ITRP Comments on Question 19GEK 90604

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ITRPComments 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 RD 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

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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.

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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.
• ????????

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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 RD to develop the NLC PPM
  klystron
• Being done at KEK/Japanese industry, but v.
  important.

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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

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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.

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Conclusions(Vulnerabilities and RD needed for
a full technical design)

• 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.
• Modulator
• 2-pack modulator design still needs finalising
  and testing with two PPM klystrons.
• 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??

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Conclusions (cont)

• 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.
• 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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• 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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• The present 2-pack modulator undergoing tests is
  not the
• final version and has a lower efficiency than
  design.

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• YES
• HYBRID UNDER TESTlt NO FINAL DESIGN
• ONLY 2 TUBES BUILT OPERATING AT 120 Hz. ANOTHER
  TUBE BEING TESTED.
• EXPENSIVE AND INEFFICIENT, BUT MEETS SPECS.

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