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| MOPCH051 | Operation of the First Undulator-based Femtoslicing Source | laser, electron, photon, radiation | 154 | ||
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At the BESSY II storage ring, a source of sub-100-fs x-ray pulses with tunable polarization and excellent signal-to-background ratio has been constructed in 2004, based on laser-induced energy modulation ("femtoslicing"*) and subsequent angular separation of the short-pulse x-rays from an elliptical undulator. After commissioning and characterizing the source, short-pulse radiation is now routinely delivered for pump-probe applications. The paper summarizes the results from commissioning and operational experience as well as possible upgrade options.
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*A. Zholents and M. Zoloterev, PRL 76 (1996), 912. |
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| MOPCH056 | Development of High Brightness Soft X-ray Source Based on Inverse Compton Scattering | laser, electron, MCP, scattering | 166 | ||
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Compact soft X-ray source based on inverse compton scattering have been developed at Waseda University. Using 1047nm laser light from Nd:YLF laser scattered off 4.2MeV electron beam generated from a photo-cathode rf-gun, we have already suceeded to generate the soft X-ray. The energy of this x-ray is included in the part of water window, in which absorption of water is much less than that of moleculars that organize a living body. Furthermore, this x-ray source has other features such as short pulse, proportional mono-energy and energy variableness. Because of these tures, the application to the biological microscope have been expected. However, the flux of x-ray is not satisfied for the biological microscope application. Therefore, to multiply a soft X-ray flux, we utilized multi-pass amplifier for the laser light and improved a collision chamber. In this conference, we will report the experimental results and future plans.
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| MOPLS002 | The Study of the Machine-induced Background and its Applications at the LHC | LHC, insertion, shielding, CERN | 529 | ||
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We present the recent advances in the analysis of the machine-induced background generation and formation at the LHC. Different aspects of the study of the machine background problem at the LHC are reviewed, including the background production at the different stages of the machine operation, the role and influence on the background from the collimators in the experimental insertions and the background shielding. The potential use of the machine background for the purposes of detector testing and alignment is also discussed.
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| MOPLS003 | Tertiary Halo and Tertiary Background in the Low Luminosity Experimental Insertion IR8 of the LHC | shielding, LHC, insertion, simulation | 532 | ||
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In our report we present the results for numerical simulation of tertiary halo and tertiary background in the LHC. We study the case of the proton losses in the betatron cleaning insertion IR7 with the subsequent tertiary halo generation in the downstream experimental insertion IR8. We analyze the formation of tertiary background in the experimental area of the IR8 and evaluate the performance of the machine-detector interface shielding with respect to this source of the background. The results obtained are compared with the previous estimates of the machine-induced background in the low luminosity insertions of the LHC, and the balance between different sources of the background is discussed.
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| MOPLS004 | Estimation and Analysis of the Machine-induced Background at the TOTEM Roman Pot Detectors in the IR5 of the LHC | LHC, optics, simulation, hadron | 535 | ||
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The problem of background generation in the experimental insertion IR5 of the LHC during machine operation in the dedicated TOTEM mode with low intensity beams and the specially designed beta* = 1540 m optics is discussed. The sources of the machine-induced background in the IR5 forward physics areas are identified and their relative importance is evaluated. The results of the background simulation in the IR5 are presented, based on the most recent estimates of the residual gas density for TOTEM beam conditions. The methods for background analysis and rejection are explained.
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| MOPLS049 | Anomalous High Radiation Beam Aborts in the PEP-II B-factory | vacuum, radiation, SLAC, luminosity | 652 | ||
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The PEP-II B-factory at SLAC has recently experienced unexpected beam losses due to anomalously high radiation levels at the BaBar detector. The problem was finally traced to the occurrence of very high pressure (>100 nTorr) spikes that have a very short duration (few seconds). We describe the events and show analysis predicting where in the vacuum system the events originated and describe what was discovered in the vacuum system.
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| MOPLS076 | The Stimulated Breit-Wheeler Process as a Source of Background e+e- Pairs at the ILC | photon, electron, resonance, electromagnetic-fields | 727 | ||
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Passage of beamstrahlung photons through the bunch fields at the interaction point of the ILC determines background pair production. The number of background pairs per bunch crossing due to the Breit-Wheeler, Bethe-Heitler and Landau-Lifshitz processes is well known. However the Breit-Wheeler process also takes place in and is modified by the bunch fields. A full QED calculation of this Stimulated Breit-Wheeler process reveals cross section resonances due to the virtual particle reaching the mass shell. The one loop Electron Self energy in the bunch field is also calculated and included as a radiative correction. The bunch field is considered to be a contant crossed electromagnetic field with associated bunch field photons. Resonance is found to occur whenever the energy of contributed bunch field photons is equal to the beamstrahlung photon energy. The Stimulated Breit-Wheeler cross section exceeds the ordinary Breit-Wheeler cross section by several orders of magnitude and a significantly different pair background may result.
