12-March-04
To: Laboratory Directors
From: ITRP
To guide and make our site visits most useful, we have assembled a set of questions we would like to pose to the proponents of each technology. Clearly the status and plans for the TRC R1 – R4 have a large overlap with our questions and are a prime focus.
Nevertheless, we have formulated a set of questions that address scientific issues and technical considerations that we need to better understand as we work toward making a technology recommendation. Some of this may already be documented and only needs to be pulled out for us. We propose that you give us written answers to these questions, but they may also provide some guidance to you in where to place the emphasis in your presentations during our site visits.
Clearly, our panel process is just getting underway and our focus and questions will become sharper as our process evolve.
1) Please analyze for us the prospects and problems associated with achieving the parameter goals outlined in the report of the Parameters Subcommittee of the ILCSC.
2) Describe the methods for measuring the luminosity profile with energy, absolute beam energy and polarization to the specified precision.
3) Are the klystrons now developed sufficiently to power the LC in an efficient way at full energy? What further development is necessary? What margins are needed for adequate performance in the number of spares, MTBF, delivered power, pulse shaping? What is required for breakdown recovery, repair and replacement procedures?
4) Describe the tests and simulations needed to demonstrate that the couplers between waveguides to the linac vacuum within structures or cavities will be sufficiently robust.
5) How will the low level rf systems required for bunch compression, cavity tuning, machine protection, etc. be designed so as to perform reliably enough not to compromise machine operation?
6) Describe the positron production design, and detail the measurements and simulations needed to establish the mechanical, thermal designs and the system reliability. Describe the reasons for your particular choice and the advantages and disadvantages.
7) Describe the steps in the scheme to align the rf structures/cavities, quadrupoles, BPMs, and beam delivery elements needed to obtain the ab initio gold orbit and subsequent corrections on the time scale of intrabunch train, train to train, and slower time scales from seconds to days. What tests assure that this procedure will work and what R&D remains? Describe the time requirements for the tuning procedures and distinguish between intercepting and non-intercepting techniques.
8) Evaluate the electron-cloud effects for the positron beam in damping ring, bunch compressor, linac, and beam delivery system. Is there an R&D plan to cure them?
9) What demonstration can be offered now, or during the R&D phase, that the damping rings design is robust with respect to space charge induced emittance growth, fast kickers, the x-y emittance coupling and emittance growth limitation. What estimates for loss of beam availability can be made? Describe the timing requirements for the tuning procedures.
10) What are the most severe radiation damage (to electronics or machine elements) issues, and how will they be mitigated? Describe the machine protection system and the studies needed to demonstrate its effectiveness? Describe the analysis of probabilities for catastrophic beam loss.
11) Describe how the effects of power supply failures on integrated luminosity will be mitigated.
12) Describe the way that vacuum failures in the linacs will be controlled so as not to compromise machine operation or cause damage to sensitive components. What is the impact from repairs that require bringing major sections of the linac to atmospheric pressure?
13) Describe the steps needed to operate the LC for precision electroweak measurements at 90 (or 160) GeV with the necessary control of beam energy calibration and stability. What special hardware modifications are needed? What luminosity may be expected? What setup time is required to change from high to low energy operation?
14) What is the time estimated to change the energy and re-establish stable operation by steps of ~1% (threshold scan), a few%, or more than 10%?
L-band specific questions
15) How can the R1 cryomodule test issue be addressed without the full cryomodule availability at this time?
16) What evidence can be given that the 2.5 km cables for transporting high voltage pulses from moderators to klystrons will provide adequate repairability and reliability?
17) How will the TESLA cryogenic systems be controlled to avoid loss of luminosity or component damage?
X-band specific questions:
18) Detail the status of the rf structure design and testing. What vulnerabilities still exist for structure damage that could limit the useful life of the accelerator complex. What further studies of the structures are needed to arrive at an engineering design?
19) 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.
20) The X-band collider has much tighter requirements for the alignment of the beam orbit with the structure axis, yet the basic instrumentatal precision for alignment is the same as for the L-band collider. The SLC had great difficulty reaching its design luminosity in part because of the difficulty in controlling the beam orbit How can it be demonstrated that the necessary control of the orbit can be obtained for the GLC/NLC?
21) Comment on the construction costs and life cycle costs for the two technologies, noting any exceptions or additional information that will help our understanding of the cost comparison.
22) What are the reasons and comparisons between one and two tunnel designs for cost optimization, radiation damage, rf system repairs and reliability?
23) What is the ratio of the cost increment for raising the energy from 500 to 1000 GeV to the cost of the baseline 500 GeV machine?
24) For L-band, provide a modified cost estimation for 500 GeV, assuming 35 MV/m operation and a shorter linac from the beginning. .For X-band, provide a modified cost estimation with unloaded gradients 60 and 55 MV/m.
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 the approximate cost of the technical system R&D needed to validate the design.
26) Show a technically limited schedule for proceeding to a full TDR, and estimate the schedule for the subsequent linear collider construction. What are the controlling milestones? What are the major technical schedule vulnerabilities?
27) Outline the key steps for industrialization of machine components, the likely remaining vulnerabilities in achieving them.
28) What is the site power required?
29) Provide a technically limited schedule, starting with construction, moving to operation at 500 GeV until 500 fb-1 have been accumulated, and followed by an upgrade to 1 TeV.
C. General LC related Questions:
30) Machine Goals
· Does your technology allow an earlier start to the physics programme, so as to be as concurrent as possible with LHC operation?
· How do you make the case for determining the final energy choice for the LC prior to LHC results? What if LHC results indicate that a higher energy than design is required ?
· What are the prospects of a luminosity upgrade ?
· Considering that LC will start much later (although it can have concurrent operation period) than LHC, what physics capability does LC have which LHC does not share? Can this be realized at 500Gev or does it require much higher energy?
31) : Does your technology offer a higher probability of reaching the baseline energy goal earlier, and why ? Would your technology allow an easier upgrade path ?
32) Does your technology offer a higher probability of reaching luminosity goal of acquiring 500 fb-1 within 5 years of turn-on?
33) Describe the effect upon your laboratory of a) the warm vs. cold decision, and b) choice of site.
34) Discuss the support of the accelerator community for your technology and to whatever extent your technology has outreach into other accelerator areas?