beam instrumentation overview status for initial commissioning & recent results with bbq &...
DESCRIPTION
Beam Instrumentation Overview Status for initial commissioning & recent results with BBQ & PLL. LHC Machine Advisory Committee 7 th December 2006 Rhodri Jones (CERN – AB/BI). Overview. What’s required & when Status of BI Systems Orbit & trajectory measurement Beam loss measurement - PowerPoint PPT PresentationTRANSCRIPT
Beam Instrumentation Overview
Status for initial commissioning & recent results with BBQ & PLL
LHC Machine Advisory Committee
7th December 2006
Rhodri Jones (CERN – AB/BI)
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Overview
• What’s required & when
• Status of BI Systems Orbit & trajectory measurement Beam loss measurement Synchrotron light monitor Other Systems
• Recent Results with the BBQ & PLL system US-LARP Collaboration with BNL & FNAL Tune, chromaticity & coupling measurements
• RHIC and SPS results
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Instrumentation – the essentials• First turn
Screens, BPMs, fast BCT, BLMs
• Circulating beams at 450 GeV BPMs, DC BCT & lifetime, BLMs Tune & chromaticity Emittance: wire scanners.
• Snapback and Ramp Continuous Tune, Coupling & Chromaticity Orbit (+ feedback) BLMs to beam interlock controller etc. Continuous emittance monitoring: synchrotron light
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
100 Warm, Button Electrode BPMsButtons Recuperated from LEP
LHC BPM System - General Layout
24 Directional Couplers52 Enlarged Button& 8 Trigger BPMsInteraction Regions912 Button Electrode BPMs (24mm)
for theMain Arcs & Dispersion Suppressors
Total of 1186 BPMs for the LHCand its Transfer Lines
36 Warm BPMs -34mm Button Electrodes
54 Special BPMs for Tune & Chromaticity,Transverse Damper & RF, Beam Dump
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Delivery Status of BPM Hardware
• BPM components all delivered 3750 standard and 500 enlarged buttons 3724 pre-formed arc cables and 592 special configurations 430 coupler feedthroughs 1000 cryostat feedthroughs
• Warm BPM & stripline electrode production Manufactured by BINP
• initial delivery non conform• delivery schedule was a worry in 2005 MAC presentation
Extensive follow-up during 2006 by both AB/BI & AT/VAC• Delivery of all components now complete (few non-conformities pending)
• Special BPMs for Tune Measurement & Dump Design only completed early 2006 Production by TS/MME and CECOM (Italy) Delivery was “just in time” for LSS4 installation Awaiting final delivery of dump line BPMs
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Installed BPMs• Total of ~660 cold BPMs installed (~330 SSS)• Warm BPMs in LSS 8, LSS 1L and LSS 4 all installed
Enlarged button BPMsinstalled in Point 4
Warm directional couplerinstalled in Point 8
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Status of BPM Acquisition System• Series Production of all components underway
Wide Band Time Normaliser(40MHz position measurement)
• 480 of 2400 front-end cards received• 200 of 2400 digitiser cards received• all delivery to be completed by March 2007
Digital Acquisition Board(DAB64x - TRIUMF)
• Standard for BPM, BLM, Fast BCT, Wire Scanners,Luminosity & Q measurement
• 220 of 1200 BPM type modules received• 185 of 500 BLM type modules received• all delivery to be completed by March 2007
• Reception Testing 2 automated test benches constructed and manned by external personnel Used for adjustment and calibration of all Wide Band Time Normaliser Cards Beam simulator allows position & intensity linearity measurement for all cards All data stored in MTF & linked to serial number chip located on each card
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Status of BPM Acquisition System
• Installation Tunnel installation and hardware
commissioning has started in 8L• 23 of 34 positions in place
(92 channels)
• Infrastructure Nearly all fibre-optic, coaxial cable and WorldFIP control links in place
• LSS7 and LSS3 will be equipped with radiation hard fibres
• Produced by Fujikura (Japan) – first batch in production
• Tests by Fraunhofer Institute and mixed field test in the SPS has shown them to be an order of magnitude less susceptible than the standard CERN mono-mode fibre
BPM/BLM limit of 6dB
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
The LHC Beam Loss SystemRole of the BLM system:
1. Protect the LHC from damage
2. Dump the beam to avoid magnet quenches
3. Diagnostic tool to improve the performance of the LHC
Name Type Number Area of use MaskableTime resolution
BLMQI Ionisation Chamber ~3100 Arcs yes 1 turn
BLMCIBLMCS
Ionisation ChamberSEM
~150~150
Collimation regions
no 1 turn
BLMEIBLMES
Ionisation ChamberSEM
~400~150
Critical aperture limits or positions
no 1 turn
BLM__ ACEM (phase II) ~10Primary collimators
yesbunch-by-bunch
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Beam Loss Detectors• Design criteria: Signal speed and reliability
• Dynamic range (> 109) limited by leakage current through insulator ceramics (lower) and saturation due to space charge (upper)
