Transcript The LHC Beam Position System BI Review CERN - 19

The LHC Beam Position System
BI Review
CERN - 19th-20th November 2001
Christian Boccard, Eva Calvo-Giraldo, Daniel Cocq, Lars Jensen,
Rhodri Jones, Jean-Pierre Papis, Jean-Jacques Savioz,
Hermann Schmickler. (CERN)
Daryl Bishop, Bill Roberts, Bill Rawnsley, Graham Waters. (TRIUMF, Canada)
Outline
• The LHC Beam Position Monitors
 General Layout
 Arc BPM
 Insertion BPM
• The LHC BPM Acquisition System




Layout
Wide Band Time Normaliser
Radiation Issues
Digital Acquisition Board (TRIUMF)
• Expected Performance
• Current Status
• Summary
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
LHC BPM System - General Layout
24 Directional Couplers
& 44 Enlarged Button
44
Warm BPMs
BPMs
for theBPMs
~922
24
for
Transverse
Damper,
100Special
Warm,
Button
Electrode
BPMs
Button
Electrode
BPMs
Total
of 1158
BPMs
for
the (24mm)
LHC
Interaction
Regions
24mm
Button
Electrodes
Tune
& Chromaticity
Buttons
Recuperated Measurements
from LEP
for the Lines
and its Transfer
Main Arcs & Dispersion Suppressors
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Arc BPM - SSS Layout
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Arc BPM - Detailed Layout
Beam
Pipes
BPMs
Cryogenic
Coaxial Cables
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Arc BPM - Button Feedthrough
Button Feedthrough
Beam Screen
Liquid Helium
Cooling Capillary
49mm aperture
24mm button
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Arc BPM - Feedthrough Technology
Classical Ceramic Seal
Glass-Ceramic Seal
Ceramic
Metallic
Pin
Glass-Ceramic
Brazing
Stainless Steel Body
Prone to cracks
& fissures
Excellent adhesion
to all surface blemishes
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Arc BPM - Technical Specifications
• Button Feedthrough
 24/34mm Diameter Stainless Steel Button
 Button Capacitance (8.0  0.6)pF
 Glass Ceramic Dielectric
– Vacuum Seal to 10-11 Pa.m3.s-1
– (50  1)W Impedance for coaxial line
 Normal Operation between 5-25K
 Radiation Resistant
• Signal Levels (after 40m cable & 70MHz Low Pass Filter)
 Pilot bunch (5109) gives ~30mV [peak]
 Ultimate bunch (1.71011) gives ~1V [peak]
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Arc BPM - Technical Specifications
• Cryogenic Cables
 (50  1)W Impedance, with Frequency range up to 2GHz
 Electrical length difference in each quadruplet < 10ps
 Copper Cladded Stainless Steel Inner & Outer Conductors
– Good Electrical Conductivity & Poor Thermal Conductivity
 Silicon Dioxide Foam Dielectric
 N-Type Connectors using Glass Ceramic Dielectric Seal
 Operation from 5K to room temperature
 Radiation Resistant
• Warm Cryostat Feedthough
 (50  1)W Impedance
 Electrical length differences < 4ps
 Radiation Resistant
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Interaction Region BPMs
Liquid Helium
Capillaries
Stripline
Electrode
Q2 Coupler
• 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
 Not sufficient to give requested 50mm resolution
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Improving the Directivity
Use Time Structure of Beams to Enhance Directivity IP 1 or 5
Additional Coupler
Original Coupler Locations
New Coupler Locations
Ideal position - maximum bunch1 to bunch 2 separation (6.25ns)
Zone 1 limit - 50mm resolution possible for nominal & weak-strong beams
Zone 2 limit - 50mm resolution possible only for nominal beam
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Outline
• The LHC Beam Position Monitors
 General Layout
 Arc BPM
 Insertion BPM
• The LHC BPM Acquisition System




Layout
Wide Band Time Normaliser
Radiation Issues
Digital Acquisition Board (TRIUMF)
• Expected Performance
• Current Status
• Summary
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
LHC Beam Position System Layout
Acquisition
Acquisition
Acquisition
Chassis
Acquisition
Chassis
Chassis
44
Chassis

