atw 2017-06

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atw Vol. 62 (2017) | Issue 6 ı June RESEARCH AND INNOVATION 420 | | Fig. 3. Cryo-Simulation supports, one atmospheric pressure (0.1Mpa) was applied to the six surfaces of the vacuum chamber; the four bottom supports were fixed. As seen from Figure 2, the vacuum displacement occurs mainly in the central area around the horizontal and vertical zone of support are 0.42 and 0.62 mm respectively; and the central region is larger than the lateral area, with pot-shaped. B Cryo-displacement The two cooling experiments were cooled using Radiation cooling firstly (300 to 210 K); then the cryomodule is precooled with liquid nitrogen (210 to 150 K). After that, the cooldown of the cryomodule begins with liquid helium (150 to 4.2 K). The helium reservoir and cavity can be filled with liquid helium once temperature becomes 4.2 K. Liquid helium is pumped to reduce the vapor pressure of the liquid helium in the helium reservoir and cavity in order to make 2 K. Internal stresses are also developed in the statically indeterminate structure if the free movement of the joint is prevented. According to the analysis of displacement in a statically determinate structures induced by temperature changes [24-25] (eq. 5), if the temperature of the member is decreased uniformly throughout its length, a denotes the coefficient of thermal expansion of the material (mm/K); ΔT denotes the temperature change (K); L denotes the length of the structure (mm). (5) In the model, Magnets, the helium tank, and its welding bracket adopted 316 L stainless steel materials, HWR cavity and its welding bracket used titanium material, cold quality support components used titanium material, collimation bracket and cross hair targets used G11 materials. The contact surface of support was operated at 300 K. The thermal conductivity of materials varies strongly with a temperature between 300 and 77 K [17]. The surface heat load of 77 K (BPMs) was 1 W/m 2 [26-27]. The boundary conditions and load [28] contain a self-gravity of the cold mass assembly, a distributive load of temperature, a force of the cold mass assemblies and the top suspending support. The force of the cold mass assemblies acting on the Ti support frame is decided by the gravity of each cold mass assembly. According to the mechanical characteristics of cold mass [28], the simulated results of the solenoid and HWR cavity were contracted 0.77 mm in Horizontal and risen 2.98 mm in Vertical direction, respectively (As shown in Figure 3). 4 Results and Analysis A Vacuum displacement As shown in Figure 4, the two processes of vacuum pump started at 18:00 on November 30 and 16:00 on December 2, 2016, respectively. The vacuum level reached 0.1 Pa about 3 hours later and 10-3 Pa about 11 hours later. The two processes of vacuum release started at 8:00 on December 2 and 7:00 on December 4, 2016, respectively. The vacuum level returned to 0:1 Pa about 8 hours later. Figure 5 illustrates the vertical and horizontal displacements monitored by the Laser Tracker from the top and left of the vacuum vessel. The Laser Tracker system is able to compensate for temperature and humidity effects based on the measurement conditions. The monitored displacements are 0.42 mm in the vertical direction and 0.62 mm in horizontal direction respectively. The monitored and simulated displacements are matching very well: the differences are 0.02 mm in the vertical direction and 0.04 mm in the horizontal direction. B Cryo-displacement The optical instrument microalignment telescope (MAT) was adopted to monitor the displacement. Fig. 5 shows the monitor results of Hori zontal (Vertical) direction during one thermal cycling: as the target was located on the right (below) of solenoid and HWR cavity, A plus sign means that it is close to center(rise up); A minus sign means that it is off center (go down). After cooled down 24 hours, cold mass has contracted 0.8 mm in horizontal and 2.27 mm in vertical direction respectively on average(with respect to the pumped). And then cold mass has warmed up to 290 K after warmed up 24 hours, and has expanded 0.5 mm horizontal and 1 mm vertical respectively on average. | | Fig. 4. Vacuum displacement (DX: horizontal; DY: vertical). | | Fig. 5. Cryo-displacement. Research and Innovation Displacement of Cryomodule in CADS Injector II ı Yuan Jiandong, Zhang Bin, Wang Fengfeng, Wan Yuqin, Sun Guozhen, Yao Junjie, Zhang Juihui and He Yuan
