ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The accelerator systems are equipped with variety of beam diagnostics. The beam diagnostics played important role during beam commissioning, they are used for accelerator tuning and monitoring beam status during production runs. The requirements to the various diagnostics systems are changing in the process of beam power ramp up. This talk will give an overview of the evolution of the major SNS beam diagnostics systems: commissioning, operation, power ramp up, and power upgrade.
CERN, Geneva
EPFL, Lausanne
LAL, Orsay
Within the framework of the second Joint Research Activity PHIN of the European CARE program, a new photo injector for CTF3 drive beam has been designed and installed by collaboration between LAL, CCLRC and CERN. The laser driven rf photo injectors are recent candidates for high-brightness, low-emittance electron sources. One of the main beam dynamics issues for a high brightness electron source is the optimization of beam envelope behavior in the presence of the space charge force in order to get low emittance. Beam based measurements have been made during the commissioning runs of the PHIN 2008 and 2009 including measurements of the emittance, using multi-slits technique. In this work the photo injector will be described and the first beam measurement results will be presented and compared with the PARMELA simulations.
INFN/LNF, Frascati (Roma)
The experimental setup implemented in the SPARC linac control system used to monitor the laser beam energy and to measure the beam charge by means of a Faraday Cup will be illustrated and discussed. The experimental setup makes use of National Instruments 2 GS/s 8-Bit digitizer board. This tool has been shown to be useful in order to monitor the laser beam energy stability and to evaluate the quantum efficiency of the cathode.
CERN, Geneva
During the 2008/2009 shutdown the electronics for the Fast Wire-scanners for the CERN PSB and PS machines will be renovated with new movement and acquisition electronics. A new test bench was produced that allows measuring the movement of wires at speeds up to 20 m/s. This poster will present the calibration system with its related software.
Uni HH, Hamburg
PSI, Villigen
DESY, Hamburg
A seeded free-electron laser operating in the soft X-ray (XUV) spectral range will be added to the SASE FEL facility FLASH. The seed beam will be generated by higher harmonics of a near infrared laser system. A dedicated transport system will guide the radiation into the electron accelerator environment. Within the seed undulator section compact diagnostic units have to be designed to control the transverse overlap of the photon and the electron beam. These units contain a BPM a wire scanner and an OTR screen for the electron diagnostic. A Ce:YAG screen and a MCP readout for the wire scanner are foreseen to measure the photon beam position.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Imperial College of Science and Technology, Department of Physics, London
The RAL front end FETS is currently under construction to demonstrate an H-ion beam with up to 18 kW at 3 MeV. Due to the beam power photo detachment techniques are the preferable choice for emittance instruments. Typically, measurements will be performed in just one transverse plane by using a magnet to separate ion beam from produced neutrals. Another general technique to work out a 2D emittance bases on several beam profiles applying an image reconstruction method called maximum entropy (MaxEnt). Combining both methods in one device has the significant advantage of reducing technical and physical problems which may occur by doubling magnet or laser beam path. Drawback of MaxEnt is the necessity of sufficient phase space advance to achieve reasonable results which can be either optimised by moving the particle detector or with additional focusing. The paper presents a conceptual design study discussing all possible constraints given by beam parameters and chopper/ MEBT. Simulations will help to estimate performance and errors.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
An electron beam halo monitor has been developed in order to protect undulator permanent magnets against radiation damage for the X-ray free electron Laser facility at SPring-8 (XFEL/SPring-8). The halo monitor will be installed at the upstream of the undulator and detect the electron beam that might hit the undulator magnets. Diamond detector, which operates in photoconductive mode, is good candidate for electron beam sensor, because diamond has excellent physical properties, such as, high radiation hardness, high insulation resistance and sufficient heat resistance. Pulse-by-pulse measurement suppresses the background noise efficiently, especially in the facilities having extremely high intense beam but low repetition rate, such as XFELs. The linearity of output signal on injected beam has been demonstrated in the range of 103 to 107 electron/pulse. The feasibility check for this monitor was performed at the SPring-8 compact SASE source (SCSS) test accelerator for XFEL/SPring-8. We observed the unipolar pulse signal with the pulse length of 0.4 nsec FWHM. The beam profiles of the halo can be also measured by scanning the sensor of this monitor.
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.
DESY, Hamburg
In this contribution we describe how Coherent Optical Transition Radiation can be used as a diagnostic tool for characterizing electron bunches in X-ray Free-electron lasers. The proposed method opens up new possibilities in the determination of ultra-short, ultra-relativistic electron bunch distributions.
PSI, Villigen
IAP Univ. Bern, Bern
The knowledge and control of electron bunch lengths is one of the key diagnostics in XFEL accelerators to reach the desired peak current in the electron beam. A compact electro-optical monitor was designed and build for bunch length measurements at the Swiss FEL. It is based on a mode locked ytterbium fiber laser probing the field-induced birefringence in an electro-optically active crystal (GaP) with a chirped laser pulse. The setup allows the direct time resolved single-shot measurement of the Coulomb field (THz-radiation) of the electron beam -and therefore the bunch length- with an accuracy as good as 200fs. Simulations of the signals expected at the SwissFEL and the results of first test at the SLS linac will be presented.
