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Bergoz Beam Position Monitors, BPM
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 The
Bergoz Multiplexed Beam Position Monitor (MX-BPM)
is an electronics module with superior performance in
a small volume. It is a non-intercepting system that has
been optimized for use in electron and positron Storage
Rings.
For Beam Position Monitoring of Linacs, transfer lines,
first turns, boosters or fast-cycling synchrotrons, please
refer to the LR-BPM and the BPM-AFE.
The MX-BPM is in use at <<Insert customers using
the MX-BPM here>>.
| The
MX-BPM features |
| • |
On-board
microstrip filters that elminate the need for costly
tubular filters |
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GaAs
switches to provide superior button to button isolation
and low insertion loss |
| • |
On-board
systhesized local oscillator to elimate the problem
of external oscillator signal distribution with
power supplies. |
| • |
Automatic
Gain Control with a range of greater than 90dB provides
optimum levels for the demodulator, independent
of the beam intensity and number of bunches. |
| • |
phase-locked
synchronous demodulation giving high lineariry and
noise suppression. |
| • |
button
signal range of -70dBm to +5dBm. |
| • |
X
& Y output level of ±10V. |
| • |
X
& Y resolution of 1µm. |
| • |
Sample
rate of up to 10,000 samples per second. |
Operating
Principle
Button Scanning Mode
The signals from the four button electrodes are fed in
to the BPM module where they are processed sequentially
to give three outputs: X, Y and Sum.
Four on-board variable 1dB attenuators are used to equalize
the button signals, then the microstrip low-pass filters
eliminate the unwanted beam harmonics before the signals
are multiplexed by the GaAs switches. The switches close
in sequence under the control of the local clock, sampling
each button 2,000 times per second. An external clock
signal may override the on-board clock, to provide sample
rates up to 10,000 times per second. The output of the
multiplexer is then filtered by a band-pass filter to
allow easy selection of the chosen beam harmonic. A low-noise
preamplifier with AGC is used to amplify the signal before
it is processed with a superhetrodyne receiver. A mixer
gives the intermediate frequency using its own on-board
synthesized local oscillator. The local oscillator frequency
is given by a string of bits generated by a plug-in programmable
frequency key. The automatic gain control of the intermediate
frequency amplifier normalizes the sum of all button signals.
A PLL synchronous demodulator provides high linearity.
The demodulated signal is filtered and memorized by four
sample-and-hold circuits under the control of the button
scanning clock. The X and Y positions are obtained from
the memorized value of the four buttons. Only additions
and subtractions are needed to obtain the X and Y positions,
because the sum of all four buttons is normalized at all
times to a constant value. The Difference over Sum linearity
errors are thus avoided.
Single Turn Sampling
The fast gating mode can be enabled with an external command
line, and a fast gate can be applied to define the sampling
window. |
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