| Paper | Title | Page |
|---|---|---|
| PT01 | Beam Position And Phase Measurements Using A FPGA For The Processing Of The Pick-Ups Signals | 169 |
|
||
| We have implemented the signal processing needed to derive the transverse beam position and the beam phase from the signals of a four electrodes BPM block on a FPGA (field programmable gate array). The high processing rate of a FPGA allows taking the full benefit of the high data acquisition rate of the most recent ADC circuits. In addition, it is possible to implement on a FPGA a processing algorithm exactly tailored to the measurement of the beam parameters. The efficiency of the signal processing has also been improved by a careful choice of the frequency of the sampling clock and of the RF front-end local oscillator, which are derived from the storage ring RF frequency. This paper describes the BPM, the RF front-end electronics and the FPGA algorithm. It presents some of the application of this BPM at ESRF and gives measurement results. | ||
| PT02 | Pill-Box Cavity BPM For TESLA Cryomodul | 172 |
|
||
| A new cavity BPM with 10 μm resolution is designed and fabricated to perform single bunch measurements at the TESLA linear collider. In order to have a low energy dissipation in the cryogenic supermodule, the inner surface of the cavity is copper plated. Cross-talk is minimised by a special polarisation design. The electronics, at 1.5 GHz, is a homodyne receiver normalised to the bunch charge. Its LO-signal for down-conversion is taken from the same cavity. | ||
| PT04 | Advantages Of Implementing Digital Receivers In Field Programmable Gate Arrays (FPGA) | 175 |
|
||
| Today’s state-of-the-art FPGA technology allows designers to satisfy almost any demand for high-speed data processing needed in DSP applications and fast data transfers. Dedicated FPGA resources are used in DSP applications to perform down conversion, filtering and data formatting. New trends in system architecture favor serial data transfer rather than parallel by using FPGA’s internal resources, BRAMs, high speed serial IOs and hard core processors. | ||
| PT05 | Experience With Sampling Of 500 MHz Rf Signal For Digital Receiver Applications | 178 |
|
||
| This article will present test results of a prototype system that was built to evaluate feasibility of a direct sampling of a 500 MHz RF signal for use in digital receiver applications. The system consists of a variable gain RF front end, a fast analog to digital converter (ADC) and a field programmable gate array (FPGA) providing glue-logic between the ADC and a PC computer. | ||
| PT06 | Dynamic X-Y Crosstalk / Aliasing Errors of Multiplexing BPMs | 181 |
|
||
| Multiplexing Beam Position Monitors (BPM) are widely used for their simplicity and inherent drift cancellation property. These systems successively feed the signals of (typically four RF) pickups through one single detector channel. The beam position is calculated from the demultiplexed (base band) signal. However, as shown by this contribution, transverse beam motion results in positional aliasing errors due to the finite multiplexing frequency. Fast horizontal motion, for example, can alias into an apparent, slow vertical position change. A thorough analysis is presented and the impact of essential parameters such as the multiplexing rate and the scanning pattern/sequence of classical 4-button pickups is discussed. | ||
| PT07 | Cavity Beam Position Monitor For The TESLA Energy Spectrometer | 184 |
|
||
| In order to measure the beam position with a precision of better than 1μm in the TESLA energy spectrometer a cavity beam position monitor is proposed. The waveguide coupling is used to achieve a good common mode rejection and therefore a better precision. The paper gives a short overview of the monitor functionality and describes resolution measurements which were made on the cavity prototype. | ||
| PT08 | The LHC Orbit and Trajectory System | 187 |
|
||
| This paper describes the definitive acquisition system selected for the measurement of the closed orbit and trajectory in the CERN-LHC and its transfer lines. The system is based on a Wide Band Time Normaliser (WBTN) followed by a 10-bit ADC and a Digital Acquisition Board (DAB), the latter developed by TRIUMF, Canada. The complete chain works at 40 MHz, so allowing the position of each bunch to be measured individually. In order to avoid radiation problems with the electronics in the LHC tunnel, all the digital systems will be kept on the surface and linked to the analogue front-ends via a single mode fibre-optic connection. Slow control via a WorldFIP fieldbus will be used in the tunnel for setting the various operational modes of the system and will also be used to check power supply statuses. As well as describing the hardware involved, some results will be shown from a complete prototype system installed on four pick-ups in the CERN-SPS using the full LHC topology. | ||
| PT09 | Cavity-Type BPMs For The TESLA Test Facility Free Electron Laser | 190 |
|
||