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| TUPCH010 | Profile Measurement by Beam Induced Fluorescence for 60 MeV/u to 750 MeV/u Heavy Ion Beams | ion, vacuum, photon, heavy-ion | 1013 | ||
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At the planned heavy ion facility FAIR very intense beams of heavy ions will be transported between various synchrotrons and focused on targets for secondary ion productions. For the transverse profile determination only non-destructive methods are suited due to the large deposed beam power. We investigated experimentally the Beam Induced Fluorescence (BIF) method. Due to the atomic collision by the beam ions the residual gas N2 is excited to fluorescence levels. Single photon detection is performed by a double MCP image intensifier coupled to a digital CCD camera. Extensive experimental studies (with the today available lower ion currents) were performed to determine the photon yield and the background contribution for different ion species and beam energies. The measured profiles show a good correspondence to other methods as long as the vacuum pressure by a regulated N2 inlet is below 10-1 mbar. Based on the experimental results, the layout for a BIF profile determination will be discussed.
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| TUPCH042 | The Optical System for a Smith-Purcell Experiment at 45MeV | radiation, vacuum, cryogenics, electron | 1097 | ||
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Smith-Purcell (SP) radiation has been used to investigate the longitudinal profile of a 45MeV, picosecond long bunched beam at the FELIX facility, FOM Institute. The three important optical elements that made this experiment possible were (i) high quality optical filters, (ii) nonimaging light concentrators, (iii) and a system to rapidly change between gratings.
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| TUPCH043 | Observations of the Longitudinal Electron Bunch Profile at 45MeV Using coherent Smith-Purcell radiation | radiation, electron, linear-collider, collider | 1100 | ||
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Coherent Smith-Purcell (SP) radiation has been used to determine the longitudinal profile of the electron bunch at the FELIX facility, FOM Institute. Far-infrared radiation was detected using a simple, compact arrangement of 11 pyroelectric detectors. Background radiation was suppressed through the use of high quality optical filters, and an efficient light collection system. The measured bunch profile was most closely in agreement with 90% of the particles contained within 5.5ps, with an approximately triangular temporal profile.
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| TUPCH080 | Bunched Beam Current Measurements with 100 pA rms Resolution at CRYRING | pick-up, CRYRING, acceleration, ion | 1196 | ||
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In CRYRING molecular beams with currents down to 1 nA are used for experiments. To extend the rms resolution of the bunched beam current measurements down to 100 pA, a BERGOZ Integrating Current Transformer (ICT) and one of the the capacitive pick-up's sum signal are integrated simultaneously. The absolute calibration of the pick-up integrator signal is carried out at the end of the acceleration stage, during 20-60 ms. The ion beam current can be measured over a pulse width range of 100 ns to 15 us with a 20-60% bunch duty cycle. For both detectors, low noise amplifiers and a differential input double integrator have been designed. A programmable phase shifter allows measurement of the beam current during the acceleration of the ions, generating a gate signal with proper phase for the integrators in the 30 kHz-3 MHz frequency range. The bandwidth of the integrators used is 100 Hz.
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| TUPCH177 | Measurement of the Sorption Characteristics of NEG Coated Pipes: The Transmission Factor Method | vacuum, CERN, ERL, LHC | 1432 | ||
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ZrTiV Non Evaporable Getter (NEG) coatings of vacuum chambers have found application in the particle accelerators to lower the gas pressure, during the operative conditions. For that, the characterization of the actual pumping speed of the NEG coating is a key issue. It is carried out by means of the dynamic sorption method according to ASTM F798-82 standard, conducted "offline" on a sample (coupon), suitably positioned inside the chamber to be coated and recovered after the process. To evaluate in-situ the sorption characteristics of getter coated chambers, a different measurement technique (Trasmission Factor Method) is here described. It is based on the measurement of pressures ratio at the inlet and the outlet of a coated pipe, under a flow of test gas. A calibration curve permits to evaluate sticking probability of the coated surface from the pressure ratio. The use of reference samples to calibrate the method is quite difficult. A better approach is a modellistic one, finding the dependency of pressure ratio on the average sticking probability, the pipe length and the section geometry and dimensions. Preliminary experimental results will be shown.
