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1、BEPCII LinacPeiPei GuoxiGuoxi for the BEPCII-for the BEPCII-LinacLinac Group GroupInstitute of High Energy PhysicsChinese Academy of Sciences Progress of the BEPCII Progress of the BEPCII LinacLinac Commissioning Commissioning ( 4thIMAC( 4thIMAC ) )Date1BEPCII LinacThe Committee suggests paying part
2、icular attention to the following details in 3rdIMAC and our responsesIn order to obtain the specified 2degrees RF phase stability, a temperature stabilized reference drive line needs to be established with a temperature coefficient of 0.1 degree per C.The reference lines temperature coefficient is
3、5ppm/C, and will be stabilized with cooling water within 0.2C. Measuring and adjusting the RF phase with respect to the beam is not planned, but appears to be desirable. Based on some experiences, the beam induced signals are not so clear and so stable, hence the energy maximum method is adopt to se
4、t the right RF phase. The Committee encourages the LINAC team to exercise the transport of the full energy beam into the injection channel as early as possible to preserve some flexibility within the tight schedule in case of unforeseen problems.Yes, this will be done soon.Date2BEPCII LinacThe Commi
5、ttee would like to encourage the BEPC-II team to try to accommodate the full sub-harmonic bunching systems program or at least keep it as a high priority valuable upgrade option. The potential benefit may not only be the slightly increased injection efficiency but these systems may also contribute s
6、ignificantly to providing tolerable condition for the colliding beam detector during top-up operation. It is planning to apply the budget, and may finish the technical design by full 2005, construction in 2006, be measured and RF conditioned in the 1st half 2007 and will be installed in the tunnel i
7、n summer 2007. With regard to operations, the Committee would like to mention that a single spare klystron might not be sufficient to provide the high machine availability necessary for the anticipated top-up mode. The Committee suggests to re-assess the probability for system failures based on BEPC
8、-I linac and SLAC linac operations.It is planed to make each 45-50 MW klystron be operated at 35-40 MW output, then two spare klystron may be possible; as a back-up version, one more SLAC-65 MW klystron may be prepared to instead of one 45-50 MW klystron and keep the total 16 klystron constant.Date3
9、BEPCII LinacContents1. Sub-systems upgrade progress 2. Machine commissioning 3. ProblemsDate4BEPCII Linac1.1 Pre-injector 1. New electron gun (done) 2. Bunching, RF system 1. Sub-systems upgrade progressDate5BEPCII Linac200Kv High voltage station LINACElectron gunNew electron gunDate6BEPCII LinacDat
10、e7BEPCII LinacGun controller No.3, No.4, No.6 and No.9 small leaked! We soon started co-investigation with Toshiba and KEK experts, and found that No.11 window was dirty, but not too bad, No.7 and No.5 were badly contaminated with (C, Al) and (C, Cu, stainless steel) respectively. We replaced these
11、three tubes, and took many measures to protect this kind of things happen again.Date67BEPCII LinacDate68BEPCII LinacDate69BEPCII LinacDate70BEPCII LinacRenew the vacuum system 60 old ion pumps (70 l/s) and power supplies have been replaced by the new or repaired ones, due to the aging problem (more
12、than 20 years) . 22 old vacuum gauges have been replaced by new ones (Belzers), more reliable and precise, more safe interlock. 30 l/s ion pumps is added at each klystron power output. The Klystron and valve vacuum interlocks are improved.Date71BEPCII LinacDate72BEPCII Linac30L/s ion pump150L/s ion
13、pump70dB pumping waveguideDate73BEPCII LinacThe gradients of unit No.5 RF structures, presumably No.16 as well were degraded caused by arcing Without beam, we took almost a month to process No.5 klystron to 33MW, very hard. With beam, the output power gradually back to a very low level. Through hard
14、 processing, it can stay at 10MW, but once the arcing happens, out- gassing is terrible. We are going to further investigate, and replace the 4 RF structures in due time.Date74BEPCII LinacSchematic of No.5 acceleration sectionDate75BEPCII LinacBefore processAfter processDate76BEPCII LinacA8 RF struc
15、tureRF process without SLEDDate77BEPCII LinacA10 RF structureDate78BEPCII LinacRF process with SLEDPb-klyPb-A9Pb-A10JitteringDate79BEPCII LinacPb-klyPb-A8Pb-A9Pb-A10JitteringDate80BEPCII LinacSummary Through three more years hard working, weve got some preliminary, but good upgrade results. Hopefull
16、y, we can reach all design specifications by the end of July this year. But, testing and reaching a goal is one thing, long term stable operation with a very good beam quality is another story. Well pay more attention on this issue, keep system improvements and/or upgrades continuously and guarantee a single device to work properly. SHB system as one of the second phase upgrades will be sped. The rough schedule is that the system will be ready by the end
