• G.Naumenko, A.Potylitsyn, L.G.Sukhikh
  Nuclear Physics Institite, Tomsk, Russia

The requirement for the accelerator installations of the next generations such as linear collider, where a small beam size at the interaction point is required to achieve a reasonable luminosity, stimulated new techniques development for a non-invasive measuring an electron beam size as small as 10 mm. The development of the non-invasive bunch size diagnostics based on the optical diffraction radiation (ODR) is now in progress in frame of TPU-KEK-SLAC collaboration. The experimental test of a transverse beam size measurement was performed successful on the KEK-ATF extracted electron beam using the optical diffraction radiation from a flat conductive target with a slit. However many difficulties emerge if we going from the one GeV electron energy to the several tenth GeV electron beams. The extremely high Lorenz-factor value gives rise to the some problems, such as a catastrophic decreasing of the method sensitivity to the beam size, extremely pre-wave zone effect even in the optical range and so on. We discuss here the origins of these difficulties and suggest the ways of these problem solutions. To provide the necessary method sensitivity to the ~5mm beam size we suggested to use the ODR from a target, consisting on two crossed conductive semi-planes. In this geometry ODR splits into two beams with phase difference depending on an electron position. If we bring together these beams, the interference picture became depending on the transverse beam size. However in contrast to the flat slit target technique this method sensitivity does not depend on a Lorenz-factor and may be used for high-energy electrons. Also the same technique may be used as a non-invasive beam size monitor by choosing of target parameters. This method was developed and successful tested on the extracted KEK-ATF electron beam. This test showed the possibility of a single bunch micron beam size measurement. All of the preceding allows us to hope to create a tools for the non-invasive beam diagnostics of electron beam with Lorenz-factor higher than 60000.

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• A.P.Potylitsyn, L.G.Sukhikh, A.V.Kostousov
  Tomsk Polytechnic University, Tomsk, Russia

• J.Urakawa, A.Aryshev
  KEK, Tsukuba, Japan

• S. Boogert, P.V.Karataev
  John Adams Institute at RHUL UK

The processes of generation of coherent diffraction radiation (CDR) by a short electron bunch of 45-MeV S-band electron accelerator and it’s Thomson scattering on one of the subsequent bunches have been simulated. Backward CDR is emitted when electron bunch with population and length passes in a vicinity of a conducting target along the direction of specular reflection. In the wavelength region all electrons in a bunch emit coherently and CDR intensity becomes proportional to the square of a bunch population. For a target with inclined angle 45^o CDR beam may be extracted from the accelerator chamber at right angle to an electron beam. For this geometry we calculated CDR spectral-angular distributions from concave targets with different profiles which allow to focus radiation at different distances. If the direction of specular reflection coincides with electron path it is possible to use a concave target with a focal distance providing the maximal overlapping of CDR pulse and a subsequent electron bunch. In this case one may obtain hard radiation in forward direction for the photon energy range as a result of Thomson scattering. The yield of hard photons is proportional to [1]. For the following accelerator parameters [2]: Beam energy - 45 MeV; Charge/bunch - 500 pC; Beam emittance - 3 mm mrad; Bunch length - 0.3 mm. we estimated the efficiency of considered schemes for obtaining of radiation and soft X-ray radiation ( eV) with duration ps.

REFERENCES [1] A.P. Potylitsyn, Physical Review E, vol. 60, 1999, p. 2272. [2] H. Koichiro et al., Nucl.Instrum. and Methods A, 2006 (to be published).