thin films for superconducting cavities hzb. outline introduction to superconducting cavities the...
TRANSCRIPT
![Page 1: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/1.jpg)
Thin Films for Superconducting Cavities
HZB
![Page 2: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/2.jpg)
2
Outline
• Introduction to Superconducting Cavities• The Quadrupole Resonator• Commissioning• Outlook
![Page 3: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/3.jpg)
3
Basics of RF Cavities
• Acceleration of charged particles using a radio frequency field
• There are normal conducting and superconducting (sc) cavities
• Qnc ≈ 105 vs. Qsc ≈ 1010
• The needed power for operation is about a factor of 200 less than for superconducting cavities
![Page 4: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/4.jpg)
4
Materials for sc Cavities
• Niobium (from sheet)– Critical temperature Tc = 9.2K– Accelerating gradients reaching the theoretical limit
(≈45MV/m) due to improved treatment techniques– Expensive
• Niobium on copper– 1-2μm niobium on copper cavity– Less need of niobium– Accelerating gradients up to 10MV/m
![Page 5: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/5.jpg)
5
Where can we improve?
Understanding the dominant loss mechanisms in niobium
Reducing losses
Improving the performance of niobium films
Reducing material costs
Finding new materials ?
![Page 6: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/6.jpg)
6
How can we improve?
• Power consumption in a superconducting cavity is proportional to its surface resistance RS
• RS shows a complex behavior on external parameters, such as temperature, frequency, magnetic and electric field
),,,(Sc EBTfRP
Systematic studies on cavities are no option
![Page 7: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/7.jpg)
7
The Quadrupole Resonator
361
mm
• The Quadrupole Resonator enables RF characterization of small, flat samples over a wide parameter range
• Samples of 75mm diameter are welded to a niobium cylinder with flange so that they can be mounted to the host cavity
![Page 8: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/8.jpg)
8
Field Configuration & Features
• Resonant frequencies: 400MHz, 800MHz, 1.2 GHz
• Almost identical magnetic field configuration
• Ratio between peak magnetic and electric field proportional to frequency
B ׀׀
0
max
50 mm1 E. Mahner et al.
Rev. Sci. Instrum., Vol. 74, No. 7, July 20032 T. Junginger et. al
Rev. Sci. Instrum., Vol. 83, No. 6, June 2012
![Page 9: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/9.jpg)
9
DC Heater
Quadrupole Resonator Thermometry Chamber
Heat Flow
The Calorimetric Technique
• Measuring the temperature on the sample surface
• Precise Calorimetric measurements over wide temperature range
TemperatureSensorsSample Surface
![Page 10: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/10.jpg)
10
time
Temperature
Bath Temperature
Temperatureof Interest
P DC,
1
P DC,
2P RF
Power
DC on RF on≈60 s ≈40 s
dSHRPPPSample
SurfaceDCDCRF 22,1, 21
dSH
PPR
Sample
DCDCSurface
2
2,1, )(2
TemperatureSensors
DC Heater
Heat Flow
The Calorimetric Technique
Measured directly
• Measurement of transmitted power Pt
• Pt=c∫H2ds, c from computer code
![Page 11: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/11.jpg)
11
Imperfect Meissner Effect
Meissner effect
Trapped magnetic flux
![Page 12: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/12.jpg)
12
Flux Trapping in the Quadrupole Resonator
Sample
DC Coil
![Page 13: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/13.jpg)
13
Flux Trapping in the Quadrupole Resonator
DC Coil�⃗�
![Page 14: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/14.jpg)
14
First test with trapped flux
• Bulk niobium sample• Reactor grade, RRR • Standard BCP, no bake out
![Page 15: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/15.jpg)
15
RS(B) at 400MHz, 2-4K
• Convex curve for • Concave curve for • Different loss
mechanisms dominant
![Page 16: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/16.jpg)
16
Trapped Flux at 400MHz and 4K
![Page 17: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/17.jpg)
17
Outlook
• MgB2 from Superconductor Technologies, Inc.– Tc = 39K, Bc up to 1T
– expected: Eacc > 75MV/m, RBCS(4K,500MHz) = 2.5nΩ
• HiPIMS: Nb/Cu from CERN and Berkeley– Dense film, low cost, but competitive to bulk Nb?
• ECR: Nb/Cu from Jlab– High RRR, low cost, but competitive to bulk Nb?
![Page 18: Thin Films for Superconducting Cavities HZB. Outline Introduction to Superconducting Cavities The Quadrupole Resonator Commissioning Outlook 2](https://reader035.vdocuments.net/reader035/viewer/2022062421/56649db65503460f94aa8a92/html5/thumbnails/18.jpg)