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| CT01 |
An Inductive Pick-Up for Beam Position and Current Measurements
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53 |
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- M. Gasior
CERN, Geneva, Switzerland
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An Inductive Pick-Up (IPU) senses the azimuthal distribution of the beam
image current. Its construction is similar to a wall current monitor, but
the pick-up inner wall is divided into electrodes and each of which forms
the primary winding of a toroidal transformer. The beam image current
component flowing along each electrode is transformed to a secondary
winding, connected to a pick-up output. Four pick-up output signals drive
an active hybrid circuit, producing two difference signals proportional
to the horizontal and vertical beam positions, and one sum signal,
proportional to the beam current. The bandwidth of these signals, ranging
from below 1 kHz to beyond 150 MHz, exceeds five decades. Each electrode
transformer has an additional turn to which a pulse from a precise
current source is applied to calibrate the sensor for accurate beam
position and current measurements. The IPU has been developed for the
drive beam linac of the CLIC Test Facility 3. For that purpose it had to
be optimized for low longitudinal coupling impedance in the GHz range.
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| CT02 |
Single Shot Measurements of the 4-Dimensional Transverse Phase Space Distribution of Intense Ion Beams at the UNILAC at GSI
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56 |
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- L. Groening, W. Barth
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
- D.A. Liakin
ITEP, Institute for Theoretical and Experimental Physics, Moscow, Russia
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The UNILAC is used as an injector for the synchrotron SIS. It is designed
to fill the synchrotron up to its space charge limit. The upper limit for
the useful beam emittance of the UNILAC is given by the finite acceptance
of the SIS during the injection process. In order to remain within this
acceptance the emittance growth during beam acceleration and
transportation due to space charge effects must be minimized by applying
an appropriate beam focusing. Therefore, the influence of the magnetic
focusing strength on the beam emittance growth was investigated
experimentally for different beam currents. Measurements of transverse
phase space distributions were performed before and after the Alvarez
accelerator with a periodic focusing channel, respectively. In order to
perform such a wide parameter scan within a reasonable time with respect
to machine stability, the pepper pot technique was applied. The pepper
pot method allows for single-pulse measurements. For comparison several
measurements using the slit-grid technique, which averages over many
pulses, were performed. Both transverse planes were measured
simultaneously. Using two pepper pot devices more than 60 single shot
measurements of the full 4-dimensional transverse phase space
distribution were performed within 8 hours. In this paper we report on
the results of the measurements and we compare them to beam dynamic
simulations and we give an outlook on further developments on pepper pot
devices.
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| CT03 |
Beam Instrumentation for the Single Electron DAΦNE Beam Test Facility
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59 |
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- G. Mazzitelli, F. Sannibale, P. Valente, M. Vescovi
INFN-LNF, Laboratori Nazionali di Frascati dell'INFN, Frascati, Italy
- P. Privitera, V. Verzi
INFN-Roma, Istituto Nazionale di Fisica Nucleare, Sez. di Roma, Roma, Italy
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The DAΦNE Beam Test Facility (BTF) has been successfully commissioned in
February 2002, and started operation in November of the same year.
Although the BTF is a beam transfer line optimized for single particle
production, mainly for high energy detectors calibration, it can provide
electrons and positrons in a wide range of multiplicity: between 1-1010,
with energies from a few tens of MeV up to 800 MeV. The large
multiplicity range requires many different diagnostic devices, from
high-energy calorimeters and ionization/fluorescence chambers in the few
particles range, to standard beam diagnostics systems. The schemes of
operation, the commissioning results, as well as the beam diagnostics are
presented.
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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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| CT05 |
Beam Loss Detection at Radiation Source ELBE
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65 |
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- P. Michel, J. Teichert, R. Schurig, H. Langenhagen
FZR, Forschungszentrum Rossendorf, Dresden, Germany
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The Rossendorf superconducting Electron Linac of high Brilliance and low
Emittance (ELBE) delivers an 40 MeV, 1 mA cw-beam for different
applications such as bremsstrahlung production, electron channelling,
free-electron lasers or secondary particle beam generation. In this
energy region in case of collisions of the electron beam with the pipe
nearly all beam power will be deposited into the pipe material. Therefore
a reliable beam loss monitoring is essential for machine protection
at ELBE. Different systems basing on photo multipliers, compton diodes
and long ionization chambers were studied. The pros and cons of the
different systems will be discussed. Ionization chambers based on
air-isolated RF cables installed some cm away parallel to the beam line
turned out to be the optimal solution. The beam shut-off threshold was
adjusted to 1 μC integral charge loss during a 100 ms time interval. Due
to the favourable geometry the monitor sensitivity varies less than ±50%
along the beam line (different shielding conditions).
