Profiles of the Balmer lines D,(H,), Db(Hs) and D, (H,) have been measured in the scrape-off layer and within the edge of the TEXTOR (upgrade) plasma, under Ohmic conditions and with neutral-beam injection. Each line profile shows a strong Zeeman effect in the vicinity of line centre, and a marked central dip when mainly the ( I components are observed. The line core evidently originates from cold atoms in the edge plasma, excited in the course of molecular dissociation, while the broad pedestal on which the core rests is radiated by excited atoms produced through chargeexchange recombination of deuterons (protons), transported outwards from the much hotter plasma interior, and by atoms heated directly by collisions with the deuterons (protons). Core temperatures of about 0.5 eV and less are obtained from line profile analysis.

The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating in the m=n 3=1 mode configuration, are presented. The deeply penetrating external magnetic field perturbation of this configuration increases the toroidal plasma rotation. Staying below the excitation threshold for the m=n 2=1 tearing mode, this toroidal rotation is always in the direction of the plasma current, even if the toroidal projection of the rotating magnetic field perturbation is in the opposite direction. The observed toroidal rotation direction is consistent with a radial electric field, generated by an enhanced electron transport in the ergodic layers near the resonances of the perturbation. This is an effect different from theoretical predictions, which assume a direct coupling between rotating perturbation and plasma to be the dominant effect of momentum transfer. Helical magnetic field perturbations are introduced in tokamak plasmas to study, on the one hand, the ergodic divertor concept [1,2] and, on the other hand, the interaction of such perturbations with the magnetohydrodynamics (MHD) stability of the plasma [3,4]. Recent experiments, for instance, suggest a control method to mitigate edge localized modes while maintaining the pedestal pressure and thus plasma confinement [5][6][7]. However, open questions remain, in particular, with regard to the influence on the momentum transport of the plasma. Indeed, one motivation to equip the tokamak TEXTOR with the Dynamic Ergodic Divertor (DED) [8] was to be able to study the interaction between helical magnetic field perturbations and plasma transport and stability.The DED consists of 16 magnetic perturbation coils (four quadruples), plus two additional coils for the compensation of the magnetic field imperfections at the feeder regions of the coils. The coils wind helically around the inner side of the torus (major radius: R 1:75 m; minor radius of the circular plasma cross section typically a 0:47 m) with a pitch corresponding to the magnetic field lines of the magnetic flux surface with a safety factor of q 3. Depending on the choice of coil connections to the power supplies, base modes with different poloidal and toroidal mode numbers can be produced. For the DED these are m=n 12=4, 6=2, and 3=1. The penetration depth into the plasma strongly depends on the mode numbers: While the m=n 12=4 affects the edge plasma only, the m=n 3=1 mode reaches into the plasma center (the maximum radial magnetic field component achievable by the DED at the q 2 surface is 10 ÿ3 of the total magnetic field).In this Letter we present results obtained by the m=n 3=1 mode operation. Covering about one-third of the poloidal cross section of the torus, the mode spectrum of the DED does not contain many sidebands. For the m=n 3=1 configuration the three dominant resonant components inside the plasma are m 1, 2, and 3. In Fig. 1 their strengths at the respective resonances are PRL 94, 015003 (2005) P H Y S I C A L

Recently, the dynamic ergodic divertor (DED) of TEXTOR has been studied in an m/n = 3/1 setup which is characterized by a relatively deep penetration of the perturbation field. The perturbation field creates (a) a helical divertor, (b) an ergodic pattern and/or (c) excitation of tearing modes, depending on whether the DED current is static, rotating in the co-current direction or in the counter-current direction. Characteristic divertor properties such as the high recycling regime or enhanced shielding have been studied. A strong effect of the ergodization is spin up of the plasma rotation, possibly due to the electric field at the plasma edge. Tearing modes are excited in a rather reproducible

Four new low field side antennae grouped in pairs have been installed on TEXTOR. It is found that the interaction with the wall (density rise, impurity generation) is significantly reduced when operating each pair out of phase (E) as opposed to in phase (0). The beneficial effect in the n configuration is obtained without drop in plasma loading. This experimental property is shown, from theory, to be explained by the judicious choice of the geometrical configuration. A further improvement in the wall interaction is made possible by an appropriate choice of wall conditioning (wall carbonization with liner at 400'C or. above all, boronization). As a result record low values of PYsd/Ptota, were achieved during ICRH. The large reduction in wall interaction during ICRH allows routine long pulse (> 1 s) ICRH operation at the maximum power level available (g 2.5 MW).

I o n c y c l o t r o n h e a t i n p on TEXTOR has now reached t h e ?:exajoule l e v e l , The h e a t i n g s c e n a r i o is normally mode conversion b u t o c c a s i o n a l l y minority h e a t i n g i n 2 D-(H) plasma. i i i t h a p p r o p r i a t e wall c o n d i t i o n i n g by c a r b o n i z a t i o n more than 1 >lid of RF power has been i n j e c t e d f o r lone pulse d u r a t i o n s (?. 1 s). The ICRF heated plasma i s c h a r a c t e r i z e d by 2 q u a s is t a t i o n a r i t y of a l l plasma parameters, l i t t l e i f no impurity i n c r e a s e 2nd 2 l o o p v o l t a g e r e d u c t i o n r e s u l t i n g i n t h e t o t a l power coupled to t h e plasma reaching s i x times t h e remainine ohxic power i n p u t .