Option – 5m Undulators What is the optimum length for an LCLS undulator?  XFEL is using 5m undulator segments.  Is this optimum?  What are the advantages and disadvantages of long (or short) undulators. Slide 1Undulator Alternatives- 5m, M. Rowen,

XFEL Undulators Joachim Pflueger claims 5m devices are more cost effective than short undulators.  A quick and crude calculation for 5m undulator for LCLS- II is a savings on the order of $12M.  Undulator costs based on Pflueger’s reported costs.  Requires 34 vs. 50 segments.  The saving is in the reduced number of inter-space quads and phase shifters. Slide 2Undulator Alternatives- 5m, M. Rowen,

Technical Differences LCLS-II:XFEL LCLS-II undulators must go to smaller gap:  7.2mm vs. 10mm. SXR undulator longer period:  55mm vs. 48mm. There is debate at XFEL about their SXR undulator parameters so do not know what there current SASE-3 plans are. Both lead to larger force at minimum gap. Recommend more prototyping for 5m device to reduce risk.  This would cost in ~$2M for addition generation of prototype.  Add ~one year on to schedule. Slide 3Undulator Alternatives- 5m, M. Rowen,

Technical Differences (cont.) The SXR undulator is calculated for 8m  :  Would have to increase  for beam based alignment down to 4.3GeV.  Increased  lightly lower performance  Or limit operations to higher energies The converse is also true: Setting a higher limit to low energy operation and keeping 3.4m segments could allow slightly improved performance. Aligning longer devices will take less effort:  Similar layout possible with fewer monuments and fewer set ups => faster process. Slide 4Undulator Alternatives- 5m, M. Rowen,

5m XFEL Undulator The XFEL undulator is a highly engineered device. It is operating at near the limits of tolerances. Might not extrapolate to the higher LCLS-II forces. Slide 5Undulator Alternatives- 5m, M. Rowen, Point Support System - reduces deflection of beam – less rotational stable. Rotational stabilizers.

Other Potential Costs The $12M does NOT include Costs of:  Longer vacuum system. Not calculated, but likely to increase with length.  Larger Magnetic Measurement Facilities. To expand MMF at SLAC to accommodate 5m segments $+5M, vs. $1-2M to expand for 3.4m devices. (rough estimate) As LBNL is starting fresh on an MMF the incremental costs would be less. Both plan to do MMF upgrades off project. –Higher off project costs might not be acceptable. Hall probe benches ~$1M vs. $700k.  Stiffer beams and large drive systems for larger forces. Probably could be achieved at some higher cost, say 10%, or ~$1.7M. Slide 6Undulator Alternatives- 5m, M. Rowen,

Summary Technical:  Risk is higher with long device & due to the larger forces.  Have to modify the  on the SXR undulator line slightly. Cost:  5m devices should save on alignment (not calculated).  MMF cost for 5m devices is significantly higher (~$3M). Not on project, but still an issue.  Increased bench costs ~$900k.  Additional prototyping ~$2M.  Increased cost in undulators ~$1.7M  Delaying the schedule 1 year +$?M. Slide 7Undulator Alternatives- 5m, M. Rowen,

3 factors indicate that 5m is too long for LCLS-II. 1.MMF’s for 5m devices would cost significantly more at SLAC. 2.5m devices are higher risk. 3.5m devices will take longer to develop if risk is to be minimized. Slide 8Undulator Alternatives- 5m, M. Rowen,

Conclusion $3-8M in savings are not a strong driver to go to 5m undulator segments. To reduce risk it will take ~1 year longer to develop. Stick with shorter devices:  It is not clear what the exact optimum length for LCLS-II undulator segments is.  It does not have to be 3.4m. Slide 9Undulator Alternatives- 5m, M. Rowen,