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93/R-031 (CERN)
ADTC
Laurette reported on the AD operation over the last 2 weeks. An MD was organized with reduced injection energy, as a first step towards observation of possible anti deuterium injection in AD ring. More MD's will be needed before we can have conclusions.
The BCCCA has been lost following the failure of 1 turbopump of vacuum insulation, causing helium boiling. A repair plan is being worked on by BI. Meanwhile, the beam intensity is obtained via an LPU, but only during bunched beam sequences, and with uncertain calibration.
Injector complex caused also beam time losses, with rather lengthy recovery times for AD.
The problems occurring on the magnetic horn were then discussed at length: 2 flashovers have been encountered on 13th and 14th of July, causing vaporisation of 2 bolts. Since then, the horn has been operated at lower voltage, causing a small drop by 5% of the beam intensity.
OP proposes to synchronize an intervention on the BCCCA and on the horn to fix the problems possibly during next week.
Sven explained the current understanding of the issue encountered on the horn, by comparison with a horn being pulsed on a test bench. It appears that due to repeated thermomechanical stress, some bolts become loose, and cause arcing. This is apparently due to a conception defect, making the system sensitive to the slightest deviation in geometry. As a consequence, the replacement by an identical horn is likely to give the same effects, with a delay difficult to estimate (the present production horn did not show any sign of degradation during visual inspection at the occasion of the TS in June). A new version of the horn (v3) is being worked on at the conception level to address the current defects observed on v2, but v3 requiring still design + construction + testing will not be available before end of August. In order to reduce the amount of highly activated wastes, STI proposes to delay the maintenance intervention till a v3 is available, probably in September. Lars argued that beam time losses are less damageable to experiments during the summer than later in the year when they are more actively taking data.
The subsequent discussion aimed at finding a compromise between all constraints. It was decided that OP will discuss with BI the intervention that could be planned on the BCCCA to check it could be useful to match it with a possible intervention on the horn. During this time, STI will continue development of a horn v3 and in parallel, put on the test bench the horn that could replace the current production one that is known to be degraded. Meanwhile, OP will continue operating the horn at reduced voltage. The experiment represented at the meeting (GBAR) indicated that they do not mind the 5% intensity reduction and that the next 2 weeks could be a suitable time for them for an intervention on the AD machine.
The conclusions will be discussed at the next Monday morning operation meeting with users.
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