compact superconducting cavities for ...uspas.fnal.gov/materials/15rutgers/tuners.pdf373 267 ~300...
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![Page 1: COMPACT SUPERCONDUCTING CAVITIES FOR ...uspas.fnal.gov/materials/15Rutgers/Tuners.pdf373 267 ~300 (calc) > 100 290 230 315 Page 4 Tuner Requirements & Specifications CEBAF CEBAF Upgrade](https://reader031.vdocuments.net/reader031/viewer/2022022517/5b06ad3b7f8b9abf568d58a3/html5/thumbnails/1.jpg)
Page 1
Jean Delayen
Center for Accelerator Science
Old Dominion University
and
Thomas Jefferson National Accelerator Facility
TUNERS
USPAS@Rutgers
June 2015
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Introduction – “Big Picture” for Tuners
• SRF/RF system should consume RF power efficiently
– Minimizes klystron size and capital cost
– Higher Qexternal (> 107) more efficient ER
– Reduced Microphonics – actively controlled?
• RF Stability
– Attained by controlling cavity RF phase (0.05°, RMS) and RF amplitude (2 x 10-4,RMS)
• Availability / Reliability / Maintainability
– Use machine as scheduled
– Operate machine as desired
– Repair machine (if required) for use and operation
Examine what has been achieved on some existing systems to stimulate discussion
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Introduction: Pertinent Cavity Info
CEBAF CEBAF
Upgrade
(SL21,FEL03)
CEBAF
Upgrade
(Renascence)
RIA,
=0.47
SNS,
=0.61
SNS,
=0.81
TESLA 500
Frequency (MHz) 1497 1497 1497 805 805 805 1300
Gradient (MV/m) 5 12.5 18 10 10.3 12.1 23.4
Operating Mode CW CW CW CW Pulsed,
60 Hz, 7%
Pulsed,
60 Hz, 7%
Pulsed,
60 Hz, 1%
Bandwidth (Hz)
Qexternal
220
6.6 x 106
75
2.0 x 107
75
2.0 x 107
40
2.0 x 107
1100
7.0 x 105
1100
7.0 x 105
520
3.0 x 106
Lorentz Detuning
(Hz)
75 312 324 1600 470 1200 434
Microphonics (Hz,
6)
- ±10 ±10 ±10 ±100 ±100 NA
Stiffness (lb/in) 26,000
(calc’d)
37,000
(calc’d)
20,000-40,000
(calc’d)
< 10,000 8,000
(meas’d)
17,000
(meas’d)
31,000
(est’d)
Sensitivity
(Hz/m)
373 267 ~300 (calc) > 100 290 230 315
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Tuner Requirements & Specifications
CEBAF CEBAF
Upgrade
(SL21,FEL03)
CEBAF
Upgrade
(Renascence)
RIA,
=0.47
SNS,
=0.61
SNS,
=0.81
TESLA 500
Coarse Range
(kHz)
±200
±200 ±400 950 ±245 ±220 ±220
Coarse Resolution
(Hz)
NA < 2 2 - 3 < 1 2 - 3 2 - 3 < 1
Backlash (Hz) >> 100 < 3 < 3 NR < 10 < 10 NR
Fine Range No Fine
Tuner
> 550 Hz /
150 V
1.2 kHz / 1000 V
30 kHz / 30 A
11 kHz /
100 V
> 2.5 kHz /
1000 V
>2.5 kHz /
1000 V
No Fine
Tuner
Fine Resolution
(Hz)
NA < 1 < 1 < 1 < 1 < 1 < 1
Demo of Active
Microphonics
Damped?
No ? No Yes No No No
Tuning Method Tens. &
Comp.
Tension Tension NA Comp. Comp. Tens. &
Comp.
Mechanism,
Drive Comp.
