Transcript Document 7311809

LLRF for ILC facilities at FNAL
CD ILC Forum
5/23/2016
Gustavo Cancelo
1
Outline
• Introduction to the problem of LLRF.
• LLRF collaboration.
• LLRF for Fermilab facilities.
– LLRF deliverables, cost and schedule.
• CCII update.
• Status of LLRF projects at CD.
• Conclusions.
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ILC project
Extracted from S. Nagaitsev talk at CD, “Plans and goals of ILC activities at FNAL”
• Develop world class SCRF expertise: module fabrication facility + module test facility
• “Reference Design Report effort”: machine design and site studies
~350 RF stations
and LLRF systems
per LINAC
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ILC RF station
One of three
cryomodules in
each RF station
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Cryomodule
• 1st cryomodule for NML is a kit
from DESY.
• 2nd and 3rd cryomodules will
be designed at FNAL.
• Technical Division leads the
work in cryomodules for NML.
Cryomodule number 4 at FLASH (DESY)
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Klystrons
(Shekar Mishra @ ILC Industrial forum)
Klystron specification: 10MW, 1.5ms pulse, 65% efficiency
e.g. Thales
The klystron is not part of the LLRF, but is controlled by the
LLRF.
The power budget specs for ILC locate the klystron
operational point in the nonlinear region, close to saturation.
This is a big deal for the LLRF control.
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What is Low Level RF?
•
Low power RF circuits used to regulate the cavity field. LLRF includes:
– Master oscillator (MO) and Local Oscillator (LO)
• The MO provides reference frequencies for all RF components.
• The LO provides a frequency slightly higher/lower than 1.3GHz used to
downconvert the cavity probe signal in the frequency domain.
– RF down-converters
• Convert the cavity probe signal spectrum to an Intermediate Frequency (IF)
domain.
– Timing hardware
• Time accelerator related events such as the start of a beam pulse.
– Cavity controller
• Controls the amplitude and phase of the power delivered by the klystron to the
cavities.
•
LLRF is critical to achieve the beam energy and luminosity goals for ILC.
– LLRF project requires relatively small M&S but intensive manpower.
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Simplified LLRF block diagram
Master
oscillator
Vector
modulator
High level RF (all RF 1.3 GHz)
Klystron and
Pre-amplifiers
Input couplers
waveguides
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
...
Channel 1
(IF carrier)
RF
cavity
probe
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Low level RF (IF or lower
frequencies)
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LLRF specifications
• For ILC
– Pulsed mode, 5 Hz repetition rate.
– Amplitude: ±0.5%
– Phase: ±0.03º
•
For NML
– Pulsed mode, 3 Hz repetition rate.
– Amplitude: ±0.5%
– Phase: ±0.5º
– Stable feedback loop with 100KHz bandwidth.
•
Beam structure:
– Bunched.
– ~2ps pulse.
– 1 MHz rate.
– 8 mA average current.
– Beam loading modeled as a current sink.
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Simplified LLRF block diagram
Master
oscillator
Cavities
Vector
modulator
High level RF (all RF 1.3 GHz)
Klystron and
Pre-amplifiers
Input couplers
waveguides
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
...
Channel 1
(IF carrier)
RF
cavity
probe
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Low level RF (IF or lower
frequencies)
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Single cell pillbox cavity
The pillbox cavity is an oversimplified model of a real cavity but has the
property that its fields are expressed by simple electromagnetic equations.
It gives a good insight to cavity modes for LLRF control
• TM010 is the monopole mode
used for beam acceleration.
• Dipole TM modes are bad
because they deflect the beam.
• TE modes are not interesting
because they have no
longitudinal electric field. They
cannot accelerate the beam.
All this becomes much more complicated in real multi-cell cavities.
Cavity design makes extensive use of 2D and 3D simulation packages.
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Multi-cell cavity modes
•
A N-cell cavity can be modeled
as an N-cell coupled oscillator
Cavities are operated in π mode
The phases in neighboring cell
differ in π radians.
This gives the beam the
maximum acceleration.
