DESY, Hamburg
The former electron and proton preaccelerator PETRA at DESY is currently reconstructed and will be converted into the most brilliant storage-ring-based X-ray source worldwide called PETRAIII. The commissioning is scheduled for January 2009. It will operate at 6 GeV with 100 mA stored current and with a design emittance of 1 nm rad. Top-up operation is foreseen right from the beginning to reduce changes in heat-load and thermal drifts to a minimum,. Suitable beam diagnostic instrumentation and machine protection systems have to be established to guarantee the low emittance, a sub-micron beam stability as well as a save machine operation. To ensure a very high availability of the beam in top-up mode, the injector and preaccelerator diagnostic systems will be refurbished as well. A complete overview of the instrumentation and their latest developments to achieve these goals will be presented.
NewPath Research L.L.C., Salt Lake City
NewPath, Salt Lake City, Utah
We have shown that a group of sinusoidally-wound non-ferrous coaxial toroids can be used to determine the transverse distribution of a time-dependent current that passes through their common aperture. A single current filament requires one uniformly-wound toroid, and two others having turn densities proportional to the sine and cosine of the azimuthal coordinate. Three simple algebraic equations give the magnitude and phase of the current and its position in terms of the voltages induced on the three toroids, and there is no ill-conditioning. Two current filaments require two additional toroids with turn densities proportional to the sine and cosine of two times the azimuthal coordinate, and the solution may be obtained by using steepest descent to minimize the residuals. Ill-conditioning makes it impractical to use more than two currents. We have tested our algorithms numerically by specifying the magnitudes and phases of the currents and their locations, calculating the voltages that would be induced on the toroids, adding Gaussian noise to these voltages, and then using the algorithms to calculate the currents and their locations from the simulated voltage measurements.
PSI, Villigen
DESY, Hamburg
Currently, a prototype fast intra bunch train feedback system is under development which is to be tested at FLASH. For pickups as well as kickers, stripline devices have been developed. The new pickup is based on the earlier designs used in the transfer lines of the swiss light source as well as in the proton cyclotron PROSCAN at PSI; in particular, the stripline electrode output coupling is intentionally mismatched in order to increase the shunt impedance seen by the beam. Two versions have been designed for a center frequency of 1.65 GHz and a loaded Q of 35. Prototypes have been fabricated and built into FLASH. The stripline kicker consists of four main elements (all in-vacuum): two stripline electrodes fabricated from extruded aluminum and two metallic ground planes, held in place by ceramic spacers. The latter reduce the mutual inductance between the electrodes and optimize the RF match for asymmetries in the RF feed. Prototypes have been built, measured in the lab, and are now in the process of being inserted into FLASH.
LBNL, Berkeley, California
The Advanced Light Source Transverse Feedback System currently consists of a refrigerator sized analog delay line system. The new system is the 2nd generation Transverse Feedback System, derived from work done for PEP-II in 2004. It uses the latest generation Virtex-5 FPGA, and has 12-bit ADCs and DACs for bunch-bunch feedback at 500MHz. In addition, this system provides networked capability for setup and diagnostics.
SLAC, Menlo Park, California
Bunched beam signals from button-style Beam-Position Monitor (BPM) electrodes can have spectral content up to 20-30 GHz and time-domain structure of narrow impulsive trains. Multi-bunch feedback systems require receivers to process such beam signals and generate ΔX, ΔY, and ΔZ beam motion signals. To realistically test these receivers, we have developed a 4-bunch programmable impulse generator, which mimics the signals from a multi-bunch beam. Based on step-recovering diode techniques, this simulator produces modulated 100-ps impulse signals. The programmable nature of the system allows us to mimic Betatron and Synchrotron signals from 4 independent bunches with adjustable beam spacing from 1 to 8 ns. Moreover, we can observe nonlinear effects and study the noise floor and the resolution of the receiver. This paper presents the design of the system and shows typical achieved results.
