1. LHC MAC June 15th 2006 T. Linnecar on behalf of the AB-RF Team
LHC RF Status
LHC MAC June 15th 2006
T. Linnecar
on behalf of the AB-RF Team

2. LHC MAC T. Linnecar AB-RF
Acknowledgements
a lot of work by and help from:
AT – VAC , ACR
TS – EL, CV, IC, CS, SU, MME, DEM
AB – PO, CO
June 15th 2006
LHC MAC T. Linnecar AB-RF

3. LHC MAC T. Linnecar AB-RF
Outline
Specifications, issues and status
RF cavities and modules
High power system
Transverse damping system
Longitudinal wide-band monitor
Beam and cavity control electronics
Installation in the cavern and tunnel
Summary
June 15th 2006
LHC MAC T. Linnecar AB-RF

4. LHC MAC T. Linnecar AB-RF
Cavities and modules – 1
Specifications
4 cryostats (2/beam) plus 1 reserve, each module 4 SC cavities
400 MHz cavities, VRF = 2 MV (nominal max.)
Variable coupler, 300 kW full reflection, all phases, Qext = injection - full control voltage Qext = 180,000 in coast - minimise power
Tuner: mechanical, large tuning range (180 9kHz/s) for beam-loading compensation
Total VRF = 8 injection – nominal intensity MV/beam in coast
June 15th 2006
LHC MAC T. Linnecar AB-RF

5. LHC MAC T. Linnecar AB-RF
Cavities and modules -2
June 15th 2006
LHC MAC T. Linnecar AB-RF

6. LHC MAC T. Linnecar AB-RF
Cavities and modules -3
Some issues/changes:
Coupler
Window: ceramic cylinder with Cu rings to minimise RF heating. Fabrication problems  modifications to the Cu ring profile and brazing procedures
Polarisation ceramic: vacuum seal leaks  quality control of seals
Cavity frequency
Thermal cycling necessary to stabilise central frequency - outside range  adjustable disc-spring assemblies installed to provide mechanical pre-tuning (On roughly ½ of the cavities)
Tuning bellows
Failure of bellows (at the end weld) on tuner mechanism during tests (cryostat vacuum lost)  re-design of bellows collar and life test
June 15th 2006
LHC MAC T. Linnecar AB-RF

7. LHC MAC T. Linnecar AB-RF
Cavities and modules -4
Cryogenics
Nominal He pressure 1.35 bar, 2.5 bar max., but ~20 bar on cryo. return line with magnet quench !
Cavity protection and personnel safety (He discharge).
 2 discharge valves (2 bar) and 2 rupture discs (2.5 bar)
Recent modifications
Safety Outlet Domes: Re-design (double walled tubes - increased warm-cold transition), following analysis by AT-CR, to ensure tubes not damaged by icing after repeated discharges
Warm recovery line: with heater to empty cavity in controlled manner after He stop  new dome added.
He inlet dome
Coupler
Warm recovery line
Safety dome
He outlet dome
June 15th 2006
LHC MAC T. Linnecar AB-RF

8. LHC MAC T. Linnecar AB-RF
Cavities and modules -5
Status
Modules:
All 16 cavities in 4 modules conditioned to 8MV/m (5.4MV/m spec.) – conditioning of one cavity takes ~ one week
Final assembly details remain (e.g pre-tuning assemblies). All 4 ready for installation in August; 5th module ready in Oct. 2006
Extended power/field run with no polarisation – outburst typically after 5-6 hrs; with polarisation kW  cooling improved
Couplers:
18 (20 required) have been manufactured, 16 installed. All couplers conditioned to 300kW: full reflection, all phases, no polarisation used – typically 2 weeks. 10 spares will be built and conditioned (fragile item, window brazing challenging)
Equipment controls
Slow control system crates (programmable logic devices) ready for installation – interface software to main control system under test
Fast interlock system defined, crates constructed and tested
Installation as planned
June 15th 2006
LHC MAC T. Linnecar AB-RF

