CLIC potential baseline changes CTC items
H. Schmickler, G. Riddone - 11.12.2009
2
Item Baseline Alternative
Machine protection Next pulse permit: 18 ms + 2 ms protection for slow lossesCollimators/masks for fast losses
?
Tunnel cross-section Tunnel diameter (4.5 m) mainly imposed by transverse ventilation
Longitudinal ventilation
Bigger tunnel
BDS L* 3.5 m 6-8 m
MB + DB girder 2 individual girders Common girder
MB + DB girder 2m long girders Longer girders
3
Item Baseline Alternative
Damping ring wigglers:
superconducting Normal conducting; at least for 500 GeV parameters
Drive beam RF power generation
33 MW (peak power) klystrons
10 – 15 MW (peak power) klystrons
Drive beam phase and amplitude control
Baseline under workBy BDWG
As soon as baseline available, will need follow-up through CTC.
DB, MB phase alignment RT feedback
Baseline under work By BDWG
Turnaround magnets
Normal-conducting magnets
Permanent magnets + 10 % trims
Motivated by stability requirements? For phase stability; also power consumption
4
Item Baseline Alternative
Corrector dipoles (main beam)
No corrector dipoles Common actuators for stabilization and BBF
Re-introduce corrector dipoles
Stabilization system(main beam)
Electromechanical sensors and actuators in RT feedback
Common MIMO system with BBF
Pre-alignment system
Conventional WPS/HDL sensorsSnake system with articulation point andlinear actuators
Low-cost sensors Cam system moversLaser system
Beam Instrumentation (MB)
4000 cavity BPMs with one horizontal/one vertical read-out
4000 cavity BPMs with two horizontal/ two vertical read-outs
Beam instrumentation (DB)
One BPM per Q Fewer BPM
Conclusiontaken from M.Jonker; last Friday (56 pages)
The base line machine protection provides an adequate framework for protection against fast and slow failures.
The large amount of time available between pulses allows an exhaustive post pulse analysis to authorize the next pulse.
The challenging issues: mask and spoilers to– Intercept a single main bunch up to a full main train
– intercept a “derailed” decelerator train.
More info is needed to estimate consequences of RF failures.
Kickers reliability to be looked into.
L*=3,5m and L*=6(8)m• Complicated optimization:
Shorter L*= higher luminosity, easier insertion tuningLonger L* = lower luminosity, easier to achieve technical solution for vibration stability
• Lots of progress in the past months on:- design of FF magnets- vibration measurements- studies on possibilities of active stabilization- physics detector size- knowledge on boundary conditions from experiments
• Still it seems not possible to decide for a layout with convincing feasibility for the CDR now: Conclusion: Follow studies and designs for both optionsL*=3,5m and L*=6(8)m; Can we at least decide 6 or 8 or 6,42?
How does the cost of a klystrons scale with peak power?
• Probably: cost per klystron proportional to (peak power)1/2 (*)
• At a level of around 15 MW peak, the slope will become steeper due to increased system complexity.
• This leads to the following model:
• Blue: present state of the art • Red: assuming a major investment into the development of a dedicated 30
MW tube(*) rule of thumb given by T. Habermann/CPI. Rees/LANL estimates P0.2 for 0.5 to 5 MW tubes.
807/Apr/2009 CTC#13: Erk Jensen - RF system for the Drive Beam Linac
Erk Jensen
Cost per MW
• Using the above model, here’s the klystron cost per MW (peak)
• Blue: present state of the art • Red: assuming a major investment into the development of a
dedicated 30 MW tube
907/Apr/2009 CTC#13: Erk Jensen - RF system for the Drive Beam Linac
Tube lifetime
• In spite of its price, a klystron is a consumable! • A klystron has a finite lifetime; this will also depend on its
internal complexity (and on the peak power!).• The lifetime will depend on many parameters, primarily the
current density, but here’s one estimate ...
1007/Apr/2009 CTC#13: Erk Jensen - RF system for the Drive Beam Linac
What about an MBK?: is the tube dead if one of n beams fails? If the design is good, the n beams would fail at around the same time ...
