Transcript Beam phase and intensity measurement

Beam phase and intensity
measurement
Grzegorz Kasprowicz
Richard Jacobsson
BPMs
Button Feedthrough
Beam Screen
Liquid Helium
Cooling Capillary
Pick-ups at IPs (BPTXs)
~150m to the IP
• 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
BPTXs
• Use Button Electrode BPM type
• Peak voltage (one button) of ~5V after 200m
of cable for nominal bunch
Amplitude (V)
– Sum voltage from all buttons  Independent of
beam position
Time (ns)
M
C
-
BPIM specifications:
- Measuring beam intensity
- 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
Beam intensity measurement

LPF
dt
ADC
Coefficients
RAM
Linearization
Block
Threshold
Pulse
detect
Ethernet
Credit
Card
PC
L`
Delay
Line 2
Delay
Line 1
Glue
Card
Local Bus
Histogram
Calculation
Block
RAM
FPGA
Result
40MB/s
Beam phase measurement
LPF
Threshold
Flip
BCLK Flop
Delay
Line 3
Ethernet
Credit
Card
PC

Coefficients
RAM
Pulse
detect
dt
ADC
12 bit
Histogram
Calculation
Block
Delay
Line 4
Glue
Card
Linearization
Block
Local Bus
RAM
FPGA
Simulation results – beam intensity measurement
rectified input signal
integrator’s output
ADC sampling moment
input signal
Simulation results – beam phase measurement
input signal integrator’s output
D flip-flop output
ADC sampling moment
BCLK
rectified input signal
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 = a*Xreal + 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
BPIM PCB design