Journal of Nuclear and Particle Physics

p-ISSN: 2167-6895    e-ISSN: 2167-6909

2014;  4(4): 123-128

doi:10.5923/j.jnpp.20140404.02

Measurement of Magnetic Field Fluctuations and Plasma Rotation Speed

F. Hedayatian, M. Ghoranneviss, A. Salar Elahi

Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran

Correspondence to: A. Salar Elahi, Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Email:

Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved.

Abstract

An experimental investigation of effects of external resonant helical field on poloidal and radial components of magnetic field fluctuations, plasma rotation speed and plasma current in IR-T1 tokamak was presented. Eight Mirnov coils in poloidal direction and four Mirnov coils in radial direction were installed on outer surface of the IR-T1 tokamak chamber to measure poloidal and radial components of external magnetic field fluctuations. Also we inserted a Mach probe with four tips 5mm inside the IR-T1 tokamak chamber to measure plasma rotation speed. In case of absence of RHF, poloidal and radial components of external magnetic field fluctuations were measured. On the other hand, the external RHF applied to tokamak plasma and again the magnetic field fluctuations were measured. Measurement results with and without RHF (L=2, L=3, L=2 & 3) show that the addition of a relatively small amount of RHF could be effective for improving the quality of tokamak plasma discharge by flatting the plasma current and decreasing the magnetic field fluctuations.

Keywords: Tokamak, Resonant helical field, Magnetic field fluctuations, Plasma rotation speed

Cite this paper: F. Hedayatian, M. Ghoranneviss, A. Salar Elahi, Measurement of Magnetic Field Fluctuations and Plasma Rotation Speed, Journal of Nuclear and Particle Physics, Vol. 4 No. 4, 2014, pp. 123-128. doi: 10.5923/j.jnpp.20140404.02.

Article Outline

1. Introduction
2. Measurement of Magnetic Field Fluctuations with Mirnov Coils
3. Resonant Helical Field (RHF) Setup on IR-T1 Tokamak
4. Experimental Results of Effects of RHF on Poloidal and Radial Components of External Magnetic Field Fluctuations
5. Measurement of Plasma Rotation Speed with Mach Probe
6. Experimental Results of Measurement of Plasma Rotation Speed
7. Experimental Result of Effect of RHF on Plasma Current
8. Summary and Discussion

1. Introduction

In magnetically confined plasmas, reducing the magnetic field fluctuations is important to confine plasmas. These magnetic field fluctuations can be measured by magnetic pick up coils such as Mirnov coils. The Plasma rotation speed can improve fusion power gain in fusion reactor. So it is important to discover parameters can affect magnetic field fluctuations and Plasma rotation speed in tokamak plasmas [1-65]. In this paper we present an experimental investigation of effects of resonant helical field on poloidal and radial components of external magnetic field fluctuations and measurement of plasma rotation speed in IR-T1 tokamak plasma which it is a small, low Beta and large aspect ratio tokamak with a circular cross section. The external RHF applied to plasma and then poloidal and radial components of external magnetic field fluctuations were measured. Measurement results with and without RHF (L = 2, L = 3, L = 2 & 3) show that the addition of a relatively small amount of RHF could be effective for improving the quality of tokamak plasma discharge by flatting the plasma current and decreasing the external magnetic field fluctuations. Measurement of magnetic field fluctuations will be presented in ‘‘Measurement of Magnetic Field Fluctuations with Magnetic Coils’’ and RHF setup on IR-T1 tokamak will be presented in ‘‘Resonant Helical Field (RHF) Setup on IR-T1 Tokamak’’. Experimental results of effects of RHF on poloidal and radial components of external magnetic field fluctuations will be presented in ‘‘Experimental Results of Effects of RHF on Poloidal and Radial Components of External Magnetic Field Fluctuations’’. Also, experimental results of effects of RHF on plasma current will be presented in ‘‘Experimental Results of Effects of RHF on Plasma Current’’. Measurement of plasma rotation speed will be presented in ‘‘Measurement of Plasma Rotation Speed with Mach Probes’’. Summary and conclusion also will e presented in ‘‘Summary and Conclusion’’.

