Superconducting radiofrequency accelerating structures
Download
1 / 71

Superconducting Radiofrequency Accelerating Structures - PowerPoint PPT Presentation


  • 123 Views
  • Uploaded on

Superconducting Radiofrequency Accelerating Structures. Lutz Lilje DESY -MPY- ‘Physics at the Terascale’ 406. WE-Heraeus-Seminar Bad Honnef 30.4.2008. Acknowledgement. Several people were supporting with viewgraphs etc. H. Hayano KEK H. Padamsee Cornell

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Superconducting Radiofrequency Accelerating Structures' - saima


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Superconducting radiofrequency accelerating structures

Superconducting Radiofrequency Accelerating Structures

Lutz Lilje

DESY -MPY-

‘Physics at the Terascale’

406. WE-Heraeus-Seminar

Bad Honnef

30.4.2008


Acknowledgement
Acknowledgement

  • Several people were supporting with viewgraphs etc.

    • H. Hayano KEK

    • H. Padamsee Cornell

    • J. Sekutowicz, D. Reschke, W. Singer DESY

Lutz Lilje DESY -MPY-


References
References

  • Superconducting RF

    • RF Superconductivity for Accelerators, H. Padamsee, J. Knobloch, and T. Hays, John Wiley & Sons, 1998.

    • The Superconducting TESLA Cavities, B. Aune et al., PRST-AB, 3, September 2000, 092001.

  • SRF Workshop Tutorials

    • http://www.lns.cornell.edu/public/SRF2005/program.html

    • http://www.pku.edu.cn/academic/srf2007/program.html#tutorial

  • Accelerators

    • XFEL: http://xfel.desy.de/tdr/tdr/index_eng.html

    • ILC: http://www.linearcollider.org/cms/

Lutz Lilje DESY -MPY-


Outline
Outline

  • Superconducting Radiofrequency Accelerating Sturctures (‘SRF Cavities‘)

    • History

    • Properties

    • Technology

  • Example for Accelerator Systems

    • XFEL and ILC

Lutz Lilje DESY -MPY-


1. Introduction and History

Milestones that led to accelerators based on SRF

Superconductivity

RF Acceleration

1924: Gustaf Ising (Sweden)

The First Publication on the RF Acceleration, Arkiv för Matematik, Astronomi och Fysik,18 (1924) 1-4.

1908: Heike Kamerlingh Onnes (Holland)

Liquefied Helium.

1911: Heike Kamerlingh Onnes

Discovered Superconductivity.

1928: Rolf Wideröe (Norway, Germany)

Built the first RF Accelerator.

Arch. für Elektrotechnik 21 (1928),387-406.

1928-34: Walther Meissner (Germany)

Discovered Superconductivity of Ta, V, Ti and Nb.

1930: Russell and Sigurd Varian (USA)

Invented Klystron.

1947: Luis Alvarez (USA)

Built first DTL (32 MeV protons).

1947: W. Hansen (USA)

Built first 6 MeV e-accelerator, Mark I (TW-structure).

J. Sekutowicz, SRF2007 Beijing

Lutz Lilje DESY -MPY-


1. Introduction and History

Superconductivity

RF Acceleration

1961: Bill Fairbank (Stanford Univ.) presented the first proposal for a superconducting accelerator.

1964: Bill Fairbank, Alan Schwettman and Perry Wilson (Stanford University)

First acceleration of electrons with sc lead cavity.

1967: John Turneaure (Stanford University)

Epeak =70 MV/m and Q~1010 in 8.5 GHz cavity !!

1968-1981: Mike McAshan, Alan Schwettman, Todd Smith, John Turneaure and Perry Wilson (Stanford University)

Development and Construction of the Superconducting Accelerator SCA.

J. Sekutowicz, SRF2007 Beijing

Lutz Lilje DESY -MPY-


Why superconducting cavities
Why Superconducting Cavities?