Secondary Emission Monitor(SEM):
Length 10 cm P < 10-7 bar ~ 30000 times smaller gain
Ionization chamber: N2 gas filling at 100 mbar
over-pressure Length 50 cm Sensitive volume 1.5 l Ion collection time 85 s
• Both monitors: Parallel electrodes (Al, SEM:
Ti) separated by 0.5 cm Low pass filter at the HV
input Voltage 1.5 kV
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
BLM production at IHEP
• After readjustment of the production schedule in March a constant rate has now been achieved
• SEM production to start after ionisation chamber production is complete
Ionisation chamber production
0
500
1000
1500
2000
2500
3000
3500
4000
4500
24/03/06 02/07/06 10/10/06 18/01/07 28/04/07 06/08/07
time
# o
f io
nis
ati
on
ch
am
be
rs
schedule
at CERN
needed for installation
Sector 7 – 8fully equipped with ionisation chambers
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
BLM integration and installations• Integration of monitors in layout of ARC, IR 1 and IR 8 finished• Integration will continue for the remaining points following installation schedule• IHEP installation team (1 team leader and 4 technician):
test of monitors with radiation source, shrinking of insulation tube, mounting of monitors, cable tray/cable fixation and electrical test of system
in case of accelerated interconnection closure an increase in the team is possible
ARC quadrupole with 3monitors on either site
Beam I
Beam II
Triplet quadrupole magnets IR 8
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
First use of LHC chamber design at CERN
270cm
comparison measurement-simulation, vertical pit1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
-157.5 -146.3 -135 -123.8 -112.5 -101.3 -90 -78.75 -67.5 -56.25 -45 -33.75 -22.5 -11.25 0 11.25 22.5 33.75 45 56.25 67.5 78.75 90 101.25
112.5 123.75
135 146.25
157.5
cm
char
ges/
pot
meas: nominal
sim: nominal
Fluka simulation; P. Sala et al
3.20 m
• CNGS Secondary beam width measurements• Interleaved CERN produced and IHEP
produced LHC type Ionisation Chambers Give very similar response
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
BLM Acquisition Electronics
Threshold Comparator: Losses integrated and compared to threshold table (12 time intervals and 32 energy ranges).
Implemented on BDI DAB64x
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
BLM test measurements at the SPS dump
Remaining beam dumped at end of slow extraction
FULL beam intensity ondump
Remnant decay after full intensity dump
Injection & acceleration losses
• Validation of complete BLM readout electronics chain 200MHz fixed target beam Use of SPS ionisation chamber located near the internal SPS dump
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Measuring Beam Size
• Beam Profile Measurements in the LHC Workhorses
• Synchrotron light monitor
• Wire scanners for cross calibration
For injection & matching• OTR screens
For ions• Rest Gas Ionisation Monitor (BGI)
– Also used as back-up for SR monitor
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Synchrotron Light Monitors (BSRx)
BSRT light source: 5T Superconducting undulators• Latest news: both SC undulators in place, see next CERN bulletin!
Congratulations to the AT/MAS team
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Synchrotron Light Monitors
• 36 Tons of shielding and support structure in place
• Dielectric coated silicon extraction mirror first of its type - replaces traditional beryllium mirror over 98% reflectivity in visible/IR achieved by a small Scottish company
(Helia) using similar techniques to coating silicon diodes
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
• LHC BSRT fast camera tested in the SPS, Nov 2006 Image is single turn beam intensity seen by OTR screen Scale in pixels optical magnification gives 20x20mm frame.
• Able to capture and store raw images at the SPS revolution frequency Will have to optimise the trade off between transfer rate, data treatment &
dead time between measurements
Synchrotron Light Monitor (BSRT)
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Abort Gap Monitor (BSRA)• System based on gated photomultiplier
• Tested in the SPS with synchrotron light source on fixed target beam Observation of injection kicker gap while beam is debunched before extraction.
• Worked extremely well
• Gain of photomultiplier is not as high as advertised Requires 15x more light
• For LHC a longer integration time is possible (every ms for SPS)
• BUT BSRA will require more light than anticipated at expense of BSRT
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Wire scanner tanks and mechanisms
in place
DCCT and FBCTawaiting final
installation
Rest gas ionisation chambers and compensation
magnets in place
Dump line BTV tanks
awaiting final installation
Other Systems• Nearly all specialised BI equipment located in LSS4
After LSS8 this was the second full LSS to be installed A big effort made by BI technicians and engineers during 2006 together
with TS/MME and AT/VAC to get everything ready in time• We just about made it !!
