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)
•
•
•
•
•
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
−
−
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
–
–
–
–
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
•
•
•
•
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:
–
–
–
–
–
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:
–
–
–
–
–
–
–
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)
•
•
•
•
Check the cryogenic performance
Understand the processes and establish
commissioning and operating procedures
Validate instrumentation
Cavity frequency verification
•
•
•
•
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:
•
•
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
•
•
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