CERN, Geneva
At present more than 15000 particle accelerators exist worldwide, being built and optimised to handle a large variety of particle beams for basic research and applications in industry and medicine. Diagnostic tools have been developed and optimised according to the special requirements of these machines and to meet the demands of their users. Storage rings for ultra cooled heavy ion beams, third generation synchrotrons for the production of high brilliant radiation, super conducting protons machines working at the energy frontier and finally linear electron accelerators for FEL applications or high energy physics are just the most prominent representatives of the large variety of accelerators and each of them needs highly sophisticated tools to measure and optimise the corresponding beam parameters. Accordingly the issue addressed here is not to cover in full detail the different diagnostic devices but rather to concentrate on the aspects and needs as seen by the accelerator physicists and machine designers.
LBNL, Berkeley, California
The 13th edition of the Beam Instrumentation Workshop (BIW08) took place at the Granlibakken Conference Center on the beautiful shores of Lake Tahoe in California during the first week of May 2008. About 130 participants registered for the workshop. Included in the program during the three and a half days were three tutorials, eight invited and seven contributed oral presentations, and more than 50 poster contributions. A discussion group session, and the vendor exhibition simultaneously held with the single day poster session, afforded many opportunities for informal discussion and idea exchange between attendees. During the workshop, the 2008 Faraday Cup Award that recognizes innovative achievements in beam diagnostics was also presented. In this talk, I will present the highlights from BIW08. The overall quality of the contributions was notably high, which made the selection of the topics for this talk quite difficult. Although I endeavored to produce a balanced choice of highlights, the final list is surely incomplete due to time limitations of the talk, and also it unavoidably reflects my personal point of view and preferences.
SSRF, Shanghai
SSRF is a 432 m-circumference synchrotron light source with a 150MeV linac, a 3.5GeV full energy booster, and a 3.5GeV storage ring. Principal diagnostics systems have been installed and nearly all have been commissioned during past two years. Data have been obtained on beam position, beam profile, current, and synchrotron radiation diagnostics beamline on the storage ring. Multi bunch transverse feedback system has been applied on the ring. Results for the 150MeV electron beams in the linac, up to 3.5GeV in the booster, and 3.5GeV in the ring will be presented.
CERN, Geneva
The CERN Proton Synchrotron has been fitted with a new trajectory measurement system (TMS). Analogue signals from the forty beam position monitors are digitized at 125MS/s, and then further treated entirely in the digital domain to derive the positions of all individual particle bunches on the fly. Large FPGAs handle all digital processing. The system fits in fourteen plug-in modules distributed over three half-width cPCI crates. Data are stored in circular buffers of large enough size to keep a few seconds-worth of position data. Multiple clients can then request selected portions of the data, possibly representing many thousands of consecutive turns, for display on operator consoles. The system uses digital phase-locked loops to derive its beam-locked timing reference. Programmable state machines, driven by accelerator timing pulses and information from the accelerator control system, direct the order of operations. The cPCI crates are connected to a standard Linux computer by means of a private Gigabit ethernet segment. Dedicated server software, running under Linux, knits the system into a coherent whole.
DESY, Hamburg
The new synchrotron light source PETRA III is powered by a chain of pre-accelerators including Linac II, PIA, transfer lines, and DESY II. The whole chain is equipped with upgraded versions of diagnostic systems that were installed during the 2008 shutdown. This paper presents the upgrade of the beam position monitor (BPM) systems at PIA together with the transfer lines and DESY II. All systems rely on the ‘Delay Multiplex Single Path Technology’ (DMSPT). It is demonstrated that the self-triggered design of the BPM electronics is specifically suited to the different needs of such a heterogeneous pre-accelerator chain. Structures and dependencies of the BPM systems will be described in detail.
ISA, Aarhus
This paper presents an overview of the proposed beam diagnostic for Astrid2, which is the new 580 MeV 3rd generation synchrotron light source to be build in Aarhus, Denmark. Astrid2 will use the present Astrid1 as booster, allowing for full energy injection and thereby top-up-operation. The diagnostics will include viewers, beam current monitors, electronic beam position monitors, striplines, etc. The description will include both the storage ring and the transfer beam line.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The commissioning of the ALBA Linac (Autumn 2008) required a careful measurement of the beam parameters. This paper describes the diagnostics devices installed at the ALBA Linac and our experience with them.