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All non-π modes are undesired,
but the 8/9 π mode is the most
dangerous one because is the
closest in frequency to the π
mode and can easily make its
way into the LLRF bandwidth.
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Pulsed mode of operation
Flattop
RF off
•
•
•
Filling
•
•
•
•
•
Only one cavity simulated:
Blue trace is the pulse set point
Magenta trace is the actual
cavity response under LLRF
control.
A 9-cell cavity operating at 31.5MV/m of gradient stores about 116.8 joules.
It takes ~500µs to fill a cavity.
The beam is injected when the cavity reaches flattop.
The flattop is of the order of 800µs to 1ms.
At the end of the flattop the RF is turned off
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Cavity signals for LLRF
x24 cavities per LLRF system
Imag.
Im{A(t)} A(t)
ω~
ωg
Φ(t)
Re{A(t)}
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•
Real
•
Cavity voltages due to set-point
changes and disturbances modulate
the 1.3GHz RF in amplitude and
phase:
– A(t) not constant.
– ω~ ωg not constant.
We model the signals as complex
vectors (phasors).
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Cavity Q’s
• a
Rgen
L
R
C
1: n
Vcav
Igen
ZC n2
Z ext  n 2 Z 0
Zc
Q0: unloaded Q ~ 1010.
• The Q of the cavity alone is very high (~ 1010) and determined by
loses in the cavity walls.
• When the cavity is “loaded” by the external circuit, the Q falls to ~ 3
to 4 million.
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Simplified LLRF block diagram
Master
oscillator
Vector
modulator
High level RF (all RF 1.3 GHz)
Klystron and
Pre-amplifiers
waveguides
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
Down converters
...
Channel 1
(IF carrier)
RF
cavity
probe
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Low level RF (IF or lower
frequencies)
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Up/Down conversion
Down conversion in frequency Domain
Envelope spectrum
down-converted to
baseband
Envelope spectrum
down-converted to IF
Envelope of RF
signal spectrum
ZL(ω)
ω
ωIF
0
Done in digital
domain inside the
LLRF controller
•
ωg
Done by analog
hardware
Up conversion inverts this process. It brings baseband control signals to RF
band.
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Up/Down conversion
Uros Mavric and Brian Chase (Feb 2007)
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Simplified LLRF block diagram
Master
oscillator
Vector
modulator
High level RF (all RF 1.3 GHz)
Klystron and
Pre-amplifiers
Input couplers
waveguides
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
...
Channel 1
(IF carrier)
RF
cavity
probe
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Low level RF (IF or lower
frequencies)
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Master Oscillator
Julien Branlard and Brian Chase
• High frequency
stability,
temperature
controlled oscillator.
DRO
• Provides the
frequencies needed
for all other LLRF
components such
as Timing system,
LO distribution,
LLRF controller,
up/down converters,
etc.
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Simplified LLRF block diagram
Master
oscillator
Vector
modulator
High level RF (all RF 1.3 GHz)
Klystron and
Pre-amplifiers
waveguides
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
...
Channel 1
(IF carrier)
RF
cavity
probe
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Low level RF (IF or lower
frequencies)
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LLRF Cavity controller
• The LLRF controller is “the brain” of the LLRF system.
• One LLRF controller controls one klystron which, in the ILC design,
powers 24 cavities (i.e. 3 cryomodules = 1 LLRF station)
– 24 cavity prove voltages are “averaged” by the controller (Vectorsum).
• The controller’s goal is to regulate the amplitude and phase of the
vectorsum:
– ±0.5% amplitude, ± 0.03º phase (± 0.5º phase for NML)
• Required from the LLRF controller
– Instrumentation precision electronics (i.e. very low noise ~-150dBm/√Hz).
– Long list of algorithms to be developed and implemented in firmware and
software (i.e. for FPGAs and microprocessors).
– Communication interface with Controls System.
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Cavity electrical and mechanical models
Ig
v  (v r , v i )  A(t ). e
Electrical Model
of the cavity
Δω
v2
Mechanical Model
of the cavity
j ( t )
v r  A(t ). cos  (t )