2. Measurement of Magnetic Field Fluctuations with Mirnov Coils

Mirnov coils measure induced voltage on its output Vin, that could be obtained theoretically from the Faraday’s law [1]:
(1)
According to this relation, Vin is proportional to external magnetic field fluctuations (dB/dt). N is the number of turns in the coil of area A. So, measuring Vin by coils gives a measure of external magnetic field fluctuations directly. According to this approach, in the IR-T1 tokamak eight Mirnov coils were installed on outer surface of tokamak chamber to measure poloidal component of external magnetic field fluctuations as shown in Fig. 1(a) and four Mirnov coils were installed on outer surface of tokamak chamber to measure radial component of external magnetic field fluctuations, as shown in Fig. 1(b). Output of these coils yield Vin that is proportional to external magnetic field fluctuations.
Figure 1. Arrangment of (a) poloidal (b) radial Mirnov coils on the outer surface of IR-T1 tokamak chamber

3. Resonant Helical Field (RHF) Setup on IR-T1 Tokamak

The RHF is an external helical magnetic field which can improve the tokamak plasma confinement. In the IR-T1, this field is produced by two winding with optimized geometry conductors wound externally around the tokamak chamber with a given helicity. The minor radius of these helical windings are 21 cm (L = 2, n = 1) and 22 cm (L = 3, n = 1) and also major radius is 50 cm (see Fig. 2). In this experiment, the current through the helical windings was between 200 and 300 A, which is very low compared with the plasma current (32 kA).
Figure 2. Positions of the RHF coils (L = 2 & L =3 modes) on outer surface of the IR-T1 tokamak chamber

4. Experimental Results of Effects of RHF on Poloidal and Radial Components of External Magnetic Field Fluctuations

In order to measurement of poloidal and radial components of external magnetic field fluctuations, eight Mirnov coils were installed in poloidal direction and four Mirnov coils were installed in radial direction on the outer surface of the IR-T1 tokamak chamber as shown in Fig. 1. First of all, we measured poloidal and radial components of external magnetic field fluctuations without RHF and then we measured them with RHF in L= 2, L = 3 and L = 2 & 3 modes separately. After data analyzing and programming, we obtained 48 figures, for each coil we plotted four figures in four states: without RHF and with RHF in L= 2, L = 3 and L = 2 & 3 modes separately. We have shown some results in Figs. 3, 4, 5, …, 10. Measurement results with and without RHF (L = 2, L =3, L = 2 & 3) show that the addition of a relatively small amount of RHF, specially L=2 mode, could be effective for decreasing the poloidal and radial components of external magnetic field fluctuations.
Figure 3. Poloidal component of external magnetic field fluctuations was measured by coils (a) p1, (b) p3, (c) p5, and (d) p7, without RHF
Figure 4. Poloidal component of external magnetic field fluctuations was measured by coils (a) p1, (b) p3, (c) p5, and (d) p7, with RHF (L=2 mode) at 13-19 ms
Figure 5. Poloidal component of external magnetic field fluctuations was measured by coils (a) p1, (b) p3, (c) p5, and (d) p7, with RHF (L=3 mode) at 13-19 ms
Figure 6. Poloidal component of external magnetic field fluctuations was measured by coils (a) p1, (b) p3, (c) p5, and (d) p7, with RHF (L=2&3 mode) at 13-19 ms
Figure 7. Radial component of external magnetic field fluctuations was measured by coils (a) r2, (b) r4, without RHF
Figure 8. Radial component of external magnetic field fluctuations was measured by coils (a) r2, (b) r4, with RHF (L=2) at 13-19 ms
Figure 9. Radial component of external magnetic field fluctuations was measured by coils (a) r2, (b) r4, with RHF (L=3) at 13-19 ms
Figure 10. Radial component of external magnetic field fluctuations was measured by coils (a) r2, (b) r4, with RHF (L=2&3) at 13-19 ms

5. Measurement of Plasma Rotation Speed with Mach Probe

Mach probes measure saturation voltage Vs that is proportional to saturation current Is. We used the Mach probe with four tips, two tips measure saturation voltage in poloidal direction and two tips measure saturation voltage in toroidal direction as shown in Fig. 11. All of the theories express the ratio of the Mach probe upstream and downstream currents as follows [2]:
Figure 11. Mach probe with four tips
(2)
or, rearranging,
(3)
M is the Mach number and K is a calibration constant.
In this work, we used the Hutchinson model with K=1.7 for Ti/Te=0.2. Then, plasma rotation velocity obtains from [3]:
(4)
Vp is plasma rotation speed and Cs is ion acostic velocity that can obtain from [4]:
(5)
That, Mi=1.673×10-27kg, is ion mass. In this experiment KTe=200eV .