NSRRC, Hsinchu
A new high brilliant 3 GeV storage-ring-based light source - Taiwan Photon Source (TPS) - is planned to be built at the National Synchrotron Radiation Research Center. Various diagnostics will be deployed to satisfy stringent requirements for commissioning, operation, and top-off injection of the TPS. Specifications and an overview of the planned beam instrumentation system for the TPS will be summarized in this report. Efforts in diagnostic devices and subsystems will also be addressed.
YerPhI, Yerevan
BERGOZ Instrumentation, Saint Genis Pouilly
ANL, Argonne, Illinois
YSU, Yerevan
The Vibrating Wire Monitor (VWM) was developed for precise transversal profiling/monitoring of charged particle/photon beams. The extremely high sensitivity of VWM is achieved by sensitivity of wire natural oscillation frequency to wire temperature. Due to the rigidity of the wire support structure, the VWM is also sensitive to the environmental parameters. In this paper, it is shown that the main parameter of influence is the ambient temperature. The magnitude and character of this influence is investigated along with the effect of electromagnetic interference on the VWM electronics in an accelerator environment.
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
DESY, Hamburg
The characterization of the transverse phase space for high charge density and high energy electron beams is demanding for the successful development of the next generation light sources and linear colliders. Due to its non-invasive and non-intercepting features, Optical Diffraction Radiation (ODR) is considered as one of the most promising candidates to measure the transverse beam size and angular divergence. A thin stainless steel mask has been installed at 45° with respect to the DR target and normally to the beam propagation to reduce the contribution of synchrotron radiation background. In addition, interference between the ODR emitted on the shielding mask in the forward direction and the radiation from the DR target in the backward direction is observed. This is what we call Optical Diffraction Interferometry (ODRI). The contribution of this interference effect to the ODR angular distribution pattern and, consequently, its impact on the beam transverse parameters is discussed. Results of an experiment, based on the detection of the ODRI angular distribution to measure the electron beam transverse parameters and set up at FLASH (DESY, Hamburg) are discussed in this paper.
UniDo/IBS, Dortmund
iThemba LABS, Somerset West
FZJ, Jülich
DELTA, Dortmund
Scintillation is one of the outcomes of beam interaction with residual gas. This process is utilized for non-destructive beam profile monitoring. Test bench measurements at various gas compositions and pressures as well as ones with the circulating proton beam at COSY-Juelich were performed. This was done using a single large photocathode PMT to estimate the photon yield. A multichannel photomultiplier was used along with a lens system to monitor the ion beam profile. Experimental results are presented and the challenges of the approach are discussed.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
Beam diagnostics based on synchrotron radiation can use imaging techniques that allow monitoring beam transverse dimensions in real time. In particular the bunch-by-bunch transverse beam diagnostics is a powerful method that allows investigations of transient phenomena in which bunch motion and beam instabilities are correlated to the position in the bunch train. Such diagnostic methods need photon array detectors with response time in the ns down to ps range and dedicated fast electronics. At DAΦNE, the e+/e- collider of LNF/INFN, preliminary measurements with a prototype of an IR array detector made by 32x2 pixels are in progress. The array has pixel of 50x50 μm2 characterized by a response time of about 1 ns per pixel measured with the IR emission of the SINBAD beamline. The array detector and the 64 channels dedicated electronics has been installed at the 3+L experiment, a dedicated diagnostics of the e+ DAΦNE ring used to monitor the transverse dimensions of the beam. In this paper we describe the apparatus built to obtain IR imaging of a SR source and a turn-by-turn and a bunch-by-bunch transverse diagnostics of the stored bunches with a sub-ns time resolution
MPI-K, Heidelberg
The University of Liverpool, Liverpool
The majority of particles in a beam are located close to the beam axis, called the beam core. However, particles in the tail distribution of the transverse beam profile can never be completely avoided and are commonly referred to as beam halo. The light originating from or generated by the particle beam is often used for non- or least destructive beam profile measurements. Synchrotron radiation, optical transition, or diffraction radiation are examples of such measurements. The huge difference in particle density between the beam core and its halo, and therefore the huge intensity ratio of the emitted light is a major challenge in beam halo monitoring. In this contribution, results from test measurements using a flexible core masking technique are presented indicating way to overcome present limitations. This technique is well-known in e.g. astronomy, but since particle beams are not of constant shape in contrast to astronomical objects, a quickly adjustable mask generation process is required. The flexible core masking technique presented in this paper uses aμmirror array to generate a mask based on an automated algorithm.
