A." Iwamoto

T. "Okamura

National Institute for Fusion Science (NIFS-Repository)

The superconducting magnets for the SiD and ILDdetectors are essential components of the InternationalLinear Collider (ILC) experiment. As shown in the Fig.1the central region can be regarded as interface betweendetector and accelerator i.e. final focusing magnets,which are referred to as QD0 and QF1, are installed in-side and adjacent to the detectors. Cryostats for crabcavity (CC) are also installed adjacent to QF1 magnets.Both detectors (SiD, ILD) are cooled by gas-liquid twophase flow of helium with the temperature of 4.5 K. Thefinal focusing magnets (QD0, QF1) and crab cavity (CC)have to be cooled by pressurized and saturated super-fluid helium, respectively. Therefore from the viewpointof cryogenics, we have to consider the cryogenic systemnot only for detectors but also for accelerator such asQD0, QF1 and crab cavity to configure more sophisti-cated cryogenic flow scheme in the central region. In thecentral region, there are two notable points. First oneis push-pull operation of the detectors i.e. two detec-tors move from collision point to maintenance locationup to twice a month. The moving distance for push-pulloperation is 28 m in the case of Japanese mountain site.The cryogenic system has to employ some kind of flexibletype tube for warm or cold helium. Whether warm orcold flexible tube has to be employed strongly dependson cryogenic flow diagram of the central region. Secondone is that acceptable vibration level for final focusingmagnet, QD0, is very small. Actually, the maximumallowable vibration level is around 50 nm. To reduce vi-bration generated in the QD0, we have to pay specialattention to various kinds of vibration source due to themechanical vibration and fluid motion etc.In this study, following 3 kinds of simulation toolshave been developed to establish optimal design of thecryogenics for the central region of ILC.1. Two phase flow simulations with respect to theforced cooling and thermosyphon cooling for thelarge superconducting solenoid.2. Superfluid simulation for the cooling of final focus-ing magnets.3. Dynamic Simulation on 2K-4K combined cryogenicsystem in order to find optimal cryogenic flow dia-gram for central region.In the FY2013, we developed the numerical simulationcode for two phase flow in horizontal and vertical chan-nels and parallel channel system. Parallel cooling chan-nel systems are often employed in the large supercon-ducting magnet system. But in this case we have topay attention to the two phase flow instability generatedin the parallel cooling channel. Fig.2 (A) shows flowpattern in the horizontal and vertical channels obtainedfrom simulations. Fig.2 (B) indicates time dependent ofliquid fraction generated in the 4 parallel cooling chan-nels. As shown in the Fig.2 (B), if the inlet quality isless than 0.1, flow instability does not occur in the out-let channels. On the contrary, in the case that the inletquality is 0.3, flow instability occurs in a outlet 1. In thiscase, cooling efficiency in the outlet1 decreases in com-parison with other cooling channels due to the existenceof mass flow inhomogeneity in the outlet1.Experimental hallQF1QF1Crab cavityCrab cavity28 m28 mUtility space  (6F)Flexible TRT        (one in one)Rigid TRT(Four in one)4K distribution box2K refrigerator for QD0Chimney and current lead box for detectorPower supply for detector and QD0Fixed TRT for 7 K and shield gas (Four in one)Fixed TRT for 4.2 K liquid helium (Four in one)Fixed TRT for superfluid helium (2K, 4K 70K shield).Cold Box (2)Cold Box (1)Flexible TRT for 7 K and shield helium gas with One in Oneor Two in One or Four in One ?Cold box (2 kW)Platform for cryogenic equipment Bus bar for detector between PS and chimney.Flexible TRT        (one in one)Rigid TRT(Four in one)QD0QD0ILDSiDQD0QD0Maintenance location for SiDMaintenance location for ILDCollision PointFig. 1: Schematic view of cryogenic system in the cen-tral region for ILC.00.20.40.60.811.20 5 10 15 20 25 30 35 40VoidFraction(-)Time (sec)inletoutlet1outlet2outlet3outlet4inlet quality = 0.1 inlet quality = 0.3 liquid fraction (-)ti  (sec)horizontal cooling channelvertical cooling channel00.20.40.60.811.20 5 10 15 20 25 30 35 40VoidFraction(-)Time (sec)inletoutlet1outlet2outlet3outlet4liquid fraction (-)tim  (sec)steady stateLiquidHeliumGasHeliumflow directionFlow pattern in the horozontal and vertical cooling channel(A)(B)Fig. 2: (A) Flow pattern in the horizontal and verticalchannel. (B) Flow instability generated in the 4 parallelchannels.311§21. Development of Dynamic Simulator for Large Superconducting Magnet SystemOkamura, T. (KEK),  Iwamoto, A.

Development of Dynamic Simulator for Large Superconducting Magnet System

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