A compact beam position monitor for use inside a Free Electron Laser wiggler
An all-aluminum, non-intrusive beam position monitor (BPM) with a 27-mm diameter, clear aperture is described, along with its associated electronics. The device is small enough to fit inside a Free Electron Laser (FEL) wiggler magnet as part of the beam pipe, and all signal leads are brought out horizontally to accommodate the wiggler geometry. A stripline configuration is used to allow precise mechanical construction and alignment of the probe electrodes, although the nominal 50-ns electron beam pulse length makes the electrical performance resemble that of a loop coupler. The large effective loop area generates nearly 0.5 V.ns/A of signal amplitude from each loop. The maximum beam current to be accommodated is 3 kA. The probes are spaced axially so as to be insensitive to the wiggling motion of the beam, and a special design feature allows the cancellation of signals due to direct charge interception from beam halo, and of x-ray Compton signals. Overall accuracy is expected to be better than 0.1 mm over a 2-mm diameter aperture, and 1 mm over a 20-mm diameter aperture. With gain control, the electronics channels have a 50-dB instantaneous dynamic range on the position signal. Hybrid junctions provide front-end differencing, and gated integrators allow sampling of different parts of the signal pulse. We have developed a procedure for separate calibration of position error components, such as the offset of the electrical from the mechanical axis and the electronics channel errors. An on-line calibration signal allows frequent recalibration of the electronics channel gains. After calibration, both fixed and variable errors are entered in the signal processing software and are used for real-time correction of the position signal. In this paper, bench test results are given for the first prototype BPM. 7 refs., 6 figs., 1 tab.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5610809
- Report Number(s):
- UCRL-97732; CONF-8709110-16; ON: DE88004354
- Resource Relation:
- Conference: 9. international free-electron laser conference, Williamsburg, VA, USA, 14 Sep 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
BEAM MONITORS
DESIGN
FREE ELECTRON LASERS
ALUMINIUM
BEAM POSITION
CALIBRATION
ELECTRON BEAMS
WIGGLER MAGNETS
BEAMS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELEMENTS
EQUIPMENT
LASERS
LEPTON BEAMS
MAGNETS
MEASURING INSTRUMENTS
METALS
MONITORS
PARTICLE BEAMS
440101* - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments
420300 - Engineering- Lasers- (-1989)