| Paper | Title | Other Keywords | Page | ||
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| IT03 | Single Pass Optical Profile Monitoring | instrumentation, emittance | 10 | ||
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Beam profiles are acquired in transfer lines to monitor extracted beams
and compute their emittance. Measurements performed on the first
revolutions of a ring will evaluate the matching of a chain of
accelerators. Depending on the particle type and energy, these
measurements are in general performed with screens, making either use of
Luminescence or OTR [Optical Transition Radiation], and the generated
beam images are acquired with detectors of various types: CCD, CMOS, CID,
TV Tubes or Multi-Anode Photo-Multipliers. The principles, advantages and
disadvantages of both families of screens will be discussed in relation
with the detectors used. A possible evaluation method for luminescent
screens and beam test results will be presented. Finally other optical
methods used will be mentioned for completeness.
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| IT06 | Short Bunch Beam Profiling | diagnostics, instrumentation, linac, free electron laser, photon, 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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| PM03 | Studies of OTR Angular Distribution on CTF2 | CLIC, diagnostics, instrumentation, transverse-dynamics | 92 | ||
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Today, Optical Transition radiation (OTR) is widely used in beam
diagnostics. The most common application is the imaging of the transverse
and longitudinal beam profiles. Other beam parameters like divergence and
energy can also be deduced by observing the angular distribution of the
OTR emission (“Donuts”). In order to investigate the possibilities
and the limits offered by this technique we have performed a test on the
48 MeV, 1 nC electron beam of the CLIC Test Facility 2 (CTF2).
Beam divergences between 2 and 6 mrad were measured with an accuracy of
few percent. A good agreement was also found between the energy
measurements obtained with a classical spectrometer and the OTR based
technique. We conclude describing some possible future applications of
OTR based diagnostics for CLIC.
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| PM04 | OTR from Non-Relativistic Electrons | CLIC, diagnostics, instrumentation, transverse-dynamics | 95 | ||
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The CLIC Test Facility 3 (CTF3) injector will provide pulsed beams of
high average current; 5 A over 1.56 μs at 140 keV. For transverse beam sizes
of the order of 1mm, as foreseen, this implies serious damages to the
commonly used scintillating screens. Optical Transition Radiation from
thermal resistant radiators represents a possible alternative. At low
energy the OTR emission is feeble and distributed over a large solid
angle. In order to investigate the feasibility of such a diagnostic
studies have been carried out on a test 80 keV photo injector. The
experimental set-up is described and the results are compared to the
calculations based on the OTR emission theory. Our conclusions for the
design of the CTF3 injector profile monitor are also given.
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| PM05 | Optical Transmission Line For Streak Camera Measurements at Pitz | diagnostics, electron, gun, longitudinal-dynamics, PITZ | 98 | ||
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The photoinjector injector test facility at DESY Zeuthen (PITZ) [1]
produces electrons with a momentum of about 4 MeV/c. It is the aim to
measure the temporal characteristics of the electron bunch train and
single bunches with high accuracy of the order of 1 ps and less. Several
types of streak cameras will be used in combination with different
radiators which transform particle energy in light. The problem to be
solved is the light transport over a distance of about 27 m. Basic demands
to the optical system and design principles will be explained. The
optical and technical solutions will be presented. The strategy of
adjustment and commissioning of the optical system will be described. The
system contains switchable optics to use different radiators (OTR,
Cherenkov radiators). Diagnostic tools are foreseen at different
positions along the optical axis. The results of different measurements
in the lab and using the original system will be presented. The problems
on the minimalization of the time dipersion in the system will be
discussed.
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[1] F.Stephan, et al., Photo injector test facility under construction at DESY Zeuthen, FEL 2000, Durham |
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| PM18 | Residual Gas Fluorescence for Profile Measurements at the GSI UNILAC | diagnostics, instrumentation, photon, linac | 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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| PT31 | Optical Fibre Dosimeter for SASE FEL Undulators | beam-losses, diagnostics, free-electron-laser, instrumentation | 248 | ||
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Single pass Free Electron Lasers (FELs) based on self-amplified
spontaneous emission (SASE) are developed for high brightness and short
wavelength applications. They use permanent magnet undulators which are
radiation sensitive devices. During accelerator commissioning beam losses
can appear anywhere along the undulator line. To avoid damage of the
permanent magnets due to radiation, an optical fibre dosimeter system can
be used. The increase of absorption caused by ionizing radiation is
measured in radiation sensitive optical fibers. The dose system enables
relatively fast particle loss tuning during accelerator operation and
allows the monitoring of the accumulated dose. Dose measurements in
narrow gaps which are inaccessible for any other (online) dosimeter type
become possible. The electromagnetic insensitivity of optical fibre
sensor is an advantage of applications in strong magnetic undulator
fields. At each location the light absorption is measured by using an
optical power-meter. The dynamic range is about 50 dB and covers the
linear range of the dose calibration of the fibre. The resolution of the
system is 140 mGy. The time between successive measurements is about 5
minutes. The system was installed and successfully tested at the TESLA
Test Facility TTF1. The fibre sensors will be a standard diagnostic tool
in the soft X-ray user facility TTF2.
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