22P049-P
Generation of Tandem Type of Modulated Induction Thermal Plasmas
タンデム型変調誘導熱プラズマによる変動温度場の生成
Katsuya Kuraishi, Yosuke Uesaka, Akao Mika, Yasunori Tanaka and Yoshihiko Uesugi
倉石 克弥, 上坂 洋介, 赤尾 美香，田中 康規, 上杉 喜彦
Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan
金沢大学 〒 920-1192 石川県金沢市角間町
A tandem type of modulated induction thermal plasma (Tandem-MITP) system has been developed by using two RF power supplies to control temperature and reaction fields temporally and spatially in thermalplasmas. The present report describes the temperature variation of an Ar Tandem-MITP. Time variation ofAr excitation temperature was estimated by the two-line method. Results suggested that Ar excitation temperature in the thermal plasma could be controlled temporally and spatially by the Tandem-MITP system.

1. Intorduction
Rectifier DC-DC
DC-RF Impedance
RF power supply
circuit converter
inverter Matchingfor Lower coil
We have so far developed a pulse modulated induction thermal plasma (PMITP) system [1], an arbitraryv
waveform modulated induction thermal plasma (AMITP)
Specification
3-phase-Drive freq. :Powersystem [2] and a feedback control type of modulated
225 kHzsource-Rated power :induction thermal plasma (FBC-MITP) system [3] toPWM
RF power supply Plasma torch 30 kW
controlfor Upper coil Function generator
Specification
control the temperature in the time domain. These-Drive freq. : 430 kHz-Ratedpower:
30kW
systems can modulate the coil current amplitude toExternal signal 1
External signal 2
control the temperature in the time domain. For example, we have investigated the application of Ar-O2 Fig. 1: Schematic of the tandem type of modulated induction therPMITP for TiO2 nanoparticle. Those results implied mal plasma (Tandem-MITP) system.
Sheath gas: Arthat PMITP could control size and phase of TiO2 nanoparObserved at 10, 25 mm
below the upper-coil end
ticles synthesized [4]. We have also investigated the50 mm
Observed at 10 mm
application of Ar-N2 PMITP for surface nitridation ofbelow the lower-coil end
130 mmmetallic specimen [5].
ACalc. Ar excitation
50 mm B
temperature in real-time
OpticalIn this report, a tandem type of modulated induction
130 mmfiber
Ar at 703 and 714 nm
40 mm CContinuum at 709 nm
thermal plasma (Tandem-MITP) system has been developed using RF power supplies and two coils for one
Plasma torch Lens
Monochromator
DSP
PMT
plasma torch. This system was developed to control
temperature and reaction fields temporally and spaFig. 2: Plasma torch and spectroscopic observation system.
tially in thermal plasmas. We measured time variation in the Ar excitation temperature estimated by thetwo-line method. Results suggested that Ar excitation tance between upper-coil-end and lower-coil-top is 50
temperature in the thermal plasma could be controlled mm. Two-coils are connected with a RF power suptemporally and spatially by the Tandem-MITP system. plies, respectively. The driving frequency for the upper
2. Experimental setup
coil f1 was fixed at 430 kHz due to the power supply
2.1. Experimental conditions
rating. The driving frequency for the lower coil f2 wasFig. 1 shows a schematic of the Tandem-MITP sys- 225 kHz, i.e almost a half of f1 . This f2 was detertem, and Fig. 2 portrays the plasma torch and spectro- mined to avoid a mutual resonance between the upper
scopic observation system. The torch is composed of and lower coil circuits, and to obtain high input power
two coaxial quartz tubes with 430 mm length. The in- to the plasma because the input power is generally proner tube has an inside diameter of 70 mm. The plasma portional to square of frequency.
torch wall is cooled by the flowing water. For estab- 2.2. Spectroscopic observation systemlishing Tandem-MITP, we used Ar as a sheath gas. The
Spectroscopic observation was carried out at 10, 25gas flow rate is 40 slpm for axial gas and 40 slpm for mm below the upper-coil end and at 10 mm below theswirl gas. The pressure in the chamber is fixed at 70 lower-coil end, which are designated by A, B and C intorr. This torch has two eight-turn induction coils. Dis- Fig. 2. We measured temporal variations in the radiinv

iinv

0709

tn 140er ] 120
ru [A 100C 80(a)Inverter output current for the upper-coil in rmsre ] 108w
k[ 64oP W
20(b)Inveter
output effective power for the upper-coiltn 140er ]A 120
100ru [ 8060C 4020(c)Inveter output current for the lower-coil in rms

re ] 54
3woP W[k 210(d)Inverter output effective power for the lower-coilreu 8.0ta ] 7.5
re K 7.0
p k[ 6.56.0meT 5.55.0