6. Experimental Results of Measurement of Plasma Rotation Speed

According to this approach, we inserted a Mach probe with four tips inside the IR-T1 tokamak chamber and 50cm inside the plasma. Firstly we measured saturation voltages in poloidal direction and calculated the Mach number in poloidal direction by equ.3, and then we calculated plasma rotation speed by eq.4 and eq.5. Result has been shown in Fig. 12.
Figure 12. Measurement of poloidal component of plasma rotation speed

7. Experimental Result of Effect of RHF on Plasma Current

For measurement of plasma current Ip a Rogowski coil was installed on the outer surface of the IR-T1 tokamak chamber. We measured plasma current without RHF and with RHF in L = 2, L = 3 and L = 2 & 3 modes separately. Results show that the addition of a relatively small amount of RHF, specially L = 3 mode, could be effective for improving the quality of tokamak plasma discharge by flatting the plasma current as shown in Fig. 13.
Figure 13. Measurement of plasma current (a) without RHF, (b) with RHF(L=2 mode), (c) with RHF(L=3 mode), (d) with RHF(L=2&3 mode)

8. Summary and Discussion

In this paper we present an experimental investigation of effects of resonant helical field on poloidal and radial components of external magnetic field fluctuations, and plasma current in the IR-T1 tokamak plasma, also we measure plasma rotation speed. Eight Mirnov coils in poloidal direction and four Mirnov coils in radial direction were installed on outer surface of the IR-T1 tokamak chamber to measure the poloidal and radial components of external magnetic field fluctuations as showed in Fig. 1, also we inserted a Mach probe with four tips inside the IR-T1 tokamak chamber and 50 cm inside the plasma to measure the plasma rotation speed in the IR-T1 tokamak. On the other hand, the external RHF applied to tokamak plasma and again the external magnetic field fluctuations were measured. Measurements with and without RHF (L = 2, L = 3, L = 2 & 3) show that the addition of a relatively small amount of RHF could be effective for improving the quality of tokamak plasma discharge by flatting the plasma current and reducing the external magnetic field fluctuations.

