ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source accelerator systems are designed to 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 a variety of beam diagnostics, which played important roles during beam commissioning. They are used for accelerator tuning and monitoring beam status during production runs. This talk will give an overview of our experience with the major SNS beam diagnostics systems.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on the transverse and longitudinal diagnostics. The coherence effects of the beam profile monitors and the challenges of measuring fs-long bunches are discussed.
CERN, Geneva
CLASSE, Ithaca, New York
PSI, Villigen
In the CLIC project, highest luminosity will be achieved by generation and preservation of ultra low beam emittances. It will require a mechanical stability of the quadrupoles down to 1 nm rms above 1 Hz through up to 24 km of linac structures. Studies are being undertaken to stabilize each quadrupole by an active feedback system based on motion sensors and piezoelectrical actuators. Since it will be very difficult to prove the stability of the magnetic field down to that level of precision, an attempt was made to use a synchrotron electron beam as a sensor and the beam motion was observed with a standard button BPM equipped with high resolution electronics. Hence in two consecutive experiments at CESR-TA (Cornell University, Wilson Lab) and at SLS (PSI-Villingen) the residual eigenmotion of the electron beam circulating in these two machines was measured in the frequency range 5700 Hz. This paper describes in detail the achieved results alongside with purpose of the measurement, the equipment used for observation of the beam rest-motion, and the vibration measurements of mechanical machine elements.
Fermilab, Batavia
Optical transition radiation (OTR) imaging for transverse beam-size characterization is a well-established technique at many accelerators including the Fermilab A0 photoinjector (A0PI) facility. However, there is empirical evidence for gamma greater than 1000 beams that the utilization of the polarization component orthogonal to the dimension of interest resulted in a smaller projected image profile. Generally, at the A0PI low beam energies of 14-15 MeV and emittances of 3 mm mrad, one encounters beam sizes of 0.8 to 1.5 mm (σ). However, the use of 50-micron wide slits to sample the beam’s transverse phase spaces significantly alters the required resolution of the converter screen and imaging system. In this case, we dealt with slit-image sizes of about σ 100 microns and less, depending on drift distance and beam divergence. In the course of our study of the slit images, we have found that the OTR polarized component orthogonal to the narrow beam dimension of interest systematically gave us ~20-micron smaller projected image sizes than with the total OTR intensity. This is one of the first reports of this polarization effect at such a low-gamma regime (~30).
Fermilab, Batavia
Ionization profile monitors (IPMs) are installed in the Fermilab Booster, Main Injector and Tevatron. They are used routinely for injection matching measurements. For emittance measurements the IPMs have played a secondary role to the Flying Wires, with the exception of the Booster (where it is the only profile diagnostics). As Fermilab is refocusing its attention on the intensity frontier, non-intercepting diagnostics such as IPMs are expected to become even more important. This paper gives an overview of the operational use of IPMs for emittance and injection matching measurements at Fermilab, and summarizes the future plans.
BNL, Upton, Long Island, New York
Four ionization profile monitors (IPMs) in RHIC measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. In 2007 a prototype of a new design was installed in the yellow ring. During the 2007-2008 run it proved to be almost completely free from backgrounds from rf coupling, electron clouds and x-rays from upstream beam loss. In 2009 two more IPMs of this new design were installed and in the 2010 shutdown we will complete installation of four identical IPMs. This paper describes the new IPMs and shows data from the 2010 beam run. The new IPMs have been extremely important in the commissioning of the RHIC stochastic cooling system.
GSI, Darmstadt
Technical University Darmstadt, Darmstadt
TU Darmstadt, Darmstadt
Scintillating screens are widely used for transverse beam profile monitoring and pepper-pot emittance measuring instruments at accelerator facilities. For high current beam operations at the GSI heavy ion UNILAC, several inorganic scintillators were investigated under different ion beam conditions in the energy range from 4.8 to 11.4 MeV/u and currents up to some mA. The imaging properties of various scintillating screens were studied with respect to light yield and imaged beam width, i.e. important parameters for precise beam profile measurements. The measured light yield and beam width show a strong dependence on the scintillating material and change significantly with screen temperature. The spectral response of the materials was mapped for different temperature levels, using a spectrometer in the visible and near UV range. The results clearly demonstrate that the scintillating properties of the materials, and their temperature, are critical issues for high current operations and have to be taken into account for correct beam profile reading.
MEPhI, Moscow
DESY Zeuthen, Zeuthen
The Photo Injector Test Facility at DESY, Zeuthen site (PITZ) develops electron sources of high brightness beams, required for linac based free electron lasers (FELs) like FLASH or the European XFEL. One of the key issues in electron beam optimization is the minimization of the transverse emittance. The main method to measure emittance at PITZ is a single slit scan technique, implying local beam divergence measurement by insertion of the slit mask at a definite location within the beam and measurements of the transmitted beamlet profile downstream of the slit station. “Emittance Measurement Wizard” (EMWiz) is the program used by PITZ operators for automated emittance measurements. EMWiz combines an acquisition program for beam and beamlet image recording and a postprocessing tool for the analysis of the measured transverse phase space of the electron beam. It provides a way to execute the difficult emittance measurements in an automatic mode and to get a calculated emittance result.
IAP, Frankfurt am Main
In beam diagnostics optical techniques had become increasingly important as they provide information with the advantage to have only minimal effect on the beam. The planned Frankfurt Neutron Source will consist of a proton driver LINAC providing beam energies up to 2.0 MeV. The rotatable diagnosis tank hybrid ion beam tomography tank HIBTT will be placed at the end of the low energy beam transport section (LEBT) to provide beam tomography based on the visible radiation of the ion beam in front of the RFQ. The beam energy in this section will be 120keV and the current 200 mA. Additional to the CCD camera that takes optical data for the tomography, other non-interceptive devices could be used to gain additional information. The question behind this hybrid approach on non invasive beam diagnostics is: which and how much information can be extracted from an ion beam without disturbing or destroying it. The actual contribution deals with the information of profile width in beam profile measurements. The presentation introduces a definition and an information sensitive method for profile width determination and verifies them using experimental and numerical data.