9. LHC MAC T. Linnecar AB-RF
RF high power -1
Specification
16 klystrons, 1/cavity, 400 MHz, 300kW CW
Connection via circulator (load) to waveguide system
4 power converters (LEP) on surface; 4 klystrons per converter
1 modulator/klystron to adjust operating conditions (slow changes)
Modulator, fast protection unit and high voltage components in fire-proof bunker
June 15th 2006
LHC MAC T. Linnecar AB-RF

10. LHC MAC T. Linnecar AB-RF
RF high power -2
June 15th 2006
LHC MAC T. Linnecar AB-RF

11. LHC MAC T. Linnecar AB-RF
RF high power -3
Issues
Klystrons
Careful tuning of each klystron frequency response to give optimum loop stability.
Saturation – characteristics measured consequences for low-level evaluated
Arcing in klystron HV connector box – solved and remedied by manufacturer (Thales)
Reduction of 50 Hz harmonics
Optimisation of power convertor (phase balancing)
Modulator filtering
Waveguides
Layout to minimise bends (arc sources)
Arc detectors – positioning/design definition
June 15th 2006
LHC MAC T. Linnecar AB-RF

12. LHC MAC T. Linnecar AB-RF
RF high power -4
Status
To shorten installation time – most items are pre-cabled and assembled
20 klystrons have been received and tested (long duration)
16 circulators and loads received and tested – support chassis under construction
Focus supplies and 200 W drivers (LEP) refurbished, modified and tested
Fast protection systems and HV commutators built
Modulators (LEP) upgraded – Si oil for safety
16 klystron control racks and support chassis built and ready for installation
Waveguides installed up to cavity position (see later)
Installation as planned
June 15th 2006
LHC MAC T. Linnecar AB-RF

13. Transverse damping system - 1
Specification
16 electrostatic kickers – 2 plates
4 kickers/plane/beam
32 tetrode amplifiers - 1 tetrode amplifier/plate
Injection damping; ± 7.5 kV/kicker,
2 μrad/turn/plane/beam (450 GeV); power bandwidth 1 MHz
Instability damping, 20 MHz bandwidth
Collaboration between JINR (Dubna, RU) and CERN
Design CERN/JINR
Kicker/Supports/Power amplifier production JINR
Power convertors / Electronics / cabling and installation CERN
June 15th 2006
LHC MAC T. Linnecar AB-RF

14. Transverse damping system - 2
Amplifiers and kickers
June 15th 2006
LHC MAC T. Linnecar AB-RF

15. Transverse damping system - 3
Some issues
Higher order modes  damping electrodes
Feedthroughs  vacuum issues solved
Electrode strength – copper electrode geometry maintained during bakeout (± 50μm)  strict temperature monitoring (150ºC max.)
Amplifier/cavity resonances eliminated  smooth response
Noise in electronics – under study  first estimations suggest <1μm equivalent possible
June 15th 2006
LHC MAC T. Linnecar AB-RF

16. Transverse damping system - 4
Status
Kickers, supports and tetrode amplifiers
19/20 built, 18 joined in pairs (16 to be installed, 1 for test stand), parts delivered to CERN and assembled by JINR
9 pairs; bakeout and vacuum test completed
supports all delivered
2/20 amplifiers in test stand, 2 under assembly at CERN
16 under construction in JINR – delivery and assembly – end 2006
Drivers and Power Convertors
All 40 drivers, ± 150 V, 1k Hz-30 MHz (Thales) delivered/accepted
All 9 PCs, 210 kW (Imtech Vonk) delivered. Tested up to half power. 8 installed in surface building SR4
Slow controls and Feedback Electronics
slow control system working in test area, series ordered
Feedback electronics being finalised (Noise issues). Uses mod. of one-turn feedback electronics digital card for main processing
Kickers and amplifiers: installation as planned 2006, electronics ready mid-2007
June 15th 2006
LHC MAC T. Linnecar AB-RF

