Question 25: Delineate the R&D program remaining before a technical design review (TDR) and full cost estimate can be prepared. What are the major projects and approximate cost of the technical system R&D needed to validate the design? Analysis: 1.Summarize the proponent responses 2.Use the TRC issues (R1-R3) to guide understanding of needed R&D 3.Some evaluative comments Paul Grannis June 2004

TESLA response: “all basic R&D for innovative components were done by end of 2000, and all tested in TTF; thus cost estimate is done.” But they do identify remaining major component R&D:  Demonstration of operable 35MV/m cryomodule  Long operation of RF power system at maximum loads, including modulator, HC pulse cable, klystron, rf power delivery  Optimization of electropolish facility and process procedures  System and value engineering for all large quantity components. TESLA identifies 77M€ (92M$) for R&D in (no salaries), of which 43M€ are associated with the XFEL, which serves as a TESLA testbed.

Further R&D noted:  Fast kicker for damping ring  Reliability studies  Accelerator physics studies  Full LC simulation (including ion instability, electron cloud, alignment tolerances) “Full cost estimate can be done in less than 1 year after site selection.”

What remains according to TRC (2003)? TESLA specific: R1: 35 MV/m cryomodule test (partially satisfied for components, not module) ‡ R2: several cryomodules in correct environment, with proposed power systems, beam, HOM couplers, alignment systems. Evaluate operational quench and breakdown rates. Both for 500 and 800 GeV. ‡ R2: development of damping ring kicker ‡ R2: simulation for damping ring particle loss, systematic and random multipole errors, wiggler errors; dynamic aperture of DR optimization ‡ R2: DR alignment tolerance for 500 → 800 GeV; suppression of e-cloud and ion instabilities ‡ R2: review of head on collisions and implication for extraction line design; possible redesign for crossing angle. R2: evaluate reliability and operability analysis for single tunnel. ‡ = noted in TESLA response

My comments on TESLA:  The damping ring for cold LC is not noted as major R&D item, but the range of issues here (vacuum, e-cloud, kicker, emittance control, operability constraints) make me believe that this will remain a necessary high priority area for R&D.  The high dark current seen on one cavity at 25 MV/m (not electropolished, non-standard assembly sequence) is a worry, and sufficient R&D to demonstrate that this is not a limitation for SC acceleration will be needed. Long term cryomodule tests at full gradient remain crucial.  Further evaluation of the e + production system and the impact of using full energy e  beam on commissioning will take effort  Ability of all components (not just cavities) to sustain higher rf power for 35 MV/m should be demonstrated.  If 0 o crossing, demonstration needed of electrostatic separators in radiation field, radiation effects on final doublet, masking, beam losses

X-band response: “baseline technologies are in hand and tested. Main R&D needed is for value engineering, industrialization, reliability, serviceability. Some R&D remaining for specialized components, and for seeking improvements to baseline design.” Many remaining issues are site specific (ESH, site preparation etc.) Final engineering and design will need to be done by GDO. Identified remaining R&D needs:  Life tests of X-band klystrons  Continued study of high gradient structures  Longer pulses length rf for klystrons, and DLDS studies  Positron production target lifetime and serviceability  Damping ring vacuum systems; chamber coatings to control e-cloud  Collimator materials and design  Optimization of IR design and detector interface  Instrumentation and controls

 Major effort will be industrialization; value engineering done by vendors. High volume components (modulators, klystrons) tested in stand-alone test stands.  Test component interfaces with NLCTA and GLCTA, expanded to 5-10 times number of sections as currently available (combined). Will include bunch compressor, full beam loading tests. About 1% of full LC. Upgraded NLCTA/GLCTA will be used to test interfaces of systems, integration and operations issues. Will also be used to support high-power processing of structures during initial industrialization phase.  Development of instrumentation for emittance control (BPMs, girder, quad movers etc.) will be tested at NLCTA/GLCTA and ASSET. Final demonstration of control of emittance growth requires a linac of about 50 GeV; this much of X-band LC would be available 1-2 years before LC completion.

