BNL, Upton, Long Island, New York
A beam profile and energy monitor for H- beams which measures electrons stripped from the beam by a laser has been installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. Also electrons are stripped by the residual gas at a rate of ~1.5 x 10-8/cm at 1 x 10-7torr. Beam electrons have the same velocity as the beam and so have an energy of 1/1836 of the beam protons. There is a chamber in which the laser light passes through the ion beam followed by a dipole magnet which deflects the electrons by 90° through a biased retarding grid (V<125kV) into a Faraday cup detector. To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H- beam intercepted by the laser. To measure the energy spectrum of the electrons, we use either the gas-stripped or laser-stripped signal. The total current is measured as the voltage on the grid is raised in small steps. We deduce the energy spread of the H- beam by deconvolving the electron spectrum into components from beam energy and from space-charge fields.
NSTec, Los Alamos, New Mexico
LANL, Los Alamos, New Mexico
An optical diagnostic instrument developed for the acquisition of high-speed time-resolved images has been fielded at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The instrument was developed for the creation of time histories of electron-beam cross-section through the collection of Cerenkov light. This is accomplished through four optical lines of sight that optically collapse an image, an optical fiber relay, recording instruments, and a tomographic reconstruction algorithm. The instrument may be operated, adjusted, and calibrated remotely due to potential adverse environmental conditions. The instrument was operated over the course of various activities during and after DARHT commissioning, and tomographic reconstructions reported verifiable beam characteristics. Results from the collected data and reconstructions and analysis of the data are discussed.
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.
Fermilab, Batavia
A system was developed for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations based on the signal from a single beam-position monitor (BPM) located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, the beam is excited with band-limited noise for about one second, and this was shown not to significantly affect the circulating beams even at high luminosity. The system is used to measure betatron tunes of individual bunches and to study beam-beam effects. In particular, it is one of the main diagnostic tools in an ongoing study of nonlinear beam-beam compensation studies with Gaussian electron lenses. We present the design and operation of this tool, together with results obtained with proton and antiproton bunches.
ORNL, Oak Ridge, Tennessee
Recent improvements to the next generation beam loss monitor analog front end used on the SNS accelerator have proved successful. Particularly in the removal of incident EMI noise sources and the reduction of RF cavity X-Rays and non beam related "loss" signals. The prototype system under development allows the users to view true beam loss integrated as part of the machine protect system. Sucessful measurements of activation during non-beam times have also been made. This paper is an overview of the improved electronics and the results of the ongoing checkout and verification of this system.
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.