atw Vol. 62 (2017) | Issue 6 ı June | | Fig. 6. Stress Analysis. C Discussion As shown in Figure 6 (a), due to the supports were located on the outer surface of the bottom vacuum chamber, the direct vertical stress exerted on the inside cold mass (cavity, solenoid and so on) comprised the negative atmospheric pressure (the force F normal to the surface per area A), gravity and thermal stress during the process of cooling down. Therefore, the complete displacements in the vertical direction were the superposition effect of the above stress. However, the horizontal displacement resulted only from the thermal stress. Root mean square value of the measurements was 0.03 mm in the vertical direction and 0.02 mm in the horizontal direction. As shown in Fig. 6 (b), the direct vertical stress exerted on the inside cold mass (cavity, solenoid and so on) comprised the negative atmospheric pressure, gravity and positive thermal stress during the process of warming up. Therefore, the complete displacements in the vertical direction were the subtraction of the above stress. As shown in Fig. 5, the differences of cryo displacement ( released) with respect to nominal zero resulting from plastic displacement [29] and the not fully released pressure of the vacuum. The above results indicate that the reproducibility of the horizontal and vertical position is 0.3 mm and 0.6 mm respectively. 5 Conclusion Cryomodules are extremely complex systems, and their design optimization is strongly dependent on the accelerator application for which they are intended. We have demonstrated that the simulated vacuum and cryo-displacement shows a good agreement with the measured values. The above data provides information not only on the nature of the heat exchange phenomena and their effect on the structural stability of the internal components of the Cryomodule, but also benefit to an optimization for future Cryomodules design. The analysis procedure will be helpful for the estimation of displacements in working conditions like mechanical and thermal loads. We will study the on-line continuous monitoring system in the future, which will further reveal low-temperature displacement mechanism of the cryostat. Acknowledgment This work was supported by the National Natural Science Foundation of China (No.11605262). This work could not have been accomplished without the advice and support of our colleagues: Juihui Zhang and Bin Zhang. References [1] Zhao Jijiu, Yin Zhao Sheng. Particle Accelerator Technology [M]. Beijing: Higher Education Press, 2006:30-36 (in Chinese). [2] Zhihui Li, Peng Cheng, Huiping Geng, et al. Physics design of an accelerator for an accelerator-driven subcritical system [J]. Physical Review Special Topics-Accelerators and Beams. 2013, 16, 080101-1:080101-23. [3] Shuhui Liu,Zhijun Wang,Huan Jia, et al. Physics design of the CIADS 25 MeV demo facility [J]. Nuclear Instruments and Methods in Physics Research A.2017, 843:11-17. [4] ZhiJui Wang, Chi Feng, Yuan He, et al. No interceptive transverse emittance measurements using BPM for Chinese ADS R&D Project [J]. Nuclear Instruments and Methods in Physics Research A. 2016, 816:171-175. [5] Weisend II, J. G. Cryostat design [M]. Springer; 1st ed. 2016 edition (August 13, 2016). [6] G. Kautzmann, J-C. Gayde, F. Klumb, et al. Hie Isolde – General Presentation of Mathilde [C]. The 13 th International Workshop on Accelerator Alignment, 13-17 October 2014, IHEP, Beijing, P.R. China. [7] Hiroshi Sakai, Kazuhiro Enami, Takaaki Furuya, et al. Improvement of the Position Monitor Using White Light Interferometer for Measuring Precise Movement of Compact Erl. Superconducting Cavities in Cryo module [C]. The Proceedings of IPAC2014, Dresden, Germany, 2014, TUPRI092:1787-1789. [8] A. Bertolini. Vibration diagnostics instrumentation for ILC [J]. Measurement Science & Technology -Meas Sci Technol, 2007, 18, 8: 2293-2298. [9] Zhu Hong-Yan, Dong Lan, Men Ling- Ling, et al. Alignment of ADS beta cryostat with wire position monitors [J]. Nuclear Science and Techniques, 2015, 26, 040401:1-4. [10] N. Eddy, B. Fellenz, P. Prieto, A. Semenov, D. C. Voy, M. Wendt, A Wire Position Monitor System for the 1.3 GHz Tesla-Style Cryomodule at the Fermilab New-Muon-Lab Accelerator [C]. The 15th International Conference on RF Superconductivity (SRF2011), Chicago, Illinois, USA, 25-29 Jul 2011, 2011, FERMILAB-CONF-11-382-AD. [11] Remy Beunard, Alexis Lefevre, François Legruel, Michel Fontaine, IRFU, Survey and Alignment Concept for the Spiral 2 Accelerator (Status Report) [C]. The 11th International Workshop on Accelerator Alignment, DESY, Hamburg, Germany, September 13-17, (2010). [12] D. Passarelli , M. Parise, T. H. Nicol, et al. High-Vacuum Simulations and Measurements on the SSR1 Cryo Module Beam-line [C]. Proceedings of SRF2015, Whistler, BC, Canada, TUPB074:754-756. [13] X L Guo, L Wang, J Wang, et al. Thermal and Mechanical Analysis on the Cold Mass Support Assembly of Test Cryomodule for IMP ADS Injector-II. Advances in Cryogenic Engineering. AIP Conf. Proc. 1573, 1341-1348 (2014); doi: 10.1063/1.4860862. [14] Frank Marhauser and Kai Tian. Optimization of the Cryo module Cold-to- Warm Transitions and the VTA QA Test Configuration for CEBAF Upgrade Cavities with Regard to Critical HOMs above Cutoff. 2009,JLAB-TN-09-61. [15] T. Powers, T. Allison, G. Davis, et al. Upgrade to Cryo module Test Facility at Jefferson Lab [J]. Accelerators, 2003. [16] J.R. Delayen, L.R. Doolittle, T. Hiatt, et al. An R.F. Input Coupler System for the Cebaf Energy Upgrade Cryo Module [C]. Proceedings of the 1999 Particle Accelerator Conference, New York, 1999, 1462-1464. RESEARCH AND INNOVATION 421 Research and Innovation Displacement of Cryomodule in CADS Injector II ı Yuan Jiandong, Zhang Bin, Wang Fengfeng, Wan Yuqin, Sun Guozhen, Yao Junjie, Zhang Juihui and He Yuan
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