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The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 309-311 (2000)., The TESLA Test Facility Linac (TTFL) at DESY uses two modules with 8 TESLA superconducting accelerating structures each to accelerate an electron beam up to 360MeV. At present, the beam has been used to perform the proof-of-principle test of the TTF Free Electron Laser and to continue various experiments for the TESLA linear collider project. For this, an rf-gun based photoinjector was installed late 1998 and is in operation since then. It produces a 0.8 ms long train of 1 nC or optionally 8 nC bunches spaced by 1 $\mu$s with low transverse emittance. Theperformance of the injector during the last run from July 1999 to end of April 2000 is reported., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 3 pp. (2000)., A method for measuring electron beam energy using resonance absorption of laser light by electrons in a static magnet field is proposed. The method permits measurement of the average electron beam energy for a wide range up to a few hundred GeV. The relative accuracy of the measurement can reach 10$^{-4}$ – 10$^{-5}$ if the arrangement is calibrated using an electron beam of known energy. The required typical laser power can be much less than 1 W/cm2., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 2069-2071 (2000)., The basic elements of the TESLA linear collider with integrated X-ray FEL are superconducting accelerating cavities. The standard TESLA rf system is designed for a long (1300μs) rf pulse with a flat-top of 800μs and has several elements for the rf power distribution and protectionagainst reflected rf power. Together with the superconducting cavities, normal conducting (NC) cavities are used in TESLA for different purposes, for example as a rf gun. As a rule, one NC cavity uses the total rf power from one klystron (5MWor 10 MW). During the short transient period (the filling time for the L-band NC cavity is near 3μs) the reflected rf power and overvoltage in the waveguide (due to the interference of the forward and backward waves) exceeds the safety limit for the L-band waveguide operation (without SF6 filling). With a special shape of the start up of the rf pulse it is possible to reduce the reflected power several times and limit the overvoltage to a safe level. The increasing of the total pulse length is in the order of two filling times (6μs) and hence negligible in comparison with the total pulse length of 800μs. Different shapes of the beginning of the rf pulse are both considered to reduce the reflected power and to restrict the overvoltage. Results of experiments are presented., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 1107-1109 (2000)., Higher order modes (HOM) can have a destructive influence on the beam emittance in the future linear colliders. Therefore it is important that the quality factor of the high impedance modes be damped under a safe level. Although attentive care was taken in designing the superconducting 9-cell cavities and the HOM couplers for the TESLA collider, a high Q and high impedance mode was discovered in some cavities at the TESLA Test Facility (TTF). In order to discover the reason for which this particular mode is very little damped, a series of investigations have been carried out. The mode frequency is higher for the studied cavities comparatively to others, where this mode seems to be properly damped. Field distribution measurements at the separate cavities show a quasi-trapping of the mode. The simulations andmeasurements done at individual cavities show that for certain boundary conditions the field is minimum at the location of both HOM couplers in a tube., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 187-191 (2000)., The operation of future linear colliders and X-ray Free Electron Lasers places stringent demands on the required beam quality. Setting up and optimization of the machine requires reliable and effective beam diagnostics tools. Different measurement methods and reconstruction techniques for both the transverse and longitudinal phase space distributions are discussed., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 2016-2018 (2000)., A chain of four non-resonantly coupled 7-cell cavities is thought to replace the 9-cell cavities considered in the standard design of the accelerating structures for the TESLA main linac. The main advantages of these so called superstructures are the reduced number of power couplers and the increased fill factor in the linac. This paper deals with the damping of the higher order modes (HOM) to a level where they cause no harm on the beam. Calculations have been performed in order to set a safety limit to the quality factors. The measurements done on a copper model of the superstructure show that the required damping level can be achieved., Published by DESY, Hamburg

The 7th European Particle Accelerator Conference EPAC 2000, EPAC 2000, Vienna, Austria, 26 Jun 2000 - 30 Jun 2000; Hamburg : DESY 462-464 (2000)., The TESLA linear collider with integrated X-ray FEL is based on superconducting accelerating cavities. Behind the positron production target normal conducting cavities have to be used in order to cope with high particle losses and with focusing solenoids surrounding the cavities. With the long rf pulse (800$\mu$s flat-top) the achievable gradients are limited by rf power and heat load restrictions. Beam dynamics calculations of a standing wave preaccelerator will be discussed. The proposed preaccelertor includes an electron-positron beam separator section and is followed by a long transfer line and a matching section into a superconducting booster linac in which the positrons are accelerated to the damping ring energy of 5 GeV. The overall layout of the injector linac and the optimization of relevant parameters, as well as beam dynamics calculations will be presented., Published by DESY, Hamburg