Cost for 100,000 operating hours and MW
• Even if this model may be wrong, there will be a cost per MW and per operating hour: With the above model, this becomes:
• Blue: present state of the art • Red: assuming a major investment into the development of a
dedicated 30 MW tube1107/Apr/2009 CTC#13: Erk Jensen - RF system for the Drive Beam Linac
C L I CC L I C
17th November 2009CTC meeting L. Rinolfi
Pre-Injector e- Linac
MKS 01 MKS 02 MKS 03
2 GHz
40 MW
2 GHz
DC Gun
PB2 B1A1 A2 A3 A4
SLED
40 MW
2 GHz
SLED
50 Hz50 Hz50 Hz
40 MW
PB1
20 MeV200 MeV
Accelerating cavities:
• Number of cavities: N = 4• Length: L = 3 m• Aperture radius: r = 20 mm• Energy Gain: E = 45 MeV• Accelerat. gradient: Ez = 15 MV/m• Frequency: f = 2 GHz
Louis Rinolfi
C L I CC L I C
17th November 2009CTC meeting L. Rinolfi
• Erks optimization of the unit klystron power isbased on maintenance and reliability questions combined with lowest price/MW.
• The optimization has been done for the DB linac, since there we have the largest klystron installation.
•The base line change for the klystron power demands a reoptimization of the linac structures (#cells).This is almost done; base line change should be made.
• The same logic should be applied for all other linacs (injectors, bunch compressors…). This also needs a (re)design of the connected RF-structures.
Background (1/2)
• 4000 MB quads, need about 80 correctors close to quads for beam-based feedback (BBF);
• Pre-choice of 80 locations impossible? equip all 4000 quads with correctors
• Frequency range covered by BBF: sub-Hz to ~1 Hz• In order to
- have some feedback gain at f_cl =1 Hz (f_cl = f_s/gain)- to average over several BPM readings the BBF will run at a sampling frequency f_s=50 Hz;
i.e. the corrections are applied every pulse:requested settling time of corrections is 5 ms( in-between 2 beam pulses )
Background (2/2)
• Technical implementation in 2008:- additional windings onto quad jokes in order to produce “a sort of dipole correction field”
• Pre-Choice of non-laminated MB quads for stabilization and mechanical engineering (late 2008)excludes correction coil (bandwidth problem)
• Present design approach: Extend dynamic range of stabilization actuators by 100 ! and make BBF corrections by displacing the MB quads.Fullscale = +- 5 um compared to +- 50nm
Problems with present implementation
• Actuator dynamics, in particular for the (long) heavy magnets
• Absolute position of quad in beam reference frame not know (Hexapod design with sub-nm position readout in each leg)
• BPMs (50 nm required resolution) will move with quad.Needs sophisticated bookkeeping of past displacements.BPM close to “zero” and for longer elongations non-linear (monopole and quadrupole mode signals)
• Machine protection: non-energized position of quad (vertical) is max.down, not middle; might need interlocks.
Implementation• Required corrector strength (Bdl):
200 T/m *10 um * 2m (@ 1.5 TeV) = 4 mT * m = 0,4 T * 1 cm - very week magnet
assumed strength: scales with length of Q corrector@ Q1: 0,1 mTm
• 1 cm long 0.1 - 0.4 T magnets• - end-field problems?
- interference with quad field?- will create synchrotron radiation?(200 times higher bending radius)
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19
20
21
22
23
24
MB-Q
Prealignment
Stabilization
2 x 2000 MB-Qs
4 types (lengths)
All MB-Qs need stabilization equipment:
Postion sensors (v- sensors+ integration ora-sensors + double integration)
Piezoelectrical actuators (presently hexapod design)
WPS and HLS plus overlapping wires as reference
Linear motors as actuators
Controller – topology?
Sensors and Actuators?