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| TUPCH182 | Radiation Monitors as a Vacuum Diagnostic in the Room Temperature Parts of the LHC Straight Sections | radiation, LHC, vacuum, hadron | 1441 | ||
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In the absence of collisions, inelastic interactions between protons and residual gas molecules are the main source of radiation in the room temperature parts of the LHC long straight sections. In this case the variations in the radiation levels will reflect the dynamics of the residual pressure distribution. Based on the background simulations for the long straight section of the LHC IP5 and on the current understanding of the residual pressure dynamics, we evaluate the possibility to use the radiation monitors for the purpose of the vacuum diagnostic, and we present the first estimates of the predicted monitor counts for different scenarios of the machine operation.
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| WEPCH088 | High Order Aberration Correction | controls, simulation, multipole, quadrupole | 2125 | ||
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It is known that modern accelerators fall under nonlinear aberrations influence. The most of these aberrations have harmful character, and their effect must be maximally decreased. There are a set of approaches and codes to solving this problem. In this paper, we consider an approach for solving this problem using the matrix formalism for Lie algebraic tools. This formalism allows reducing the starting problem to linear algebraic equations for aberration coefficients, which are elements of corresponding matrices. There are discussed results evaluated using suggested approach and nonlinear programming tools. Some examples of corresponding results are given.
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| WEPLS096 | Design and Calculation of a Superferric Combined Magnet for XFEL | quadrupole, dipole, XFEL, DESY | 2598 | ||
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A planned European X-ray Free Electron Laser so-called XFEL is being developed within the framework of an international collaboration. The design and fabrication of a prototype of a combined magnet is part of the Spanish contribution to this project. This magnet consists of a superferric quadrupole for focusing and two dipoles (horizontal and vertical) for steering, glued around the beam tube. The magnet will be operated in a superfluid helium bath. The aperture is 78 mm. The quadrupole gradient is 35 T/m whereas each dipole field is about 0.04 T. The magnetic saturation is limited to 5% at nominal current, which is quite a challenging specification for such aperture and gradient. As the overall length of the helium vessel is just 300 mm, the calculation of the magnetic field is a pure 3-D problem which has been solved and optimized using two different FEM codes to cross-check the results. This paper also gives some guidelines about the fabrication techniques most suitable for the first prototype, which is now under construction.
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| THESPA01 | Before the Big Bang: An Outrageous New Perspective and its Implications for Particle Physics | radiation, LANL, electron, LEFT | 2759 | ||
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The second law of thermodynaics implies that big bang must have been an extraordinarily precisely organized state. What was the geometrical nature of this state? How can we resolve, in any scientific way, the mystery of how such precision came about? In this talk, a novel (and perhaps outrageous) solution is suggested, which involves an examination of what is to be expected of the very remote future of our universe, with its observed accelerated expansion. Some possible observational consequences of the proposal will be indicated, together with some apparent implications for particle physics, some of which are non-standard.
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| THPCH089 | The Electromagnetic Background Environment for the Interaction-point Beam Feedback System at the International Linear Collider | feedback, SLAC, target, linear-collider | 2997 | ||
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The Interaction Point (IP) feedback system is essential for maintaining the luminosity at the International Linear Collider (ILC). It is necessary to demonstrate the performance of the feedback beam position monitor (BPM) in an electron-positron pair background similar to that expected in the ILC interaction region (IR). We have simulated the ILC beam-beam interactions and used a GEANT model of the IR to evaluate the pair and photon flux incident on the BPM, for both the 2 mrad and 20 mrad crossing angle geometries. We present results as a function of the proposed machine parameter schemes, as well as for various system layouts within the IR. We plan to study the degradation of BPM resolution, and the long term survivability, in beam tests at End Station A at SLAC. To simulate the background environment of the ILC a 'spray beam' will be produced, which will scatter from a mechanical mock-up of the forward region of the IR, and irradiate the BPM with realistic flux of secondary pairs. We present the proposed experimental layout and planned beam tests.
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| THPLS074 | Ground Vibration Measurement at NSRRC Site | site, storage-ring, emittance, simulation | 3454 | ||
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For the future 3GeV TPS project in the NSRRC, ground vibration would be important for this low emittance machine. We have monitored the ground vibration under various experimental conditions at the NSRRC site. Sensors were installed in the bare site, underground 35 meters deep and ground of TLS storage ring, including an electricity shutdown in the NSRRC. From the collected data, we compare the effect about day and night, traffic effect, internal machine vibration propagation. Specific vibration sources and their propagations are also discussed.
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