Immersed,
Vac/Warm
Vacuum,
Vac/Warm
Vacuum,
Vac/Cold
Vacuum,
Vac/Ext
Vacuum,
Vac/Cold
Vacuum,
Vac/Cold
Vacuum,
Vac/Cold
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Upgrade Tuner for SL21 and FEL03 Cryomodules -
Description
• Scissor jack mechanism
– Ti-6Al-4V Cold flexures & fulcrum bars
– Cavity tuned in tension only
– Attaches on hubs on cavity
• Warm transmission
– Stepper motor, harmonic drive, piezo and ball screw mounted on top of CM
– Openings required in shielding and vacuum tank
• No bellows between cavities
– Need to accommodate thermal contraction of cavity string
– Pre-load and offset each tuner while warm
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Page 6
Prototype Tuner for CEBAF Ugrade
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Page 7
Prototype Tuner for CEBAF Ugrade
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Warm Drive Components and Cross Section of
Upgrade CM
• Stepper Motor
– 200 step/rev
– 300 RPM
• Low voltage piezo
– 150 V
– 50 m stroke
• Harmonic Drive
– Gear Reduction = 80:1
• Ball screw
– Lead = 4 mm
– Pitch = 25.75 mm
• Bellows/slides
– axial thermal contraction
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CEBAF Upgrade Coarse Tuner
Resolution/Deadband Test
Resolution/Deadband < 2 Hz
Drift due to Helium pressure fluctuations
0
100
1st
Qtr
3rd
Qtr
East
West
North
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Upgrade Tuner – SL21 / FEL03 : Range and Resolution (Piezo Hysteresis)
Cavity Position #5 (SL21) Tuner Performance
y = 4E-06x + 1497.4
R2 = 0.9993
1496.95
1497
1497.05
1497.1
1497.15
1497.2
1497.25
1497.3
1497.35
1497.4
-1.2E+05 -1.0E+05 -8.0E+04 -6.0E+04 -4.0E+04 -2.0E+04 0.0E+00
# Steps
Fre
qu
en
cy (
MH
z)
Piezo tuner voltage vs frequency Difference From
Maximum for FEL03-6 at 10 MV/m
0
100
200
300
400
500
600
700
800
0 25 50 75 100 125 150
Voltage (V)
Fre
qu
en
cy
Dif
fere
nc
e (
Hz)
First cycle
Second cycle
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Upgrade Cryomodule – Access to Tuner Drive Components
Motor, Limit Switches,
Harmonic Drive and
Piezo Actuator are all
situated on the stack
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Cavity String Support Schemes :
Tuning approach affect supports
SNS MB
Upgrade Cryomodule Fixed
Fixed Fixed Fixed
Tunin
g
Cooldown
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Renascence Tuner Assembly with Two Cold
Piezo Actuators
Piezo Actuator in
SST Cartridge –
40mm Stack
(Model # PSt
1000/16/40 VS25)
Primary lever that
transmits tuning
force
Secondary lever –
divides load
symmetrically
Motor: Phytron VSS-52, 52 in*oz.,
Harmonic Drive: HDC-14-100-
2ASP
With 100:1 Reduction
316L
Stainless Steel
Frame
Dicronite-
coated
Beryllium
Copper
Drive
Screw, M12
x 1.5
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Renascence Tuner Description
• Mechanism – “Rock Crusher” –
All cold, in vacuum components
– Stainless steel frame
– Attaches to chocks on cavity
– Attaches via shoulder bolts to
helium vessel head
– Dicronite coating on bearings
and drive screw
– Cavity tuned in tension only
Shown hanging in VTA Test Stand,
attached to EP3 cavity, ready for
cold testing
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Renascence Tuner – VTA Testing : Range (Helium vessel compliance reduces actual stroke)
Renascence Cavity Frequency Response :
VTA Test Data & Ideal Curve - High Gradient and Low Loss Cavities
0
200
400
600
800
1000
1200
1400
1600
0 1000000 2000000 3000000
Stepper Motor Driver Steps (= 1/2 motor step)
Fre
qu
en
cy C
han
ge (
kH
z)
Calculation (300kHz/mm,
No flex)HGPT Measurement
LL004 Measurement
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RIA Tuner (MSU)
• Mechanism
– Stainless steel rocker arm and drive rod
• Attaches to chocks on cavity
• Attaches via flexures and threaded studs to helium vessel head
– Cavity tuned in compression or tension
• Cold transmission – compressive/tensile force on drive rod
• Stepper motor and piezo external to vacuum tank
• Bellows on vacuum tank
– Need to accommodate relative thermal contraction of cavities
– Allow tuner transmission to float (unlocked) during cooldown
– Pre-load each tuner while warm, account for vacuum loading on
bellows
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RIA Tuner (MSU) – Rocker Arm / Schematic
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RIA Tuner – Test Results: Coarse and Fine Tuner Range; Active Feedback Control
6 4 2 0 2 4 6
Displacement (mm)
50
00
5
00
ff 0
(kH
z)
pulling
pushing
0 20 40 60 80 100
Piezo drive signal (V)
0
4
8
12
ff 0
(kH
z)
Cycle
second
third
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SNS Tuner - Description
• Mechanism scaled from original DESY/Saclay design
– Stainless steel frame
• Attaches to chocks on cavity
• Attaches via flexures and threaded studs to helium vessel head
– Dicronite coating on bearings and drive screw
– Cavity tuned in compression only
• Cold transmission
– Components in insulating vacuum space
– Stepper motor and harmonic drive rated for UHV, cryogenic and
radiation environment (www.phytron.com)
• Bellows between cavities
– Need to accommodate relative thermal contraction of cavities
– Pre-load each tuner while warm
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SNS Tuner Assembly w/ Piezo Actuator
Piezo Actuator in
SST Cartridge
(Model # PSt
1000/16/200
VS25)
Flexure Connection
to Cavity (2X)
Flexure Connection
to Helium Vessel (2X)
Motor: Phytron VSS-52, 52 in*oz.