BPM on each Quaddipole corrector on each quad
Prealignment without beamWith beam:
Beam based feedback (all BPMs + about 80 actuators)
Quad Stabilization (sensors + actuators on each Quad)
• Pre-alignment:- overlapping stretched wires, WPS, HLS as baseline for CDR- linear actuators- continuing studies on laser systems (start with IP)and on camshaft movers- controller: local or central: decision not needed
• Beam based feedback:- based on MB BPMs: open question for CDR:- online dispersion measurements by in-pulse energy variation or by pulse to pulse variation?- actuators: small dipole correctors- controller: First design needed for CDR
• MB-Q stabilization- for CDR: sensors and actuators, independent (local) controllersinteresting alternative to be studied: sensors as before, but common controller with BBF and small dipole correctors as actuators (“move the beam within a vibrating quadrupole rather than stabilizing the magnet”)
HFSS EigenMode Calculation
(II) Bunch trajectories (I) Matched Impedance, P_coax
HFSS Data:
W - Stored EnergyP_coax - Exited RF PowerEz - E-field along bunch
pathgsym - Symmetry coefficient
Cavity BPM spectrum calculation
00 0*
*2*
L j t
scaleHFSS sym
Ez e dzq qk
q g W
Scale Factor:
Output Power:
211 )(*)(_)( scaleTM krcoaxPrP
r
e- Estimated Sensitivity (q0 = 1nQ):
r
OhmrPS TM ][50*)(11 V/nQ/mm
Choice not obvious: tradeoff between number of BPMs and precision; availibility, cost versus precision, risk….
Taken from E.Adli’s presentation
July 2009A. Lunin, Fermilab
Port 1Port 2
Port 4Port 3
a)
b)
c)
BPM Mechanical Tolerances
There is no visual advantage of particular scheme of coaxial layout (a, b, c)
The most sensitive to mechanical errors part of the BPM is a coupling slot.
The required mechanical tolerances of a cavity with coupling slots:
Mechanical
Tolerances1,2
Cross
Coupling
-40 dB
Cross
Coupling
-30 dB
Cross
Coupling
-20 dB
Slot Rotation, [deg] < 0.05 < 0.2 < 0.6
Slot Shift, [μm] < 5 < 15 < 40
Other, [μm] < 50 < 50 < 50
Max Dynamic
Range, [μm]
100 25 10
1 - In-phase signals reflection (worse case) is taken into account.2 – The reflection from LLRF part is assumed less than -20 dB.
Summary BPMs MB: At each MB-Q Cavity BPMs (FNAL Design)
with integrated reference cavity for intensity information.Small study needed for extra cost of double readout vs redundancy and on-line calibration benefits.
DB: Large number: at each DB quadtechnical choice of DB BPM: BI group + collaborators in 2010- compromise between cost reduction, extra effort for better alignment in case of reduction of BPMs etc not before CDR.
Color codes used
= could be decided today
= needs some work, decision before CDR writeup ..i.e. before summer 2010
= interesting alternative, decision not before CDR
33
Item Baseline Comment Follow-up
Machine protection Next pulse permit: 18 ms + 2 ms protection for slow lossesCollimators/masks for fast losses
Tunnel cross-section Tunnel diameter (4.5 m) mainly imposed by transverse ventilation
Overall coherent machine layout (BDS, RTML….) to be defined before CDR
BDS L* 3.5 m 6 m
MB + DB girder 2 individual girders Common girder
MB + DB girder 2m long girders Longer girders
Describe both options in CDR
34
Item Baseline Follow-up
Damping ring wigglers:
superconducting Normal conducting; at least for 500 GeV parameters
Drive beam RF power generation
33 MW (peak power) klystrons
10 – 15 MW (peak power) klystrons
Drive beam phase and amplitude control
Baseline under workBy BDWG
As soon as baseline available, will need follow-up through CTC.
DB, MB phase alignment RT feedback
Baseline under work By BDWG
Turnaround magnets
Normal-conducting magnets
Permanent magnets + 10 % trims
Motivated by stability requirements? For phase stability; also power consumption
35
Item Baseline Alternative Follow-up
Corrector dipoles (main beam)
No corrector dipoles Common actuators for stabilization and BBF
Re-introduce corrector dipoles
Stabilization system(main beam)
Electromechanical sensors and actuators in RT feedback
Common MIMO system with BBF
Pre-alignment system
Conventional WPS/HDL sensorsSnake system with articulation point andlinear actuators
Low-cost sensors Cam system moversLaser system
Beam Instrumentation (MB)
4000 cavity BPMs with one horizontal/one vertical read-out
4000 cavity BPMs with two horizontal/ two vertical read-outs
Beam instrumentation (DB)
One BPM per Q Fewer BPM