| For measurements of the beam position at the undulator section of the TESLA Test Facility (TTF) at DESY cavity-type beam position monitors were developed, installed and brought into operation. Besides of some theoretical aspects results of in-beam measurements at the TTF are presented and pros and cons of this monitor concept are discussed. | ||
| PT12 | Beam Phase Measurements in the AGOR Cyclotron | 193 |
|
||
| Beamphase measurement to optimize the isochronism is an essential part of the diagnostics in multi-particle, multi-energy cyclotrons. In the AGOR cyclotron an array of 13 nondestructive beamphase pick-ups is installed. To reduce the large disturbances from the RF-system the measurements are traditionally performed at the 2nd harmonic of the RF-frequency. To further improve the sensitivity intensity modulation of the beam has been introduced. This creates side-bands in the Fourier spectrum, that are completely free of interference from the RF-system. These side-bands contain information on both the beamphase with respect to the accelerating voltage and the number of revolutions up to the radius of the measurement. A specific case is intensity modulation at the orbital frequency, where the side-bands contain only information on the beamphase. Measurements with the different methods will be presented, demonstrating that the intensity modulation strongly improves the sensitivity of the measurement. Useful beamphase measurements can now be made for beam intensities down to 10 nA. | ||
| PT13 | An X-Band Cavity for a High Precision Beam Position Monitor
Work supported by Dept. of Energy Contract DE-AC03-76F00515 |
196 |
|
||
| The next generation of accelerators will require increasingly precise control of beam position. For example designs for the next linear collider require beam-position monitors (BPMs) with 200 nm resolution. The accelerator designs also place difficult requirements on accuracy and stability. To meet these requirements a cavity BPM operating at 11.424 GHz was designed. The BPM consists of two cavities: an xy-cavity tuned to the dipole mode and a phase cavity tuned to the monopole mode. The xy-cavity uses a novel coupling scheme that (in principal) has zero coupling to the monopole mode. This report will present the mechanical design, simulations, and test results of a prototype BPM. In addition BPM designs with even higher precision will be discussed. | ||
| PT14 | Design of BPM PU for Low-Beta Proton Beam Using Magic Code | 199 |
|
||
| We have designed the BPM PU based on capacitive buttons for use in the KOMAC (Korea Multi-purpose Accelerator Complex), the high-intensity proton linac that are under development at the KAERI (Korea Atomic Research Institute), Korea. The KOMAC is aiming to produce CW 20 mA beam current at the 100 MeV energy. We have chosen the button-type PU since it is easier to fabricate than other type PUs including the stripline, and it could provide enough signal power because of the high beam current. The PU sensitivity was calculated by the MAGIC that is a kind of the Particle-In-Cell code that originates from the plasma science community. The utilization of the MAGIC code is especially useful for BPM PUs in the low-beta sections of the accelerator, because it is difficult to obtain the PU sensitivity experimentally due to the difficulties in simulating the low-beta beams by the electromagnetic waves in a test bench. In this presentation, we report on the design of the BPM PU based on the MAGIC calculation. | ||
| PT15 | Performance of the ELBE BPM Electronics | 202 |
|
||
| The ELBE radiation source is based on a superconducting linac. Initially it was designed to be used in CW mode with repetition rates either 13 MHz either 260 MHz. Later it was decided to operate the accelerator with reduced repetition rates for diagnostic reasons and for certain users. Now it is possible to operate at repetition rate 13/n MHz, where n can be 2, 4, 8, 16, 32, 64, and 128. It is required that the BPM system supports any of these operation modes. A core element of the BPM electronics is a logarithmic amplifier AD8313 made by Analog Devices Inc. The logarithmic amplifier is a direct RF to DC converter rated up to 2.5 GHz. Initial design of the BPM electronic was sophisticated only for CW operation with repetition rate more than 10 MHz, since bandwidth of the AD8313 is about of 10 MHz. Additionally a sample and hold amplifier is built in to provide enough time for an ADC to make measurements. The sample and hold amplifier is synchronized with a micropulse frequency. In the paper we present results of the modified BPM electronics test. | ||
| PT16 | A High Dynamic Range Beam Position Measurement System for ELSA-2 | 205 |
|
||
| New beamlines are presently under construction for ELSA, a 20 MeV electron linac located at Bruyères-le-Châtel. These lines need a beam position measurement system filling the following requirements: small footprint, wide dynamic range, single-bunch/multi-bunch capability, simple design. We designed a compact 4-stripline sensor and an electronic treatment chain based on logarithmic amplifiers. This paper presents the design, cold and hot test results. | ||
| PT17 | Impedance-Matching-Transformer for Capacitive Pick-Ups | 208 |
|
||
