Paper | Title | Page |
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TUP071 | The ISAC-II SC-Linac Over Current Monitoring System | 557 |
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A personnel protection system is used to monitor the ion beam current into the experimental hall from the ISAC-II SC-linac. Two resonant capacitive pickups in the transfer line operate at the third harmonic of the bunch rate, 35.36 MHz, Ion charge, velocity and bunch width affect the sensitivity so calibration with dc Faraday cups is needed. Each monitor has a single conversion receiver with an active mixer. LO signals are provided by a frequency synthesizer locked to the accelerator synthesizer. The 1250 Hz IF signals are amplified, filtered with a 100 Hz bandwidth and amplitude detected. No image rejection is used as the background is due to on-frequency leakage from the RFQ and bunchers. An antenna in each monitor loosely couples a pulsed rf test signal to each pickup. These induced signals are mixed down to 11875 Hz, filtered, detected and used to provide watchdog signals. The measured currents are displayed through our EPICS control system which allows setting of the gain ranges, trip levels and conversion factors. The signals are also processed independently by dedicated ADC's and FPGA's to cause the Safety system to trip the beam if the current exceeds a nominal 10 nA. |
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TUP072 | AIRIX Diagnostic Devices for Focal Spot Size and Dose Measurements | 560 |
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Funding: CEA-DAM, Polygone d'Experimentation de Moronvilliers 51 490 Pontfaverger Moronvilliers (France). olivier.pierret@cea.fr |
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TUP073 | Tailoring the Emittance of a Charged Particle Beam with a Tunnel Emittance Meter | 561 |
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Based on the 'tunnel' emittance used for electron focusing, a similar procedure with two pairs of slits with variable widths is proposed to evaluate fractional emittances and brilliances for ion beams. The measurement starts with closing both slits (one after the other), until a certain fraction of the beam current is cut out. The emittance and brilliance then is well defined for the passing beam part. Formulae are given for the emittance as well as for the brilliance in dependence of the slit width and current. This emittance measurement is free from the background subtraction problem found in the classical density measurement of phase space(s). The functions for the decrease of the emittance and for the increase of the brilliance in dependence of the transmitted beam current provide a figure of merit for the quality of the investigated beam. The device at the same time is also an adjustable emittance filter for the passing beam. At the expense of current the emittance and/or brilliance of a beam can be tailored to any value, which is available by the beam quality. |
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TUP074 | Commissioning of the HITRAP Decelerator Using a Single-Shot Pepper Pot Emittance Meter | 564 |
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Funding: Work supported by BMBF under contract 06FY160I. *HITRAP webpage of AP division at GSI, http://www.gsi.de/forschung/ap/projects/hitrap/index_e.html |
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TUP075 | DITANET: A European Initiative in the Development of Beam Instrumentation for Future Particle Accelerators | 567 |
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Without an adequate set of beam instrumentation, it would not be possible to operate any particle accelerator, let aside optimize its performance. In a joint effort between several major research centres, Universities, and partners from industry, DITANET aims for the development of beyond-state-of-the-art diagnostic techniques for future accelerator facilities and for training the next-generation of young scientists in this truly multi-disciplinary field. The wide research program covers the development of beam profile, current, and position measurements, as well as of particle detection techniques and related electronics. This contribution introduces this new Marie Curie Initial Training Network, presents the DITANET partner institutes, and gives an overview of the networks broad research and training program. |
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TUP076 | Design of a Beam Halo Monitor with a High Dynamic Range | 570 |
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A thorough understanding of halo formation and its possible control is highly desirable for essentially all particle accelerators. Limiting the number of particles in the halo region of a beam would allow for minimizing beam losses and maximizing beam transmission, i.e. the experimental output. Measurements based on either optical transition radiation (OTR) or synchrotron radiation (SR) provide an interesting opportunity for high dynamic range measurements of the transverse beam profile, since the signal is linear with the beam charge over a wide range and is routinely used in many diagnostic applications. In this contribution, first results on beam halo measurements obtained from a flexible core masking technique and an innovative CID camera system are summarized. |
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TUP077 | Development of Screen Monitor with a Spatial Resolution of Ten Micro-meters for XFEL/SPring-8 | 573 |
