Lessons Learned from LCLS-1 2009

1. Lessons Learned from LCLS-1 2009 Rick Iverson 2-Nov-2011 for the LCLS Commissioning Team

2. LCLS-I 2009 Design and Typical Measured Parameters at 1.5 Å Paul Emma 2009

3. First e- to dump First e- from gun Commissioning Time-Line (2007-2010) • Commissioning • Project Milestones • Installation Periods First FEL Light Install Undulators Project complete First Light in FEH PEP-II ends X-Rays in NEH FEE/NEH Install First Light in FEE LTU/Und Sys Install First Users Injector Install BC2 Install 120 Hz J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J J F M A M J J A S O N D D A D M M 2007 2008 2009 2010 Down Down Down Down NEH FEH Linac Injector LTU/Und FEL/FEE Linac/BC2 Paul Emma 2009

4. 1) Many detailed injector, linac, and FEL computer simulations during the design stage lead to a good understanding of where things can go wrong, including unforeseen instabilities, identification of tuning strategies, and detailed tolerance studies, including stability tolerances. 2) Detailed pre-beam checkout conducted from the actual controls panels and verified in the tunnel with Hall probes, clip-on ammeters, simple tape measures, etc, ensures that the hardware and software is functioning at a fundamental level prior to beam. 3) Process automation and data analysis software fully prepared ahead of time to support commissioning activities, such as RF phasing, emittance measurement, general parameter scanning and correlation plotting, machine configuration control, beam-based alignment, etc. These processes are sufficiently complex that they would not be completed accurately or promptly enough without well prepared automation software, which must be ready BEFORE the commissioning begins. 4) Beam-based feedback loops implemented as the commissioning moves downstream so that upstream systems are locked in while the downstream systems are brought on line. Paul Emma 2009

5. 5) A 'layered' approach to commissioning whereby fundamentals are verified first (BPM scaling, linear optics, magnet operation, etc), before plunging into the more exciting phase of beam characterization. 6) A uniform plan focused on getting the machine up and running reasonably well and quickly, rather than a more academic approach where many various machine and system studies are executed sequentially, leaving the machine in an unknown and constantly changing state. 7) Detailed Physics Requirements documents written for each major system or class of components so that the hardware and software are designed to perform at the necessary level consistent with the expected performance of the full machine with minimal ambiguity. 8) Adequate budget and time to “do it right” Thanks, -PE

6. I would also include the technical review process. While we didn't always follow the committees' recommendations, it was still very beneficial to present our designs and plans to a fresh set of eyes. The injector and gun greatly benefited by being reviewed. Recall the laser heater chicane idea came from Todd Smith during an early injector review. And there were several good suggestions generated by the gun technical reviews. For example: z- coupling+racetrack, deformation tuning, controversy over gun probes, etc. In fact, Erik Jongewaard started as a reviewer but became so interested he volunteered to design the gun instead. So good technical reviews are high on my list. Also I would expand on your simulations and calculations point and include the integration of the RF-thermo-mechanical modeling of the gun with the desired beam dynamics. Electron beam simulations were used to define the required RF fields, which were used to produce the RF interior shapes, which were used to produce the metal surfaces, which were used to determine the cooling, ports etc. The final 3-d fields were then put back into the e-beam sims to verify everything was still good. This includes Cecile's hard work on the wakefields in the gun-to-linac region. And I'd like to mention the hard lessons we learned at GTF. Projects like LCLS need some form of test facility. Dave Dowell 2009

7. 1. Leaving as few mysteries as possible - not leaving a system until we understand what it is doing. We've had to give up a couple of times (the model problem early in the injector), but mostly we track down what is wrong before moving on. This is related to our unwillingness to move away from design without a good physics understanding. 2. Good BPMs. It is difficult to appreciate how good the LCLS / SLAC BPMs are unless you have worked at other labs. Without the ability to understand the orbit we would be in real trouble. 3. A control system that makes it easy for physicists to develop scripts. Imagine running without phase scans, correlation plots, matching, etc, etc, etc. 4. Spending LOTS of money. It is easy to forget that LCLS is a very expensive project (especially considering that we already had the linac). We had the luxury of having very high quality equipment throughout the machine. For example, for all that we may like to malign the RF system, most the time it provides sub 100fs phase jitters. 5. (number of commissioners) X (cups of coffee) - (hours of sleep) was a very big number. --- Joe Frisch 2009

8. Four additions for the undulators system - Having an exceptionally well tuned undulator system with minimum phase errors inside the undulator segments and the breaks. - Canted undulator poles and horizontal stage mounting enabled undulator K values to be set within tolerance. - Having a well thought-out alignment strategy for the beamline components in the undulator line, i.e., CMM girder component alignment and high-precision remote girder positioning mechanism with simple, orthogonal controls. - A well carried-out conventional alignment program positioned the components very close to their target locations. - Heinz-Dieter Nuhn 2009

9. 1. electron beam was good, a. laser worked well and was reliable b. cathode produced sufficient charge c. source emittance was small - good choice/design of gun d. emittance diagnostics and optics design were excellent e. dispersion matching in dog leg and bends could be precisely tuned f. high energy of electron beam helped to minimize effects of stray fields g. physicist checkout removed many obstacles h. flexibility of control system, ie. matlab and epics and scp i. plenty of time was available for commissioning the electron beam in stages 2. undulator system was good a. field quality/tuning/stability was excellent b. cam movers worked very well c. rfbpms had good resolution d. physicist checkout removed many obstacles 3. theory was good a. bba did what it was supposed to b. sasefel theory is solid, design parameters realistic c. understanding of COTR and other coherent effects was timely d. impedance were well understood e. compression/csr well understood and optimized in the design - Jim Welch 2009

10. Safety considerations: Commissioning of electrical systems was initially without oversight and procedure. Basically, we initiated a system of administrative lockout (by LCLS - RMB), and release when system commissioning and lockout safety planning (and documentation) was completed. (See RM Boyce) This worked so well, it was instituted in each phase of electrical commissioning from the injector to presently FEE. - Jim Turner 2009

11. Commissioning resources… http://www-ssrl.slac.stanford.edu/lcls/commissioning/