A020406080

Time [ms](e)Ar excitation temperature

BC100Fig. 3: Time evolution in (a)inverter output current for the uppercoil in rms, (b)inverter output eﬀective power for the upper-coil,(c)inverter output current for the lower-coil in rms, (d)inverter output eﬀective for the lower-coil, (e)Ar excitation temperature. The
upper-coil current amplitude is modulated into a sawtooth waveform and the lower-coil current amplitude is non-modulated.

tn 140120
rer ]Au [ 100C 80(a)Inveter output current for upper-coil in rms
re ] 108
woP W
k[ 6420(b)Inveter
output effective power for upper-coiltn 140er ] 120
100ru A[ 8060C 40
20(c)Inveter output current for lower-coil in rms
re ] 54woP W
k[ 3210(d)Inverter output effective power for lower-coiler 7.0AB
ut 6.5ar ]K
ep k[ 6.0CmeT 5.5
5.0020406080
100
Time [ms](e)Ar excitation temperature
Fig. 4: Time evolution in (a)inverter output current for the uppercoil in rms, (b)inverter output eﬀective power for the upper-coil,(c)inverter output current for the lower-coil in rms, (d)inverter output eﬀective for the lower-coil, (e)Ar excitation temperature. The
upper-coil current amplitude is non-modulated and the lower-coilcurrent amplitude is modulated into a sawtooth waveform.

ation intensities at 703 and 714 nm for Ar lines and coil current, as seen in Fig. 3(e). Whereas, Figs. 4(a)709 nm for continuum. Use of the radiation inten- and 4(b) indicate that the eﬀective power of the uppersities of these spectral lines yields the Ar excitation coil keeps constant of 6 kW according to the uppertemperature between the specified levels by the two- coil current. In this case, only the eﬀective power forline method. This calculation was done in real-time in the lower-coil rises rapidly just after a jump-up in thelower-coil current. In Fig. 4(e), the Ar excitation temDigital Signal Processor(DSP).
perature at C increases rapidly from 5000 K to 5800 K
3. Exprimental results
immediately after an increase in the lower-coil current.
Fig. 3 shows time evolution in (a)inverter output
The temperature-changes at A and B are smaller thancurrent for the upper-coil in rms as shown in Fig. 1,that at C. The above results implied that a Tandem(b)eﬀective power for the upper-coil, (c)inverter outMITP can control the Ar excitation temperature temput current for the lower-coil in rms, (d) eﬀective power
porally and spatially in thermal plasmas.
for the lower-coil, (e)Ar excitation temperature. These
results were obtained for the non-modulated current of 4. Conclusion
In this report, we measured time variation of Ar exthe lower-coil and the modulated current of the uppercoil. Similarly, Fig. 4 indicates those for the non- citation temperature estimated by the two-line method
modulated current of the upper-coil and the modulated using Ar atomic lines. Results suggested that Ar excicurrent of the lower-coil. The current modulation was tation temperature in the thermal plasma could be controlled temporally and spatially by the Tandem-MITP
conducted in a sawtooth waveform.
As illustrated in Figs. 3(a) and 3(b), the eﬀective system.
power of the upper-coil changes according to the upper- References[1] T. Sakuta, Y. Tanaka, Y. Hashimoto and M. Kazuki:
coil current. On the other hand, the eﬀective power forTrans. IEEJ, 120-A (2000) 972.
the lower-coil changes between 1.9 kW and 4 kW re[2] Y. Tanaka, Y. Morishita, S. Fushie, K. Okunaga andgardless of non-modulated current of the lower-coil as
Y. Uesugi: Appl. Phys. Lett., 90 (2007) 071502.
shown in Fig. 3(a). This is because of high-temperature [3] Y. Tanaka, Y. Uesaka, Y. Tsubokawa and Y. Uesugi:
thermal plasma flowing into the lower-coil, which causes
APCPST-10, OCC-08，2010．
[4] Y. Tanaka, T. Nagumo, H. Sakai, Y. Uesugi, Y. Sakai
higher joule heating in the lower-coil region. Thus,and K. Nakamura: J. Phys. D., 43 (2010) 265201.
the Ar excitation temperature at any position changes[5] Y. Tanaka, T. Muroya, K. Hayashi and Y. Uesugi:with an amplitude of 1500 K according to the upperAppl. Phys. Lett., 89 (2006) 031501.