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At SPring-8, the 8 GeV linac for an X-ray free electron laser (XFEL) is now under construction. In order to realize the XFEL, highly qualified electron beams are required. A measurement of spatial structure of such beam is very important for the beam tuning of XFEL. The spatial structure is measured with a screen monitor, which we now develop. The resolution of the measurement is required within 10 um. The screen monitor comprises a vacuum chamber with a thin metal (100 um, SUS) foil to emit OTR, lenses for focusing and a CCD camera system. The main feature of the monitor is a bright and high-resolution optical system. In order to realize this system, the lenses are placed close to the foil, the distance between the lenses and the foil is 100 mm, and the lenses have a large diameter (2 in.). This optical-geometrical structure also contributes much to reduce the airy radius of a near field image. Although the range of an observation wavelength is wide as which is form 400 to 800 nm, the resolution of the measurement on the foil is calculated as 2.5 um. The experimental data of the developed screen monitor also suggested the same resolution. |
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TUP078 | Development of Integrator Circuit for Charge Monitoring | 576 |
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At the SPring-8 1 GeV linac, a beam current or charge is measured by means of an integrator circuit. A signal from a current transformer is processed into an integrated voltage. The Fast Gated Integrator and Boxcar Averager Module (Stanford Research Systems) is presently used as the integrator. However we plan to expand a dynamic range and an integration time of the integrator. Because the noise level of the present integrator becomes too large for the expansion, we developed a low-noise and high-resolution integrator. Both the present and developed integrators have the same functions such as signal gating, accumulation of analog signal and sample hold. The principal noise of the integrator was found to be a switching noise of the gate switch. To reduce the switching noise a GaAs transfer switch SW-283-PIN (M/A-COM) was adopted as the gate switch. The experimental data of the developed integrator showed 1/10 of the noise level of the present integrator. |
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TUP079 | Operational Performance of a New Beam-Charge Interlock System for Radiation Safety at the KEKB Injector Linac | 579 |
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A new beam-charge interlock system has been developed for radiation safety and machine protection at the KEKB injector linac. Although the previous software-based interlock system was working, it was replaced by the new hardware-based one. The new interlock system restricts the integrated amount of beam charges delivered to four different storage rings (KEKB e+, KEKB e-, PF, PF-AR) at six locations along the linac. When the integrated amount of beam charges exceeds a certain threshold level prescribed at each location, the beam-abort requests are directly sent through a twisted hardwire cable to the safety control system of the linac. The new interlock system boosted its reliability in comparison with the previous system. The full-scale operation of the new interlock system has been started since the end of March 2008. In this report we describe the operational performance of the new beam-charge interlock system. |
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TUP080 | Numerical Study of a New Bunch Length Monitor Utilizing a Detection of Electromagnetic Fields in Millimeter-Wave Region | 582 |
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A new nondestructive bunch-length monitor has been numerically investigated. The monitor detects electromagnetic fields generated through a ceramic gap of a vacuum pipe when a charged particle beam passes through the pipe gap. The frequency spectrum of the electromagnetic fields detected in wave zone spreads over a millimeter-wave length from a microwave length region for a short pulse beam with a bunch length of pico-second region. The frequency spectrum strongly depends on the bunch length of the relativistic charged beam if the geometrical structure of the pipe gap is fixed. The detection principle of the bunch-length monitor and some numerical analysis results applied to a single-bunch electron beam of the KEKB injector linac are described in this report. |
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TUP081 | Transient Beam Loading Compensation in CTF3 | 585 |
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In the CLIC Test Facility 3 (CTF3), the strong coupling between the beam and the accelerating cavities (full beam loading) induces transient effects such that the head of the pulse is accelerated almost twice as much as the steady-state part of the pulse. The beam optics in the machine is tailored for the steady-state and not for the higher energy electrons, which are gradually lost. This can lead to inefficiency and contributes to the activation of the machine. A beam loading compensation scheme has been proposed to minimize this effect. By delaying appropriately the arrival time of rf pulse in accelerating cavities with respect to the beam, the transient energy can be brought close (to within a few percent) of the steady-state one. This paper presents the measurements done on CTF3 using time resolved energy measurements. |
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TUP082 | Bunch Length Measurements in CTF3 | 588 |
