch charge and rep rate for 120 kWand 26 undulator segments.3~4x more power at 5.0 keVwith 24 mm than 26 mm Options for 5 keV, October 15, 2014

  22. Tuning Ranges from SCRF for 26 and 24 mm period HXR 26 mm HXR period 24 mm HXR period HD Nuhn 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 Options for 5 keV, October 15, 2014

  23. Pulse Energy from SCRF for 26 and 24 mm period HXR 26 mm HXR period 24 mm HXR period With 26 undulators at 5 keVget roughly ½ pulse energy With 100 pC get ~8uJ at 5 keV 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 Options for 5 keV, October 15, 2014

  24. Tuning Ranges from CuRF for 26 and 24 mm period HXR 26 mm HXR period 24 mm HXR period HD Nuhn 24 mm offers greater energy reach than 26 mm (38 versus 35 keV) but reduces pulse energy in mid-energy range Options for 5 keV, October 15, 2014

  25. Pulse Energy from CuRF for 26 and 24 mm period HXR 26 mm HXR period 24 mm HXR period HD Nuhn 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 Options for 5 keV, October 15, 2014

  26. Summary • 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 • 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 • 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 Options for 5 keV, October 15, 2014

  27. End

  28. Recommendations from DOE Status Review Tor Raubenheimer October 15, 2014

  29. DOE Status Review (Sect 30 – Oct 2) Accelerator Physics Recommendations (Stephen Milton & Bruce Carlsten) 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. 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.

  30. DOE Status Review (Sect 30 – Oct 2) • Injector/Linac Recommendations (D.C. Nguyen & P. Piot) • 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 • 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) • Explore the effect of laser-bandwidth on laser-heater trickle effect.

  31. DOE Status Review (Sect 30 – Oct 2) RF System Recommendations (Ali Nassiri/ Alessandro Fabris) 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. Develop a preliminary design of the LLRF Controllers system. Hold a peer-review of the system due by December 2015. 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.

  32. DOE Status Review (Sect 30 – Oct 2) Undulator Recommendations (ToshiTanabe & Joachim Pflueger) 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. Continue working on the collimator system and provide more detailed information.

  33. End

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