update on srf activities at argonne mike kelly, peter ostroumov, mark kedzie, scott gerbick (phy)...
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Update on SRF Activities at Argonne
Mike Kelly, Peter Ostroumov, Mark Kedzie, Scott Gerbick (PHY)Tom Reid, Ryan Murphy (HEP)
Thomas Proslier, Jeff Klug, Mike Pellin (MSD)
June 7, 2010
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I. ATLASII. ILCIII. National SecurityIV. Atomic Layer DepositionV. SRF at the Advanced Photon Source (SC undulator and crab
cavity)
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I. ATLAS Energy Upgrade: Commissioned June 2009Exceeds previous state-of-the-art (at TRIUMF) by ~50%
EP in Joint Facility
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CARIBU
MHB RFQ New cryomodule Energy upgrade cryomodule
Tandem
CARIBU
MHB RFQ New cryomodule Energy upgrade cryomodule
Tandem
I. ATLAS Efficiency and Intensity Upgrade Phase I: RFQ and new cryomodule New 60.625 MHz CW RFQ
New cryomodule with 7 QWRs OPT=0.077 Total $9.86M ARRA funds Complete in March 2013
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I. ATLAS Energy and Intensity Upgrade: CryomoduleCommissioning in July 2012
(for scale)
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I. Pushing performance for low-beta SRF cavities
Obvious benefits for ATLAS– Replace aging split-ring cryomodules– Higher energies (30-40% beam energy increase with Phase I)– Higher intensities
Real possibilities for high-gradient low-beta for applications– National security (non-destructive interrogation methods)– Nuclear medicine (accelerators as solution to Mo99 crisis)– Renewed interest for waste transmutation
To push for better performance in the intensity upgrade…1. VCX fast tuner Piezoelectric transducer + 4 kW coupler2. Better performance through the use of techniques learned in FNAL collaboration;
particularly horizontal electropolishing on completed jacketed niobium cavity
30 cm
=0.077f=72.5 MHzBp/Eacc= 4.8 mT/MV/mEp/Eacc=3.25
New center conductor dieCourtesy AES, June 4, 2010
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Full operations (chemisty/clean room) since Mar 2009
Two new EP operators trained Excellent single cell results, recent good 9-
cell results Electropolishing system refinements
– Possible improvements still to be had in operating parameters
– Collaboration with JLab on KEK on EP optimization
II. Joint ANL/FNAL Cavity Processing Facility
Electropolishing
High-pressurerinse
Ultrasonic Cleaning
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II. Cavities Electropolished/Assembled at the ANL/FNAL SCSPF in 2010
Date Cavity Name Cavity Type EP Type Target Removal (μm) Process Run Time (min)
1/27/2010 TB9RI026 9-Cell Bulk 130 390
1/28/2010 TB9ACC007 9-Cell Light 20 70
2/15/2010 TB9RI026 9-Cell Heavy 100 300
2/18/2010 TE1ACC003 1-Cell Light 40 120
2/22/2010 TE1CAT002 1-Cell Bulk 120 360
3/26/2010 TB9RI024 9-Cell Light 20 70
3/30/2010 TB9RI026 9-Cell Light 20 70
4/2/2010 TB9AES003 1-Cell Light 20 70
4/7/2010 TE1CAT001 1-Cell Light 20 70
4/8/2010 NR-6 1-Cell Light 20 70
4/16/2010 TE1CAT001 1-Cell Light 30 100
4/20/2010 NR-6 1-Cell Light 30 100
4/28/2010 TB9RI029 9-cell Light 20 110
5/11/2010 TB9RI024 9-cell Light 20 120
5/25/2010 TB9RI020 9-cell Heavy 120 450
6/3/2010 TB9RI024 9-cell Light 20 100
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II. Feedback from FNAL SRF Cavity Diagnostics (KEK Camera) to ANL Cavity Processing
Intra-grain structure is due to disruption of viscous layer from acid injection Cathode holes covered and orientation changed to upward to reduce/remove this
effect
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II. New Low Voltage 9-cell cavity electropolishing parameters
Cavity Temp.
Current
Voltage
Acid Temp.
Acid Temp.
Water Temp
Acid Flow
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II. In the 2nd Chemistry Room: QWR electropolishing based on existing mechanical and electrical hardware
sliding Bosch rail
rotating carbon brush assembly
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II. Electropolishing for 650 MHz 5-cell cavity
Scaled cavity geometry shown with the existing EP hardware– Cavity with twice radial dimension of the 1.3 GHz 9-cell fits into the existing system with
modest modification (no cavity frame shown, may need to shim under blue stands)– 55 gallon acid handling limit OK– 2 ½ times surface area, EP supply OK, 50% larger chiller– Cavity handling similar to 9-cell (crane in hi-bay, hoist in chemistry room)– No major difficulties in adapting EP to this geometry
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III. SRF for National Security
Accelerators for interrogation of special nuclear materials Based short high-intensity pulse of protons Secondary neutron production induces detectable -rays Very high accelerator real estate gradients needed (both low and high-
ANL-PHY funded to develop high real estate gradients for low-– Fabrication/processing/diagnostic technique to achieve ILC type surface fields (~120 mT)– Innovative design techniques to reduce surface fields/increase packing factor
Concept for a “stackable” half-wave cavity with very low surface fields
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Bake 120C Bake 180C3 parameters: -ε, α : effect of Magnetic impurities on the Nb superconductivity, give Rres , Δ and TC. Here ε=0.2 fixed.
-Normal conductivity σ0: shift RS[T] vertically, give the mean free path L
Experimental evidence:-Data courtesy JLab (Ciovati)-Theory, Argonne
Hot spots have higher concentration of Magnetic impurities than cold spots
IV. Surface impedance & Magnetic impurities: the residual resistance and more
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IV. Surface impedance & Magnetic impurities: the residual resistance and more
Summary of results:-More magnetic impurities after baking (consistent with Casalbuoni SQUID), Conc ~ 200 ppm-Longer mean free path thus cleaner after baking.-Smaller gap but larger Δ/kTc after baking.
Unknowns and next experiments:-Where are the magnetic impurities coming from: Oxides for sure but something else also?
EPR (electron paramagnetic resonance) to probe mag. moments on EP samples.-Refine the model: introduce inhomogeneity or surface layer.
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IV. Superconducting layer by ALD
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Thin films: 10 nm
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Summary SRF at ANL
Phase I ATLAS Intensity Upgrade funded; work proceeding; completion in 2013
Cavity processing at the joint ANL/FNAL facility– Good cavity throughput– Tweaking chemistry and clean room techniques based on test results and discussions
with JLab/KEK
Interest and support for SRF for non-basic science applications
Material Science– Atomic layer deposition to produce new superconducting layers for cavities– Magnetic impurities to explain SRF properties of niobium