The Low Energy Demonstration Accelerator (LEDA) facility has been used to characterize the pulsed- and cw-beam performance of a 6.7 MeV, 100 mA radio frequency quadrupole (RFQ). Diagnostic instrumentation, primarily located in a short beam transport downstream of the RFQ, allow facility commissioners and operators to measure and monitor the RFQ’s accelerated and total beam transmission, beam loss, bunched beam current, beam energy and output phase, and beam position. Transverse beam profile measurements are acquired under both low and high duty-factor pulsed beam conditions using a slow wire scanner and a camera that images beam-induced fluorescence. The wire scanner is also used to acquire transverse beam emittance information using a technique known as a “quad scan”. This paper reviews the measurement performance and discusses the resulting data.

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LEDA beam diagnostics instrumentation: Measurement comparisons and operational experience

The LEDA facility has been used to characterize the pulsed- and cw-beam performance of a 6.7-MeV, 100-mA radio frequency quadrupole (RFQ). Diagnostic instrumentation, primarily located in a short beam transport downstream of the RFQ, allowed facility commissioners and operators to measure and monitor the RFQ's accelerated and total beam transmission, beam loss, bunched beam current, beam energy and output phase, and beam position. Transverse beam profile measurements are acquired under both low and high duty- factor pulsed beam conditions using a slow wire scanner and a camera that images beam-induced fluorescence. The wire scanner is also used to acquire transverse beam emittance information using a technique known as a "quad scan". This paper reviews the measurement performance and discusses some of the resulting data.

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Beam diagnostic instrumentation for the low-energy demonstration accelerator (leda): commissioning and operational experience

Beam position measurements are being designed and fabricated for the Low Energy Demonstration Accelerator (LEDA), a 20-MeV, 100-mA-cw proton-accelerator, presently under construction at Los Alamos. Similar position measurements will provide position information for a steering scheme within the Accelerator Production of Tritium (APT) linac magnetic lattice. The steering scheme, which centers the beam in the magnetic lattice, uses two position measurements and two translatable quadrupole magnets every 5.5-FODO-lattice periods. What makes these beam position measurements unique is how they will attain, maintain and verify the required accuracy. The position measurement systems consist of micro-stripline beam position monitors (BPMs) and RF coaxial cables, log-ratio processors, on-line error correction sub-systems, and a control system interface including associated algorithms and computer software. This paper discusses the mapping of the BPM probe response, the algorithm used to calculate low beam-velocity response, and the expected log-ratio processor performance.

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LEDA and APT beam position measurement system: Design and initial tests

A 52 quadrupole-magnet FODO lattice is presently being installed in the Low Energy Demonstration Accelerator (LEDA) facility between the radio frequency quadrupole (RFQ) and a high-energy beam transport (HEBT) [1]. The purpose of this lattice is to provide a beam transport to measure the formation of beam halo and compare the measured data with halo simulations. To attain this goal, several types of beam-diagnostic instruments are being installed in the magnet lattice. There will be nine beam-profile-measurement stations. Each station will have use of a slow wire scanner to detect the projected-distribution beam core, and a set of graphite or copper scrapers that measures the "tails" of the distribution down to 0.01% of the distribution peak. Also included in the instrumentation suite are ten beam position monitors (BPM), five beam loss monitors (BLM), three pulsed-current toroids, and an energy measurement similar to existing beam instrumentation [2,3]. This paper describes the instruments, initial test data, and their expected performance.

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Beam diagnostics instrumentation for a 6.7-mev proton beam halo experiment

The Low Energy Demonstration Accelerator (LEDA) facility located at Los Alamos National Laboratory (LANL) accelerates protons to an energy of 6.7 MeV and current of 100 mA operating in either a pulsed or cw mode. Of key importance to the commissioning and operations effort is the Beam Position Monitor system (BPM). The LEDA BPM system uses five micro-stripline beam position monitors processed by log ratio processing electronics with data acquisition via a series of custom TMS320C40 Digital Signal Processing (DSP) boards. Of special interest to this paper is the operation of the system, the log ratio processing, and the system calibration technique. This paper will also cover the DSP system operations and their interaction with the main accelerator control system.

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LEDA beam diagnostics instrumentation: Beam position monitors

Beam position monitor (BPM) signal-processing electronics utilizing the Analog Devices AD8307 logarithmic amplifier has been developed for the Low Energy Demonstration Accelerator (LEDA), part of the Accelerator Production of Tritium (APT) project at Los Alamos. The low-pass filtered 350 MHz fundamental signal from each of the four microstrip electrodes in a BPM is “detected” by an AD8307 log amp, amplified and scaled to accommodate the 0 to +5 V input of an analog-to-digital (A/D) converter. The resultant four digitized signals represent a linear power relationship to the electrode signals, which are in turn related to beam current and position. As the AD8307 has a potential dynamic range of approximately 92 dB, much attention must be given to noise reduction, sources of which can be digital signals on the same board, power supplies, inter-channel coupling, stray RF and others. This paper will describe the operational experience of this particular analog front-end electronic circuit design.

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BPM Analog front-end electronics based on the AD8307 log amplifier

An automated and highly accurate system for “mapping” 5 cm-diameter beam position monitors (BPMs) used in the Low Energy Demonstrator Accelerator (LEDA) at Los Alamos is described. Two-dimensional data is accumulated from the four micro-stripline electrodes in the probe by sweeping an antenna driven at the LEDA bunching frequency of 350 MHz in discrete steps across the aperture. These data are then used to determine the centroid, first- and third-order sensitivities of the BPM. These probe response coefficients are then embedded in the LEDA control system database to provide normalized beam position information to the operators. A short summary of previous systems we have fielded is given, along with their attributes and deficiencies that had a bearing on this latest design. Lessons learned from this system will, in turn, be used on the next mappers that are currently being designed for 15 cm and 2.5 cm BPMs.

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J. D. Gilpatrick

Papers

BPM Analog front-end electronics based on the AD8307 log amplifier

An automated BPM characterization system for LEDA