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SRF DEVELOPMENT AT
DARESBURY LABORATORY
A. Wheelhouse
ASTeC, STFC Daresbury Laboratory
2nd PASI Workshop, RAL 3rd – 5th April
2013
Outline
• Mini PIPSS / IPS Programme
– Aims & Objectives
– Progress & Results
• SRF Cryomodule Development
– Aims & Objectives
– Progress
• Summary
4th April 2013
PASI Workshop
A Wheelhouse
Mini PIPSS & IPS Programme
4th April 2013
PASI Workshop
A Wheelhouse
Aims
• The fundamental remit of the Mini PIPSS & IPS, Industry Partnership
Schemes is to develop the capability of UK industry in the
manufacturing of superconducting RF cavities
• Mini PIPSS
– Fabrication of a single cell niobium cavity (1-year)
• IPS
– Fabrication of a bulk niobium 9-cell accelerating structure (3-year)
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Cell to cell alignment
Tuning robustness and uniformity
Tolerance management
Cleaning/processing compliance
RF surface integrity management
• Technology directly applicable to future large scale accelerator
facilities.
Opportunity for Daresbury Laboratory and Shakespeare Engineering
Ltd to develop unique capabilities in the UK
Enable Shakespeare Engineering Ltd to exploit the large SRF
commercial opportunity
4th April 2013
PASI Workshop
A Wheelhouse
Objectives
• Mini PIPSS
– Fabrication of a single cell TESLA SRF cavity
– Acceleration gradient > 15 MV/m at a Qo better than 1 x 1010
• IPS
– Fabrication of a 9-cell TESLA SRF cavity which will be qualified in
2 ways:– Accelerating gradient > 20 MV/m at a Qo better than 1 x 1010 after
conventional Buffer Chemical Polishing (BCP) is performed
– Accelerating gradient > 30 MV/m at a Qo better than 1 x 1010 when
Electro-Polishing (EP) chemical processing is performed
Aim to provide a clear indication of Shakespeare’s capability
and assist in qualifying them as a potential supplier
4th April 2013
PASI Workshop
A Wheelhouse
Cell and Beampipe Forming
• Cavity half cells and beampipes fabricated by
Shakespeare Engineering
• Half cells pressed on a 60 t hydraulic press
– Pressing performed in 3 operations
• Beampipes were spun using a CNC spinning
machine
– Eliminates additional welded seam joint
– Spinning of cones performed with intermediate
heat-treatments
– Beam tube finally formed on a mandrel
3 single cell cavities welded at JLab
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #01 (JLab)
Multipactor
•
Target
4th April 2013
PASI Workshop
•
•
Achieved 15.7 MV/m with a
Q0 of 1.15 x 1010
CW and pulsed conditioning
Gradient - 17.6 MV/m with a
Q0 of 2.17 x 109
A Wheelhouse
PIPSS #01 (JLab)
• Additional BCP etch
−
4th April 2013
PASI Workshop
Approximately 41µm removed
A Wheelhouse
PIPSS #01 (JLab)
• Vac furnace run at 600ºC for 10 hours
• Plus an additional BCP etch
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−
4th April 2013
Approximately 28µm removed
Further high pressure rinses
PASI Workshop
A Wheelhouse
PIPSS #01 (JLab)
• Further high pressure rinses
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #02 (Daresbury)
• Acid fume cupboard used to perform the BCP
etch
• Thickness removed measured on a sample
piece which doubled as a stirrer
• Acid temperature monitored
85µm removed in 2 etch runs
– Cavity turned up the other way for the 2nd run
• HPR performed for 1 hour
• Cavity sealed in a ISO4 class cleanroom
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #02 Evaluation
• VTF manually filled from a 1000lt
dewar
• Reduced performance achieved on
second cavity processed at DL
Ineffective temperature control on
the BCP etch
• Improvements to BCP processing is
underway
– Further testing to be performed
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #03 (FNAL)
EB weld inspection
FERMI Lab Standard Preparation
Electro-polish - 150µm
High Pressure Rinse
Ultrasonic Clean
Vertical Test Assembly
High Pressure Rinse
High Pressure Rinse
Vacuum Bake - 800ºC 2
hrs, <5x10-07 mBar
Slow evacuation and leak
check
Electro-polish - 30µm
Vacuum Bake - 120ºC 2
hrs, <5x10-07 mBar
Ultrasonic Clean and Rinse
Vertical Test
Electro-polishing monitoring
• EB weld good
– Some inclusions
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #03 Tests
FermiLab Tests
• Cavity tested at 2K
• Maximum accelerating gradient 25 MV/m with Q0=1.5x1010
• Gradient limited by a quench
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First quench at 18 MV/m
Quenched twice at 21 MV/m
Finally quenched at 25 MV/m
Limited by repetitive quenches at 25 MV/m which showed no sign
of conditioning after 20 mins
• No field emission above background was observed
• Some multipacting was noted at around 18 MV/m
– Instabilities in Ptransmitted signal were observed
– Common ILC-shape multipacting range
– Multipacting processed
Successfully met target
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #03 Tests
Target
4th April 2013
PASI Workshop
A Wheelhouse
PIPSS #03 - Further Qualification
• Further processing performed
• Cavity has been CBP
CBP
– Removing ~180µm
• Light 30µm electro-polish to
remove a weld inclusion
• Vacuum bake at 800ºC
• Cavity to be tested 5/4/13
Typical
before and
after CBP
4th April 2013
PASI Workshop
A Wheelhouse
IPS Programme
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•
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3-year programme on-going
Cavity drawings complete
Tooling has been manufactured
Pressing trials being completed
with Copper
– Assessing repeatability and
reproducibility
9-cell cavity drawings
Niobium half cells to be pressed
soon
• Further beampipe spinning trials
– Thicker sheets
• SRF infrastructure development
– Automated BCP process
– Automated HPR
• It is hoped that FNAL can
continue to assist in qualifying
Shakespeare with this structure.
