Dermati, K.

Dolinskyy, O.

Fuchs, R.

Gorda, O.

Shim, S. Y.

Wilfert, S.

GSI Repository

Eddy current effect of quadrupole and CR dipole magnet beam chambersS. Y. Shim, K. Dermati, S. Wilfert, A. Dolinskii, O. Gorda, and R. FuchsGSI, Darmstadt, GermanyIn order to keep the stable particle operation, beamchamber needs to have the high-quality vacuum stateand thermal stability from external influence. The time-dependent magnetic field produces the secondary effectsof heating and stray magnetic field, which can disturb thequality of the inside vacuum and the magnetic field. Wepresent here the numerical simulation results for the recentissues related to the vacuum beam chambers of SIS100quadrupole magnets and the current ripple effect of CRdipole magnet for the field stability optimization.QP Star shaped beam chamberThe rib distance of the star-shaped beam chamber forquadrupole (QP) magnet has been changed from 17 mm to7 mm. More number of ribs increase mechanical stabilityand the heat conduction between cooling pipe and beamchamber surface. The opposite effect is that it reduceselectric resistance on the beam chamber which can be acause of increasing eddy current. Therefore, we need toconfirm the results of this design modification. The eddyloss depends on magnetic field operation scenario and weconsider the 2c and triangular cycle which have higheroperation load compared to other scenarios. Consideringthe planned boundary and initial conditions, we could findthe effect of changing rib distance. Compared to previousdesign, the 7 mm rib distance shows small increasement ofheat loss and temperature. The magnitude of incrementsare ∆T = 0.17 K, ∆W = 0.3 W/m at 2c and ∆T = 0.23 K,∆W = 0.7 W/m at triangular cycle. These opposite effectsare compensated and not considerably high.Jump QP beam chamberJump QP has an operation scenario with ramping rateof 1600 T/s. It is the ramping rate of the integral field ofthe field gradient in QP magnet. After considering the realmagnet dimensions, we found the ratio of 13.333 betweenthe effective length and reference radius. With this dimen-sional ratio, we can interpret 1600 T/s to the value of 120T/s at the reference radius and the corresponding maximumfield is 300 G. Even though it is not extreme operation con-dition, this high ramping rate initiates us to confirm theeffect of this operation. The simulation result shows thatthe time delay is ∼ 22.4µs between driving current andmagnetic field. Figure 1 shows the maximum temperatureon the beam chamber as a function of time. Each cyclecorresponds to the ramping cycles. Due to the short dutycycle with high field ramping rate, it has dynamic temper-ature variation. The conversed maximum temperature isestimated ∼ 7.5 K after infinite operation. The influence ofJump QP magnet operation on beam chamber is less thanSIS100 main QP magnet.0 5 10 15 20 25 304.55.05.56.06.57.07.5  T (K)t (sec)Figure 1: Maximum temperature on the beam chamberwith respect to operation time.CR dipole beam chamberThe magnet for the Collector Ring (CR) is designed tokeep constantly accurate magnetic field. Therefore, the sta-bility of the applied electric current is an important param-eter for the field stability. The maximum tolerance of fieldvariation is ∆Bmax/B0 ∼= 10−6. The reported maximumcurrent ripple is ∆Imax/I0 ∼= 10−4 considering all magnetcircuits. Based on these parameters, we simulate the fre-quency dependence of the magnetic field from 10 Hz to 10kHz. The maximum normalized field variation is found tobe ∼ 6.3 × 10−5 at 10 Hz. This value shows exponen-tial decay with increasing the ripple frequency. Throughthe simulation procedure, we found that the reason of thisfield shielding effect was the secondary magnetic field byeddy current in the beam chamber. The field tolerance lessthan 10−6 have been found around 2 kHz and 5.5 kHz inthe middle of magnet and the beam space inside the beamchamber, respectively.References[1] A. Dolinskii, et.al. Proceedings of IPAC’11 Conference, San-Sebastian, 2011, WEPC054[2] S. Y. Shim, The Influence of Driving Current Ripple on CRDipole Magnet, 6th BINP-FAIR-GSI workshop, 2014GSI SCIENTIFIC REPORT 2014 FG-CS-01DOI:10.15120/GR-2015-1-FG-CS-01 505

Eddy current effect of quadrupole and CR dipole magnet beam chambers

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Eddy current effect of quadrupole and CR dipole magnet beam chambers

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