 v i  A(t ). sin  (t )
Due to detuning
the cavity models
are time variant.
Control is more
complex.
Electrical model: 1st order differential equation modeled using 2 statevariables, I and Q components of cavity voltage
Vr   1 / 2
 
V i   
   V r  1 / 2 RL   I r 
.   
. 


 1 / 2  V i  1 / 2 RL   I i 
Model is time-varying because Δω varies. Δω is a function of the cavity gradient.
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Detuning
•
Detuning is caused by high gradients in the cavity (Lorentz forces)
– Predictable intra-pulse and pulse to pulse behavior.
•
Microphonics
– Environmental, random nature.
detuning
Vcav(ω)
Pre-detuning
ω
ω0 ωg ω0
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Mechanical Model (Lorentz force detuning only)
d 2 m  2f m d m 
2
2
2





.

2

f



2

f
K
V
(t )
m
m
m
m
2
dt
Qm
dt
•
The 2nd order model is very underdamped (i.e. lots of ringing in the detuning).
m 
1
 0.005
2Qm
For ωm= 280, 340 and 420 Hz
 m  mm 1  [0.114 0.094 0.0758] seconds
A cavity mechanical resonance at 160
Hz has a transitory of ~0.15 sec.
5ζ decay of 0.75 sec.
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Single pulse simulation. Detuning
Cavity can be
predetuned to optimize
generator power during
beam time (flattop).
The detuning plot shifts
up a constant amount.
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Single pulse simulation. Generator Power
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Detuning
Master
oscillator
Vector
modulator
~
...
LO
Generator
LO signal
Phase reference
I & Q Control
Timing
Generator
•
•
Piezo
Control
Klystron and
Pre-amplifiers
waveguides
RF
cavity
probe
...
Channel 1
(IF carrier)
LO signal
...
Channel N
(IF carrier)
LLRF Controller
Pulse Trigger
Lorentz force detuning can be partially compensated by feed forward piezo
control.
Feedback control to reduce Lorentz force and Microphonics is part of the LLRF
R&D.
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Klystron Power Overhead
It is a control problem
x
r
e +
+
+
+
-
System
stability ?
FF
C
n
d
+
+ u
K
+
+
a1
x1
x2
a2
P1
+
y
+
m
P2
.
.
.
Klystron
power?
a24
x24
P24
• The ai blocks model waveguide and coupling asymmetries between
cavities.
• The Pi blocks represent the cavity state or transfer function models.
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Disturbance sources for the LLRF control system
Disturbance source
Location
Type
Field Probe
n
Gaussian, white (WGN), Wide Band (WB)
Down-converter phase noise
n
WGN, WB
Down-converter harmonics
n
Definite spectrum, Narrow Band (NB)
ADC quantization
n
Uniform, white, WB
ADC phase noise
n
WGN, WB
ADC thermal noise
n
WGN, WB
Aliasing from sampling and filtering
d
Band limited, spectrum based, WB, etc
DAC noise (similar to ADC noise)
d
As before for ADC noises
QL dispersion
d
Parameter variation (Static disturbance)
RF distribution (amplitude & phase)
d
Parameter variation (Static disturbance)
Vector sum calibration
d
Static disturbance (limited by calibration algorithm)
Beam charge fluctuation
d
WGN, WB
Lorentz force detuning
d
Deterministic to some extent,
Microphonics detuning
d
Uniformly?, colored noise
Klystron ripple
d
Band limited, narrow band?
Klystron thermal noise
d
WGN, WB
Klystron 1/f noise
d
1/f characteristic, NB
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RF system disturbances (cavities):
31
Disturbance analysis – Cavity parameter variations
No disturbance, no detuning
Disturbance ON, detuning OFF
Disturbance ON, detuning ON
P 
g
2S11  S12  a1
N
Sigma of power spread due to
cavity parameter variation
(Ref: https://docdb.fnal.gov/ILC-private/DocDB/ShowDocument?docid=369)
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RF station with cavities at different gradients
• Not all cavities in the ILC will be able to operate at the same
gradient. We must be able to set flattops at different gradients.
• This must be true for all cavity fill time conditions.
• If we calculate flattops for beam=ON then the pulses do not have a
flattop when the beam is OFF.
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LLRF interface to Controls
•
The LLRF must be able to operate using the ILC Control System.
•
Two Control Systems are in use DOOCS and EPICS.
•
CCII
– LLRF is using DOOCS
– Cryogenic systems use EPICS.
•
DOOCS/Epics will be present at New Muon Lab (NML)
– Many components have interfaces in one or the other, but not both.
•
NML can probably be used as a test bed for Controls.
•
DOOCS is migrating from SUN/Solaris to VME-processors/Linux.
•
Controls is a whole separate talk.