HIT, Heidelberg
GSI, Darmstadt
The transverse emittance of the ion beam at the Heidelberg Ion Therapy Center (HIT) will be measured within the Low Energy Beam Transport (LEBT) using a pepper-pot measurement system. At HIT, two ECR sources produce ions (H, He, C and O) at an energy of 8keV/u with different beam currents from about 80 μA to 2mA. The functionality and components of the pepper-pot device is reviewed as well as the final design and the choice of the scintillator. For that, results from recent beam test at the Max Planck Institute für Kernphysik at Heidelberg are presented. The material investigation was focused on inorganic doped crystal, inorganic undoped crystal, borosilicate glass and quartz glass with the following characteristics: availability, prior use in beam diagnostics, radiation hardness, fast response, spectral matching to CCD detectors.
LBNL, Berkeley, California
University of Applied Sciences Karlsruhe, Karlsruhe
Two ECR* ion sources are currently available to inject beams into the 88-Inch Cyclotron at LBNL.** The recently commissioned pepper-pot emittance scanner at LBNL was used to measure the beam emittance for various ion species of both sources. A pepper-pot scanner is capable of extracting the full four-dimensional transverse phase space of the beam, allowing for the calculation of the cross coupled emittances xy' and yx'. This is especially of interest for ECR ion sources where asymmetric beams are extracted in the presence of a strong solenoid field. The axial field adds a rotational momentum to the extracted beam, resulting in a transverse emittance growth, which depends on the magnetic stiffness of the extracted species. In this paper, the pepper-pot setup is described and emittance data from both LBNL ECR sources are presented and compared. The data confirm a strong mass dependence of the normalized emittance for ions with the same mass to charge state ratio as previously also measured by other groups. This dependence indicates a different particle distribution at the extraction aperture for different ion species.
GSI, Darmstadt
To avoid beam losses of intense beams stored at the GSI heavy ion synchrotron SIS-18 a precise tune measurement during a whole acceleration cycle is required. This contribution presents a sensitive method of tune determination using data of Beam Position Monitor (BPM) measured in bunch-by-bunch manner. The signals induced in the BPM electrodes were digitized by 125 MS/s and integrated for each individual bunch. The tune was determined by Fourier transformation of the position data for typically 512 subsequent turns. Coherent betatron oscillations were excited with bandwidth-limited white noise. The presented method allows for tune measurements with satisfactory signal-to-noise ratio already at relatively low beam excitation i.e. without a significant increase of transverse beam emittance. In parallel the evolution of transverse beam emittance was monitored by means of Ionization Profile Monitor. The system for online tune measurement is an integral part of the new digital BPM System, presently under commissioning.
LAL, Orsay
The PHIL (PhotoInjector at LAL: http://phil.lal.in2p3.fr/ ) accelerator is the new LAL (Orsay, France) facility dedicated to test state-of-the-art RF and beam sources technologies used for future electron accelerators. The machine based on 3 GHz RF gun triggered with a 262 nm wavelength laser, delivers a low energy ( E<10 MeV) single pulse electron beam at 5 Hz, with a low charge (0.1 nC) for now. The machine is about 5 meters long, with one direct and one deviated beam line (created after a 60° dipole). This paper describes the current status (first beam in november 2009) and the development of the diagnostics sections of the machine. At present, the machine is equipped by a transverse beam profile monitor based on «YAG:Ce» screen (30 mm diameter and 300 micrometers thick), two BPMs (one "button type" and one "reentrant resonators" type) and two Faraday cups (at the end of each line). The paper will present some preliminary results of the dimension and position of the beam at specific point for different charges and phase, and will present the expected development of the diagnostics of the machine (measurement of mean and energy dispersion, 2D emittance, beam length).
LANL, Los Alamos, New Mexico
In a nutshell, the role of a beam diagnostic measurement is to provide information needed to get a particle beam from Point A (injection point) to Point B (a target) in a useable condition, meaning with the right energy and size and with acceptable losses. Specifications and performance requirements of diagnostics are based on the physics of the particle beam to be measured, with typical customers of beam parameter measurements being the accelerator operators and accelerator physicists. This tutorial will be a physics-oriented discussion of the interplay between tuning evolutions and the beam diagnostics systems that support the machine tune. This will include the differences between developing a tune and maintaining a tune, among other things. Practical longitudinal and transverse tuning issues and techniques from a variety of proton and electron machines will also be discussed.
LBNL, Berkeley, California
Electron Cyclotron Resonance (ECR) ion sources are an essential component of heavy-ion accelerators due to their ability to produce wide range of ions as required by these facilities. The ever-increasing intensity demands have led to remarkable performance improvements of ECR injector systems, due to advances in magnet technology as well as an improved understanding of the ECR ion source plasma physics. At the same time, enhanced diagnostics and simulation capabilities have improved the understanding of the injector beam transport properties. However, the initial ion beam distribution at the extraction aperture is still a subject of research. Due to the magnetic confinement necessary to sustain the ECR plasma, the ion density distribution across the extraction aperture is inhomogeneous and charge-state-dependent. In addition, the ion beam is extracted from a region of high axial magnetic field, which adds a rotational component to the beam; this leads to emittance growth. This talk will review the ongoing simulation and diagnostics efforts at LBNL to develop a consistent modeling tool for the design of an optimized beam transport system for ECR ion sources.