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*Subject*: [CCB-930] RF Power Accounting Issue with CCR#20*From*: N.Toge <toge@xxxxxxxxxxxx>*Date*: Mon, 20 Nov 2006 12:57:20 +0900 (JST)

Dear Colleagues, CCB has received a communication on Nov.16 from Brian Chase concerning the topic above. Although all of you must have received a summary from Stefan Simrock and a write-up from Sergei Nagaitsev earlier, since not all of you may have received Brian's email, I am attaching it below. I hope this is OK with him. Brian has produced an excel sheet in which he tried to list up the power losses to consider in each of our systems. While there may be some differences of opinions among us all, I would highly appreciate his attempt at putting many issues to consider into a very nice perspective. Now, I have picked up Brian's excel sheet and created my version where I tried to compare his claim with what I think we heard from Chris Adolphsen during the CCB hearing at Valencia on Nov.9. I am attaching my excel sheet, too. The first page shows the calculations for 9-8-9. Several notes. 1. Brian proposes to consider 5% de-rating factor for the klystron performance during its lifetime, and has done his accounting as such. My objection is that when we say 10MW, we had better mean to mean that a tube is to produce 10MW for ITS ENTIRE LIFE. In other words, "10MW lifetime" is the lifetime + performance to consider for klystrons. (I think CCB had better clarify this "assumption" in its recommendation report, whatever CCB ends up saying) Therefore, I produced my column labeled "Toge (20061120)", and it it the de-rating factor is 0%. 2. Brian is considering 3% loss due to the circulator, besides the waveguide, and he also considers modulator ripples, and power loss due to cavity gradient variation in the area of HLRF. His net HLRF power loss amounts to 18%, as opposed to Chris's 5% or Toge's 13%, whose only difference from Brian is that Toge does not consider klystron de-rating 5% to be a valid entry to consider here. 3. Brian moves on to account for LLRF loss factors, or loss factors and tuning factors put together, to be more exact. By taking a linear sum of these factors he ends up with 12.3%, while Chris claimed that approximately 10% is available. Brian's individual accounting for the LLRF factors seems reasonable to me. However, I am not entirely sure if we should take a linear sum or a square sum for these LLRF elements, so I have inserted rows indicating both. The truth would be somewhere in between, I guess. 4. The net result is that if one uses up all the "headrooms", Chris claims we can still reach 33.5MV/m. However, in Brian's accounting he can reach only 28.2MV/m... or the other way of saying is that Brian's result is short of the power headroom by 1.36MW. If we adopt a square-sum of LLRF loss factors, Brian reaches 30MV/m or the power headroom is -0.90MW. Similar calculations are shown for Toge's case where klystron de-rating is not assumed. 5. In summary, if we adopt Brian's ways of accounting for the HLRF and LLRF factors, although there are some variations of numbers depending on exactly what you include how, we are barely able to ensure operation at 31.5MV/m, The second page shows a case with 8-8-8. The differences of this page with respect to the first page are - Somewhat bigger loss factor for the WG, and - 24 cavs instead of 26 cavities. It shows, even in case of 8-8-8, if we follow Brian's accounting, we are barely ensuring 31.5MV/m. If that is the case, what we are observing is that - Before even talking about 8-8-8 vs 9-8-9, the CCB will have to ask the ML AG leaders to redo an adequate power accounting and come up with a version of the ML unit design that safely ensures operation at 31.5MV/m "on average" first. I WOULD LIKE TO UNDERSTAND HOW PEOPLE WOULD AGREE OR DISAGREE WITH ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ THESE ESTIMATES AND WHY, POINT-BY-POINT, AS SOON AS POSSIBLE. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Thank you for your attention and comments, remarks, words of wisdom, whatever constructive on this matter. Sincerely, - Nobu Toge (KEK, Accelerator Lab) email: toge@xxxxxxxxxxxx voice: +81-29-864-5224 fax: +81-29-864-3182

**Attachment:
CCR20-RF-Toge20061120A.xls**

---Begin Message---

Subject: [CCB-913] Response to CCR#20From: Brian Chase <chase@xxxxxxxx>Date: Thu, 16 Nov 2006 22:07:49 -0600To address the complexity of CCR#20, the LLRF team of Sefan Simrock,Shinichiro Michizono and Brian Chase have prepared a spreadsheet tocreate acommon format for discussion. The spreadsheet gives place holdersfor parametersthat impact the power delivered and the power required by the cavities.The values that we have chosen are our best 50% estimates. The othertwo sheetsexplore the effect of detuning and multi-gradient response to beamand no beam conditions.Best Regards, Brian Chase

Attachment:ILCPower_Mic.xls

Description:Binary data

---End Message---

**Follow-Ups**:**Re: RF Power Accounting Issue with CCR#20***From:*Sergei Nagaitsev

**[CCB-932] RF Power Accounting Issue with CCR#20 -- corrections***From:*N . Toge

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