| The transfer line from the GSI heavy ion synchrotron (SIS) to the experimental set ups is equipped with segmented capacitive pick-ups for beam position measurement. This beam position measurement will be designed to cover a dynamic range of 160 dB and single-bunch evaluation. For taking measurements with maximum sensitivity the best choice is a high-impedance tap at the pick-up referring to the bunch length of 50...500 ns. Therefore the feeding of 50 Ω coax-cables will be realized by an impedance-matching-transformer located close to the pick-up. It has an impedance >10 kΩ at the primary side and 50 Ω matching at the secondary side with a foreseen bandwidth of 200 MHz. So it is possible to use low noise amplifiers with 50 Ω input in a radiation-safe environment without loading the pick-up with 50 Ω. A specialized impedance-matching-transformer is now under development and the result will be presented. | ||
| PT18 | Development of a bunch frequency monitor for the preliminary phase of the CLIC Test Facility CTF3 | 211 |
|
||
| In the framework of the CLIC RF power source studies, the feasibility of the bunch train combination by injection with RF deflectors into an isochronous ring has been successfully demonstrated in the preliminary phase of CTF3. In order to monitor this scheme, a new method based on beam frequency spectrum analysis was experimented. For this purpose, a coaxial pick-up and its detection system were designed and mounted in the CTF3 ring, in order to allow comparison of the amplitudes of five harmonics of the fundamental beam frequency (3 GHz) while combining bunch trains. The commissioning of the monitor was a successful proof of principle for this new method, despite the short length of the bunch trains and the presence of parasitic signals associated to high-order wave guide modes propagating with the beam inside the pipe. | ||
| PT19 | Transverse Feedback System For The Cooler Synchrotron COSY-Jülich - First Results | 214 |
|
||
| The cooler synchrotron COSY delivers unpolarized and polarized protons and deuterons in the momentum range 300 MeV/c up to 3.65 GeV/c. Electron cooling at injection level and stochastic cooling covering the range from 1.5 GeV/c up to maximum momentum are available to prepare high precision beams for internal as well as for external experiments in hadron physics. In case of electron cooled beam the intensity is limited by transverse instabilities. The major losses are due to the vertical coherent beam oscillations. To damp these instabilities a transverse feedback system is under construction. First results with a simple feedback system are presented. Due to the feedback system operation the intensity and lifetime of the electron cooled proton beam at injection energy could be significantly increased. Measurements in frequency and time domain illustrate the performance of the system. | ||
| PT20 | A New Wide Band Wall Current Monitor | 216 |
|
||
| Wall current monitors (WCM) are commonly used to observe the time profile of particle beams. In CTF3, a test facility for the future CERN Linear Collider CLIC, high current electron beams of 1.5 μs pulse length are bunched at 3 GHz and accelerated in a Linac working in fully loaded mode, for which a detailed knowledge of the time structure along the pulse is mandatory. The WCM design is based on an earlier version developed for CTF2, a previous phase of the test facility, in which the beam duration was only 16 ns. Due to the longer pulse width the low frequency cut-off must be lowered to 10 kHz while the high frequency cut-off must remain at 10 GHz. The new WCM therefore has two outputs: a direct one for which an increase of the inductance results in a 250 kHz to 10 GHz bandwidth while the second one, using an active integrator compensating the residual droop, provides a 10 kHz to 300 MHz bandwidth. The new WCM has been installed in CTF2 late 2002 in order to test its high frequency capabilities prior to its use in CTF3. Design considerations and first results are presented. | ||
| PT21 | Microwave measurement of intra bunch charge distributions | 219 |
|
||
| A direct way of obtaining intra bunch charge distributions is to measure the amplitude roll off as well as the phase behavior of the spectrum of the single bunch self field. To that effect, a microwave pickup together with a microwave front end has been installed in the storage ring of the Swiss Light Source (SLS). As pickup, button type bpms are used, which have been designed for a broad band behavior in the excess of 30 GHz. Three bpms together with their individual front ends are used in order to sample the beam spectrum at frequencies of 6, 12 and 18 GHz, which compares to the standard spectrum of a 1 mA single bunch extending to approximately 12 GHz (13 ps rms bunch length). The signals are mixed to base band in loco using the multiplied RF frequency as a LO. By shifting the LO phase, simultaneously the amplitude roll off as well the complex phase of the beam spectrum can be obtained. Where using a resonator as a pickup would smear out the response over several bunches, allowing only the determination of average values, the current setup has a band width of approximately 2 GHz, so that individual bunches in the 500 MHz bunch train can easily be resolved. | ||
