| Paper | Title | Page |
|---|---|---|
| MOO2A01 | Physics And Diagnostics Of Laser-Plasma Accelerators | 11 |
|
||
| The recent and continuing development of powerful laser systems, which can now deliver light pulses containing a few Joules of energy in pulse durations of a few tens of femto seconds, has permitted the emergence of new approaches for generating energetic particle beams. By focusing these laser pulses onto matter, extremely large electric fields can be generated, reaching the TV/m level. Such fields are 10,000 times greater than those produced in the radio-frequency cavities of conventional accelerators. As a result, the distance over which particles extracted from the target can be accelerated GeV energy range is reduced to distances on the order of millimetres. A few years ago, several experiments have shown that laser-plasma accelerators can produce electron beam with maxwellian-like distribution [1], in 2004 high-quality electron beams, with quasi-mono energetic energy distributions at the 100 MeV level [2] and recently in the GeV range using a capillary discharge [3]. These experiments were performed by focusing a single ultra short and ultra intense laser pulse into an under dense plasma. More recently we produced a high quality electron beam using two counter-propagating | ||
| MOD1A03 | Electron Beam Diagnostics for the ALBA Light Source | 27 |
|
||
| This paper presents the diagnostics systems that will be used to monitor the electron beam at ALBA, a 3 GeV 3rd generation synchrotron light source. The electron beam is characterized by measuring its transverse position in the beam pipe, beam current, transverse size and longitudinal structure. We provide a complete picture of all the systems to diagnose the electron beam along ALBA facility, not only in the Storage Ring but also in the injector system (Linac, Booster and transfer lines). | ||
| WEPB04 | The VEPP-4M Dynamic Aperture Determination Through the Precise Measurement of the Beam Lifetime | 238 |
|
||
| To determine experimentally the particle stable area in the electron-positron collider VEPP-4M we measure the beam life time with high accuracy as a function of moving aperture. The measurement is performed by a photodiode installed in the collider diagnostic beam line. The experimental set up and the measurement results are described. Comparison with the tracking simulation is presented. | ||
| WEPB06 | Direct Comparison of the Methods of Beam Energy Spread Determination in the VEPP-4M Collider | 244 |
|
||
|
The VEPP-4M electron-positron collider is now operating with the KEDR detector for the experiment of precise measurement of tau-lepton mass. The nearest experimental program of the accelerator includes scan of the energy area below J/psi meson to search narrow resonances. The monitoring of beam energy spread is important to know the energy spread contribution into the total systematic error. In this report we discuss the application of several diagnostics for beam energy spread measurement. The data obtained with Compton BackScattering (CBS) technique* are compared with the value of the spread derived from the betatron motion of the beam**. The measurements by all the methods were done at the same accelerator run, i.e. the different diagnostics can be compared directly. The value of the energy spread was determined for a set of collider operating modes, covering the energy area from 1200 MeV up to 1843 MeV. Width of the J/psi and psi' resonance measured with the KEDR detector is used as a reference.
References*N. Muchnoi et al. //Proceed. of EPAC 2006, Edinburg, Scotland, TUPCH074**T. Nakamura et al. // Proceed. of the 2001 Particle Accelerator Conference, Chicago, p. 1972-1974. |
||
| WEPB13 | Focusing of Optical Transition and Diffraction Radiation by a Spherical Target | 259 |
|
||
|
During the last few years Transition Radiation (TR) and Diffraction Radiation (DR) have been intensively studied for different applications such as diagnostics of electron beam size, emittance, length, energy spread, etc. For extremely high-energy electrons the broadening of TR (DR) spatial distribution due to “pre-wave” zone effect [*] leads to distortion of the radiation characteristics and decreasing of photon concentration per unit square detector. In papers [**,***] it was shown that using a spherical target one can make TR (DR) distribution in the pre-wave zone identical to a far-field one. To verify our approach we carried out an experiment at KEK-ATF extraction line with electron beam energy of 1.28 GeV using a spherical target to focus optical TR (DR) at the distance of L=440 mm which corresponds to an extreme pre-wave zone. We also measured OTR (ODR) characteristics from a flat target in order to compare them with OTR (ODR) characteristics from the spherical one. We clearly observed that OTR (ODR) angular distribution from the spherical target is narrower than from a flat one and it’s very similar to a far-field zone distribution as it was predicted by the theory.