– M. Votava will give a talk soon.
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LLRF collaboration
•
Fermilab collaboration:
– Accelerator Division:
•
•
•
•
•
•
External collaborators and participants:
– DESY
– Warsaw Univ.
– Lodz Univ.
– KEK
– INFN-Pisa
– UPENN
– ANL
– LBNL
– SNS
– SLAC
•
We have an ongoing weekly meeting that
for the last year and a half has been used
as an open forum for LLRF news and
discussions.
– Informal, but keeps everybody in
contact and informed.
•
We take advantage of facilities like FLASH
at DESY.
Helen Edwards
Brian Chase (L)
Julien Branlard
Phillipe Varguese
Uros Mavric
– Technical Division
•
•
•
•
•
Ruben Carcagno (L)
Darril Orris
Andrej Makulski
Joe Ozelis
Jerzi Nozriec
– Computing division
•
•
•
•
•
•
•
•
Gustavo Cancelo (L)
Ken Treptow
Ted Zmuda
Ron Rechenmacher
Steve Foulkes
Neal Wilcer
Bill Haynes
Rick Kwarciany
Brian Chase leads the LLRF project at Fermilab, and the LLRF work for the RDR.
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LLRF facilities: deliverables, schedule and costing
•
LLRF DELIVERABLES:
– NML
•
•
•
•
•
•
•
Photoinjector.
CCI.
CCII.
Three Cryomodules.
3.9 GHz cavity systems.
RF Reference Line.
Local Oscillator Line.
– Meson
• HTF.
• RF Reference Line.
• Local Oscillator Line.
– IB1
•
•
•
•
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VTF.
HTF.
RF Reference Line.
Local Oscillator Line.
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LLRF planning and costing
Includes NML, Meson, and IB labs, calculated in Nov. 2006
M&S
2008
TOTAL
LLRF Deliverables
$238,000
$256,000
$494,000
RF Test equipment
$120,000
$125,000
$245,000
Development software
$105,000
$105,000
$210,000
Development hardware
$40,000
$40,000
$80,000
TOTAL
$539,000
$562,000
$1,101,000
MANPOWER REQUIREMENTS
(FTEs)
•
2009
2008
2009
TOTAL
Project management
1
2
3
LLRF developments for Test Facilities
6
6
12
Commissioning to Test Facilities
3
3
6
LLRF R&D
3
3
6
Interface to Control system
1
1
2
TOTAL
14
15
29
LLRF 2008-2009 planning and costing (Doc#386)
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New Muon Lab (NML)
Gun CCI CCII
Cryomodules
URL to NML floor plan: http://docdb.fnal.gov/ILC-public/DocDB/ShowDocument?docid=382
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VTS facility (led by FNAL/TD)
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CCII at meson Lab.
• Long list of studies and results:
– 31.5 MV/m achieved.
– Manual coupler conditioning.
– Cavity multipacting studies.
– (see T. Koeth et al. for more
information)
•
•
•
•
LLRF new hardware implementations:
– Master oscillator.
– LO distribution.
– Down converter.
New firmware implementations
– New DDS and filters for Simcon3.1 controller
New software implementations
– DOOCS on Solaris
– Migration of DOOCS to Linux
Piezo studies
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LLRF results
• On Feb 1st we run the CCII on closed loop with the new high IF
system designed at FNAL.
• The S/N is about 20 times better than with the 250KHz IF system.
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LLRF infomercial:
Before
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As seen on TV
After
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LLRF results
I and Q of cavity voltage
•
Very encouraging result that opens up new questions for LLRF:
– Study undesired cavity modes (such as 8/9 π) which are now in the
pass band and will cause instabilities.
– Filter optimization.
– New control strategies.
– Migration of firmware to the new hardware
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New 10 channel LLRF controller
• Will replace Simcon3.1at FNAL facilities.
• Functionality is similar to Simcon3.1
– New design is aimed to improve S/N ratio and to have a
bigger FPGA for new algorithm development.
• Layout should be complete this week and ready for review.
– It is one of the more complex PCB designs we have done in
ESE.
– We are evaluating new CAD tools that may simplify future
developments.
• First prototype working by end of April.
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Controller block diagram
JTAG
connectors
V
M
E
6
4
JTAG Management
(Altera CPLD)
Daughtercard
Local bus
Slave VME
interface.
(Altera ACEX)
OSC
+1.8VD
Power
management
+5V
+3.3V
SRAM
LLRF
controller.
Xilinx V4LX80
+1.2VD
+2.5VD
-5VA
+5VA
+3VA
3.3VA
+3.3VD
DAC_ck
…
…
2 TTL inputs
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A/D
A/D
SMB
SMB
…
LCD
Display
RS-232
PowerQuiccII
processor
ADC_ck
Data bus
Timing
inputs
FLASH
Ethernet
USB
DDR memory
Clock
distribution