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Tune, Chromaticity & Coupling• Clear three step approach:
1) Day 1 with kicked beams and classical motion analysis• Q kicker for both planes & both beams located in Pt 4• Chirp excitation using the transverse damper
2) Day N with PLL tune tracking (US-LARP)• Recent experience gives us the hope that N is small!
3) Day N+ with PLL measurement & Feedback (US-LARP)• Tune, chromaticity & coupling
• Requirements for stable PLL operational: lowering the excitation level to an insignificant level coping with coupling coping with chromaticity achieving compatibility with resistive transverse damping
Collaboration with BNL & FNAL via US-LARP
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Measuring with Little or No Excitation – The Base Band Q Measurement (BBQ) System
Direct Diode Detection (3D)
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Continuous FFT and PLL Implemented in FPGA
3DFront-End
PID
PID
DAC
ADC
KICKERBBQ pickup
BEAM
Frequencygenerator
FixedAmplitude
Correction
Correction
Sin/CosExcitation
Ampl FB Off
Sweep/Lock
PhPh
A
A
A cos(wt)
PLL
PLL
PLL
A sin(wt)PLL
+-
+-A
I
I
BEAM
Amp. reference
Phase referenceDelay compens. f
40Mhz
A
Uses Standard DAB64x Module
PhPh
A
A
A cos(wt)
PLL
PLL
PLL
A sin(wt)PLL
A
I
I
BEAM
cordic
x
ya
a x
y
cordic
x
ya
a x
y
cordic
x
ya
x
y
aLPIIR
LPIIR
CORDIC: polar rectangular avoids large LUTs uses simple operations saves FPGA space !
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Setting-up the 25ns Beam in the SPS
Low intensity beam
Residual oscillationwithout additionalexcitation clearlyvisible
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
PLL tracking in the SPS
• Nominal Beam - PLL OFF tune hardly visible
• Nominal Beam – PLL ON tracking achieved throughout cycle
Resonantly Extracted 25ns Beam in the SPSReal-time Tune Display
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
PLL Measurement on SPS Fixed Target Cycle
Tracks tune change of ~0.1 units per second
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
PLL Measurement during Collimator MD
Resolution of 10-6 achieved with 1s integration
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Beam Transfer Functions in the SPS
• When things go wrong – thought to be due to a coupled bunch instability! Stable phase shifts – PLL can no longer lock Multiple peaks appear in Beam Transfer Function
• Standard Beam Transfer Function
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Measurement of Coupling using a PLL Tune Tracker
Frequency
Am
plitu
de
FFT of Horizontal Acquisition Plane
Start with decoupled machine
Fully coupled machine: = |C-|
Only horizontal tune shows up in horizontal FFTGradually increase coupling Vertical mode shows up & frequencies shift
Hor
Ver
Set TunesHV
By looking at contribution of vertical PLL in horizontal plane &vice-versa the degree of coupling can be calculated
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Tune & Coupling Feedback at RHIC (2006)
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Continuous Chromaticity Measurements• The focus of the development for 2007
RHIC to attempt chromaticity feedback SPS used to qualify new techniques for the LHC
• RF modulation with PLL Tune Tracking Standard technique used at RHIC & Tevatron may not be compatible with nominal collimator settings in LHC
• Other techniques under test Fast RF phase modulation – tests at FNAL & SPS (RF power an issue for LHC) Additional side exciters within PLL to measure tune width (phase slope) Continuous head-tail measurement with PLL excitation
• Constant phase shift proportional to chromaticity• Requires sensitive measurement of head & tail oscillations diode detection!!
LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Summary• Both large distributed systems (BPM/BLM) currently on schedule
Production of ionisation chambers at Protvino is progressing smoothly• One of the major worries last year
• Support for AB/BI from TS Significant support for Design and from the main CERN workshops Regular meetings have allowed problems to be solved quickly and priorities to be
juggled to fit with installation requirements
• Most Vacuum Hardware now in place in Point 4 Attention can turn to completing and testing the final electronics
• Tune, Coupling and Chromaticity Measurement Combination of BBQ and PLL is proving very powerful RHIC demonstration of combined tune and coupling feedback is very encouraging All efforts in 2007 will be focused on adding chromaticity feedback to the list
• Outlook for LHC commissioning All necessary instrumentation for the start-up foreseen to be in place Functionality will evolve through the commissioning phases