4
Real-Time Network
Ethernet
TTC Timing
Surface Point (1 of 8)
1/16th of
LHC
Tunnel
Up to 28
Quadrupoles
7 Drop-offs
max.
31 Drop-offs
max.
SSS
containing
2 BPMs
F.E.
Electronics
4
SSS
containing
2 BPMs
F.E.
Electronics
SSS
containing
2 BPMs
F.E.
Electronics
Fibre-optic Link using “blown” fibres
31.25kbit WorldFIP fieldbus for slow control
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Front-End Electronics
A
INPUT
T1 = 1.5 ns
T1 = 1.5 ns
B
A
OUTPUT
B
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Wide Band Time Normaliser
1.5
0.5
A + (B + 1.5ns)
A
B
Beam
A
2.5
2.0
0.0
1.5
-0.5
1.0
-1.0
B
-1.5
B + 1.5ns
0.5
0.0
1.5ns
-2.0
-0.5
-2.5
-1.0
Amplitude B
Amplitude A
1.0
3.0
Time [ns]
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Wide Band Time Normaliser
1.5
3.0
A + (B + 1.5ns)
A
0.5
A
0.0
A + 1.5ns
B
2.5
2.0
1.5
1.5ns
-0.5
1.0
-1.0
B
0.5
-1.5
B + (A + 1.5ns)
0.0
-2.0
Dt depends on position
-2.5
Amplitude B
Amplitude A
1.0
-0.5
-1.0
Time [ns]
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Wide Band Time Normaliser
1.5
3.0
A
0.5
0.0
1.5
A+(B+1.5ns)
1.0
0.5
B+(A+1.5ns)+10ns
-1.5
-2.0
2.5
2.0
-0.5
-1.0
B
0.0
Interval = 10  1.5ns
System output
-2.5
Amplitude B
Amplitude A
1.0
-0.5
-1.0
Time [ns]
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The Wide Band Time Normaliser
50 W
CALIBRATOR
CABLE
CAL. and TEST
GENERATOR
PICK-UP
50 W
CABLE
CALIBRATOR
LOW
PASS
FILTER
Trigger

Intensity
Measurement
NORMALISER
INTEGRATOR
ADC
DAB
OPTICAL
LINK
Auto
Trigger
LOW
PASS
FILTER
TUNNEL
SURFACE
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
WBTN - Linearity v Intensity
For LHC Arc BPMs 1% ~ 130mm
Percentage Error w.r.t. Half Radius [%]
5%
4%
3%
Pilot
Nominal Ultimate
2%
1%
0%
-1%
-2%
-3%
-4%
-5%
1E+08
Linearity - High Sensitivity
Linearity - Low Sensitivity
Noise - High Sensitivity
Noise - Low sensitivity
1E+09
1E+10
1E+11
1E+12
Number of Charges per Bunch
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
WBTN - Linearity v Position
For LHC Arc BPMs 1% ~ 130mm
Percentage Error w.r.t. Half Radius [%]
8%
6%
4%
2%
0%
-2%
Calibration Point
-4%
Measured Value
-6%
Calibrated Value
Linearised Value
-8%
-1
-0.5
0
0.5
1
Normalised Position
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
WBTN - Radiation Issues
• The Front-end Electronics for the Arc BPMs will be
located under the main quadrupoles
 can expect to see a dose of some 12Gy/year
• Tests in the SPS-TCC2 area during 2000 showed that
use of DIGITAL components in the tunnel should be
avoided
 Most memories and FPGA’s too easily corrupted
 Qualification of components long & difficult
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
WBTN - Radiation Issues
• In 2001 : Fibre-Optic Link added to LHC BPM system
 only the minimum of analogue electronics kept in tunnel
 all sensitive digital electronics located on the surface
 allows easy access to most of the acquisition system
• Cost of large scale fibre-optic installation compensated by
 elimination of 13km of expensive low loss coaxial cable
 reduction in number of acquisition crates
 no bunch synchronous timing required in the tunnel
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
WBTN - Radiation Test Results
2001 Test results of the
very front-end WBTN card
with Fibre-Optic Link
Initial performance
After 650Gy no significant
deterioration in the performance
is visible
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
The LHC BPM Acquisition System
Very Front-End WBTN Card
70MHz Low Pass Filters
Supplied by TRIUMF (Canada)
1310nm Diode Laser Transmitter
Tunnel
Single-Mode Fibre-Optic Link
Surface
VME based
Digital Acquisition Board
TRIUMF (Canada)
WBTN Mezzanine Card
(10bit digitisation at 40MHz)
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
TRIUMF Digital Acquisition Board
• Orbit Mode (Real time acquisition at up to 10Hz)
 Average of all bunches over T turns
• LEP experience - default T set to 224 turns (20ms) for 50Hz elimination
 Average of each individual batch over N turns
• Capture Mode (Triggered on demand)
 Acquisition of N bunches for T turns where NT  100000
• i.e. 1 bunch for 100000 turns or 100 bunches for 1000 turns
 Average of all bunches or individual batches for >1000 turns
• Post-Mortem (Continuously updated)
 Average of all bunches over 1 turn for last 1000 turns
 Last 1000 orbit acquisitions
• Calibration Mode (Asynchronous Mode)
 Allows acquisitions in absence of bunch synchronous clock
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Operational Prototype Results in 2001
System extensively used in SPS for electron cloud & instability studies.
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Outline
• The LHC Beam Position Monitors
 General Layout
 Arc BPM
 Insertion BPM
• The LHC BPM Acquisition System




