Kinstate intervention in ethnic conflicts : Albania and Turkey compared

Albania and Turkey did not act in overtly irredentist ways towards their ethnic brethren in neighboring states after the end of communism. Why, nonetheless, did Albania facilitate the increase of ethnic conflict in Kosovo and Macedonia, while Turkey did not, with respect to the Turks of Bulgaria? I argue that kin-states undergoing transition are more prone to intervene in external conflicts than states that are not, regardless of the salience of minority demands in the host-state. The transition weakens the institutions of the kin-state. Experiencing limited institutional constraints, self-seeking state officials create alliances with secessionist and autonomist movements across borders alongside their own ideological, clan-based and particularistic interests. Such alliances are often utilized to advance radical domestic agendas. Unlike in Albania's transition environment, in Turkey there were no emerging elites that could potentially form alliances and use external movements to legitimize their own domestic existence or claims

Status of electron temperature and density measurement with beam emission spectroscopy on thermal helium at TEXTOR

Beam emission spectroscopy on thermal helium is used at the TEXTOR tokamak as a reliable method to obtain radial profiles of electron temperature T-e(r, t) and electron density ne(r, t). In this paper the experimental realization of this method at TEXTOR and the status of the atomic physics employed as well as the major factors for the measurement's accuracy are evaluated. On the experimental side, the hardware specifications are described and the impact of the beam atoms on the local plasma parameters is shown to be negligible. On the modeling side the collisional-radiative model (CRM) applied to infer ne and Te from the measured He line intensities is evaluated. The role of proton and deuteron collisions and of charge exchange processes is studied with a new CRM and the impact of these so far neglected processes appears to be of minor importance. Direct comparison to Thomson scattering and fast triple probe data showed that for high densities ne > 3.5 x 10(19) m(-3) the T-e values deduced with the established CRM are too low. However, the new atomic data set implemented in the new CRM leads in general to higher Te values. This allows us to specify the range of reliable application of BES on thermal helium to a range of 2.0 x 10(18) < n(e) < 2.0 x 10(19) m(-3) and 10eV < T-e < 250eV which can be extended by routine application of the new CRM

10 kHz repetitive high resolution TV Thomson Scattering on TEXTOR: design and performance

In late 2003 a 10 kHz multiposition Thomson scattering diagnostic with high spatial resolution became operational on the TEXTOR tokamak. In the initial phase of operation, one burst of 18 pulses of 12 J each with a repetition rate of 5 kHz could be extracted from the laser system. The installation of a low-dope ruby rod (spring 2005) resulted in a system, which can deliver higher pulse energy and moreover a divergence of better than 0.7 mrad, leading to a big improvement in the detection of Thomson scattering photons. Furthermore, the number of laser pulses in one burst could be extended to even more than 30. The achieved laser energy of more than 15 J/pulse makes it possible to measure electron temperature and density profiles with an observational error of 8% on the electron temperature (T-e) and 4% on the electron density (n(e)) at n(e)=2.5 X 10(19) m(-3), per spatial element of 7.5 mm. The viewing optics enables sampling of either the full plasma diameter of 900 mm with 120 spatial channels of 7.5 mm each or a 160 mm long edge chord with 98 spatial channels of 1.7 mm each. The system, which has recently become available for physics exploration, has already been used to study the structure of m=2 magnetic islands and the response of the plasma to off-axis electron cyclotron resonance heating. (c) 2006 American Institute of Physics

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

Runaway electrons represent a serious problem for the reliable operation of the future experimental tokamak ITER. Due to the multiplication factor of exp(50) in the avalanche even a few seed runaway electrons will result in a beam of high energetic electrons that is able to damage the machine. Thus suppression of runaway electrons is a task of great importance, for which we present here a systematic study of runaway electrons following massive gas injection in TEXTOR.Argon injection can cause the generation of runaways carrying up to 30% of the initial plasma current, while disruptions triggered by injection of helium or of mixtures of argon (5%, 10%, 20%) with deuterium are runaway free. Disruptions caused by argon injection finally become runaway free for very large numbers of injected atoms.The appearance/absence of runaway electrons is related to the fraction of atoms delivered to the plasma centre. This so-called mixing efficiency is deduced from a 0D model of the current quench. The estimated mixing efficiency is 3% for argon, 15% for an argon/deuterium mixture and about 40% for helium.A low mixing efficiency of high-Z impurities can have a strong implication for the design of the disruption mitigation system for ITER. However, a quantitative prediction requires a better understanding of the mixing mechanism