PSI, Villigen
The PSI 250 MeV Injector, a precursor to the SwissFEL with its extreme jitter and stability demands poses new challenges for the synchronization system. Our concept is double-tracked: low risk electrical and best potential performance and flexibility optical. The electrical distribution system, being established first, relies on reliable technology. Optimized to achieve a benchmark jitter performance of around 10fs and a long term drift stability of some 10fs in the most critical parts of the machine it will also backup the optical system. Sub 10fs jitter and drift figures are being aspired for the latter. In this contribution, both systems are presented, measurements of electrical and optical reference signal jitter and long term cable and coupler drifts will be shown. A cable temperature stabilization system and the influence of mechanical noise will be discussed, too. Finally, first jitter measurements of the optical system will be presented.
DESY, Hamburg
Uni HH, Hamburg
The need for timing and bunch-length monitors for free-electron lasers and other accelerators makes the electro-optic spectral decoding (EOSD) a promising diagnostic technique. Being non-destructive, it allows a single shot-measurement within the accelerator environment. In some cases, e.g. low charge or necessity to resolve time-structures below 20 fs, the bunch length is measured indirectly, using the spectrum of the coherent transition radiation (CTR). We present results of EOSD measurements on the CTR beam line at FLASH, using a chirped Ti:Sapphire oscillator pulse focused simultaneously with the THz radiation on a GaP crystal in vacuum. The CTR spectrum is in the range 200 GHz-100 THz and and the pulse energy in the focus is over 10 mJ. The measured narrow CTR temporal profiles in the order of 400 fs FWHM demonstrate, that the ultra short THz-pulses, emitted by the compressed electron bunches are transported through the 19 m long beam line without significant temporal broadening.
INFN/LNF, Frascati (Roma)
The SPARC FEL facility is under commissioning at the Frascati National Laboratories of INFN. The synchronization system is working as expected and various devices are used to monitor its performances. In particular this paper is focused on a comparison between the results obtained using different methods and instruments to perform laser, RF and beam synchronization measurements. Both electro-optical and full electrical techniques are used to obtain information about the phase noise of the RF fields inside the accelerating structures, the phase noise of the IR laser oscillator, the time of arrival of the laser UV pulse on the cathode and the time of arrival of the accelerated electron bunch at a selected reference position along the linac.
PSI, Villigen
IAP Univ. Bern, Bern
Pulsed Yb fiber lasers emit at 1030 nm which provides a better phase matching in standard EO crystals (GaP, ZnTe) than Ti:Sa lasers (800nm). We present a mode locked ytterbium fiber laser which is phase locked to the RF. A subsequent fiber amplifier is used to boost the power and to broaden the spectrum due to nonlinear effects. The produced pulses have a spectral width of up to 100 nm and are therefore suitable for EO bunch length measurements, especially for spectral decoding. The laser delivers a chirped pulse of some ps, the fourier limited pulse duration of ~30 fs can be almost reached by an additional shaper setup with a spatial light modulator in the Fourier plane.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
The RAL Front End Test Stand is under construction with the aim of demonstrating production of a high-quality, chopped 60 mA H- beam at 3 MeV and 50 pps. In addition to the accelerator development, novel laser-based diagnostics will be implemented. This paper reports on a device that will be able to measure multiple profiles of the beam density distribution in such a way that the full 2D density distribution can be reconstructed. The device is currently being commissioned. The status of the device is presented together with results of the commissioning and plans for future development.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
NSCL, East Lansing, Michigan
IAP, Frankfurt am Main
STFC/RAL, Chilton, Didcot, Oxon
The pepperpot provides a unique and fast method of measuring emittance, providing four dimensional correlated beam measurements for both transverse planes. In order to make such a correlated measurement, the pepperpot must sample the beam at specific intervals. Such discontinuous data, and the unique characteristics of the pepperpot assembly, requires special attention be paid to both the data acquisition and the error analysis techniques. A first-principles derivation of the error contribution to the rms emittance is presented, leading to a general formula for emittance error calculation. Two distinct pepperpot systems, currently in use at GSI in Germany and RAL in the UK, are described. The data acquisition process for each system is detailed, covering the reconstruction of the beam profile and the transverse emittances. Error analysis for both systems is presented, using a number of methods to estimate the emittance and associated errors.
Uppsala University, Uppsala
Uni HH, Hamburg
DELTA, Dortmund
FYSIKUM, AlbaNova, Stockholm University, Stockholm
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
We present very promising recent results from the optical replica synthesizer experiment in FLASH where we manipulate ultrashort electron bunches in FLASH with a laser in order to stimulate them to emit a coherent light pulse with the temporal structure of the electron bunches and subsequently analyze the light pulses with laser diagnostic (FROG) methods.