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FermiLab Recycler Ring BPM Upgrade Based on Digital Receiver Technology

R. Webber, J. Crisp, P. Prieto, D. Voy, C. Breigel, C. McClure,

M. Mengel, S. Pordes

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 System Overview 

1. Beam position split-plate capacitive pickups in the beamline vacuum.2. Signal preamplifiers in the beam enclosure near the beamline.3. Analog signal receiver (transition modules) and digital signal processing

electronics in the service buildings.4. Timing signal generators.5. VME based “front-end” data acquisition and control computers and support

hardware.6. Integrated position and intensity calibration system.

Pre-Amp GC-814

Software

Position

(A-B)/(A+B) * (-1)*Scale Factor + Offset

B

A

A

B

Calibration

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Signal Path

FOR MORE INFO...

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Dynamic Range Specifications

Bunched Beam: 4 Bunches in successive 2.5 MHz RF buckets separated by 396 ns with sigma_t = 25ns to 50ns Intensity Range 2e10 to 30e10 particles total

Un-Bunched Beam : Beam without modulation structure

position for 20e10 to 400e10 stored particles Barrier Bucket Separation of 1824ns to 11172ns

Absolute Position Measurement = +/- 1.0 mm +/ 5%Relative Position Measurement = +/- 0.4 mm +/- 5%

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Signal Processing Modes

1)      2.5 MHz Ensemble-This mode measures the magnitude of the 2.5 MHz signal, the 4 bunch beam structure.

2)      2.5 MHz Bunch-by-Bunch-Measures the position of each of the four 2.5 MHz bunches.

3)      2.5 MHz Narrow Band-Measures the magnitude of the 2.5 MHz signal integrated over an interval corresponding to about 64 TBD Recycler turns.

4)      Un-bunched Ensemble-This mode measures the magnitude of the signal from beam confined in a barrier bucket.

5)      Un-bunched Head or Tail-This measures the position of the head and/or the tail of the barrier bucket structure beam.

6)      89 KHz Narrow Band-This mode measures the magnitude of the 89 KHz signal integrated over an interval corresponding to 32 Recycler turns).

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VME vs. DMA Transfers

FIFO

0

10000

20000

30000

40000

50000

60000

0 10 20 30 40

LongWord Count

usec

s pe

r boa

rd

usecs per board

DMA64

0

50

100

150

200

250

300

350

400

450

0 100 200 300

LongWord Count

use

cs p

er b

oar

dSeries1

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Signal Attenuation In Datalene Twisted Pair Multi-Conductor Cable Between Pre-Amp Output and Transition Module Input

Cable Attenuation For Bunch Length

0

0.2

0.4

0.6

0.8

1

0 500 1000 1500

Cable Length (feet)

UnBunch

50ns

25ns

Signals with small sigma_t are attenuated more than larger sigm_t (50ns)

Signals with small sigma_t are attenuated more than larger sigm_t (50ns)

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Frequency Response Measurements:

Green trace: BPM plate terminated in 50 Ω

Red Trace: BPM, PreAmp, and Transition Module

-100.0

-80.0

-60.0

-40.0

-20.0

0.0

20.0

0.01 0.10 1.00 10.00 100.00

MHz

S21 [

db

]

Vertical

1.5kohm preamp

into 50 ohms

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Un-Bunched Pbar Beam Digitized through DDC Board Displayed Using Engineering Page

Fs = 80 MHz

Display Range= +/- 32768

Fs = 80 MHz

Display Range= +/- 32768

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Engineering Page Display of Plate A and B I and Q Pair, Magnitude, Phase, Position, and Intensity

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System Noise Contributions to Position Error

RMSRMSRMSDA VVV 58.6983.1773889.0/

m

mmrmsnoise

1.5

4

128

1

V62

V1.1

V75.1284P

rmsTranseAmpVPr rmsrms VHzeHz

nV6.1083899.417.22

rmserror me

emcorrectedP 9.17

1020

1070*1.5

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-40

-20

0

20

40

-70 -60 -50 -40 -30 -20 -10 0 10

A+B [db]

Pos

[mm

]

0

0.25

0.5

0.75

1

-70 -60 -50 -40 -30 -20 -10 0 10

A+B [db]

Pos

Nois

e [m

m]

DDC Position vs Intensity Scan for 53 MHz 84 Bunches Using AWG Source and Switchable Attenuators Plotted as Measured Position vs. Intensity

Calculated Position noise and Measured Position Noise vs Measured Intensity (70μVrms of A/D noise at Highest Intensity)

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Recycler TBTBPM Measured Positions Fitted To Sine Function

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Histogram of RMS Position Deviation For Vertical and

Horizontal BPM’s