| Paper | Title | Page |
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| IT01 | Review Of Diagnostics For Next Generation Linear Accelerators | 1 |
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| New electron linac designs incorporate substantial advances in critical beam parameters such as beam loading and bunch length and will require new levels of performance in stability and phase space control. In the coming decade, e- (and e+) linacs will be built for a high power linear collider (TESLA, CLIC, JLC/NLC), for fourth generation X-ray sources (TESLA FEL, LCLS, Spring 8 FEL) and for basic accelerator research and development (Orion). Each project assumes significant instrumentation performance advances across a wide front. This review will focus on basic diagnostics for beam position and phase space monitoring. Research and development efforts aimed at high precision multi-bunch beam position monitors, transverse and longitudinal profile monitors and timing systems will be described. | ||
| IT02 | Instrumentation And Diagnostics Using Schottky Signals | 6 |
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| Schottky signal measurements are a widely used tool for the determination of longitudinal and transverse dynamical properties of hadron beams in circular accelerators and storage rings. When applied to coasting beams, it is possible to deduce properties as the momentum distribution. the Qx,y-values and the average betatron amplitudes. Scientific applications have been developed in the past few years, as well, namely nuclear Schottky mass spectrometry and lifetime measurements. Schottky signals from a coasting beam are random signals which appear at every revolution harmonic and the respective betatron sidebands. Their interpretation is more or less straightforward unless the signal is perturbed by collective effects in the case of high phase space density. Schottky signals from bunched beams reveal the synchrotron oscillation frequency, from which the effective rf voltage seen by the beam can be deduced. The detection devices can be broad-band or narrowband. The frequency range is usually in the range between a few hundred kHz up to about 150 MHz. In connection with stochastic cooling, Schottky signals are used at frequencies up to 8 GHz. Narrow-band devices are needed if signal-to-noise problems arise, e.g. in the case of antiproton beams. Heavy ion beams require less effort, it is relatively easy to detect single circulating highly charged ions. | ||
| IT03 | Diagnostics and Instrumentation for FEL | 11 |
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| Free Electron Laser are coherent sources of radiation based on the interaction of a relativistic electron beam in an undulator field. According to the energy of the accelerator, they presently cover a wide spectral range, from the infra-red to the VUV. FELs combine the diagnostics of typical laser systems (for the measurement of spectral and temporal characteristics, the transverse mode pattern, the polarisation) and the diagnostics of relativistic electron beams. The electron beam is characterised in order to evaluate and control the FEL performances, but also in order to measure the effect of the FEL on the electron beam. The FEL characteristics are monitored with various types of detectors, depending mainly on the spectral range. Diagnostics for Linac based Infra Red FELs and storage ring FELs in the UV-VUV will be described. Particular instrumentation, required for FEL operation, such as the optical resonator, possible diagnostics inside the undulator will also be analysed. | ||
| IT04 | Review of Emittance and Stability Monitoring Using Synchrotron Radiation Monitors | 16 |
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| Different techniques of emittance and stability monitoring using bend magnet and undulator radiation will be reviewed. Besides imaging methods for emittance monitoring , the problem of XBPM's used for the measurement of the centre of mass position of the undulator beams will be treated in detail. The key feature of these monitors is a careful electron optical design to take account of gap dependent changes of the shape and photon energy of the undulator beam as well as spurious signals from dipoles and high heat load. The reason for the fact that these monitors work well on low energy machines like BESSY II but often fail due in high energy machines will be demonstrated by experimental results obtained on different types of BESSY II insertion devices such as undulators, wavelength shifters, multipole wigglers and electromagnetic undulators. Experimental results of global and local orbit monitoring and a proof of principle of a XBPM-based local feedback will be shown. | ||
| IT05 | Results with LHC Beam Instrumentation Prototypes | 21 |
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| The beam instrumentation foreseen to provide the necessary diagnostics in the transfer lines and in the main rings of the LHC was conceived in the past years. The requirements expected from the different systems are now being closely analyzed and specified. In a few cases, tests of prototypes have already been performed, profiting from the facilities offered by existing machines. The beam position measurement system had to be tackled first, as the pick-ups had to be integrated into the cryogenic part of the machine. Over the last two years other topics started to be experimentally investigated in order to define the best way to meet the requirements for the LHC era. Amongst these different studies are luminosity monitoring devices, various instruments for the measurement of the transverse beam distributions, the use of head-tail sampling to measure the beam chromaticity and quadrupole gradient modulation to derive the local amplitude of the lattice function. The paper discusses the results of these tests. | ||
| IT06 | Measurement of Small Transverse Beam Size Using Interferometry | 26 |
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| The principle of measurement of the profile or size of small objects through the spatial coherency of the light is known as the van Cittert-Zernike theorem. We developed the SR interferometer (interferometer for synchrotron radiation) to measure the spatial coherency of the visible region of the SR beam, and we demonstrated that this method is able to measure the beam profile and size. Since the small electron beam emits a SR beam which has a good spatial coherency, this method is suitable for measuring a small beam size. In this paper, the basic theory for the measurement of the profile or size of a small beam via the spatial coherency of the light, a design of the SR interferometer, and the results of beam profile measurement, examples of small beam size measurements and recent improvements are described. | ||
| IT07 | Accelerator Physics Experiments with Beam Loss Monitors at BESSY | 31 |
