Paper | Title | Other Keywords | Page | ||
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IT06 | Short Bunch Beam Profiling | diagnostics, instrumentation, free electron laser, photon, optics, SPPS, LCLS | 25 | ||
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The complete longitunal profiling of short electron bunches is discussed
in the context of 4th generation light sources. The high peak current
required for the SASE lasing process is achieved by longitudinal
compression of the electron bunch. The lasing process also depends on of
the preservation of the transverse emittance along the bunch during
this manipulation in longitudinal phase space. Beam diagnostic
instrumentation needs to meet several challenges: The bunch length and
longitudinal profile should be measured on a single bunch to characterize
the instantaneous, peak current along the bunch. Secondly, the transverse
emittance and longitudinal energy spread should be measured for slices of
charge along the bunch. Several techniques for invasive and noninvasive
bunch profiling will be reviewed, using as examples recent measurements
from the SLAC Sub Picosecond Photon Source (SPPS) and the planned
diagnostics for the Linac Coherent Light Source (LCLS). These include
transverse RF deflecting cavities for temporal streaking of the electron
bunch, RF zero-phasing techniques for energy correlation measurements,
and electro-optic measurements of the wake-field profile of the bunch.
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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 | diagnostics, instrumentation, ion, transverse-dynamics | 56 | ||
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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 | diagnostics, instrumentation, controls, electron, positrons | 59 | ||
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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 | diagnostics, instrumentation, electron, free-electron-laser | 62 | ||
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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 | diagnostics, instrumentation, electron, radiation, beam-losses, beam-transport | 65 | ||
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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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CT11 | Beam Based HOM Analysis of Acceleating Structures at the TESLA Test Facility LINAC | diagnostics, instrumentation, higher-order-mode, wakefield | 83 | ||
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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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PM10 | Characterisation of Fast Faraday Cups at the ELETTRA Linac | diagnostics, electron, ELETTRA, instrumentation | 113 | ||
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A major upgrade of the ELETTRA injector is currently on going: the 1 GeV
LINAC will be replaced with a 100 MeV LINAC and a 2.5 GeV Booster
Synchrotron. A new set of diagnostics is now under development for these
two new machines. The new Fast Tune measurement system for the Booster
represents a significant improvement as compared to the present Tune
measurement system.
With the Booster cycling at 3 Hz, horizontal and vertical tunes have to be
measured during the energy ramp, whose duration is 160 ms. To completely
characterise the dynamics of the Booster during the energy ramp, a set of
25 tune values has been required, corresponding to a 6.4 ms interval
between successive measurements. The accuracy of this measurement is
<10-3. Such frequency spans are achievable using a Real Time Spectrum
Analyser (Tektronix 3026), which is a fast sampling instrument with
built-in FFT algorithm and data presentation.
In this paper, after describing the system specifications and
architecture, we present the results of the preliminary tests, which have
been carried out both in the laboratory and on the Storage Ring.
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PM14 | Upgrade Of The ESRF Fluorescent Screen Monitors | instrumentation, emittance, luminosity | 125 | ||
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The ESRF injector system contains 23 Fluorescent Screen monitors: 4 in
the TL-1 transferline (200 MeV), 8 in the Booster, and 11 in the TL-2
transferline (6 GeV). They are based on Chromium doped Alumina screens
that are pneumatically inserted at 45o angle in the beam path with an
optical system, at 90o angle, collecting and focusing the emitted
light onto a low-cost CCD camera with standard 75Ω video output.
Serving mainly alignment purposes in the past 10 years, the present
upgrade aims at a 200 μm fwhm resolution for beam-size and profile
measurements. The particularity of the Alumina screen not in vacuum but
in atmosphere will be explained. Details of the mechanics, the optic
system and a cost-efficient way of light flux adjustment will be given.
The analysis of the factors determining the ultimate spatial resolution
will show that it is dominated by the screen characteristics. Results
obtained with different screen material will be presented.
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PM18 | Residual Gas Fluorescence for Profile Measurements at the GSI UNILAC | diagnostics, instrumentation, photon, optics | 137 | ||
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The high beam currents, delivered at the LINAC at GSI (UNILAC) can
destroy intercepting diagnostics within one macro-pulse. As an
alternative for a non-destructive profile measurement the methode for
residual-gas-fluorescence is investigated. The fluorescence light is
emitted by the N2 molecules of the residual gas at the blue wavelength
range and can be monitored with a modern CCD-camera. The images are
transferred via digital bus (IEEE 1394 'FireWire') and the profiles are
generated by analysis of the images with a modern software tool (National
Instruments 'LabView'). Due to the short beam pulses (about 0.2 ms) the
light intensities emitted by the residual gas are low and require a high
amplification (gain >106) which is realized with an image intensifier
with double MCP (multi channel plate), connected with a fiber taper to
the CCD-chip. The design parameters of the optics and electronics are
discussed as well as the advantages of the digital data transmission.
Measurements with heavy ion beams of several 100 μA and a comparison to
other profile measurement methods show a good signal-to-noise ratio and
prove a good applicability.
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PM28 | Application of Beam Diagnostics for Intense Heavy Ion Beams at the GSI UNILAC | heavy ion, space charge, longitudinal-dynamics | 161 | ||
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With the new High Current Injector (HSI) of the GSI UNILAC the beam pulse
intensity had been increased by approximately two orders of magnitudes.