Layout
Wide Band Time Normaliser
Radiation Issues
Digital Acquisition Board (TRIUMF)
• Expected Performance
• Current Status
• Summary
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Accuracy and Resolution
MECHANICAL
ELECTRONICS
Bunch Type
Pilot Bunch
Bunches of Nominal Intensity
Mode of Operation Trajectory Orbit
Trajectory
Trajectory
Orbit
(single
(224 turn (single shot, (single shot,
(average of all
shot)
average) single bunch) average of all bunches over 224
bunches)
turns)
Resolution
(rms)
200mm
20mm
50mm
Accuracy
(rms)
150mm
Alignment
Error (rms)
200mm
Residual after
k-modulation
(rms)
<50mm
BI Review - Rhodri Jones (CERN - SL/BI)
5mm
5mm
3 = 750mm
20% of 4mm
Closed Orbit ‘budget’
(Spec = 500mm)
The LHC BPM System
Current Status
• Beam Position Monitors
 Button Feedthrough
• Contract for 4250 placed with CERAMASEAL (USA)
– pre-series delivery foreseen for Dec 2001
 Coupler Feedthrough
• Contract for 280 placed with CERAMASEAL (USA)
 Cryogenic Cable
• Contract for 4250 placed with KAMAN (USA)
– pre-series production awaiting final approval of SSS integration issues.
 Warm Cryostat Feedthrough
• Contract for 1000 placed with HUBER+SUHNER (CH)
– pre-series delivery Feb 2002
 Arc BPM body
• Under construction - responsibility of LHC/VAC
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Current Status (cont.)
• Acquisition System
 WBTN 70MHz Low Pass Filters
• Contract placed by TRIUMF with LORCH MICROWAVE (USA)
– 140 pre-series pairs delivered & accepted
– remaining 2360 pairs to be delivered by mid 2002
 WBTN Front-end and Mezzanine Cards
• Prototypes successfully tested in 2001
• Front-end card qualified for radiation environment
• Manufacture of pre-series to begin in 2002
 Fibre-optic Transmission Components
• Transmitters and receptors under test
• Radiation qualification & final component choice foreseen in 2002
• Fibre-Optic cable - call for tender in progress (responsibility of ST/EL)
 Digital Acquisition Board (TRIUMF)
• Prototype successfully tested in 2001
• Pre-series to be delivered by mid 2002
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System
Summary
• Arc Button BPMs
 All hardware designed and in production
• Directional Couplers
 Locations fixed & design underway
• Acquisition system
 Single complete prototype tested successfully in 2001
 Prototype of a complete operational acquisition chain to be installed and
tested on 6 BPMs in the SPS during 2002
Outstanding Issues
•
•
•
•
•
Precision requirements and integration of BPMs in the Collimator Regions
Integration issues in the Dispersion Suppressor and Interaction Regions
Approval of the routing for the Cryogenic Cables of the Arc BPMs
WorldFIP fieldbus yet to be tested
Software development for real-time orbit acquisition
BI Review - Rhodri Jones (CERN - SL/BI)
The LHC BPM System