gek 16/6/041 ITRP Comments on Question 19 GEK 9/06/04 19) For the X-band (warm) technology, detail the status of the tests of the full rf delivery system. What vulnerabilities still exist, and how much R&D is required to reach a full technical design? Note: This was interpreted in the responses by GLC/NLC as only referring to the SLEDII pulse compression system. I will interpret it more broadly

gek 16/6/042 Summary: R1:  Validation of performance of low group velocity structures with acceptable performance. Achieved, but testing with a significant number of structures only just started. Trip rates and damage needs more thorough investigation.  Demonstrate full power and energy handling capabilities of the dual-moded SLED-II pulse compression system. Achieved. R2:  Full test of a PPM klystron at 120 or 150 Hz Achieved, but only with 1 klystron so far, others in pipeline.

gek 16/6/043 Summary, (cont.): R2 (cont):  Klystrons to be tested with NLC modulator (at full specs and include arcing tests)………….. The tests should be made with beam. Partially achieved??? Tests done with 8 accelerator structures (1 girder), but some of these structures used the 8- stack modulator and it is not clear if they were powered by the only full spec. klystron.  Static tuning studies, including dynamic effects during correction, must be completed. In progress, but much has been done.  A detailed prototype of the main linac module (girder) must be developed to provide info. about on girder vibration. ????????

gek 16/6/044 Summary (cont.): R2 (cont.)  The performance of beam based tuning procedure to align magnets and structures must be demonstrated by complete simulations, in the presence of a wide variety of errors, in both the beam and in the components. Much has been done, but I believe much more needs doing. R3  The low level rf system needs further improvements ………. This is a complex and critical system. ??????  Long term testing of rf modules is required before mass production. Yes!!!  Continuation of R&D to develop the NLC PPM klystron…… Being done at KEK/Japanese industry, but v. important.

gek 16/6/045 Summary (cont): R3 (cont):  Development of the JLC-X linear induction modulator should continue ……… to improve the overall performance and reliability. I think this is happening at KEK.  The test recommended in R2 with a girder should be extended to a full test, with beam, of a complete linac unit, with 24 structures and 8 klystrons. I believe this is highly desirable as it would start to test linac rather than the components. However it is not likely to occur for some time, due at least in part to the availability of 8 PPM klystrons!  The magnetic centre stability (at the 1-10micron level) required in the quads must be demonstrated, over the relevant time scales of minutes to days. Yes! Not sure if this is being actively worked on we have heard almost nothing about the quads in the system

gek 16/6/046 Summary (cont): R3 (cont)  For the linac, the tuning procedures require structure alignment as well as quadrupole centering. There is a need to evaluate the systems aspects of a large interrelated alignment system. I believe that this is a crucial point in achieving the integrated luminosity goals of the machine. The complexity, size and tolerances of the whole machine is hugely challenging compared to anything yet achieved.

gek 16/6/047 Conclusions: (Vulnerabilities and R&D needed for a full technical design) 1.Klystrons Need to obtain several full spec. PPM klystrons from more than one manufacturer and lifetime test them under operating conditions. Further work on design of klystron to improve lifetime would be highly desirable both to reduce the labour of frequent replacement and replacement cost. 2.Modulator 2-pack modulator design still needs finalising and testing with two PPM klystrons. 3.Pulse compression SLED II has been demonstrated to meet spec. It requires engineering to improve manufacturability and therefore reduce price. DLDS (Delay Line Distribution System) development should, if possible be pursued, it should be more power efficient, cheaper??

gek 16/6/048 Conclusions (cont) 4.Accelerator Structures Industrialisation of full construction, not just components should be pursued. Larger assemblies of structures (at least 24) should be tested under full operating conditions in order to learn more about breakdown and damage as well as stability. Enough structures incorporating the quads and BPM and moving mechanisms should be assembled so that the stability can be verified. This will require powering and cooling. Further optimisation of the basic design to achieve even higher gradients would clearly be beneficial. 5.System integration This is a major concern for the warm machine. So far the largest unit is an 8-structure beam. Even this was not quite of final design. Really need a much larger prototype.

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gek 16/6/0412  Will not discuss the 8-pack Project, but assume that the modulator of choice is the “Next Generation Induction Modulator” the “Two Pack”.  This is a Solid State Induction Modulator using Insulated Gate Bipolar Transistors

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gek 16/6/0414  The present 2-pack modulator undergoing tests is not the final version and has a lower efficiency than design.

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gek 16/6/0421 YES HYBRID UNDER TEST< NO FINAL DESIGN ONLY 2 TUBES BUILT OPERATING AT 120 Hz. ANOTHER TUBE BEING TESTED. EXPENSIVE AND INEFFICIENT, BUT MEETS SPECS.

gek 16/6/0422 NEED TO UNDERSTAND BETTER CAUSE AND EFFECT OF BREAKDOWNS INDUSTRY NOT YET MADE ANY FULL STRUCTURES? STILL VERY SMALL SCALE, 5m OUT OF 10000m!