Beam phase and intensity measurement

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Beam phase and intensity measurement
Grzegorz Kasprowicz Richard Jacobsson
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BPMs
Button Feedthrough
Beam Screen
Liquid Helium Cooling Capillary
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Pick-ups at IPs (BPTXs)

• Located 150m from the IP in front of the D2
  Magnet
• One BPTX either side of the IP on the incoming
  beam
• Exclusively used by the experiments
• Monitoring phase of the beam with respect to LHC
  clock
• Monitoring bunch intensity

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BPTXs

• Use Button Electrode BPM type
• Peak voltage (one button) of 5V after 200m of
  cable for nominal bunch
• Sum voltage from all buttons ? Independent of
  beam position
• Acquisition and processing?

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BPIM specifications M - Measuring beam
intensity C - Collecting intensity results
per bunch and averaging them -     - Outputting
intensity measurement at 40 MHz via LVDS
interface -     -  Resolution of intensity
measurement - 8 bits -     -  Measuring phase
between incoming bunch signal and bunch
clock -     -  Collecting delay results for
every bunch and averaging them -     -  Digital
approximation of converter characteristics -     -
  Resolution of phase measurement better than
50ps -     -  Data processing in FPGA -
Ethernet based control interface -     -  All the
adjustments via the Ethernet - 6U VME
board
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Beam intensity measurement
L
FPGA
ADC
Coefficients RAM
LPF
Linearization Block
Result 40MB/s
Delay Line 1
Delay Line 2
Pulse detect
Histogram Calculation Block
Threshold
RAM
Credit Card PC
Glue Card
Local Bus
Ethernet
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Beam phase measurement
FPGA
Coefficients RAM
LPF
Pulse detect
Threshold
Linearization Block
ADC
Flip Flop
12 bit
BCLK
Histogram Calculation Block
Delay Line 3
Delay Line 4
RAM
Credit Card PC
Glue Card
Local Bus
Ethernet
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Simulation results beam intensity measurement
rectified input signal integrators output
ADC sampling moment
input signal
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Simulation results beam phase measurement
 
input signal integrators output
D flip-flop output BCLK ADC
sampling moment
rectified input signal
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Approximation   A first order polynomial
approximation is used All ADC range (0 to 4095)
is divided into 32 sub ranges In each of them,
measured value is described by equation
Ym aXreal b
where Xreal real measured value, Ym
measured value with error, a scaling
coefficient, b shift value   In order to
obtain a real value, circuit must realize
following equation
Xreal (Ym b) / a  
Implementation of this needs only one multiplier
and adder
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BPIM PCB design