* V. A.Verzilov, PLA 273(2000)135** P. V.Karataev, PLA 345(2005)428*** A. P. Potylitsyn and R. O. Rezaev, NIMB 252(2006)44 |
||
| WEPB18 | Electron Beam Temperature Measurements at the Fermilab Medium Energy Electron Cooler | 268 |
|
||
| The Fermilab Recycler ring employs an electron cooler to store and cool 8.9-GeV antiprotons. The cooler is based on an electrostatic accelerator (Pelletron) working in an energy-recovery regime. Several techniques for determining the characteristics of the beam dynamics have been investigated. Beam temperature measurements using OTR in conjunction with a Pepper-pot have been made at several settings of the upstream optics of the machine. Without temperature the pepper-pot hole images would have sharp boundaries. A finite temperature makes these boundaries broader. Thus, comparison of the ratios of the hole image boundaries and intensities is a measure of the beam temperature. In this paper we report the results so far obtained using this technique. | ||
| WEPB22 | Touschek Lifetime Measurement with a Spurious Bunch in UVSOR-II Electron Storage Ring | 280 |
|
||
|
We have developed a method to measure the Touschek beam lifetime of an electron storage ring using spurious bunches in single-bunch operation by measuring change in the single-bunch impurity over time. To measure a spurious bunch and the main bunch simultaneously, we use a photon counting method with sufficient dynamic range and response time. We demonstrated the method by measuring the Touschek beam lifetime in the UVSOR-II electron storage ring. We find that the Touschek beam lifetime dominates the total beam lifetime in UVSOR-II in usual vacuum condition. The Touschek beam lifetime measurement in multibunch operation with the method will be discussed in the presentation.
A. Mochihashi, M. Katoh, M. Hosaka, Y. Takashima, Y. Hori, NIM-A 572 (2007) 1033-1041. |
||
| WEPB29 | Bunch-by-Bunch Longitudinal Diagnostics at DAΦNE by IR Light | 298 |
|
||
| Compact uncooled HgCdTe semiconductor detectors optimized in the mid-IR range have been used to record time resolved single bunch synchrotron radiation (SR) emissions from the DAΦNE e- main ring. These devices allow a low cost bunch-by-bunch longitudinal diagnostics. Indeed, the detectors make possible to record a train of 2.7 ns long bunches per turn. A comparison with synchrotron light signals coming from the e+ ring is stimulating but at DAΦNE only two SR beamlines are operational and because of the lack of apertures in the main wall no easy alternatives exist for the e+ ring. To solve the problem, a compact SR port has been considered and is going to be implemented on the positron ring. A small dedicated vacuum chamber with a ZnSe infrared window and remote controlled mirrors will be installed to focus the light on the IR detectors. The source characteristics have been simulated and the optical system with the complete acquisition system will be described. When ready, the real time comparison between data collected on the two beams will be performed improving accelerator diagnostics and as a major tool to increase the stored currents in the e+ ring and the collider luminosity. | ||
| WEPB30 | Current Status of the SQUID Based Cryogenic Current Comparator for Absolute Measurements of the Dark Current of Superconducting RF Accelerator Cavities | 301 |
|
||
| This contribution gives an overview on the current status of a LTS-SQUID based Cryogenic Current Comparator (CCC) for detecting dark currents, generated for example by superconducting cavities for the upcoming X-FEL project. To achieve the maximum possible energy the gradients of the superconducting RF accelerator cavities should be pushed close to the physical limit of 50 MV/m. The so-called dark current of the superconducting RF cavities at strong electric fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value classify the cavities. The main component of the CCC is a LTS-DC SQUID system which allows us to measure extremely low magnetic fields, caused by extracted dark currents of RF cavities under test. For this reason the SQUID input coil is connected across a toroidal superconducting pick-up coil (inner diameter: about 100 mm) for the passing electron beam. A noise limited current resolution of 40 pA/sqrt(Hz) with a measurement bandwidth of up to 70 kHz was achieved. Design issues and the application for the CHECHIA cavity test stand at DESY as well as experimental results will be discussed. | ||
| WEPC07 | Injection Diagnostics Using Triggered Bunch-by-Bunch Data Acquisition | 322 |