References

[1]  K. Nakamura and M. Ghoranneviss, Fusion Eng. Des. 66-68 (2003) 771-777.
[2]  V. S. Mukhovatov and V. D. Shafranov, Nucl. Fusion 11, (1971), 605.
[3]  I. P. Shkarofsky, Phys. Fluids 25 (1) 89-96, (1982).
[4]  G.S. Lee and and M. Ghoranneviss, Nucl. Fusion 41, 1515 (2001).
[5]  S.H. Seo, Phys. Plasmas 16, 032501 (2009).
[6]  A. Salar Elahi and M. Ghoranneviss, IEEE Trans. Plasma Science 38 (2), 181-185, (2010).
[7]  A. Salar Elahi and M. Ghoranneviss, IEEE Trans. Plasma Science 38 (9), 3163-3167, (2010).
[8]  A. Salar Elahi and M. Ghoranneviss, J. Plasma Physics 76 (1), 1-8, (2009).
[9]  A. Salar Elahi and M. Ghoranneviss, Fusion Engineering and Design 85, 724–727, (2010).
[10]  A. Salar Elahi and M. Ghoranneviss, Phys. Scripta 80, 045501, (2009).
[11]  A. Salar Elahi and M. Ghoranneviss, Phys. Scripta 80, 055502, (2009).
[12]  A. Salar Elahi and M. Ghoranneviss, Phys. Scripta 81 (5), 055501, (2010).
[13]  A. Salar Elahi and M. Ghoranneviss, Phys. Scripta 82, 025502, (2010).
[14]  M. Ghoranneviss, A. Salar Elahi, Phys. Scripta 82 (3), 035502, (2010).
[15]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 346-349, (2009).
[16]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 416-419, (2009).
[17]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 408-411, (2009).
[18]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 412-415, (2009).
[19]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 394-397, (2009).
[20]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 404-407, (2009).
[21]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 390-393, (2009).
[22]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 28 (4), 385-389, (2009).
[23]  A. Rahimi Rad, M. Ghoranneviss, M. Emami, and A. Salar Elahi, J. Fusion Energy 28 (4), 420-426, (2009).
[24]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 1-4, (2010).
[25]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 22-25, (2010).
[26]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 29-31, (2010).
[27]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 26-28, (2010).
[28]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 32-35, (2010).
[29]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 36-40, (2010).
[30]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 62-64, (2010).
[31]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 76-82, (2010).
[32]  A. Rahimi Rad, M. Emami, M. Ghoranneviss, A. Salar Elahi, J. Fusion Energy 29 (1), 73-75, (2010).
[33]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 83-87, (2010).
[34]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (1), 88-93, (2010).
[35]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (3), 209-214, (2010).
[36]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (3), 232-236, (2010).
[37]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (3), 251-255, (2010).
[38]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (3), 279-284, (2010).
[39]  M. Ghoranneviss, A. Salar Elahi, J. Fusion Energy 29 (5), 467-470, (2010).
[40]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 29 (5), 461-465, (2010).
[41]  A. Salar Elahi and M. Ghoranneviss, Brazilian J. Physics 40 (3), 323-326, (2010).
[42]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 30 (2), 116-120, (2011).
[43]  M.R. Ghanbari, M. Ghoranneviss, A. Salar Elahi, Phys. Scripta 83, 055501, (2011).
[44]  A. Salar Elahi, J. Fusion Energy 30 (6), 477-480, (2011), 477-480.
[45]  A. Salar Elahi and M. Ghoranneviss, Fusion Engineering and Design 86, 442–445, (2011).
[46]  A. Salar Elahi and M. Ghoranneviss, J. Fusion Energy 31 (2), 191-194, (2012).
[47]  M.R. Ghanbari, M. Ghoranneviss, A. Salar Elahi, R. Arvin and S. Mohammadi, Radiation Effects & Defects in Solids 166 (10), 789–794, (2011).
[48]  A. Salar Elahi and M. Ghoranneviss, IEEE Trans. Plasma Science 40 (3), 892-897, (2012).
[49]  Z. Goodarzi, M. Ghoranneviss and A. Salar Elahi, J. Fusion Energy 32 (1), 103-106, (2013).
[50]  M.R. Ghanbari, M. Ghoranneviss, A. Salar Elahi, Phys. Scripta 85 (5), 055502, (2012).
[51]  A. Salar Elahi and M. Ghoranneviss, Radiation Effects and Defects in Solids 168(1), 42-47, (2013).
[52]  K. Mikaili Agah, M. Ghoranneviss, A. Salar Elahi, J. Fusion Energy 32 (2), 268-272, (2013).
[53]  A. Salar Elahi and M. Ghoranneviss, Fusion Engineering and Design 88 (2), 94-99, (2013).
[54]  A. Salar Elahi and M. Ghoranneviss, IEEE Transactions on Plasma Science 41 (2), 334-340, (2013).
[55]  A. Salar Elahi and M. Ghoranneviss, J. of Fusion Energy 32, 496-502, (2013).
[56]  A. Salar Elahi and M. Ghoranneviss, Review of Scientific Instruments 84 (5), 053504 (2013).
[57]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 1(1), 10-15, (2011).
[58]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(2), 1-5, (2012).
[59]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(2), 22-25, (2012).
[60]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(4), 91-97, (2012).
[61]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(4), 101-106, (2012).
[62]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(5), 112-118, (2012).
[63]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 2(6), 142-146, (2012).
[64]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 3(1), 1-7, (2013).
[65]  A. Salar Elahi and M. Ghoranneviss, J. Nuclear and Particle Physics 3(1), 14-19, (2013).