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| CT06 |
Timing Sicknesses in Control Systems: Causes, Cure and Prevention
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68 |
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- M. Werner
DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
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In some cases, Trigger Generators or Data Acquisition Systems used for
Beam Diagnostics show undefined or unreliable timing behavior. This
presentation identifies common reasons, ways to fix the problems and some
general rules to avoid them from the beginning. Examples will be given to
discuss causes for e.g. double bunches and timing and trigger jumps,
periodic as well as randomly. It will be discussed, how proper layout,
timing calculations and timing measurements can avoid these inconvenient
effects in advance.
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| CT07 |
Fast DSP Using FPGAs and DSOs for Machine Diagnostics
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71 |
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- G.A. Naylor
ESRF, European Synchrotron Radiation Facility, Grenoble, France
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Digital signal processing using digital signal processors is now a mature
field for machine diagnostics, giving significant benefits, in particular
when used to analyze BPM signals for tune measurement and fast feedback
systems. We discuss here digital signal processing using Field
Programmable Gate arrays (FPGAs) with large gate counts and intelligent
oscilloscopes. These offer great potential for the analysis of very fast
signals to maximize the information extracted from high bandwidth
sensors.
- FPGAs allow data to be filtered numerically and treated at the speed
of data collection of A/D converters in the 100 MHz range. Parallel,
fast and continuous treatment of BPM and FCT signals is possible.
Examples are given of injection efficiency, turn by turn injection
efficiency, turn by turn beam position, amplitude and phase calculation
with averaging over each turn or many turns.
- Modern oscilloscopes include much computational power. In-built DSPs
can perform correlations on the traces allowing the application of
FIR filters. Some oscilloscopes incorporate a PC and allow on-board
manipulation of the data using MATLAB. An example is given using an
FIR applied to a 5 GHz oscilloscope to extend its time response to
measure electron bunch lengths less than 100 ps with 1 ps resolution.
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| CT08 |
Capabilities of the ELETTRA/SLS Multibunch Feedback Electronics
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74 |
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- M. Dehler, R. Kramert, P. Pollet, D. Bulfone, M. Lonza
PSI, Paul Scherrer Institut, Villigen, Switzerland
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Due to the unavailability of commercial ADC and DAC boards, first
commissioning of the transverse multi bunch feedback was done in the last
year using loaned equipment from Sincrotrone Trieste. In order to remedy
that situation, development of ADC and DAC VME boards was started. The
boards do a 500 MS/s data conversion with an 8 bit resolution. The ADC
and DAC circuits are separate modules containing their own one to four
de-/multiplexing electronic reducing the data rate to 125 MS/sec. The
following stage being a common design to both ADC and DAC allows data
recording and play back using on board RAM and allows freely programmable
multiplexing/demultiplexing ratios of one to five to one to twelve. The
digital data streams flow via Front Panel Digital Ports (FPDP). A special
design criterion were low system latencies ensuring a high feedback
efficiency. Apart from lab tests, we report on full feedback system test
and show the feedback performance in the transverse and longitudinal
planes.
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| CT09 |
SLIM (SEM for Low Interception Monitoring) - An Innovative Non-Destructive Beam Monitor for the Extraction Lines of a Hadrontherapy Centre
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77 |
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- L. Badano, O. Ferrando, M. Pezzetta
TERA, Fondazione TERA, Università delgi Studi Milano, Milano, Italy
- G. Molinari
CERN, Geneva, Switzerland
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Real time monitoring of hadrontherapy beam intensity and profile is a
critical issue for the optimisation of the dose delivery to the patient
carcinogenic tissue, the patient safety and the operation of the
accelerator complex. For this purpose an innovative beam monitor, based
on the secondary emission of electrons by a nonperturbative, sub-micron
thick Al target placed directly in the extracted beam path, is being
proposed. The secondary electrons, accelerated by an electrostatics
focusing system, are detected by a monolithic silicon position sensitive
sensor, which provides the beam intensity and its position with a
precision of 1 mm at 10 kHz frame rate. The conceptual design and the
engineering study optimised for hadrontherapy, together with the results
of the preliminary tests of the first system prototype, will be
presented.
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| CT10 |
Beam Diagnostics in the AGOR Cyclotron
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80 |
| |
- S. Brandenburg, W.K. van Asselt, H. Post, H.W. Schreuder
KVI, Kernfysisch Versneller Instituut, Groningen, The Netherlands
- B. Launé
IPN, Institut de Physique Nucléaire, Orsay, France
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The beam diagnostics equipment in modern multi-particle, multi-energy
cyclotrons for research in nuclear physics is reviewed, using the
superconducting cyclotron AGOR at the KVI as an example. An extensive set
of diagnostics tools has been integrated already in the design stage. It
includes three scanning probes for beam centering, a scanning probe
for the measurement of radial and vertical beam oscillations and
beamlosses, beam phase pick-ups to optimize isochronism of the magnetic
field and profile and current measurements along the beam path through
the four movable extraction elements. The operating experience gained
since the start-up of the cyclotron in 1996 is discussed for the various
diagnostics tools and improvements are described.
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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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