J. Xu, J.D. Fox, D. Van Winkle
Stanford Linear Accelerator Center
Stanford, CA 94309, U.S.A.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) must deliver a high quality electron beam to the undulator. High resolution beam position monitoring is required to accomplish this task. Critical specifications are a dynamic range of 0.08-8.0 nC with a 5 microns resolution at 200 pC. New processor electronics was designed, processing is based on filtering the signals and direct digitization of the resulting pulse train. The processor consists of an Analog Front-End (AFE) and Analog-to-Digital Converter (ADC) boards, all are packed into 19-in rack mount chassis, 1U high. AFE board has a very low input noise, approximately 3 microV rms in a 7 MHz bandwidth centered at 140 or 200 MHz. The maximum gain is 34 dB with attenuation of up to 46 dB in 1 dB step. An on-board pulser sends the short CW burst to the striplines to perform between pulse calibration. The ADC board has four 16-bit digitizers, the sampling frequency is 120 MHz. The low-jitter clock is on a separate board in the same chassis. For the LCLS injector 22 prototypes of the processors were built and installed in 2007. Measured resolution at 200 pC is typically 3-5 microns. The 53 improved and modified processors are in production
LANL, Los Alamos, New Mexico
Beam position monitors planned for the LANSCE diagnostics upgrade will be required to measure beam position and phase of the 201.25-MHz bunched beam in the proton linac. One method to do this is direct down conversion to in-phase and quadrature-phase data of the BPM signals using either commercial digitizers or custom designed hardware. We are evaluating selected hardware for systems with emphasis on COTS hardware to the extent practical. Basic system requirements include a beam current range of 26 db, position resolution of 0.05% of beam aperture and relative phase measurement with 0.25 degree resolution. We present our results to date on three approaches including ZTEC Instruments ZT-410 digitizers, a custom four-channel ADC analog front end board combined with National instruments, Inc. digital I/O and some limited data taken with the Instrumentation Technologies Libera system. The Libera system is a stand-alone BPM system. The other two systems use PCI cards in a standard PC running Windows XP. Our primary points of comparison include measured position resolution, phase resolution, phase linearity, minimum cycle rate and approximate cost for these portions of a BPM system.
Fermilab, Batavia
SLAC, Menlo Park, California
KEK, Ibaraki
A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring is currently in progress, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital downconversion techniques, digital signal processing, also implementing a novel automatic gain error correction schema. The technical concept and realization, as well as preliminary results of the beam studies are presented.
I-Tech, Solkan
Libera Brilliance has proved successful in the field of beam diagnostics. High performance, system reliability and its high level of integration into accelerator control systems makes Libera a very accurate, robust and powerful measuring system. Although Libera Brilliance has been developed mainly for applications involving frequency domain processing, the flexibility makes it a good time domain measuring system for single pass applications. Moreover, there are other applications dealing with pulses, where a modified version of Libera Brilliance can be used. This is the case of beam phase and position measurements in accelerators, like Spiral2 (Ganil) and LANSCE (Los Alamos), dealing with heavy particles (protons, deuterons and heavy ions). The phase information extracted by the measurement in such systems is used to control the acceleration process of such heavy particles. This paper shows the approach adopted in processing the signals produced by such bunch trains. A modified Libera Brilliance unit, configured for the LANSCE bunch trains, has been tested by means of extensive laboratory measurements. Performance has been evaluated by applying different digital signal processing.
CERN, Geneva
The unprecedented intensity and energy of the LHC proton beams will require an excellent control of the transverse beam dynamics in order to limit particle loss in the superconducting systems. Due to restricted tolerances of the machine protection system and tight beam emittance blow-up budget only small beam excitation is allowed, making precise measurements of the transverse beam parameters very challenging. This paper describes the systems measuring the tune, coupling and chromaticity of the LHC beams. As manual correction of these parameters may reach its limit with respect to required precision and expected time-scales, the LHC is the first proton collider that can be safely and reliably operated only with automatic feedback systems for controlling the transverse beam dynamics. An outline of these systems is also presented.
Fermilab, Batavia
Monitoring the tunes of individual proton and antiproton bunches is crucial to understanding and mitigating the beam-beam effects in the Tevatron collider. To obtain a snapshot of the evolving bunch-by-bunch tune distribution a simultaneous treatment of all the bunches is needed. The digital tune monitor (DTM) was designed to fulfill these requirements. It uses a standard BPM as a pickup. The vertical proton monitor is installed and allows us to gain valuable operational experience. A major upgrade is underway to implement an automatic bunch-by-bunch gain and offset adjustment to maintain the highest possible sensitivity under real operational conditions. We present the concept of the DTM along with its technical realization as well as the latest experimental results. Major challenges from the design and operation point of view are discussed.
CERN, Geneva
Built at CERN by an international collaboration, the CLIC Test Facility 3 (CTF3) aims at demonstrating the feasibility of a high luminosity 3 TeV e+-e- collider by the year 2010. The CLIC project is based on the so called ?two-beam acceleration scheme? where the RF accelerating power is provided by a high current high frequency electron beam. The required performances put high demands on the diagnostic equipment and innovative monitors have been developed during the past years. This paper gives an overview of the instrumentation developed at CTF3 with a special emphasis on short bunch length measurements, high precision beam position monitors, high dynamic range beam imaging system and high precision beam phase measurements.