/fan-out
ADC_ck
Clock out
SMB
VCXO
External clock in SMB
DAC_ck
A/D
A/D
A/D
D/A
D/A
D/A
D/A
SMB
SMB
SMB
SMB
SMB
SMB
SMB
High speed
I/O
SPF
…
SPF
2 transceiver
channels
8 channels
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w/ optional DC
coupling
46
New controller layout
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LLRF at CD for the rest of 2007
•
Complete implementation and debugging of new LLRF controller by end of April.
– Total of 5 boards for end of 2007
•
Continue with algorithm development to improve cavity field control.
– Algorithms are implemented in high level language using Simulink/Matlab/SysGen
to make it platform independent and easy of sharing within the collaboration.
•
Continue with cavity modeling and simulations to improve our understanding of control
issues.
•
Follow closely TD work on piezo tuner measurements.
– Input models into our simulations.
•
Support ILC test facilities Controls
– Help in the integration of LLRF to Controls.
•
Keep working with CCII and get ready for Cryomodule 1
•
Effort:
– Current effort reported is about 3.5 FTEs
– Need 1 more FTE for the rest of 2007.
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Conclusions
•
The LLRF is very important for the ILC.
– Compared to other areas of development LLRF requires low M&S but a good level
of effort because it is still in R&D stage.
– LLRF must achieve specifications, work reliably meeting high availability standards.
•
In less than 2 years time we have built a solid internal and external
collaboration.
– active weakly forum to show progress and ask questions.
•
Good progress in hardware development.
– Some pieces are in development or testing stage.
– More hardware (e.g. piezo control) is needed.
•
Substantial progress made in algorithm development.
– Important result obtained in the stabilization of the field in CCII.
•
Continuous effort in firmware and software development.
•
The LLRF collaboration is working with two main goals in mind:
– Achieve the LLRF specifications.
– Support ILC test facilities.
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Spare slides
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Module Assembly at DESY
(Shekar Mishra @ ILC Industrial forum)
The module assembly is well
defined and about 10 modules
have been made of several
designs
ILC will need about 2000
modules/500 GeV.
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String Assembly
(Shekar Mishra @ ILC Industrial forum)
The assembly of a string of 8
cavities into a string. Class 100
clean room
Facilities being setup at Fermilab
and KEK.
The inter-cavity connection is done
in class 10 clean room
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The TTF III Power Coupler
• TTF III Coupler has a robust and
reliable design.
• Extensively power tested with
significant margin
• New Coupler Test Stand at LAL,
Orsay
(Shekar Mishra @ ILC Industrial forum)
frequency
1.3 GHz
operation
pulsed: 500 µsec rise time,
800 µsec flat top with beam
Coupler conditioning automation
is on the list of deliverables for
the LLRF
10 + 30 New Couplers in
construction by industry
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Mechanical Model (Lorentz force detuning only)
•
•
The cavity mechanical model analyzes detuning.
The cavity detuning is modeled as a linear combination of individual detunings
generated by the eigenmodes (resonant frequencies) of the cavity.
– The Tesla model uses 3 resonant frequencies at 280, 340 and 420 Hz.
– Δωm: cavity detuning for resonant mode m.
•
Each detuning mode is modeled as a 2nd order dynamic function of the square of the
cavity voltage.
d 2 m  2f m d m 
2
2





.

2

f



2

f
K mV 2 (t )
m
m
m
2
dt
Qm
dt
Km: Lorentz force detuning constant for each resonant mode.
5/23/2016
Gustavo Cancelo
54
Mechanical Model
•
A state model transforms a n-order differential equation in a n-length vector
of 1st-order differential equations.
x1 (t )  m
x2 (t )  x1 (t ) 
x2 (t )  
m
d m 
dt
.x2 (t )  m  x1 (t )  m  2K mV 2 (t )
Qm
0
 x1 (t )  
 x (t )   m 2
 2  
2
2
1  x (t ) 
0
 2
m   1   
2 V (t )



2

K

x
(
t
)
m
m 
Qm   2  
This model repeats for each resonant frequency in the mechanical mode.
The total detuning is:
Δω0 is a predetuning to compensate for
 (t )   m (t )  0
expected detunings

m
5/23/2016
Gustavo Cancelo
55
Single pulse simulation
Cavity voltage, amplitude and phase. On-crest acceleration, Q setpoint = 0
Q≠0 due to detuning and low gain
5/23/2016
Gustavo Cancelo
56
Single pulse simulation. Cavity voltage
5/23/2016
Gustavo Cancelo
57