Recent Progress of the Control System on HL-2A * HL-2A control group,

1. Recent Progress of the Control System on HL-2A* HL-2A control group,  Presented by: Li Qiang(李强) Southwestern Institute of Physics, P. O. Box 432, Chengdu, Sichuan, 610041, China *Partly supported by the Sichuan Provincial Youth Foundation for Science and Technology(No. 04zq026-032);

2. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Outline • Introduction • The control system for HL-2A • The discharge control on HL-2A • The results • Conclusion and discussion

3. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China • Introduction • HL-2A is a medium-sized tokamak put into operation in 2002. It was primarily designed to operate under axial asymmetrical DN divertor configurations; • In order to avoid the electrical isolation defects on the upper shaping coil or to study SN plasmas, only lower shaping coils are used in the experiments. • In the case of LSN operation, the designed current feeding and corresponding electrical advantages aren't valid. Extra PS systems are needed. • However with the extendibility of the machine control system, it’s easy to add a new subsystem into the whole control system. • Calculations on the field produced by coils and the plasma discharge parameters, e.g., plasma manor/major radii, position of X-point, plasma position are performed to establish the algorithm in the controller of the discharge control system. • By this way, the control on HL-2A is improved and progresses on the discharge have been achieved.

4. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China 2. The control system for HL-2A The layout of whole control system for HL-2A

5. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Schematic discharge flowchart of HL-2A

6. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China The operation of a power supply system needs lots of control systems, as well as accessory systems such as water-cooling system. It is referable if fewer number of PS systems is engaged into the experiment. When the experiment is being conducted, the net resource should be run effectively.

7. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China 3. The discharge control system on HL-2A DCS conducts the discharge; Presently, DCS control current, position of plasma, and the plasma radius, position of x-point; DCS consists of several Stations working harmoniously between shots. But only a controller works for control in the discharge; DCS needs fast AD, DA and DIO. The data for discharge are saved after a shot.

8. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China The coil system of HL-2A HL-2A was primarily designed to operate under Axial Symmetry divertor configurations, with the features of • Ohmical coil produced about 5Vs for plasma current driven. For most area of plasma, the stray field<1mT; • Vertical field coil controls plasma radial position. Radial field coils controls plasma vertical position. • MP coils produce the nulls; • MC coils compensate the field in plasma region.

9. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Current feeding and field features for DN operation Only 1 set of PS is needed; The stay field in the area of plasma is well compensated; Mutual inductances are eliminated to facilitate discharge control; The magnetic flux contributes a little to the plasma driving when Ip establishes before configuration formation. Magnetic fields in plasma region when operated under DN configurations

10. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Current feeding and field features for LSN operation If the current feeding is kept, The stray field in the area of plasma is basically increased; It makes it difficult to break down and control; The stray field in the area seems difficult to be compensated via the currents through vertical field coil and radial field coil; A new current feeding is needed. Magnetic fields in plasma region when operated under LSN configurations flux Bv Br

11. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Current feeding scheme 1 for the MP coil under LSN configurations By comparisons on the field produced by the MP&MC coils, a connection is used for the experiments’04. Another set of PS is used; The stray field is compensated to a large extent; The currents through the MP coils become unequal hereafter; However, the stray field is still large enough. New connection is still needed.

12. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Current feeding scheme 2 for the MP coil under LSN configurations If Imc=0 for scheme 1, good field distribution can be obtained. No extra PS system is needed. Evident reduction on the stray field makes it easy for control and breakdown. Helpful for saving energy. Better current feeding scheme will be used , as below,

13. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China Linear relations for discharge control Because of the delicate design on the functions of the coils, which work independently, a set of linear relations can be established, These relations are used in the controller of the discharge control system, to Quiken the response/shorten the control cycle; Simplify the algorithm of the calculation; Reduce the number for measurements.

14. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China 4. The results The progresses on the discharge waveforms in recent 2 exp. campaigns Repeatable discharges achieved in experiment’05 on HL-2A A typical plasma shape

15. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China 5.Conclusion and discussion • Great progresses have been made for the plasma control since HL-2A was put into operation in 2003. Repeatable and stable discharges have been made; • These progresses should be resulted from Powerful machine control systems,i.e., timing system, logical control system, which are of importance for ongoing expansions on the number of PS, plasma heating systems, divertor control, etc. Powerful discharge control,which takes advantage of the linear relations between the coil currents and plasma discharge parameters. • However, this simplified algorithms are only available for HL-2A, whose EPFC coils function separately. • New control system aiming at higher plasma shaping is being tested.

16. LI Qiang, Recent progress of the control system on HL-2A 核工业西南物理研究院 Southwestern Institute of Physics The 3rd PRC-US MFC Workshop, 17-20, May, 2006, Dalian, China 谢谢! Thanks!