|
||
| Quality of injection is very important for reliable and successful operation of colliders and light sources. In this paper we present a technique for real-time monitoring of injection transients in storage rings. We also demonstrate how the data can be used for tuning the injection system. A novel data processing method, coupled with triggered bunch-by-bunch data acquisition system enables one to monitor the effects of the adjustments nearly in real time. The acquisition and postprocessing technique will be illustrated with the data from PEP-II and DAΦNE. | ||
| WEPC08 | Fiberoptics-Based Instrumentation for Storage Ring Beam Diagnostics | 325 |
|
||
| We present the results of our experiments at the Advanced Light Source concerning the coupling of synchrotron radiation into optical fibers. Many beam diagnostic devices in today's synchrotron rings make use of the radiation emitted by the circulating particles. Such instruments are placed in close proximity of the accelerator, where in many instances they cannot be easily accessed for safety consideration, or at the end of a beamline, which, because of its cost, can only move the light port a few meters away from the ring. Our method, suitable for all those applications where the longitudinal properties of the beam are measured (i.e. bunch length, phase, etc.), allows placing the diagnostic instruments wherever is more convenient, up to several hundreds of meters away from the tunnel. This would make maintaining and replacing instruments, or switching between them, possible without any access to restricted areas. Additionally, one can use the vast array of optoelectronic devices, developed by the telecommunication industry, for signal analysis. | ||
| WEPC10 | Tune, Coupling, and Chromaticity Measurement and Feedback During RHIC Run 7 | 331 |
|
||
|
Tune feedback was first implemented in RHIC in 2002, as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End[1]. Continuous measurement of all projections of the betatron eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites[2,3]. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. Preliminary investigations of power line harmonics were presented earlier[4]. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort.
[1] M. Gasior and R. Jones, DIPAC 2005, Lyon, p.312.[2] P. Cameron et. al., PRST-AB, Dec 2006. [3] R. Jones et. al., DIPAC 2005, Lyon, p.298.[4] P. Cameron et. al., DIPAC 2005, Lyon, p.33. |
||
| WEPC14 | Segmented Beam Dump for Time Resolved Spectrometry on a High Current Electron Beam | 340 |
|
||
| In the CLIC Test Facility 3, the strong coupling between the beam and the accelerating cavities induces transient effects such that the head of the pulse is accelerated twice as much as the rest of the pulse. Three spectrometer lines are installed along the linac with the aim of measuring energy spread versus time with a 20ns resolution. The major difficulty is due to the high power carried by the beam which imposes extreme constraints of thermal and radiation resistances for the detector. This paper presents the design and the performances of a simple and easy-to-maintain device, called ‘segmented dump’. In this device, the particles are stopped inside metallic plates and the deposited charge is measured in the same way as in faraday cups. Simulations were carried out with the Monte Carlo code ‘FLUKA’ in order to evaluate the problems coming from the energy deposition and find ways to prevent or reduce them. The detector resolution has been optimized by choosing the adequate material and thickness for the plates. The overall layout of the monitor is described with a special emphasis on its mechanical assembly. Finally, limitations arising at high beam energies are discussed. | ||
| WEPC16 | Excitation Striplines for SOLEIL Fast Transverse Feedback | 343 |
|
||
|
SOLEIL, the French third generation light source, is equipped with excitation striplines for a tune monitor and for the (bunch-by-bunch) Fast Transverse Feedback* that has been recently implemented. A careful design of the striplines and their vacuum feedthroughs was aimed at maximizing the effectiveness of the excitation power via high shunt impedances, and minimizing the power taken from the beam via low parasitic mode losses. Three stripline kickers have been developed for these applications. We report on their design using RADIA and GdfidL simulation codes, on the fabrication of the striplines, and on the experimental results with beam.
* R. Nagaoka: Transverse Feedback Development at SOLEIL. ID 1257 |