DLDS offers 15% improvement of power efficiency over SLED II; operation at longer pulse time (  s) allows 14% improvement of modulator efficiency; longer pulses allows reduction of number of klystrons by factor 2 and reduction in number of modulators, low level rf R&D required includes demonstration that higher stored energy can be managed (can do with SLED II systems); Tests at 600MW (can do with SLED II; have run briefly at 580 MW; need time after solidifying baseline SLED II) Demonstrate that rf power sources can operate at 3.2  s R&D plan: 1.Verify baseline with SLED II; high power tests of SLED II 2.Test klystrons and modulators at 3.2 ms as they can find time 3.Potential demonstration DLDS system at NLCTA/GLCTA : decide if DLDS or SLED II

NLC estimates 111M$ for materials and supplies for , including costs of systems engineering (20M$). Manpower estimate – 782 FTE units (1800 hrs=1 working year). Further costs after site selection estimated to be 145M$ and 527 FTE units. GLC estimates 88 Oku ¥ for (80M$) including systems engineering and khrs manpower (370 FTE units). Added cost after site selection is 27.5 Oku ¥ (25M$) and 222 khrs manpower (123 FTE units). GLC estimates did not include NLCTA upgrade. Neither includes contingency, operations costs for test facilities, bid to host costs.

What remains according to TRC (2003)? R1: validate 65 MV/m structures with design detuning, irises (claim satisfied) ‡ R1: demonstrate full power full length pulse klystron/SLED-II operation (claim satisfied) ‡ R2: full test of PPM klystron at Hz and develop alternate prototype ‡ R2: test klystron with IGBT modulator at full specs. ‡ ‡ = noted in X-band response

My comments on X-band:  Although studies and tests of the method for controlling wakefields and emittance growth in X-band have been done, the small tolerances and centering techniques required suggest that further R&D with expanded sets of test structures will be needed.  Positron target needs more R&D  Extraction losses are too high, background mitigation at IR requires more study

TRC R&D issues – common to both technologies: R2: simulation of damping ring electron cloud suppression R2: fast ion instability studies R2: damping ring kicker stability (10 -3 needed) R2: simulations of emittance growth in DRs R2: static tuning studies for full low emittance transport sections R2: beam instrumentation; intra-train luminosity, laser-wire profile detector, etc. R2: prototype of main linac girder/cryomodule mechanical; vibration studies R2: subsystem reliability study to verify needed redundancy/ MTBF’s R2: beam based tuning demonstration for magnet, structure alignment in realistic operation.

My comments on common issues:  R&D on undulator positron source needed  Electron cloud effects are still worrisome, and more R&D will be needed to be sure these do not limit emittance.  Final doublet stabilization scheme needs study  Damping ring impedence budget must be verified  Collimator wakefield studies  Availability analysis – MTBF/MTTR  Study of failure modes and machine protection system needs work

Comments: 1.To date, there has been more attention to R&D on those features of a design that distinguish warm from cold than on the common problems. This is less true for X-band where more work on alignment, reliability, low level rf etc. seems to have been done. 2.Since the design will be re-evaluated by GDI after technology choice, there will be some added R&D to verify modified designs, thus lengthening the R&D phase and adding some cost. 3.Site specific issues will force some additional R&D once site is selected. 4.System and value engineering and reliability analysis will be a major theme up until start of construction; warm and cold need this equally. Budget for X-band R&D included this; L-band had less. If R&D does not converge rapidly, industrialization costs will escalate. 5.Costs of R&D effort for next three years looks comparable; excluding system engineering/industrialization, estimate materials and supplies funds of 64 M€ (77M$) [TESLA], 91M$ [NLC], 81 Oku¥ (74M$) [GLC] in three regional estimates. GLC and TESLA estimate has less for systems engineering (~$10M) than NLC (~$20M).

Comments: 6.The R&D effort in the coming years will focus increasingly on  industrialization,  reliability of components,  tests for many specific, ‘non-headline’ components (kickers, vacuum systems, mechanical supports, beam instrumentation etc. etc.),  full simulations of full LC emittance growth, electron cloud effects,  IR instrumentation,  Fault analysis and machine protection etc. The breadth of these activities, and the interplay between this R&D and LC design, will make it difficult for the R&D phase to be completed in the three years envisioned. 7.It is hard to distinguish between the remaining R&D costs for warm or cold machine. 8.Both technologies retain risks that require further R&D

Evaluation: A great deal of R&D is needed to provide a truly integrated overall LC design, for either technology. It will be a big challenge to complete the final design and this R&D in a timely fashion. This R&D will be conducted under a new organizational structure that will struggle to become efficient rapidly. Since much of the remaining R&D concerns issues other than SC rf, structure breakdown, klystrons etc. that make the primary differences between machines, it is likely that the remaining R&D time is comparable for the two machines. X-band has studied a fuller range of issues than SC; some of this work (IRs, bunch compressors, reliability and availability, sources, BPMs etc) could however be transferred to cold if chosen. R&D costs for the two technologies are comparable; both have probably underestimated the time needed for R&D and thus total R&D cost.  I do not see that the R&D needs distinguish significantly between the cold and warm LC choices.