April 14, 2006
HLRF2 TV and Indico Meeting, 3-5PM PDT
Attendees: S. Fukuda, H. Hayano, M. Shidara, M. Akemoto, A, Kazakov, KEK; N. Solyak, C. Jensen, FNAL; C. Adolphsen, C. Nantista, M. Neubauer, R. Cassel, R. Larsen, SLAC.
1. Distribution: Shigeki Fukuda reviewed the waveguide distribution tunnel layout as shown in his attached presentations. He described in detail a proposed welding procedure developed for the copper waveguide penetrations between the two tunnels. This assumes a single penetration with three waveguides, after combiners for the two 5MW window outputs, so each line carries 3.3MW. The lines are cooled by an attached copper water line. The losses in the straights are about 60W per meter average for each of 3 waveguides (not 700W as shown in the slides). The penetration size is approximately 17.5 inches or 45 cm.
The group liked the layout with two exceptions: One, the entire cryo-module should be shown much lower to the floor because the positron line (it was recently decided) will not go underneath, but above the main structure. Two, the waveguide structure on the cryo-module should be flipped vertically so the feeder waveguide is above, not below the structure. The feeder system should remain on the aisle side. The installation concept is that the feeder system be mounted on the cryo-module and all adjustments for matching made **before** being transported into the tunnel, so only one connection has to be made once installed in the tunnel.
The distribution drawing shows hybrid splitters with a tuning post (red dot in drawings) for amplitude adjustment. This is thought to be a very good design and Shigeki indicated this is being discussed with the hybrid vendor as a modification. Adolphsen wondered if this same feature could be added to the splitters that feed every cavity. There will be a phase shift which might be difficult to compensate at every cavity, but this should be looked at. On the main feeder lines it is not such an issue because a spacer could be used as a one-time adjustment.
2. Temperature effects: Chris Nantista presented some calculations on temperature rise in the waveguides and how it would affect phase shift. He also looked at feeder schemes that minimize the impact by symmetrical feeds, ideally of equal length. The effect of temperature on the waveguide is 1 degree phase for every 1.1 degree temperature rise. Adolphsen suggested that the best system would be if each feeder entered at the middle of the cryo-module and fed both upstream and downstream, and two of the three feeder lengths could be identical without extra guide. Since the fill time is very long compared with waveguide delays there is no operational loss of efficiency.
Chris Nantista also presented a response from Brian Rusnak of LLNL on how he derived the waveguide cost models shown at Snowmass. The answer is that the first costs shown in his table are single unit prices without any attempt at quantity pricing, so are artificially high for high volume parts; and the second set are his personal estimates of the cheapest possible price he could imagine for a custom design and competitive vendor manufacture situation. (Note - our intent is to make a new cost estimates for both these approaches.)
3. Modulator: Chris Jensen reported on some analysis of losses in the Bouncer Modulator system and whether these would be dealt with by water or air cooling. The **measured** wall plug to output to klystron efficiency is 86% for the 1% flat top delivered pulse. The 14% losses are distributed about equally among charger, main modulator and step-up transformer, with about 9% (13.5 KW) ending up in water and 5% (7.5 KW) in air. Chris will add these details to the cooling table started by Fukuda.
4. Klystron Cooling: Fukuda has made estimates in his table which he calculated from the Toshiba specification sheets. The inlet water temperature in the tunnel is being discussed by the Civil group. Water-cooled electronics racks would like no higher than 25C inlet, while the Thales tube apparently is happy up to 34C inlet. Civil is responsible for final design.
5. DESY Main Linac Meeting May 11-13: Adolphsen queried who from HLRF is going to the meeting. Adolphsen and Neubauer from SLAC, and Fukuda, Hayano and Shidara from KEK will attend.
6. Cost timeline and Goals: Larsen spoke to the Vancouver timeline and the review goals. To make the major milestone of having a "first cut" of all technical system costs, for **all** Areas including Linacs, Sources and Damping Rings, will require rapid gathering of data and establishment of models. The Main Linac model is near complete and will form the basis of the bulk of Sources estimates as well. The damping Ring uses CW klystrons in a system very similar to B Factories and it was suggested that Fukuda and KEK team take the lead in developing the component cost models. Then each Region can do separate costs from this model, and we will have to agree on a common solution for Vancouver. SLAC also has a lot of data from its B Factory and Neubauer worked on this system so may be very helpful as well. Finally, the general approach to the manufacturing cost model for each major component was briefly discussed. See the attachments for Larsen's talk for further details.
Ray Larsen