ILC GDE Director's Updates
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GDE Executive Committee: Public Meeting Minutes
30 November 2006
B. Barish, T. Raubenheimer, G. Dugan, B. Foster, N. Walker, K. Yokoya, M. Nozaki
When we create a CCB, we gave it a big responsibility. It was asserted in Valencia, that we had created a rubber stamp system. This is not the case. The CCB makes recommendations dependent on the classes. It is not the EC’s job to question the CCB, but to assess the CCB recommendations and broader context for the decisions going beyond CCB authority. We should ask --
- What was the process
- Is there anything about the report that is inaccurate to the outside
- Cost Issue. What can we afford and what are the other choices.
We haven’t given the CCB guidance on how to evaluate costs. EC needs to determine the cost process. We need to stick to EC guidelines.
A lot of money is involved on CR#20 and the EC will look very hard at what other opportunities do we have. What would be acceptable?
Nobu’s notes on questions and this was circulated to the CCB.
Barry, after the opening, asked if I wanted to say anything and I said the following -
1. Basically the CCB report is supposed to speak for itself, so it is OK by us (CCB) for EC to make its judgment by just reading it only.
2. If you ask, two things may be pointed out which the CCB report did not manage to fully elaborate -
- CCR#20 indicated that if cavities are assumed to be operable at 33.5MV/m that means a 6% overhead. Some within CCB pointed out (I think that was Kiyoshi), then why not claim a 6% cost reduction. After some deliberation CCB decided not to bother to remark, but it is certainly not true that CCB did not look at any cost reduction opportunities. CCB felt that it just did not make sense with given status of BCD spec definitions and actual status of R&D.
- If one looks at the HLRF/LLRF power overhead table, you find that actually Chris A's and CCB's accounting on LLRF are not that different on average. A difference is that CCB felt some ambiguities need to be taken into account in LLRF accounting. Another difference, which is actually a lot more significant is the HLRF accounting, where CCR#20 did not appear to adequately consider losses in circulators and variations of cavity gradient. Chris A seemed eased up on them, and CCB is not.
Then a few Q/As.
Q (Barry). EC heard criticisms on the CCB report concerning CCB did not seem to spend enough effort looking at CCR#20b. Comments?
A. Quite the opposite. CCR#20b was the topic that CCB spent the most of its time about first, because its cost implications are much more obvious than others. But the majority of CCB concluded that it cannot approve it. Then moved on to CCR#20a, with inputs from LLRF whose exchange with Chris started protracting. It looked better to return the whole thing to them to chew on on their own first, and that is when I decided to put an end to it. The conclusion for CCR#20c came out naturally once we settled on CCR#20b and #20a.
Q (Gerry). Is that the reason for CCB's rejection of CCR#20b came from the fact that the spec on the allowed luminosity loss in case of RF shortage was unclear?
A. That is one element but is not the whole story. The other element was that the gradient reach of the cavities, once they were installed in CMs, is unclear. BCD only says 31.5MV/m on average, and otherwise it is pretty unclear about distributions and our current understanding is unclear, too. There is a reference to 35MV/m goal at the vertical testing stage, but majority opinion of CCB was that is not enough to determine the cavity performance in the horizontal cryostats. So we lacked both the reasonable estimate for the energy reach *and* the guidelines concerning the luminosity compromise. We cannot resolve CCR#20b unless we resolve "both", and that is why CCB said it cannot approve it just for the sake of the request from ML AG alone. We need a fuller story on cavities and EC-type executive order on performance defs.
C (Tor). The distribution of available gradient reach of the cavities is not known at this moment.
A. Yes, that is exactly the point.
C (Barry). EC will look at the whole issue carefully. It is true that CCB had to work in an environment without the cost vs performance guidelines that it sought. It is also true that real final version of Hoyer's report came out only on Nov.20, and is not yet on public circulation. Its statement is somewhat different from what he reported at Valencia. They now only request the energy reach to 500GeV. No reference to the luminosity.
A. Whatever they say, GDE has to circulate its own guidelines in ways compatible with ILCSC for its internal consumption, and that is GDE's responsibility, not the physicists'. We should note that most of the engineering folks do not care exactly what the luminosity numbers are. Rather, they need some numbers that can be translated into the HW specs that they have to build. We need something that makes sense in their engineering world, not merely to AG leaders and above.
Q (Tor). What is the gradient variation CCB used for its RF accounting?
A. 2.3% for RF accounting.
Q (Tor). If that changes, and if the shape of the distribution changes, many things will change, right?
A. Exactly. The lack of our knowledge there is one of the things that plagued our way towards a straight approval.
C (Barry). Our thanks to CCB for the efforts in doing this review. However, cost reduction is important and EC will look at the issue from that perspective, too. If EC makes decisions different from what CCB recommended, it is really from that perspective, not that EC disagrees with the logic that CCB had to follow through. It does not mean any sort of repudiation (Barry used that word "repudiation") from what CCB did, and I would like to make sure you know that.
[Barry repeated this twice or three times].
A. OK, BTW, if you redefine the klystron spec to be 11MW instead of 10MW and decide to assume WGs and circulators with Cu plating the whole equation of motion changes quite significantly. CCB report did not write it since making suggestions for designs does not belong to CCB's charter, though.
C (Barry). We realize that, and EC will suggest doing something like it.
We cannot walk away from the money change. We need to stick the guideline. Some of the savings in Valencia are not there. We are to fall short of our 30%.
To accept the reformulated CR looks flimsy. CCB did get hung up on the technical details that many have derailed them. We are looking at a soft edge on energy. Policy and change design can only come from management. We are allowing the risk to increase, than many of the arguments disappear. Very caught up on numbers. We are allowing a higher level of risk.
With a statement from the parameters group we can do this.
Agreed – we have to do this without damaging structure.
Provide info that they don’t have. If we produce a graph, everything will be better defined.
This can only be done by assumption
We must provide a standard deviation.
We don’t need it, cannot be realistic.
Go to work on the issue. Timescale is an issue. Reaction is worrisome.Parameters group is the new guideline. We will send something to the TS to continue the work.
The change is going to be made. We need to put something back through the system along with assistance from Chris A. It must succeed.
Is everybody comfortable with this – yes. Tor to take the lead. Decision memo to circulate. Input needed for draft.
Agenda was circulated for the MAC and was reviewed by Ferdi. MAC should be a technical review but will be probably focus on costing. How do we approach the MAC review? Review panel is better as a technical review. For purpose of planning, we will use our agenda and gives guidance on who should be there. Assignments may change but we will use the same people. We do not have a formal charge.