17. Wideband longitudinal monitor - 1
Specification
3/beam to be installed
RF phase reference, longitudinal profile (beam diagnostics)
Bandwidth achieved: 170 kHz to 3.5 GHz
Transfer Impedance ~ 5Ω
Issues
Response optimisation  ferrite distribution
Ferrite heating from beam  cooling of ferrite by contact and radiation sufficient
Leaking SMA feedthroughs  bakeout below 200ºC
Status
5 monitors constructed  with AT-VAC for bakeout
1 permanently installed in SPS for cross reference 2006
Installation as planned
June 15th 2006
LHC MAC T. Linnecar AB-RF

18. Wideband longitudinal monitor - 2
June 15th 2006
LHC MAC T. Linnecar AB-RF

19. Beam and cavity control electronics - 1
Description
Cavity control reference signals – complex systems: digital except fast RF feedback loops
Tuner loop / cavity
Klystron polar loop / klystron
Fast RF feedback loop / cavity
1 turn delay feedback / cavity
Cavity conditioning / cavity
Beam control
Phase loop / beam (all cycle)
Frequency/radial loop / beam (acceleration)
Synchronisation loop / beam (injection and capture)
Longitudinal damper / beam (on 400 MHz RF)
Synchronisation
Bunch into bucket SPS – LHC, batch positioning
Reference signals
To kickers, experiments, other machines, beam dump
June 15th 2006
LHC MAC T. Linnecar AB-RF

20. Beam and cavity control electronics - 2
Issues
RF noise
Specification (5 400 MHz) by estimations and simulations. Critical elements are beam-phase measurement and VCXO Also all other noise sources must be sufficiently low – e.g klystron.
Measurements on full system underway
Heavy beam loading
Interlocks and control generally: will be tested in building SM18 on full system under pulsed conditions
Fast pulses (high forward and reflected powers) at n x revolution frequency. Necessity to minimise power in coast  adaptive algorithms for “Slow feedback” (allow beam to move slightly)
Saturation
Reduced gain at high powers  klystron loop
Limiters to prevent unstable loop operation
June 15th 2006
LHC MAC T. Linnecar AB-RF

21. Beam and cavity control electronics - 3
Tests on-going in SM18 on full chain
RF feedback
Tuning loop
2us/div
Tuner loop – lock from any position
RF feedback – noise reduction
4 dg pp
0.4 dg pp
power 130kW to 300 kW
50us/div
RF feedback – pulse response
of system (injection damping)
June 15th 2006
LHC MAC T. Linnecar AB-RF

22. Beam and cavity control electronics - 4
Status
Systems design complete
25/35 VME cards developed
Series production of modules started
VME crates
Crates and ancillaries defined (power supplies, active back-plane, cable passage tray, air-cooling etc. Pre-series of 5 in next weeks, series of 70 ordered
Faraday cages in cavern
infrastructure installed (see later)
Beam control area on surface in SR4
rack layout being designed
Software
Drivers for beam-control implemented
Alarms and logging under discussion with AB-CO – development started
Completion as planned for June 2007 (very tight)
June 15th 2006
LHC MAC T. Linnecar AB-RF

23. LHC MAC T. Linnecar AB-RF
Installation - 1
RF equipment in the tunnel is all in the region of point 4.
High power equipment is in the cavern around point 4 (UX45)
Cavity and fast beam control is in Faraday cages in UX45
General beam control is on the surface in building SR4
June 15th 2006
LHC MAC T. Linnecar AB-RF

24. LHC MAC T. Linnecar AB-RF
UX45 cavern 2004
June 15th 2006
LHC MAC T. Linnecar AB-RF

25. Installation – UX45 cavern
June 15th 2006
LHC MAC T. Linnecar AB-RF

26. LHC MAC T. Linnecar AB-RF
Installation - 4
Issue
Integration studies show difficult installation around modules 1 and 4 (at entry to tunnel)
Status
All cables from SR4 to UX45 to tunnel installed – inter-rack cabling to be completed
As seen in photos – according to plan
June 15th 2006
LHC MAC T. Linnecar AB-RF

