Sunday, October 20, 2019
Ribbon Electron Beam Profile Monitor For Bunched Beam Tomography

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The Problem: Bunched Beam Tomography 

Advanced accelerator beam diagnostics are essential for user facilities that require intense proton beams with small emittances and high reliability.

Important to have noninvasive diagnostics that can be used continuously with intense accelerated beams.

Determination of particle distributions within an RF bunch is one of the most difficult tasks of all.

Muons, Inc. Ribbon Electron Beam Profile Monitor (RPBM) For Bunched Beam Tomography can address the challenges.

The Solution: Ribbon Electron Beam Profile Monitor for Bunched Beams

 A short pulse of the extraction voltage can be used to produce a short time-slice of the ribbon beam. After crossing the proton bunch with an angle close to 45o, the deflected electrons are visualized on the luminescent screen (7) and recorded by a fast CCD camera for further processed by corresponding software. Several similar systems can be integrated for production of the tomographic 3-D image of proton bunches.


Schematic diagram of a Ribbon e-Beam Profile Monitor with a strip cathode. 1- strip cathode; 2-extractor; 3-anode with first slit of collimator; 4-deflecting plate; 5-second slit of collimator; 6-ribbon time- slice of electron probe; 7-luminiscent screen.

RPBM Advantages:

  • Instead of scanning with a pencil electron beam as used in previous profile monitors, a novel strip cathode is used to form a sheet or ribbon beam of electrons to measure the density of a passing bunch of particles.
  •  The strip cathode apparatus eliminates the need for quadrupoles, is smaller with simpler design, is less expensive to manufacture, and has better magnetic shielding, higher sensitivity, and higher spatial and time resolutions.
  •  With this device, almost ideal tomography of bunches is possible in linear accelerators, circular accelerators, and storage rings.

The Impact of the Technology

The detailed measurements enabled by the REPBM are important for optimizing high intensity beam accumulation and acceleration and for suppressing instabilities in order to increase beam luminosity and lifetime. The facilities that this will impact are:

  • Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL),
  • Los Alamos Neutron Science Center (LANSCE) at LANL,
  • Project-X at the Fermi National Accelerator Laboratory
  • Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL),
  • National Superconducting Cyclotron Lab and Facility for Radioactive Ion Beams (FRIB) at MSU,
  • Facility for Antiprotons and Ion Research (FAIR) at GSI, Darmstadt, Germany,
  • Japan Proton Accelerator Research Complex (J-PARC) in Japan and
  • Project-X, and next-generation projects at Fermi National Accelerator Lab (Fermilab)
  • European Spallation Neutron Source (ESS) in Lund, Sweden
  • Chinese Spallation Neutron Source at Dongguan in Guangdong province, China
  • MYRRHA: Multi-purpose hybrid research reactor for high-tech applications, in Mol, Belgium

 RPBM: Simulation of Electron Beam Formation


Edge view of the strip cathode electron gun showing the simulation of ribbon electron beam extraction, acceleration, and focusing by the deflector plates (extraction voltage Uex=10 kV, Accelerating voltage Ua=100 kV, focusing voltage on the deflector system is Uf=-5 kV). Red lines are electron trajectories, green lines are equipotentials. The scale is 1 mm/division.

RBPM Mechanical Design

RBPM Component Tests

 Next Steps

 Ready to move to:

  • System fabrication and beam testing
  • Tomography development and readout
    • Collaboration with National Instruments
    • Based on PXI & NI FlexRIO technology (FPGA)