Design and performance of Hall probe measurement system in CSNS

Transcription

1 Radiat Detect Technol Methods (2017) 1:18 ORIGINAL PAPER Design and performance of Hall probe measurement system in CSNS Xi Wu 1,2 Wen Kang 1,2 Wan Chen 1,2 Chang-dong Deng 1,2 Jian-xin Zhou 1,2 Li Li 1,2 Shuai Li 1,2 Received: 17 April 2017 / Revised: 19 July 2017 / Accepted: 21 July 2017 / Published online: 7 August 2017 Institute of High Energy Physics, Chinese Academy of Sciences; China Nuclear Electronics and Nuclear Detection Society and Springer Nature Singapore Pte Ltd Abstract Background The construction of China Spallation Neutron Source (CSNS) was started in 2011 and will be completed in The phase I CSNS facility consists of an 80MeV H- Linac, a 1.6GeV Proton Rapid Cycling Synchrotron (RCS), two beam transport lines and a target station. Magnets in the RCS and transport lines should be measured before being installed in the tunnel. Method In this paper, a new hall probe measurement system is described. The design and performance of the hall probe measurement system is presented. Conclusions The measurement results meet the design requirements. Some key issues were solved in the process. Keywords CSNS Hall probe measurement system Magnet Hall probe measurement system was built to calibrate all the DC magnets of CSNS. Some parameters are measured with the Hall probe system: magnet exciting curve, distribution of the magnetic field along the X, Y and Z axis, integral of the magnetic field, magnet exciting curve of the integral of the magnetic field and so on. The measurements show that the results meet the design requirements. Magnets of CSNS In CSNS, the magnet system mainly consists of the RCS ring [4] and the transport line magnets. Tables 1 and 2 show the principal type and number of magnets in RCS and transport line. Introduction The China Spallation Neutron Source (CSNS) [1 3] is composed of an H-linac and a proton rapid cycling synchrotron (RCS). It is designed to accelerate proton beam pulses to 1.6 GeV, striking a metal target to produce spallation neutrons for scientific research. The magnetic field s of all the magnets should be measured before they are installed. A new B Xi Wu wuxi@ihep.ac.cn 1 Institute of High Energy Physics Dongguan Campus, Chinese Academy of Sciences, Dongguan , China 2 Institute of High Energy Physics, Chinese Academy of Sciences, Beijing , China The Hall probe measurement system of CSNS The Hall probe measurement system of CSNS includes the following three parts (see Fig. 1): the marble platform, the mobile platform and the hall sensor. The mobile platform includes the linear motor, air-floatation equipment and the UMAC hardware system. The Hall sensor is embedded inside the large stiffness lever. The accuracy of the Hall probe system is listed in Table 3. The system uses the linear motor and the air-floatation equipment, so the accuracy is much better than the one which using the mechanical slide way structure. After using the system for as few months the linearity of the marble has changed a little bit. The reason is that the base of the ground is deformed somewhat. The deformation

2 18 Page 2 of 5 X. Wu et al. Table 1 Number of magnets in the RCS Names Type Number RCS160B Dipole 24 RCS206Q Quadrupole 16 RCS222Q Quadrupole 8 RCS253Q Quadrupole 8 RCS272Q Quadrupole 16 RCS230S Sextupole 16 RCS300C Corrector 34 Table 3 Accuracy of Hall probe System Items X axis Y axis Z axis Distance (mm) Velocity (mm/s) linearity (µm) ±5 ±5 ±10 Position resolution (µm) Positional accuracy (µm) ±5 ±5 ±10 Repositioning resolution (µm) ±1 ±1 ±2 Table 2 Number of magnets in transport lines Names Type Number LRBT Dipole 4 RTBT Dipole 4 LRBTQ Quadrupole 47 RTBTQe Quadrupole 21 RTC Corrector 40 becomes small after certain time. So we have to adapt the marble to the deformation, as shown in Fig Some magnetic field measurement The Hall probe measurement system has completed the measurement work of the magnets in CSNS up to now. Figure 3 shows one of the transport lines dipole magnets measured by the Hall system. The transport lines dipoles magnets including two LR-BB dipoles, one LR-BA dipole and one LD-B dipole. The tracks of measurement are arcshape in LR-BB dipoles and LD-B dipole. Fig. 2 Adapt the marble to the deformation Fig. 1 The overview of the hall probe