| PT22 | Measurement of the longitudinal phase space at the Photo Injector Test Facility at DESY Zeuthen | 222 |
|
||
| The photo injector test facility at DESY Zeuthen (PITZ) has been developed with the aim to deliver low emittance electron beams and study its characteristics for future applications at free electron lasers and linear accelerators. The energy of the electron beam varies in the range between 4 and 5 MeV. One of the important properties of the delivered beam is the longitudinal phase space of the electron beam. Measurements of the momentum distributions show a small energy spread. The principle of the measurement of the bunch length will be discussed, time resolutions will be shown and preliminary results will be given. The design to measure the correlation between momentum and time distribution of the electron bunch will be shown with calculated resolutions. | ||
| PT23 | Transverse Emittance Measurements at the Photo Injector Test Facility at DESY Zeuthen (PITZ) | 225 |
|
||
| The main research goal of the Photo Injector Test Facility at DESY Zeuthen (PITZ) is the development of electron sources with minimized transverse emittance like they are required for the successful operation of Free Electron Lasers and future linear colliders. The process of electron beam optimization requires characterization of the transverse emittance at a wide range of operation parameters. The design and functionality of the emittance measurement system at PITZ is presented. The methods applied as well as the resolution limits of the system are discussed. The latest measurements of the transverse properties of the electron beam are presented. | ||
| PT24 | Development of a Bunch-Length Monitor with Sub-Picosecond Time Resolution and Single-Shot Capability
Funding: SNF (Schweizer National Fonds) |
228 |
|
||
| A bunch-length monitor with single-shot capability is under development at the 100 MeV pre-injector LINAC of the Swiss Light Source (SLS). It is based on the electro-optical effect in a ZnTe crystal induced by coherent transition radiation (CTR). A spatial autocorrelation of the CTR in the EO-crystal rotates the polarisation of a mode-locked Nd:YAG laser to produce an image on an array detector representing the Fourier components of the CTR spectrum. Up to now a theoretical model for the emission of transition radiation has been developed in order to design optics allowing efficient transport of the CTR onto the EO-crystal. The frequency dependency of the CTR due to the finite size of the target screen has been measured in the sub-THz regime at the SLS Linac. The results strongly support the theoretical descriptions of the radiation source. By expanding the intensity pattern in higher-order Laguerre-Gaussian modes, the transmission through the optical transfer system is calculated. | ||
| PT25 | Fast Tune Measurement System for the ELETTRA Booster | 231 |
|
||
| Since several years, the Diagnostic Group at Laboratori Nazionali di Legnaro (LNL) has been designing Fast Faraday Cups (FFC) to be used on their Heavy Ion Accelerators; latest developments in this field include a stripline FFC, jointly developed with SNS, Oak Ridge. A collaborative partnership has been set-up between LNL and ELETTRA Laboratory to fully characterize new FFCs, using as electron source the ELETTRA 1 GeV Linac. Two FFCs, the stripline FFC, built at SNS, and a coaxial FFC, made at LNL, have been installed at ELETTRA who provided the wideband data acquisition and the remote control of the measurement. The first measurements carried out using 1 GHz oscilloscope allowed the proper set-up of remote control and a low jitter triggering. Wideband measurements were performed with a sampling scope equipped with 50 GHz head whereas the bandwidth of the stripline FFC is in the order of 10 GHz. A complete set of tests has been carried both on the coaxial FFC and on the stripline FFC. Thanks to the information provided by these wideband measurements, the Linac working point has been further optimized as well as the injection process into the ELETTRA SR. | ||
| PT26 | Cryogenic Current Comparator for Absolute Measurement of the Dark Current of the Superconducting Cavities for Tesla | 234 |
|
||
| A newly high performance SQUID based measurement system for detecting dark currents, generated by superconducting cavities for TESLA is proposed. It makes use of the Cryogenic Current Comparator principle and senses dark currents in the nA range with a small signal bandwidth of 70 kHz. To reach the maximum possible energy in the TESLA project is a strong motivation to push the gradients of the superconducting cavities closer to the physical limit of 50 MV/m. The field emission of electrons (the so called dark current) of the superconducting cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. This contribution describes a Cryogenic Current Comparator (CCC) as an excellent and useful tool for this purpose. The most important component of the CCC is a high performance DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the extracted dark current. For this reason the SQUID input coil is connected across a special designed pick-up coil for the electron beam. Both the SQUID input coil and the pick-up coil form a closed superconducting loop so that the CCC is able to detect dc currents down to 2 pA/√Hz. Design issues and the application for the CHECHIA cavity test stand at DESY as well as preliminary experimental results are discussed. | ||
