D.V. Kalinina

Experimental Group LHD

N. Tamura

S. Sudo

V.Yu. Sergeev

National Institute for Fusion Science (NIFS-Repository)

Fig.l. Comparison of the CXR signal intensity measured inthe visible spectral range from the TESPEL(Fluorine (AF=479.3 nm), Magnesium (AMg=478.9 nm» andfrom the pure impurity pellet (Neon (ANe=524.7 nm) andCarbon (Ac=529 nm». The amount of the impurities wasdifferent.References:1) K. Khlopenkov, S. Sudo, Plasma Phys. Control. Fusion43 (2001) 15472) Sudo S. et al., Plasma Phys. Control. Fusion 44 (2002)1293) Sergeev V.Yu. et aI., Plasma Phys. Control. Fusion 44(2002) 277and Ne, respectively, which is several orders of magnitudemore than in the TESPEL. In this case, the CXR signalmeasured at the plasma periphery was two orders ofmagnitude larger than the F tracer CXR signal levelmeasured as shown in Fig.I.Judging from these experimental results, the CXRmeasurement in the visible range is expected to be possibleby increasing the tracer amount. The inner core diameter inthe current TESPEL setup can be increased up to 300 J..l.m,and the resulting tracer amount up to 4 X 1018. As seen fromFig. 1, the increase of the CXR signal by one order ofmagnitude is expected by increasing the impurity amount, ifwe assume the same level of coefficient of visible lightemission for each tracer material. In addition, since theincrease of the CXR cross-section is expected in the VUVand ultra soft x-ray spectral range, the measurement in thatdomain will be perfonned for the next campaign.1E201E191E18amount of impurity1E17........ LU2.;i,lPF I< <,... Expected .. < •" : '. ,.:. :.. ; ",,"'h'esPEl CXR. ;. ;...1 .... :, . ' . :':':,:",'1',,: signatsafes t,;';<;';';":" , .. "': ' :": . .. in the next .' . ' ... t ....' 'I"" I!. l···' .: ", campaign: : : :::: ../., ".. . .. , ...;/r1: ..- , - - ,.',:' " ';'''':' , : '.'.' .. : :,'.: .:.",.' - ." :. -: :-::::-: <' -: .:-::'-::- • --::;C'lii 0,1.2'II)(.)o 0,01II)The behavior of impurity tracer ions deposited locally inthe core plasma by means of TESPEL injection can bemeasured by the observation of the line emission due tocharge exchange reaction of injected impurity nuclei, I(nuclear charge Z) with the neutral beam injection (NBI)hydrogen atoms, H (assumed to be in their ground state):1 2+ + HIs 1(2-1)+ + H+ (I).This method allows us to estimate the local impuritydiffusion coefficients, which is already obtained byLi III (ALi=449.9 nm) on CRS [1,2]. In TESPEL CXRSexperiments with the Li tracer on LHD, however, Li IIIemission in the visible spectral range could not be measureddue to the low SIN ratio and/or other reasons. As wasmentioned in [3], the key parameter of this problem is thecross-section of the reaction (1). It is well known that theCX total cross-section depends on NBI beam energy (ENBI)and Z impurity charge. On Li III case the value of CX cross-section for LHD (ENB1 = 150kev) is about 30 times less thatthat for CRS (36keV). During the 6th LHD campaign,according to the theoretical optimization of the TESPELCXR signals for various impurities in the visible spectralrange under the conditions of the LHD plasma [3], theTESPEL CXRS experiments with other tracer materials,such as Fluorine (F, AF(n=HH9)=479.3 nm) and Magnesium(Mg, AMg(n=12-.11)=478.9 nm), have been carried out. The Ftracer was used as a teflon (CzF4)n block and the Mg traceras a powder. In our experiments, the TESPEL outerdiameter is ranged from 600 to 900 J..l.m. Since it is difficultto evaluate the amount of these impurities due to itsamorphous shape, we assumed that the 50 % (- 2 x 10·12m-3)by volume of the inner core of the TESPEL is occupied bythe tracer material. Then, the total amount of the impuritiesinjected by TESPEL was approximately 1 x 1017 for the Ftracer, and 8 Xl016 for the Mg tracer, respectively. In thecase of the F tracer, in only few shots, a small signal wasobserved at one of the eight channels. In the case of the Mgtracer, the signal as the CXR emission was not observed.For comparison with our results, the CXR emissionsof other materials, such as Ne (ANe(n=U-.l0)= 524.7 nm), B(AB(n=7-.6)=494.6 nm) and C (A.c(n=8-'7)=529 nm), wereinvestigated. This could be done after the impurity injection,such as the gas puffing and the pure pellet injection. In thecase of the pure impurity pellet, the total amount of theimpurity in that is approximately 3 x 1019 and 1 x 1020 for C§ 45. Optimization of TESPEL CXRS Diagnosticin the Visible Spectral Range for theImpurity Transport Study on LHDKalinina, D.V. (Graduate Univ. Advanced Studies),Sudo, S., Tamura, N., Sergeev, V.Yu. (SPbSTU),LHD Experimental Group49

Optimization of TESPEL CXRS Diagnostic in the Visible Spectral Range for the Impurity Transport Study on LHD

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