Overview of 9cell Cavity Progress

1
Overview of 9-cell Cavity Progress

• C.M. Ginsburg
• Fermilab

North American Cavity Vendor Meeting March 6,
2009
2
Outline

• ILC and Project X alignment
• International context
• Americas cavity results
• Fermilab 9-cell results
• 9-cell details from other labs in subsequent
  talks
• How can FNAL help cavity vendors?
• Status, results, tracking tools
• Instrumentation
• How best to provide feedback?

3
Fermilab cavity requirements(only b1 sections
here)

• International Linear Collider
• 14560 cavities, operating at 31.5 MV/m
• 35 MV/m in vertical test
• Project X at Fermilab
• 304 cavities, operating in range 23.8-31.5 MV/m
• Minimum 25 MV/m in vertical test
• Target Oct.2013 construction start (large cavity
  purchase)
• Use knowledge gained in ILC RD for Project X
• Learn ways to remove steps/economize

4
Global Best Results /50 MV/m
Cornell
Q0
Tesla-shape cavity for comparison
World record 59 MV/m Cornell 1-cell re-entrant
shape
Ichiro shape
Eacc MV/m

• Single-cell Ichiro-shape record is 53.5 MV/m KEK
  Saito
• 46.7 - 1.9 MV/m with optimized surface treatment
  parameters
• 9-cell Ichiro-shape recently reached 32?4 MV/m in
  5 process/test cycles (KEK/JLab)
• Low-loss shape reached 47.3 MV/m (DESY/KEK)

5
Global 9-cell Status

• Europe (DESY, Saclay)
• Gradient gt 40 MV/m (max) , and 31.5 MV/m
  (av.)
• Industrial (bulk) EP demonstrated 36 MV/m (av.)
• Field emission reduced with ethanol rinsing
• Surface process with baking in Ar-gas
• Americas (Jlab, Cornell, FNAL/ANL)
• Gradient gt 40 MV/m (max), and widely scattered
  at 20- 40 MV/m
• Field emission reduced w/ Ultrasonic Degreasing
  Detergent
• Asia (KEK, China, India)
• Gradient 36MV/m (LL, KEK-JLab), 32 MV/m
  (TESLA-like, KEK)
• More global cooperation of Indian institutions
  with
• Fermilab, ANL, JLab, DESY, and KEK

A. Yamamoto
6
9-Cell and Cavity String Field Gradient
Progress for XFEL

• ILC operation
• lt31.5gt MV/m
• RD Status
• 30 MV/m to meet XFEL requirement

6

• 20 improvement required for ILC

A. Yamamoto
7
Americas Cavities (9-cell)

• We are working in a coordinated effort of
  FNAL/ANL, Cornell University and Jefferson Lab on
  9-cell cavity development
• http//tdserver1.fnal.gov/project/ILC/S0/S0_coord.
  html
• Contains web-based 9-cell cavity tracking tool
• Currently 22 cavities (13 Accel, 9 AES)
• One Accel cavity was only a loan was returned
• Next six 9-cell Accel cavities mid-March and six
  more 3 weeks later

8
Tools

http//tdserver1.fnal.gov/project/ILC/S0/S0_coord.
html
9
Cavity Naming Convention
10
Americas 9-cell Vertical Tests
Of 14 cavities, 6 cavities meet ILC VT spec 10
meet Project X VT spec NB These are the tests
which individual Labs choose to publish
ILC goal
Px goal
11
Fermilab Vertical Cavity Test Facility
Status 28.Jan.2009

• 26 cavity tests in FY08/FY09, where test
  cryogenic thermal cycle
• Performance tests for 9-cell single-cell
  elliptical cavities, and a SSR1 HINS cavity
• Cavity tests dedicated to instrumentation
  development, e.g., variable coupler, thermometry,
  cavity vacuum pump system
• Cavity tests dedicated to facility commissioning,
  e.g., for ANL/FNAL CPF

12
VCTF upgrade plans

• Cavities to accommodate
• ILC/SRF RD
• 9-cell and 1-cell elliptical ILC cavities
• HINS/Project X
• SSR1
• SSR2
• TSR
• 9-cell elliptical cavities
• VTS requirements
• VTS1 is sufficient to support FY09, FY10 test
  plans
• VTS2 with larger diameter operational by end of
  CY2011 to support SSR2, TSR, and increased
  throughput
• VTS3 needed somewhat later
• Planned upgrades for ultimate capacity 250
  cavity tests/yr
• 2 cavities per cryogenic cycle, singly RF tested
• Cryogenic system infrastructure upgrades
• Two more VTS cryostats collaborate with Indian
  Institutions

VTS 23 pits staging area
Do not fit in VTS1
13
Understanding Cavity Behavior

• Quenches and field emission appear as hot spots
  on outer cavity surface.
• Temperature mapping systems have been used for
  many years
• New hot spot detection systems include
• Individual Cernox thermal sensors (FNAL)
• 2-cell Allen-Bradley temperature map (JLab)
• 9-cell T-map under
  development
• (LANL, FNAL)
• Second sound sensors
  (Cornell)

thermal cycles
Concentrate on quenches today
14
Quench Region
magnetic field (arb norm)
cavity
Simple model (Padamsee) for power loss of
hemispherical NC Nb defect DP1/2 Rn H2 p a2
15
Quench Location with Fast Thermometry
FNAL

• Example of cavity which quenched at 16 MV/m
  without field emission
• Temp rise 0.1 K over 2 sec in sensors 3 4
  before quench seen on all sensors
• Cernox RTD sensors (precise calibration,
  expensive) with fast readout (10 kHz)
• Flexible placement of sensors, attached to cavity
  surface with grease and band slow installation
• Suitable for any cavity shape and highly portable

AES001 cell 3
4
3
16
2- and 9-cell T-mapping

• 2-cell T-map
• JLab using Allen-Bradley sensors
• Requires two cooldowns, first with mode
  measurements
• 9-cell T-map
• LANL using Allen-Bradley sensors and cold
  multiplexing
• Promising preliminary results
• FNAL using diodes
• System under development
• Could use on every test to find T-map on one
  cooldown
• Designed for specific cavity shape

17
Quench location with 2nd Sound
Cornell
0.5 V
signal amplitude (V)
20 ms
time (s)

• Second sound is a thermal wave which can
  propagate only in superfluid helium generated
  when heat pulse is transmitted from heat source
  through SF He
• Eight sensors detect arrival of wave
• Quench location from relative signal timing
• Suitable for any cavity shape

diaphragm
18
Exciting Optical Inspection
Clever lighting technique and excellent spatial
resolution 7 um/pixel
Kyoto U./KEK
19
Optical Cavity Inspection
Instance of this system now available at Fermilab
Kyoto U./KEK

• Illumination by electroluminescent strips which
  can be turned off/on individually shadows can be
  analyzed for 3D defect mapping (pit vs. bump)
  bump is shown
• Camera is inserted into cavity
• Digital images studied by a person needs
  automation
• Many defects on several cavities now found,
  50-600 um diameter

20
Use of instrumentation

• Surface defects conclusively known to cause
  premature quenches
• Location confirmation with measured heating
  (thermometry or 2nd sound) and optical inspection
• Plausible explanation of location in high-H field
  region and shape analysis
• There are also some ugly defects which do not
  apparently cause premature quenches
• We do not yet know how to conclusively state
  whether an observed defect will cause quench or
  not