| PT27 | A 40 MHz Bunch by Bunch Intensity Measurement for the CERN SPS and LHC | 237 |
|
||
| A new acquisition system has been developed to allow the measurement of the individual intensity of each bunch in a 40 MHz bunch train. Such a system will be used for the measurement of LHC type beams after extraction from the CERN-PS right through to the dump lines of the CERN-LHC. The method is based on integrating the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40 MHz. This has been made possible with the use of a fast integration ASIC developed by the University of Clermont-Ferrand, France, for the LHC-b pre-shower detector. The output of the integrator is digitised using a 12-bit ADC and fed into a Digital Acquisition Board (DAB) that was originally developed by TRIUMF, Canada, for use in the LHC orbit system. A full system set-up was commissioned during 2002 in the CERN-SPS, and following its success will now be extended in 2003 to cover the PS to SPS transfer lines and the new TT40 LHC extraction channel. | ||
| PT28 | Current Measurements of Low-Intensity Beams at CRYRING | 240 |
|
||
The demand for new ion species leads to an increasing number of cases in
which the ions can only be produced in small quantities. Thus, weak ion
currents quite often have to be handled in low energy ion storage ring,
like CRYRING. Various detector systems have been developed to measure
such low intensity coasting and bunched beams by using the overlapping
ranges of those systems.
|
||
| PT29 | Dark Current Measurements at the PITZ Rf Gun | 242 |
|
||
| For photoelectron rf guns with acceleration gradients of 40 MV/m or higher at the photo cathode operated at the rf pulse length of 100 μs or more, the amount of dark current might be comparable with the photoelectron beam. Strong dark current can cause multipacting, radiation damages and cryogenic losses. At the photo injector test facility at DESY Zeuthen (PITZ) the dark current was measured with various solenoid setups at the rf gun by Faraday cup. We compare the dark current behavior of different photo cathodes. Experimental results are discussed with simulations. | ||
| PT30 | Ionisation Chambers for the LHC Beam Loss Detection | 245 |
|
||
| At the Large Hadron Collider (LHC) a beam loss system will be used to prevent and protect superconducting magnets against coil quenches and coil damages. Since the stored particle beam intensity is 8 orders of magnitude larger than the lowest quench level value particular attention is paid to the design of the secondary particle shower detectors. The foreseen ionisation chambers are optimised in geometry simulating the probable loss distribution along the magnets and convoluting the loss distribution with the secondary particle shower distributions. To reach the appropriate coverage of a particle loss and to determine the quench levels with a relative accuracy of 2 the number of the detectors and their lengths is weighted against the particle intensity density variation. In addition attention is paid to the electrical ionisation chamber signal to minimise the ion tail extension. This optimisation is based on time resolved test measurements in the PS booster. A proposal for a new ionisation chamber will be presented. | ||
| PT31 | Optical Fibre Dosimeter for SASE FEL Undulators | 248 |
|
||
| 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. | ||
| PT32 | Beam Loss Diagnostics Based on Pressure Measurements | 251 |
|
||
| The GSI is operating a heavy ion synchrotron, which is currently undergoing an upgrade towards higher beam intensities. It was discovered that beam losses induce a significant pressure increase in the vacuum system. In order to detect the time constants of the pressure increase and decrease, fast total pressure measurements were put into operation. With the recently installed partial pressure diagnostics it is also possible to follow up which types of molecules are released. The presentation will focus on the different techniques applied as well as on some measurement results. The potential and difficulties of this diagnostic tool will also be discussed. | ||
| PT34 | DAΦNE Beam Loss Monitor System | 254 |
|
||
| At the DAΦNE collider a beam loss monitor system has been installed to continuously monitor the particle losses. The acquisition is based on 32 Bergoz beam loss monitors, of the Wittenburg type, installed close to the main rings vacuum chamber, buffering monitoring circuitry and a counting scale (SIS 3801) as acquisition board. We developed a front-end software that allows acquiring the integrated value of the BLM counts and a stream of 1000 point for each monitor, to cover an history of 3000 s. The operator program allows displaying the instantaneous BLM values over the machine together with a representation of the past history. |