Diamond, Oxfordshire
During normal operation of synchrotron third generation light source like Diamond, the measurement of the electron bunch profile, of the order of 10~ps, is perfectly done with a streak camera. However, in 'low alpha' operation, where the momentum compaction factor is reduced in order to shorten the bunch length, the measurement becomes extremely close to the resolution of the camera. In such a case, performing a good measurement and extracting the real information requires a good knowledge of the impulse response of the streak camera. We present analysis and measurement of the contributions to the point spread function of the streak camera: the static point obtained by measuring a focussed beam without any sweep, which can be achieved at best around 5.5 pixels (0.7~ps with the fastest sweep), but also the chirp introduced by refractive optics and a large spectral beam, measured with a spectrograph at 26~fs/nm. Then we discuss short bunch measured in 'low alpha' operation and the agreement between measurements and expectation from theory.
Diamond, Oxfordshire
A relatively new development for synchrotron light sources is the concept of producing two independent X-ray beams in a single straight using two canted undulators. Two beams, separated by an angular divergence in the order of 1 mrad, proceed down the same front end before being separated into two experimental hutches. This creates a challenge for the position measurement of the two adjacent X-ray beams in the front end. Traditional four blade tungsten vane XBPMs are an established solution for accurate and reliable monitoring of the position of a single beam, so this approach has been developed to create an eight blade XBPM that is capable of resolving two beams independently. This paper presents first results from Diamond’s I04 and J04 IDs and illustrates the techniques used for position calibration and background subtraction.
GSI, Darmstadt
A precise tune determination is crucial for stable operation of GSI SIS-18 synchrotron especially for intense beam conditions. In order to avoid nearby resonances in the tune diagram the fractional part of coherent betatron motion needs to be measured with a resolution of 10-3 also during ramping mode. This is achieved using a fast digital readout system for Beam Position Monitors (BPM). The broadband BPM signal is sampled with a rate of 125 MSa/s which corresponds to an average of about 50 Sa per bunch for SIS-18 machine parameters. The signal is integrated bunch-by-bunch which minimizes thermal and digitization noise and the beam position is calculated. The tune is then determined in baseband directly by Fourier-transformation of the positions of a certain bunch typically over 2048 turns. This algorithm does not require any additional input parameter. Since particle losses due to significant emittance blow-up have to be avoided, excitation power has to be kept as low as possible. This was achieved using a digital pseudo random noise (PRN) generator for beam excitation, which produces white noise on a carrier frequency with adjustable bandwidth.
CNAO Foundation, Milan
CERN, Geneva
The CNAO, the first Italian center for deep hadrontherapy, is presently in its final step of installation. Commissioning of the low energy injection lines has been successfully concluded in January 2009. The synchrotron injection chain consists of a 8 keV/u Low Energy Beam Transfer (LEBT) line, an RFQ to accelerate the beam up to 400 keV/u, a LINAC to reach the 7 Mev/u injection energy and a Medium Energy Beam Transfer line. At the end of the LEBT line, just upstream the RFQ, an electrostatic Chopper deviates the beam for about 100 micro-seconds every 2 seconds on the vacuum chamber, in order to shape the particles batch according to LINAC requirements and to minimize the beam lost at the RFQ entrance. The chamber section hit by the beam was electrically isolated from the adjacent vacuum chambers, allowing the reading of the LEBT beam current. The detector is based on the Faraday Cup working principle, but it results in a “not-interceptive” monitor that is able to measure, continuously, the source beam current ripples and stability without affecting the beam delivered to the synchrotron. The system is presently under commissioning with beam and preliminary results are presented.