The HSI was mounted and commissioned in 1999; since this time the UNILAC
serves as an injector for the synchrotron SIS, especially for high
uranium intensities. Considering the high beam power of up to 1250 kW and
the short stopping range for the UNILAC beam energies (≤12 MeV/u),
accelerator components could be destroyed, even during a single beam
pulse. All diagnostic elements had to be replaced preferably by
non-destructive devices. The beam current is mainly measured by beam
transformers instead of Faraday cups, beam positions are measured with
segmented capacitive pick-ups and secondary beam monitors instead of
profile harps. The 24 installed pick-ups are also used to measure
intensities, widths and phase of the bunches, as well beam energies by
evaluating pick-ups at different positions. The residual gas ionization
monitors allow on-line measurements of beam profiles. The knowledge of
the real phase space distribution at certain position along the linac is
necessary for optimizing the machine tuning, for the improvement of the
matching to the synchrotron and for a better understanding of beam
dynamic issues under space charge conditions. The paper will report the
application of different beam diagnostic devices for the measurement of
transverse beam emittances at different UNILAC beam energies and for
different beam intensities. Additionally, measurements of the bunch
structure after the HSI and a the design of a new device for the
measurement of the longitudinal emittance at the end of the UNILAC will
be included.
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PT02 | Pill-Box Cavity BPM For TESLA Cryomodul | diagnostics, monitoring, position, resonance, single bunch | 172 | ||
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A new cavity BPM with 10 μm resolution is designed and fabricated
to perform single bunch measurements at the TESLA linear collider. In
order to have a low energy dissipation in the cryogenic supermodule, the
inner surface of the cavity is copper plated. Cross-talk is minimised by
a special polarisation design. The electronics, at 1.5 GHz, is a homodyne
receiver normalised to the bunch charge. Its LO-signal for
down-conversion is taken from the same cavity.
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PT15 | Performance of the ELBE BPM Electronics | diagnostics, instrumentation, monitoring, pick-up, ELBE | 202 | ||
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The ELBE radiation source is based on a superconducting linac. Initially
it was designed to be used in CW mode with repetition rates either 13 MHz
either 260 MHz. Later it was decided to operate the accelerator with
reduced repetition rates for diagnostic reasons and for certain users.
Now it is possible to operate at repetition rate 13/n MHz, where n can be
2, 4, 8, 16, 32, 64, and 128. It is required that the BPM system supports
any of these operation modes. A core element of the BPM electronics is a
logarithmic amplifier AD8313 made by Analog Devices Inc. The logarithmic
amplifier is a direct RF to DC converter rated up to 2.5 GHz. Initial
design of the BPM electronic was sophisticated only for CW operation with
repetition rate more than 10 MHz, since bandwidth of the AD8313 is
about of 10 MHz. Additionally a sample and hold amplifier is built in to
provide enough time for an ADC to make measurements. The sample and hold
amplifier is synchronized with a micropulse frequency. In the paper we
present results of the modified BPM electronics test.
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PT16 | A High Dynamic Range Beam Position Measurement System for ELSA-2 | electron, diagnostics, instrumentation | 205 | ||
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New beamlines are presently under construction for ELSA, a 20 MeV
electron linac located at Bruyères-le-Châtel. These lines need a beam
position measurement system filling the following requirements: small
footprint, wide dynamic range, single-bunch/multi-bunch capability,
simple design. We designed a compact 4-stripline sensor and an
electronic treatment chain based on logarithmic amplifiers. This paper
presents the design, cold and hot test results.
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PT23 | Transverse Emittance Measurements at the Photo Injector Test Facility at DESY Zeuthen (PITZ) | diagnostics, emittance, free-electron-laser, transverse-dynamics, PITZ | 225 | ||
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The main research goal of the Photo Injector Test Facility at DESY
Zeuthen (PITZ) is the development of electron sources with minimized
transverse emittance like they are required for the successful operation
of Free Electron Lasers and future linear colliders. The process of
electron beam optimization requires characterization of the transverse
emittance at a wide range of operation parameters. The design and
functionality of the emittance measurement system at PITZ is presented.
The methods applied as well as the resolution limits of the system are
discussed. The latest measurements of the transverse properties of the
electron beam are presented.
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PT24 | Development of a Bunch-Length Monitor with Sub-Picosecond Time Resolution and Single-Shot Capability
Funding: SNF (Schweizer National Fonds) |
diagnostics, instrumentation, electron, bunching, SLS | 228 | ||
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A bunch-length monitor with single-shot capability is under development
at the 100 MeV pre-injector LINAC of the Swiss Light Source (SLS). It is
based on the electro-optical effect in a ZnTe crystal induced by coherent
transition radiation (CTR). A spatial autocorrelation of the CTR in the
EO-crystal rotates the polarisation of a mode-locked Nd:YAG laser to
produce an image on an array detector representing the Fourier components
of the CTR spectrum. Up to now a theoretical model for the emission of
transition radiation has been developed in order to design optics
allowing efficient transport of the CTR onto the EO-crystal. The
frequency dependency of the CTR due to the finite size of the target
screen has been measured in the sub-THz regime at the SLS Linac. The
results strongly support the theoretical descriptions of the radiation
source. By expanding the intensity pattern in higher-order
Laguerre-Gaussian modes, the transmission through the optical transfer
system is calculated.
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