4th April 2013
PASI Workshop
BCP facility
HPR stand
A Wheelhouse
SRF Cryomodule
Development
ALICE
4th April 2013
PASI Workshop
A Wheelhouse
Aims & Objectives
• To lead the design of a new, high current and
world leading cryomodule.
• To educate and demonstrate effective:
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–
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Processing,
Handling,
Assembly,
Testing,
QA processes.
• To integrate the new cryomodule onto ALICE
• Commission cryomodule + cryogenics systems
• To validate cryomodule performance with beam
4th April 2013
PASI Workshop
A Wheelhouse
SRF Cryomodule
• International collaboration
initiated in early 2006:
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Existing Cryomodule on ALICE
ASTeC (STFC)
Cornell University
DESY
FZD-Rossendorf
LBNL
Stanford University
TRIUMF (2009)
• Fabricate new cryomodule and
validate with beam.
• Dimensioned to fit on ALICE:
– Same CM footprint
– Same cryo/RF interconnects
– ‘Plug Compatible’
ERL (New) Cryomodule
4th April 2013
PASI Workshop
A Wheelhouse
SRF Cryomodule
Parameter
ALICE
Target
1.3
1.3
Number of cavities
2
2
Number of Cells per Cavity
9
7
1.038
0.807
3.6
3.6
1036
762
12 - 15
>20
27
>32
Qo
<5 x109
>1x1010
Qext
4 x 106
4x106 - 108
Max Cavity Fwd Power (kW)
10 SW
20 SW
Frequency (GHz)
Cavity Length (m)
Cryomodule Length (m)
Existing Cryomodule on ALICE
R/Q (Ω)
Eacc (MV/m)
CM Energy Gain (MeV)
ERL (New) Cryomodule
4th April 2013
PASI Workshop
A Wheelhouse
Coupler Conditioning
Pulsed Conditioning
• High power conditioning of
the CPI input couplers:
– Up to 30 kW (pulsed)
– Up to 10 kW (CW)
• For these tests, couplers
water/air cooled only
• No vacuum activity seen
4th April 2013
PASI Workshop
A Wheelhouse
Coupler Conditioning
CW Conditioning
• High power conditioning of
the CPI input couplers:
– Up to 30 kW (pulsed)
– Up to 10 kW (CW)
• For these tests, couplers
water/air cooled only
• No vacuum activity seen
4th April 2013
PASI Workshop
A Wheelhouse
Cryomodule Assembly
HOM assembly
µ metal installation
Cavity wiring
Cavity string
4th April 2013
PASI Workshop
A Wheelhouse
Cold Tests (Off-line)
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Check the cryogenic performance
Understand the processes and establish
commissioning and operating procedures
Validate instrumentation
Cavity frequency verification
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Issue with tuner sticking had to be resolved
Identify and resolve any unknown issues
80K tests successfully completed
Attempted to cool-down to 4K however:
•
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Large temperature gradient between the two cavities
Helium reservoirs did not fill completely
•
Parameters
Static Heat Load at 80K
Static heat losses for the cavities at
80K
Delta T across thermal shield at
equilibrium
Delta T across the two cavities during
cool-down
4th April 2013
Result of blockage between cavity bottom fill
connection and excessive heat load at the input
transfer line
Measured
Specification
~7W
20W
~ 3.5 W
15 W at 4K
< 5K
<10K
< 5K
< 5K
PASI Workshop
Currently 5060K for ALICE
A Wheelhouse
Cryomodule Evaluation
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Cryomodule installed and cooled to 2K
Optimisation presently being performed on the
cryogenic system
Evaluation Programme:• Establish gradient and Q0
• Measure Lorentz force detuning at high
gradient
• Performance measurements with piezo tuners
• Determine DLLRF control limitations wrt Qext
• Evaluate the effect of beam loading with
DLLRF, piezo control for various Qext levels
under pulsed and CW conditions
Cryomodule installed on ALICE
• Characterise cavities in CW mode at high
gradient:
– Evaluate thermal transients across cavity string
and 2-phase line
•
Synergies with PXIE operational requirements
to be evaluated
4th April 2013
PASI Workshop
A Wheelhouse
Summary
Verified the fabrication of a single cell SRF cavity
9-cell SRF cavity and infrastructure development
progressing
UK SRF capability in a stronger position thanks to
FNAL collaboration
Cavity string integrated into the cryomodule
Cryogenically commissioned cryomodule off-line
Cryomodule now installed in ALICE
Cryomodule characterisation about to commence
4th April 2013
PASI Workshop
A Wheelhouse