the lhc beam position system
DESCRIPTION
The LHC Beam Position System. Ad-hoc Working Group on LHC Experiment-Machine Parameter and Signal Exchange 26 th March 2002 Rhodri Jones (SL/BI). LHC BPM System - General. 100 Warm, Button Electrode BPMs (LEP) for TI2 & TI8 922 Button Electrode BPMs (24mm) for Arc & DS - PowerPoint PPT PresentationTRANSCRIPT
The LHC Beam Position System
Ad-hoc Working Group on LHC Experiment-Machine Parameter
and Signal Exchange
26th March 2002
Rhodri Jones (SL/BI)
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
LHC BPM System - General
• 100 Warm, Button Electrode BPMs (LEP) for TI2 & TI8• 922 Button Electrode BPMs (24mm) for Arc & DS• 44 Warm Button Electrodes BPMs for IR3 & IR7• 44 Enlarged Button BPMs (34mm) for IR1,2,5 & 8• 24 Directional Couplers for IR1,2,5 & 8• ~ 24 Special BPMs for Transverse Damper, Tune &
Chromaticity Measurements in IR4
• 1 BPTX “timing pick-up” per incoming beam for IR1,2,5 & 8
Total of 1166 BPMs for the LHC and its Transfer Lines
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
The Arc BPM - SSS Layout
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
Beam Screen
Button Feedthrough
Liquid HeliumCooling Capillary
49mm aperture 24mm button
Arc BPM - Button Feedthrough
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
Interaction Region BPMs
• Stripline length 120mm to give same response as button
• 2 Types Warm Coupler - capable of withstanding bake-out to 200°C Cold Coupler - located in Q2 cryostat (tilted by 45° for cryostat integration)
• Directivity measured as 28dB at 200MHz
StriplineElectrode
Liquid HeliumCapillaries
Q2 Coupler
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
INPUT OUTPUT
A A
BB
T1 = 1.5 ns
T1 = 1.5 ns
The Front-End Electronics
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Time [ns]
Am
plitu
de A
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Am
plitu
de B
1.5ns
A
B
B + 1.5ns
A + (B + 1.5ns)A B
Beam
The Wide Band Time Normaliser
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Time [ns]
Am
plitu
de A
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Am
plitu
de B
1.5ns
A
B
A + 1.5ns
B + (A + 1.5ns)
A + (B + 1.5ns)A B
The Wide Band Time Normaliser
t depends on position
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Time [ns]
Am
plitu
de A
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Am
plitu
de B
A B
A+(B+1.5ns)
B+(A+1.5ns)+10ns
System output
The Wide Band Time Normaliser
Interval = 10 1.5ns
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
The Wide Band Time Normaliser
CAL. and TESTGENERATOR ADC
LOWPASS
FILTER
CALIBRATOR
PICK-UP
50 CABLE
Intensity
Measurement
Trigger
AutoTrigger
50 CABLE
LOWPASS
FILTERCALIBRATOR
NORMALISER INTEGRATOROPTICAL
LINK
TUNNEL SURFACE
DAB
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
-5%
-4%
-3%
-2%
-1%
0%
1%
2%
3%
4%
5%
1E+08 1E+09 1E+10 1E+11 1E+12
Number of Charges per Bunch
Per
cent
age
Err
or w
.r.t.
Hal
f Rad
ius
[%]
Linearity - High SensitivityLinearity - Low SensitivityNoise - High SensitivityNoise - Low sensitivity
Pilot Nominal Ultimate
WBTN - Linearity v IntensityFor LHC Arc BPMs 1% ~ 130m
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
WBTN - Linearity v Position
-8%
-6%
-4%
-2%
0%
2%
4%
6%
8%
-1 -0.5 0 0.5 1
Normalised Position
Per
cent
age
Err
or w
.r.t.
Hal
f Rad
ius
[%]
Calibration Point
Measured Value
Calibrated Value
Linearised Value
For LHC Arc BPMs 1% ~ 130m
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
The LHC BPM Acquisition System
70MHz Low Pass FiltersSupplied by TRIUMF (Canada)
Single-Mode Fibre-Optic Link
VME basedDigital Acquisition Board
TRIUMF (Canada)
WBTN Mezzanine Card(10bit digitisation at 40MHz)
1310nm Diode Laser Transmitter
Very Front-End WBTN Card
Tunnel
Surface
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
Accuracy and ResolutionBunch Type Pilot Bunch Bunches of Nominal IntensityMode of Operation Trajectory
(singleshot)
Orbit(224 turnaverage)
Trajectory(single shot,
single bunch)
Trajectory(single shot,
average of allbunches)
Orbit(average of all
bunches over 224turns)
Resolution(rms) 200m 20m 50m 5m 5m
EL
EC
TR
ON
ICS
Accuracy(rms) 150m
AlignmentError (rms) 200m
ME
CH
AN
ICA
L
Residual afterk-modulation
(rms)<50m
3 = 750m20% of 4mmClosed Orbit ‘budget’(Spec = 500m)
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
Timing Pick-up for the Experiments(BPTX)
~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
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
BPTX Requirements?Choice of Pick-up?• Stripline Coupler?
Peak voltage (one button) of ~20V after 200m of cable for nominal bunch Peak voltage (one button) of ~1V after 200m of cable for pilot bunch
• Button Electrode BPM? Peak voltage (one button) of ~5V after 200m of cable for nominal bunch Peak voltage (one button) of ~250mV after 200m of cable for pilot bunch
• Other Type of Pick-up?
Type of Signal?• Sum signal (sum of all 4 pick-up electrodes 2 peak voltage)?
Virtually independent of position & requires only 1 cable
• Sum and Delta Signal? Requires 3 cables to give sum, horizontal position & vertical position
• Other Type of Signal?
The LHC BPM System LEMPSE - Rhodri Jones (SL/BI)
Next Steps
SL/BI will supply:• 2 BPTX Pick-ups per Experiment
Choice of pick-up in collaboration with Experiments
Experiments responsible for:• Cabling
All machine cabling to be defined by 15th March 2002! All machine cabling to be ordered by 15th May 2002
• Any subsequent electronics Keep in mind radiation resistance for electronics in the tunnel