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The CLIC Test Facility CTF3, being built at CERN by an international collaboration, should demonstrate the feasibility of the CLIC two-beam technology by 2010. One of the issues addressed is the control of the electron bunch length in the whole complex. A bunch length measurement system with good resolution is therefore paramount. Two different systems are presently used in CTF3, based on microwave spectroscopy and on transverse rf deflectors, respectively. In the paper we describe the two systems, we discuss the different experimental methods used and present the results of the latest measurement campaigns. |
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TUP083 | Diagnostics and Measurement Strategy for the CERN Linac 4 | 591 |
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Linac 4 is a 160 MeV H- linac which will become the new injector for CERN's proton accelerator chain. The linac will consist of 4 different rf structures, namely RFQ, DTL, CCDTL and PIMS running at 352.2 MHz with 2 Hz repetition rate and 0.4 ms pulse length. A chopper line ensures clean injection into the PS Booster. The combination of high frequency and a high-current, low-emittance beam calls for a compact design where minimum space is left for diagnostics. On the other hand, diagnostics is needed for setting up and tuning of the machine during both commissioning and operation. A measurement strategy and the corresponding choice of the diagnostic devices and their specific use in Linac4 are discussed in this paper. |
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TUP084 | Emittance Measurement Instrument for a High Brilliance H- Ion Beam | 594 |
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Funding: Work supported by EU/FP6/CARE (HIPPI) RII3-CT-2003-506395 |
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TUP085 | Four-Dimensional Emittance Meter for DC Ion Beams Extracted from an ECR Ion Source | 597 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357. |
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TUP086 | Initial Commissioning of a Dual-Sweep Streak Camera on the A0 Photoinjector | 600 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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TUP089 | Electron Beam Timing Jitter and Energy Modulation Measurements at the JLab ERL | 606 |
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When operating JLab high current ERL a strong reduction of the FEL efficiency was observed when increasing the average electron beam current. Investigating the FEL efficiency drop-off with the electron beam average current we also have measured the electron beam phase noise and the fast energy modulations. The so-called phase noise is essentially a variation of the time arrival of the electron bunches to the wiggler. That could be a very effective way of reducing the FEL efficiency if one takes in to account that the accelerator is routinely operated with the RMS bunch length of about 150 fs. Under a fast energy modulation we mean a modulation which can not be followed by the FEL due to its time constant, defined by the net gain. Such a modulation also could be a possible cause of the efficiency drop-off. Having the measurements made we could rule out the FEL efficiency drop-off due to either the fast energy modulation or the phase modulation. We also have learned a lot about instrumentation and techniques necessary for this kind of beam study. In this contribution we describe the used instrumentation and present results of the measurements. |
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TUP090 | Optical Diffraction Radiation Measurements at CEBAF | 609 |
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Optical diffraction radiation (ODR) is a promising technique, which could be used for non interceptive beam size measurements at future light sources. An ODR diagnostic station was designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor and to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 uA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters and polarizers. The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) as well as wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present first results of the measurements with the comparison to the numerical simulations. |
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TUP091 | Extracting Information Content within Noisy, Sampled Profile Data from Charged Particle Beams: Part II | 612 |
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Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. |
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TUP092 | Laser-Based Profile and Energy Monitor for H- Beams | 615 |
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A beam profile and energy monitor for H- beams based on laser photoneutralization is being developed at Brookhaven National Laboratory for use on the High Intensity Neutrino Source at Fermilab. An H- ion has a first ionization potential of 0.75 eV and can be neutralized by light from a Nd:YAG laser (λ = 1064 nm). To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H- beam intercepted by the laser. A curved axial magnet field channels these electrons into a Faraday cup. To measure the energy spread of the electrons the laser position is fixed and the voltage on a screen in front of the cup is raised in small steps. We deduce the energy spread of the H- beam by deconvolving the electron spectrum into components from beam energy and from space-charge fields. Measurements are reported from experiments in the BNL linac MEBT at 750 keV. |
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TUP107 | Longitudinal Beam Diagnostics for the ILC Injectors and Bunch Compressors | 655 |
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Funding: Work supported by US. Department of Energy, under Contract No. DE-FG02-06ER41435 with Northern Illinois University. |