Kugeler O.

Paper	Title	Page
TUP40	CW Operation of Superconducting TESLA Cavities	222
	W. Anders, J. Knobloch, O. Kugeler, A. Neumann BESSY
	Several recently proposed superconducting linacs are designed to operate in CW mode. The TELSA technology, which they are based upon, was originally developed for pulsed mode. In order to demonstrate the feasibility of CW mode with TESLA technology, BESSY has built the HoBiCaT test facility [1]. The main issues of CW operation were examined and solutions are shown on the following topics: Limits of heat conduction in the Helium vessel, gas dynamics in the two phase line, layout of a CW cryo module, heating of HOM couplers, CW operation of the main RF coupler, choice of helium bath temperature, pressure stability of the helium bath and microphonics and their compensation.
WE201	Microphonics in CW tesla cavities and their compensation with fast tuners	377
	A. Neumann, W. Anders, J. Knobloch, O. Kugeler BESSY
	Superconducting linac cavities of single pass Free Electron Lasers or Energy Recovery Facilities have a very low or near zero beamloading and are thus operated at a high quality factor with a narrow RF resonance, respectively. Following the phase and amplitude stability of the RF field is very easily degraded by any kind of mechanical detuning. InCWoperation microphonics is the main error source for cavity detuning. To achieve high field stabilities in the regime of 0.02 degree in phase and 1e-3 down to 1e-4 in amplitude a fast tuning system is mandatory to compensate the detuning. In this paper the microphonics detuning measured at HoBiCaT will be shown and analyzed with respect to a detuning controller application. The controller design is given by a combination of a feedback and adaptive feedforward approach based on fast piezo tuners implemented in the Saclay coarse tuner designs. It will be shown, that at 1.8 K and loaded quality factors between 3e7-1e8 a compensation of a least a factor of two up to seven is achievable.
	Slides(PDF)
WEP58	Investigation of passive stabilization- and different tuning systems for TESLA cavities with respect to CW operation	637
	O. Kugeler, A. Neumann, J. Knobloch, W. Anders Bessy
	BESSY has planned a free-electron-laser that will be operated with TESLA type cavities at high Q-values in CW mode. These operating parameters imply a low cavity bandwidth and thus a high sensitivity towards ponderomotive oscillations, in particular microphonics. In the Ho- BiCaT facility, located at BESSY, we have tested various tuning systems (Saclay I, Saclay II) and compared their usability for CW operation. Furthermore, the impact of "Rossendorf"-type stabilization fixtures on the mechanical properties was investigated.