DESY, Hamburg
To exploit the short radiation pulses in pump-probe experiments at single-pass free-electron lasers (FELs), stabilization of the longitudinal profile and arrival time of the electron bunches is an essential prerequisite. Beam energy fluctuations, induced by the cavity field regulation in the accelerating modules, transform into an arrival time jitter in subsequent magnetic chicanes used for bunch compression due to the longitudinal dispersion. The development of beam based monitors is of particular importance for the validation and optimization of the cavity field regulation. In this paper we present bunch-resolved energy jitter measurements that have been recorded with a synchrotron radiation monitor at the Free-electron LASer in Hamburg (FLASH). The cavity field detectors of the accelerating module have been identified as the main source of the stochastical noise which corresponds to a beam energy jitter of 0.012%. The reduction of deterministic cavity field imperfections by applying an adaptive feedforward learning algorithm for the cavity field regulation is demonstrated.
DESY, Hamburg
The basic design for the machine protection system (MPS) for the light-source PETRA III is discussed. High synchrotron radiation can damage absorbers and vacuum chambers. Therefore the MPS identifies alarm conditions from different systems, including the BPM, temperature and vacuum systems and creates a dump command within 100us. For diagnostic purposes a post-mortem trigger is implemented and a first alarm detection is planned. The initial commissioning of the MPS with its alarm-delivering systems is described.
ASCo, Clayton, Victoria
The Australian Synchrotron (AS) timing system is based on a hybrid design: an Event Generator-Event Receiver (EVG-EVR) system creates the injection trigger and various clocks, while a network of digital delay generators adjusts pulse delays and widths. This architecture, combined with a storage ring fill pattern monitor, allows the targeting of injection into specific buckets in the storage ring. Nevertheless, more demanding needs from the machine and the beamlines require an upgrade of the system. Delay generators will be removed and replaced by EVRs. This will allow fixed or variable frequency clocks to be made available to beamlines or to trigger diagnostic hardware, orbit interlock distribution, etc., while reducing jitters to below 100 ps. This paper presents the architecture of the new timing system at AS and emphasizes its benefits for diagnostic tools.
SINAP, Shanghai
KEK, Ibaraki
SR monitor for the measurements of beam profile, sizes, and bunch length has been designed and constructed at the Shanghai synchrotron radiation Facility (SSRF). A water-cooled beryllium mirror is installed to extract the visible SR. This beryllium mirror was designed via thermal analysis based on ANSYS. The extracted visible SR is relayed to dark room by three mirrors. The measurement system includes, imaging system, SR interferometers (SRI), streak camera and fast-gated camera etc are set in the dark room. Both the horizontal and the vertical beam sizes are monitored by SRI, and bunch length and temporal profile of the beam are measured by streak camera. The existed system suffers with dynamic problem for beam physics studies. The commissioning of synchrotron radiation monitor system has been performed in SSRF since December, 2007. The results obtained at SSRF will be presented.
Uni HH, Hamburg
DESY, Hamburg
A synchrotron radiation monitor (SRM) based on a multi-anode photomultiplier tube (PMT) has been installed in the first magnetic bunch compressor chicane at the Free-electron LASer in Hamburg (FLASH). The synchrotron radiation emitted in the third dipole of the magnetic chicane is imaged by a telescope onto two anodes of the PMT. In this way the horizontal beam position of the electron bunches is recorded which corresponds to the beam energy as the beam position is governed by the beam energy in the dispersive section of the magnetic chicane. The fast PMT signals are digitized by analog -to-digital converters (ADC) which enables bunch-resolved beam energy measurement within the trains of the up to 800 bunches generated by the superconducting linear accelerator of FLASH. In this paper we describe the experimental setup of the SRM and present first commissioning results for various accelerator settings.
GSI, Darmstadt
The FAIR (Facility for Antiprotons and Ions Research) accelerator complex is currently designed and projected at GSI. The unique features of the central machine SIS100, like e.g. the acceleration of high intensity beams of 2.5·1013 protons and 5·1011 Uranium ions, the operation close to the space charge limit leading to a large tune spread and the extreme UHV conditions of the cryogenic system for fast ramped superconducting magnets, make challenging demands on the beam diagnostic components. This contribution describes the general concept of beam diagnostics for FAIR and reports on the present status of prototype studies. Exemplarily the achievements for a novel type of dc transformer, beam position monitors and the ionization profile monitor are discussed and first measurements with prototype setups are presented.