Harmonic Drive: HDC-14-100-
2ASP
With 100:1 Reduction
316L Stainless Steel
Frame and Lever –
20:1 Mechanical
Advantage
Dicronite-
coated
Beryllium
Copper
Drive
Screw, M12
x 1.5
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SNS Tuner Assembly w/ Piezo Actuator
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SNS Tuner with Piezo Actuator Installed on
Helium Vessel & Cavity
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SNS Tuner – CMTF Test Results: Fine Tuner Range and Hysteresis; Piezo Compensation
Piezo Tuner Range H05 - 4
805.0100
805.0105
805.0110
805.0115
805.0120
805.0125
805.0130
805.0135
805.0140
0 200 400 600 800 1000
Piezo Voltage (V)
Fre
q (
MH
z)
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± 460 kHz tuning range
4 nm resolution = 1.2 Hz (sufficient if <5Hz)
~ 1kHz fast compensation by piezo
Saclay Lever Tuner spec.
Piezos
Stepping motor and gear box
2. TESLA Cavities and Auxiliaries as ILC Baseline Design Frequency Tuners
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Current Saclay Tuner
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Piezo
Stiffeners bars could be used in working
cond. as safety devices.
Ti ring welded on the tank
Leverage arm
± 1 mm fine tuning (on cavity) → ΔF on all piezo (sum) ≈ 3.5 kN
1 kHz fast tuning → ≈ 3 µm cavity displacement → ≈ 4 µm piezo displacement
4 µm piezo displacement → ≈ Δ F on all piezo ≈ 11.0 N
~1 Hz resolution (sufficient if <5Hz)
Blade Tuner spec.
2. TESLA Cavities and Auxiliaries as ILC Baseline Design Blade Tuners
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TESLA - Blade Tuner
• Mechanism – All cold, in vacuum components
– Titanium frame
– Attaches to helium vessel shell
– Pre-tune using bolts pushing on shell rings
– Dicronite coating on bearings and drive screw
– Cavity tuned in tension or compression – blades
provide axial deflection
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Piezoelectric Tuners
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Magnetostrictive tuners
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Renascence Cavity – VTA Test Results Magnetostrictive Actuator on Tuner
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
0 100 200 300 400 500
Time (*10^-2 sec.)
Fre
qu
en
cy
sh
ift
(Hz)
Freq. shift Input current
Tuning Range at 14000 N compressive load
0
500
1000
1500
2000
2500
3000
3500
0 2 4 6 8 10 12 14 16
Input current (A)
Fre
quency s
hift (H
z)
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Voltage-Controlled Reactance
• Has been successfully
applied at lower
frequencies
• Unlikely to be applicable
at the frequency and
power levels for TM010
cavities
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Pneumatic Tuners
Have been used successfully for many years in low velocity structures
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Waveguide Stubline Tuning
• Commonly used to adjust coupling
• Could also be used to compensate for detuning
• Issues:
– Part of the waveguide becomes part of the resonant
system
– Speed for dynamic control of microphonics
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High Power Vector Modulator
Can provide simultaneous amplitude and
phase control
Y. W. Kang et al, ORNL
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Coarse Tuners
• Typically cold, must be reliable and maintainable access ports
• Direct cavity drive reduces stiffness requirements on helium vessel
• Tuner/HV stiffness > 10x cavity
• Flexures exhibit reduced backlash
• Typically tune in tension or compression to avoid “dead band”
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Fine Tuners
• Piezo
– Operate in compression
– Warm range 5-10x > cold range
– Capacitive device, Low vs. High voltage
– Consider hysteresis
• Magnetostrictive
– Must operate cold
– Consider lead thermal design, required current ~10 Amps
– Inductive element
– Consider hysteresis
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Closing / Summary : Comparison of Tuner Features (2 of 2)
• Transmission Location (maintainability)
– Cold placement
• Materials considerations (CTE, lubrication, vacuum)
• Access for repair or replacement
• Electrical feedthroughs
– Warm placement
• Cooldown/tuning compliance
• Port for transmission
• Bellows
• Testing (minimizes risk associated with reliability and availability)
– Perform accelerated life tests on critical components
– Feedback results into design prior to production
– Develop thorough acceptance tests to verify operation