Paper |
Title |
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CT04 |
The Beam Inhibit System for TTF II
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62 |
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- D. Nölle, P. Göttlicher, R. Neumann, D. Pugachov, K. Wittenburg, M. Wendt, M. Werner, H. Schlarb, M. Staack
DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
- M. Desmons, A. Hamdi, M. Jablonka, M. Loung
CEA, Commissariat à l'Energie Atomique, Saclay, France
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The new generation of light sources based on SASE Free-Electron-Lasers
driven by LINACs operate with electron beams with high beam currents and
duty cycles. This is especially true for the superconducting machines
like TTF II and the X-RAY FEL, under construction or planning at DESY.
Elaborate fast protections systems are required not only to protect the
machine from electron beams hitting and destroying the vacuum chamber,
but also to prevent the machine from running at high loss levels,
dangerous for components like the FEL undulator.
This paper will give an overview over the different protection systems
currently under construction for TTF II. The very fast systems, based on
transmission measurements and distributed loss detection monitors, will
be described in detail. This description will include the fast
electronics to collect and to transmit the different interlock signals.
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CT11 |
Beam Based HOM Analysis of Acceleating Structures at the TESLA Test Facility LINAC
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83 |
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- M. Wendt, S. Schreiber, A. Gössel
DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
- M. Hüning
FNAL, Fermi National Accelerator Laboratory, Batavia, IL, USA
- G. Devanz, M. Jablonka, C. Magne, O. Napoly
CEA, Commissariat à l'Energie Atomique, Saclay, France
- N. Baboi* (on leave from NTLPRP)
SLAC, Stanford Linear Accelerator, Stanford, CA, USA
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The beam emittance in future linear accelerators for high energy physics
and SASE-FEL applications depends highly on the field performance in the
accelerating structures, i.e. the damping of higher order modes (HOM).
Besides theoretical and laboratory analysis (network analyzer), a beam
based analysis technique was established [S. Fartoukh, et.al.,
Proceedings of the PAC99 Conference] at the TESLA Test Facility (TTF)
linac. It uses a charge modulated beam of variable modulation frequency
to excite dipole modes. This causes a modulation of the transverse beam
displacement, which is observed at a downstream BPM and associated with a
direct analysis of the modes at the HOM couplers. Emphasis of this
presentation is put on beam instrumentation and signal analysis aspects.
A brief introduction of eigenmodes in resonant structures, as well as
some interesting measurement results are further presented.
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PT26 |
Cryogenic Current Comparator for Absolute Measurement of the Dark Current of the Superconducting Cavities for Tesla
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234 |
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- K. Knaack, M. Wendt, K. Wittenburg
DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
- R. Neubert, S. Nietzsche, W. Vodel
FSU Jena, Friedrich-Schiller Universität, Jena, Germany
- A. Peters
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
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A newly high performance SQUID based measurement system for detecting
dark currents, generated by superconducting cavities for TESLA is
proposed. It makes use of the Cryogenic Current Comparator principle and
senses dark currents in the nA range with a small signal bandwidth of 70
kHz.
To reach the maximum possible energy in the TESLA project is a strong
motivation to push the gradients of the superconducting cavities closer
to the physical limit of 50 MV/m. The field emission of electrons (the so
called dark current) of the superconducting cavities at strong fields may
limit the maximum gradient. The absolute measurement of the dark current
in correlation with the gradient will give a proper value to compare and
classify the cavities.
This contribution describes a Cryogenic Current Comparator (CCC) as an
excellent and useful tool for this purpose. The most important component
of the CCC is a high performance DC SQUID system which is able to measure
extremely low magnetic fields, e.g. caused by the extracted dark current.
For this reason the SQUID input coil is connected across a special
designed pick-up coil for the electron beam. Both the SQUID input coil
and the pick-up coil form a closed superconducting loop so that the CCC
is able to detect dc currents down to 2 pA/√Hz. Design issues and the
application for the CHECHIA cavity test stand at DESY as well as
preliminary experimental results are discussed.
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