r&d for accelerating structures h. padamsee. tesla niobium, one meter length, rf = 1.3 ghz...
Post on 22-Dec-2015
218 views
TRANSCRIPT
![Page 1: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/1.jpg)
R&D For Accelerating Structures
H. Padamsee
![Page 2: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/2.jpg)
TESLA
Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz
![Page 3: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/3.jpg)
2002
9-cell
![Page 4: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/4.jpg)
![Page 5: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/5.jpg)
0 5 10 15 20 25 30109
1010
Denis Kostin, DESY, MHF/SL
Module 5 cavities. Vertical test results. C45 AC60 AC61 AC65 AC66 AC79 AC78 AC62
Q0
Eacc [MV/m]
Q
Why do RF Losses increase above Eacc = 20 MV/m?
![Page 6: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/6.jpg)
30 MV/m
100 m
Single Cells
![Page 7: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/7.jpg)
Need to UnderstandSC materials and surface science
• Why do rf losses increase with surface roughness?
• Why do rf losses decrease with simple baking of 140 C and 48 hours
• Why does sc quench below rf critical field ≈ 50 MV/m?
![Page 8: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/8.jpg)
Possible Benefits from higher Q
• Double luminosity with 1.6 x AC power (eg double rep rate, increase Q to 5 x 1010
• Decrease number of klystrons from 680 to 330 by doubling rf pulse length, increase Q to 5 x1010 => increase reliability
• Reduce AC power of 800 GeV TESLA at 35 MV/m
![Page 9: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/9.jpg)
BCS Contribution still important
2 K
![Page 10: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/10.jpg)
T = 2 K, Rs = 14 n, Q = 2 x1010
Lower mean free path, Q = 3 x1010
Lower Temperature
T = 1.7 K, Q = 1.2 x10 11
T= 1.5 K , Q = 4.3 x1011
TESLA Q = 1010
Need to Shield Earth’s magnetic field to 0.5 mOerstedHow to achieve this in an accelerator cryostat?
T 1.8 K, Q 5 x 1010
![Page 11: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/11.jpg)
Saclay CAVITY C117 F = 1.3 GHz, T = 1.6 K
1E+08
1E+09
1E+10
1E+11
1E+12
0 5 10 15 20 25 30
Eacc (MV/m)
Q0
CEA Saclay, GECS, Jan. 1999
Q0 > 2. 1011 !!
Surface Resistance
Extremely low residual resistance experimentally obtained
![Page 12: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/12.jpg)
Lower CostOld vs. New Fabrication Methods
Hydroforming
Spinning
Half-Cells Ebeam Welding
![Page 13: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/13.jpg)
Better Material Control Methods Needed for 20,000 cavities
![Page 14: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/14.jpg)
1.8 meter 11.4 GHz
![Page 15: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/15.jpg)
J. Wang
1995
Eacc = 65-75 MV/m
![Page 16: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/16.jpg)
SLAC DS2 1.8 m long structure - Cell 8, Downstream Side AFTER RF
R. Kirby/SLAC
Sustainedspark
Individualsparks
![Page 17: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/17.jpg)
Pits are harmful to small irisG. Loew and J. Wang
![Page 18: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/18.jpg)
1.8 meter 11.4 GHz 1 meter TESLAStanding Wave
20 cm Standing Wave CavityVg ≈ 0%
3%
Vg = 3 - 5%
![Page 19: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/19.jpg)
Juicy R&D topics in physics of RF breakdown
• What is the trigger?
• field emission from microparticles? gas evolution from ion bomardment?
• How to keep the overall emission current low at operating gradient?
• How to get low spark rate ?
![Page 20: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/20.jpg)
Digital Video of Spark1 mm
![Page 21: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/21.jpg)
20 um
?
CERN Diamond Machined Copper cathode, HPR No intentional contaminants
Augerlater
![Page 22: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/22.jpg)
QuickTime™ and aDV - NTSC decompressor
are needed to see this picture.
Sustained Spark
![Page 23: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/23.jpg)
50 microns
20 microns
170 MV/m
SEM
![Page 24: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/24.jpg)
Electrons
Gas Distribution- starts by surface desorption-or melting of emitter tips- builds up by ion bombardment- may be ultimately dominated by cathode material
![Page 25: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/25.jpg)
Electrons Ions
Ions
50 microns
![Page 26: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/26.jpg)
2.25 RF Periods
Many Questions Remain
How does the plasma ball move around when fed with stored energy?
![Page 27: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/27.jpg)
Compare Nb/Cu with Bulk Nb
![Page 28: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/28.jpg)
Nb-3-Sn - Best Performance
![Page 29: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/29.jpg)
HTS - YBCOLow Field & High Field Surface
Resistance
![Page 30: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/30.jpg)
MgB2
![Page 31: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/31.jpg)
A Comparison of Superconductors @ 1 GHz
XMgB2 - estimate
R = 4 X 10-8
![Page 32: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/32.jpg)
Linac Cavity Input Coupler: TTF3
The TTF3 coupler
tested to 1.8 MW peak, 1.3 ms pulse length, 4.68 kW average power
(TW); coupling is adjustable from Qext = 106 to Qext = 2107
![Page 33: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/33.jpg)
NLC Couplers100 MW
Lots of sparking
near coupler cell
Is it the same?
![Page 34: R&D For Accelerating Structures H. Padamsee. TESLA Niobium, one meter length, rf = 1.3 GHz Copper, 53 cm, rf = 11.4 GHz](https://reader035.vdocument.in/reader035/viewer/2022062516/56649d785503460f94a5b806/html5/thumbnails/34.jpg)
The TTF4 coupler is supposed to be multipactor-free
Linac Cavity Input Coupler: TTF4