3 Design and performance of Hall probe measurement system in CSNS Page 3 of 5 18 Fig. 3 Transport lines dipoles magnet Figure 4 shows that the integral field error distribution curves are very alike between the design results and measurement results. In order to verify the 3D simulation calculation, the field measurement on RCS-272QB and RCS-300CH combination magnet by Hall probe system is conducted [5]. Two magnets are carefully aligned by level and theodolite. Figure 5 shows the magnetic field measurement device and 272QB-300CH combination magnets. The configuration of the magnets in the field measurement is similar to the 3D simulation calculation. The integral field of RCS-300CH magnet is measured along the central line of the magnet, while the RCS-272QB magnet is not excited. The results show that the integrated field of the horizontal corrector magnet is reduced by 14.9% due to the quadrupole magnet core. Then, the RCS-272QB magnet is excited, but the RCS-300CH magnet is not excited. The probe is moved in a step of 5 mm along the longitudinal direction at x =±50 mm, y = 0 mm. The measured data show that the integrated field of the RCS-272QB mag- Fig. 5 Hall probe magnetic field measurement in 272QB-300CH combination magnets net is reduced by 0.86% due to the 300CH magnet core. The comparison of the simulation data and the measurement data is summarized in Table 4. It can be seen that the measurement results have a good agreement with the simulation result. 2 Issues about Hall probe System When measuring the magnet with high magnetic field gradient such as MEBT Quadrupole, we found that the magnetic Fig. 4 Design results (left) and the measurement results (right)

4 18 Page 4 of 5 X. Wu et al. Table 4 Comparison between simulation and Hall probe measurement system Magnet Simulation value of error (@22.2 cm %) 272QB CH Hall probe measurement valueoferror(@22.2cm%) field is unstable. The range of fluctuation is about 1 % (see Fig. 6). After eliminated many possible situations such as the power supply and the water cooling system, we found that the stiffness of the lever is the cause. So when we change the lever to a large stiffness one, the phenomenon of fluctuation is almost gone (see Fig. 7). The ambient temperature is another key issue for the Hall probe measurement. The Hall sensors will drift as the temperature changes. So we built a constant temperature room to control the temperature within 20 ± 1 C. 3 Summaries In summary, we present the design and performance of Hall probe measurement system in CSNS. The Hall probe measurement system has been manufactured and putted into use in CSNS. The Hall probe measurement system has completed the magnetic fields measurement work in CSNS up to now. The measurement results meet the design requirements. Some key issues were solved in the process. Fig. 6 Fluctuation is about 1% Fig. 7 Fluctuation is about 0.01%

5 Design and performance of Hall probe measurement system in CSNS Page 5 of 5 18 Acknowledgements The author would like to acknowledge the magnet group, physics group, power supply group and the mechanical group in magnet measurement and data analysis. References 1. J. Wei, S.N. Fu, S.X. Fang., China spallation neutron source accelerators: design, research, and development. In Proceedings of EPAC. (2006) 2. W.A.N.G. Sheng, F.A.N.G. Shou-Xian, F.U. Shi-Nian et al., Introduction to the overall physics design of CSNS accelerators. CPC(HEP & NP) 33(Suppl.II), 1 3 (2009) 3. W.E.I. Jie, F.U. Shi-Nian, T.A.N.G. Jing-Yu et al., China spallation neutron source-an overview of application prospects. CPC(HEP & NP) 33(11), (2009) 4. H.U.A.N.G. Ming-Yang, W.A.N.G. Sheng et al., Effects of injection beam parameters and foil scattering for CSNS/RCS. Chin. Phys. C 37(6), (2013). doi: / /37/6/ L. Li, W. Kang, X. Wu et al., Fringe field interference of neighbor magnets in China spallation neutron source. Nucl. Instrum. Methods Phys. Res. A 840, (2016)