Beam Profile Monitors

BPM80

BPM81

BPM82

BPM83

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Product Features

• Monitors beams up to 2.75” (6.98cm) in diameter
• Handles a beam power density of 140W/mm² or more
• Custom mounting flanges and housings available

NEC beam profile monitors (BPM) provide a continuous scope display of the shape and position of the beam cross section in both X and Y coordinates. They can monitor positive or negative beams of electrons, ions and energetic neutral particles.

The unique design of NEC’s beam profile monitors has made them among the most popular and reliable beam diagnostic instruments available, with over 2,000 BPMs provided for customers worldwide. The NEC beam profile monitor reliably gives accurate information concerning the beam cross-section for ion beams with currents as low as 1nA for most models. Our newest model can monitor currents in the fA range.

Application

The NEC BPM system is ideally suited for applications that require instantaneous scope display of beam cross-sectional shape and position without significantly interrupting beam transmissions. Particle beams of electrons, ions, or energetic neutrals can all be monitored.

Beam Profile Monitor Design

The unique patented design of the NEC beam profile monitor relies on the collection of secondary electrons from a grounded scanning wire. This arrangement eliminates contact noise at the rotating scanning wire. Here’s how it works:

• A helical wire sweeps across the beam twice during each revolution to provide a Y profile and X profile in each successive half revolution.
• A cylindrical collector around the grounded wire collects beam-induced secondary electrons from the wire to provide a signal proportional to the intercepted beam intensity at every instant.
• This signal is then sent to the NEC controller and an oscilloscope for direct viewing of the beam profile.

 
NEC provides four standard models of BPMs, with various versions and options for each model. Below are brief descriptions of each model.

Model BPM80	The Original Beam Profile Monitor – and Most Popular Model Monitors beams up to 1.0″ (2.54cm) diameter Maximum beam power density of 140 W/mm2 (1kW for 3mm dia. beam) Typically provided in an NEC supplied housing
Model BPM83	For Large Diameter Ion Beams Monitors beams up to 2.75″ (6.98cm) diameter Maximum beam power density of at least 150 W/mm2 Typically provided in an NEC supplied housing
Model BPM81	For Existing Housings Monitors beams up to 1.0″ (2.5cm) diameter Maximum beam power density of 140 W/mm2 Designed for insertion into a customer supplied housing
Model BPM82	For Existing Housings & Larger Diameter Beams Monitors beams up to 2.0″ (5cm) diameter Maximum beam power density of 140 W/mm2 Designed for insertion into a customer supplied housing

The standard beam profile monitor system will routinely monitor positive or negative beams with current densities to 10nA/cm². NEC has recently developed a low current beam profile monitor with a minimum detectable beam current in the FemptoAmp range. Please contact NEC for further information.

Required Beam Profile Monitor Accessories

For a complete beam profile monitor system, the BPM must be connected to an NEC controller and a display oscilloscope.

BPM Controllers:

NEC offers three beam profile monitor controllers: model FP3A, SS5A and SS6.

• Model FP3A: single unit controller for local control
• Model SS5A: multi-unit controller (up to 12 BPMs) for local control
• Model SS6: multi-unit controller (up to 12 BPMs) for computer control

Display Oscilloscope:

The digital display oscilloscope to be used with the BPM must have the following specifications:

• Time base: 5 ms/div.
• Band Pass: 10kHz
• Vertical sensitivity: 50mV to 5 V/div.

 
An analog oscilloscope can be used if it has simultaneous Z axis intensification and remote
trigger. Upon request, NEC can recommend and/or supply an oscilloscope that meets the above requirements.

More Information

Beam Profile Monitor Specifications
Beam Profile Monitor Controllers