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| The extended use of beam loss monitoring has led to a better understanding of the linear and non-linear physics involved in the single and multiple particle dynamics at BESSY. This knowledge has been used for improving the performance of the light source in terms of lifetime, beam stability, and stability of the energy. The key to these experiments are loss monitors placed at strategic locations of the ring with high sensitivity to Touschek or Coulomb scattered particles. Coulomb-scattering depends strongly on the transverse dynamics which is determined by the magnetic guiding fields. Losses occur primarily at the vertical aperture restrictions imposed by the flat insertion device vacuum chambers. Tune scan measurements clearly show resonances produced by the lattice magnets and by some of the insertion devices. Touschek scattering depends on the 3-dimensional electron density and the spins of the colliding particles. In transfer function type experiments these dependencies have been used to observe the effect of resonant transverse and longitudinal beam excitations. Loss monitors allow to detect excited head-tail and higher longitudinal modes which are invisible in the center of mass motion. Another application is the detection of the resonant destruction of the spin polarization of the ensemble of electrons. This is used routinely in order to determine the beam energy with high accuracy. | ||
| IT08 | Breaking New Ground with High Resolution Turn-By-Turn BPMs at the ESRF | 36 |
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| This High-Resolution, Turn-by-Turn BPM system is a low-cost extension to the existing BPM system, based on the RF-multiplexing concept, used for slow Closed-Orbit measurements. With this extension Beam Position measurements in both planes, at all (224) BPMs in the 844 m ESRF Storage Ring, for up to 2048 Orbit Turns with 1 μm resolution are performed. The data acquisition is synchronised to a single, flat 1 μs, transverse deflection kick to the 1μs beamfill in the 2.8μs revolution period. The high quality of this synchronisation, together with the good reproducibility of the deflection kick and the overall stability of the Closed Orbit beam allows to repeat the kick and acquisition in many cycles. The subsequent averaging of the data obtained in these cycles yields the 1um resolution. The latter allows lattice measurements with high precision such as the localisation of very small focussing errors and modulation in Beta values and phase advances. It also finds an unique application to measure, model, and correct the (H to V) Betratron coupling which recently showed successfully the reduction of coupling and vertical emittance below respectively 0.3% and 12picometer×rad. This method takes full benefit from 64 BPM stations situated around 32 straight-sections (no focussing elements) of 6m length allowing the phase-space measurements in their centers. | ||
| IT09 | Overview of RHIC Beam Instrumentation and First Experience from Operation
Work performed under the auspices of the U.S. Department of Energy |
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| A summary of the beam instrumentation tools in place during the year 2000 commissioning run is given including the technical layout and the appearance on the user level, here mainly the RHIC control room. Experience from rst usage is reported as well as the lessons we have learned during RHIC operation so far. Upgrades and changes compared to the year 2000 systems are outlined. Described tools include beam position monitors (BPM), ionization prole monitors (IPM), beam loss monitors (BLM), bunch current measurements, luminosity monitors, tune meters and Schottky monitors. | ||
| IT10 | 6-D Electron Beam Characterisation Using Optical Transition Radiation and Coherent Diffraction Radiation | 46 |
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| The development of non-intercepting diagnostics for high charge density and high energy electron beams is one of the main challenge of beam instrumentation. Diffraction Radiation based diagnostics, being non-intercepting, are among the possible candidates for the measurements of beam properties for the new generation linacs. At the 1 GeV Sincrotrone Trieste linac, we are performing the first measurements of beam transverse parameters using Diffraction Radiation emitted by the electron beam passing through a 1 mm slit opened on a screen made of aluminium deposited on a silicon substrate. The analysis of the angular distribution of the Diffraction Radiation for a given wavelength, slit aperture and beam energy gives information about the beam size and its angular divergence. | ||
| IT11 | Possible Spin-Offs from LHC Physics Experiments for Beam Instrumentation | 51 |
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| This paper aims to introduce some of the new technology and materials used in the construction of the LHC physics experiments into the domain of the beam instrumentalist. The development of radiation hard fibre-optic technology, for example, can equally well be applied to beam instrumentation systems for the direct transmission of analogue or digital signals from high to low radiation environments. Many electronics techniques such as a system developed for the fast integration of photomultiplier signals could also prove very useful in the construction of new beam diagnostic instruments for bunch-to-bunch measurements. Other topics covered will include a fast beam synchronous timing system based on laser technology and a look at pixel detectors as a possible replacement for CCD cameras in imaging applications. | ||
| IT12 | Investigations of Longitudinal Charge Distribution in Very Short Electron-Bunches | 56 |
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| Electro-optical-sampling is a powerful technique to measure the longitudinal charge distribution of very short electron bunches. The electrical field moving with the bunch induces an optical an-isotropy in a ZnTe crystal which is probed by a polarized laser pulse. Two measurement principles are possible. In the first one a short laser pulse of lengths <50 fs is used directly to scan the time varying optical properties of the crystal. In the second method the laser pulse is frequency chirped and the temporal information is encoded into the time ordered frequency spectrum, which can be recovered by an optical grating and a CCD camera. A resolution in the 100 fs regime can also be achieved with longitudinal phase space tomography. Acceleration on the slope of the rf wave at different phases and measurements of the energy profiles are sufficient for a reconstruction algorithm based on maximum entropy methods. The longitudinal phase space distribution can be obtained without artifacts due to the limited angular range of the projections. |