27. LHC MAC T. Linnecar AB-RF
Summary
The machine elements are on target for installation as foreseen
Difficult installation around modules 1 and 4 – possible from integration studies
Production of the large number of beam-control modules on critical path but on track
June 15th 2006
LHC MAC T. Linnecar AB-RF

28. LHC MAC T. Linnecar AB-RF
3-D waveguide integration UX45
June 15th 2006
LHC MAC T. Linnecar AB-RF

29. LHC MAC T. Linnecar AB-RF
Coupler conditioning SA2
June 15th 2006
LHC MAC T. Linnecar AB-RF

30. LHC MAC T. Linnecar AB-RF
Unit
Injection
450 GeV
Collision
7 TeV
Bunch area (2)*
eVs
1.0
2.5
Bunch length (4)* ns
1.71
1.06
Energy spread (2)*
10-3
0.88
0.22
Intensity per bunch
1011 p
1.15
Number of bunches
2808
Transverse emittance V/H m
3.75
Intensity per beam A
0.582
Synchrotron radiation loss/turn
keV - 7
Longitudinal damping time h 13
Intrabeam scattering growth time - H
- L 38 30 80 61
Frequency
MHz
Harmonic number
35640
RF voltage/beam MV 8 16
Energy gain/turn (20 min. ramp)
485
RF power supplied during acceleration/ beam kW
~275
Synchrotron frequency Hz
63.7
23.0
Bucket area
1.43
7.91
RF (400 MHz) component of beam current
0.87
1.05
Main Beam and RF Parameters
* The bunch values at 450 GeV are an upper value for the situation after filamentation, ~ 100 ms after
each batch injection. The bunch parameters at injection are described in the text.
June 15th 2006
LHC MAC T. Linnecar AB-RF

31. LHC MAC T. Linnecar AB-RF
Klystron:
Output power
300 kW
Operating frequency f0
400.8 MHz
d.c. to RF conversion efficiency
≥ 62%
Operating voltage
≤ 54 kV
Maximum beam current
9 A
Gain
≥ 37 dB
Group Delay at f0 ± 1MHz and 1 dB below rated output power
≤ 120 ns
1 dB bandwidth
≥ ±1 MHz
Circulator:
Type
3-port junction circulator
Ports
WR2300 half-height waveguide
Maximum CW forward power
Maximum CW reflected power
330 kW, at any phase
Insertion loss at rated forward power
≤ -0.1 dB
Isolation:
within frequency range fo±0.25 MHz
within frequency range fo±12 MHz
≤ -28 dB
≤ -20 dB
Group delay at fo ± 0.25 MHz
≤ 30 ns
Characteristics of the RF power equipment
June 15th 2006
LHC MAC T. Linnecar AB-RF

32. LHC MAC T. Linnecar AB-RF
Parameter
Value
Units
Injection beam momentum
450
GeV/c
Static injection errors (=183 m) 2 mm
Ripple ( =183 m)
Resistive wall growth time
27.4 ms
Tolerable emittance growth
2.5 %
Overall damping time
4.1
Standard bunch spacing 25 ns
Minimum gap between batches
995
Lowest betatron frequency
> 2
kHz
Highest frequency to damp 20
MHz
Aperture of kickers 52
No. of kickers per plane & ring 4
Length of kickers (electrodes)
1.5 m
Nominal voltage up to 1 MHz
± 7.5 kV
Kick / turn at 450 GeV/c (1 MHz)
rad
Rise time 10-90%
350
Rise time 1-99%
720
Frequency range (gain)
Noise
< 1 LSB
with 10 Bit/2
Nominal Performance and Hardware Parameters of LHC ADT Systems
June 15th 2006
LHC MAC T. Linnecar AB-RF