  • Superconducting cavities offer

    • a surface resistance which is six orders of magnitude lower than normal conductors (NC)

    • high efficiency

      • even when cooling is included

    • low frequency, large aperture

      • smaller wake-field effects

    • high accelerating gradients

      • Theoretical limit for the between 45-55 MV/m depending on the cavity geometry

Lutz Lilje DESY -MPY-


Sns spallation neutron source
SNS (Spallation Neutron Source)

Beta = 0.8

800 MHz

Beta = 0.6

Lutz Lilje DESY -MPY-


Rare isotope seperator

58 MHz

117 MHz

Rare Isotope Seperator

350 MHz

175 MHz

700 MHz

700 MHz

Lutz Lilje DESY -MPY-


Accelerator facilities with scrf cavities number of cavities total active length
Accelerator Facilities with SCRF CavitiesNumber of cavities/total active length

1. Introduction and History

Dismantled Facilities

Operating Facilities

  • SCA 4 28m

  • S-DALINAC 10 10m

  • CESR 4 1.2 m

  • CEBAF 320 160m

  • KEK B-Factory 8 2.4m

  • Taiwan LS 1+1 0.3m

  • Canadian LS 1+1 0.3m

  • DIAMOND 3 0.9m

  • SOLEIL 4 1.7m

  • FLASH / TTF 48 50m

  • SNS 81 65m

  • JLab-FEL 24 14m

  • LHC 16 6m

  • ELBE 6 6m

  • TRISTAN 32 49m

  • LEP 288 490m

  • HERA 16 19m

J. Sekutowicz, SRF2007 Beijing

Lutz Lilje DESY -MPY-


Livingston plot for srf cavities courtesy h padamsee
Livingston plot for SRF cavitiesCourtesy H. Padamsee

Total >1000 meters

> 5 GV

Nb/Cu Technology

Lutz Lilje DESY -MPY-


High luminosity rings cesr
High luminosity rings (CESR)

• Low Impedance Shape

• Beam Power > 270kW

Lutz Lilje DESY -MPY-


LHC

400 MHz

16 Nb/Cu Cavities

Lutz Lilje DESY -MPY-


Niobium bulk cavities
Niobium bulk cavities

CERN 350 MHz

TESLA 1,3 GHz

Darmstadt 3GHz

Lutz Lilje DESY -MPY-


Accelerator Facilities with SCRF Cavities IINumber of cavities/total active length

1. Introduction and History

Tomorrow Facilities

Day after Tomorrow Facilities

  • CEBAF-12GeV 400 216m

  • SNS-upgrade 117 98m

  • XFEL 800 832m

  • ERL-Cornell 310 250m

  • BESSY 144152m

  • 4GLS ~40 ~42m

  • RHIC-cooling 4 4 m

  • Shanghai LS…….

  • BEPC II 2 0.6m

  • RIA option 180 122m

  • X-Ray MIT option 176 184m

  • LUX ~40 ~50m)

  • FERMI Proton Linac 384 370m

  • ERHIC………

  • ELIC …..

  • ARC-EN-CIEL 48 50m

  • ILC ~15764 ~16395m

J. Sekutowicz, SRF2007 Beijing

Lutz Lilje DESY -MPY-



Ilc layout
ILC Layout

e+ production

e- e+ damping rings

e- source+ pre-acceleration

e+ pre-acceleration

target

e- transport line

e+ transport line

undulator

2-stage bunch compression

e+ main linac

e- main linac

2-stage bunch compression

e- beam dump

e+ beam dump

IP and 2 moveable detectors

Total length: ~31 km

Global Design Effort


Outline1
Outline

  • Superconducting Radiofrequency Accelerating Sturctures (‘SCRF Cavities‘)

    • History

    • Properties

    • Technology

  • Example for Accelerator Systems

    • XFEL and ILC

Lutz Lilje DESY -MPY-


Properties of cavities
Properties of Cavities

Example: cylindrically symetric cavity - Pillbox

with

J0, J1 Besselfunctions

Frequency:

Stored Energy:

Dissipated power:

Quality factor:

Geometry factor:

Lutz Lilje DESY -MPY-


Field distributions in cavities

Electric Field (Pillbox):

Field Distributions in Cavities

TM010 : accelerating mode

L (side view)

Magnetic Field :

Other modes : e.g. deflecting modes

D (front view)

Lutz Lilje DESY -MPY-


Field distributions in cavities1
Field Distributions in Cavities

Elliptical cavity:

Numerical solution for surface fields:

Relations for the surface fields to acclerating gradient:

Epeak/Eacc = 1,98 minimize this to reduce field emission

Bpeak/Eacc = 4,17 [mT]/[MV/m] minimize because of maximum critical

field of the superconductor

Lutz Lilje DESY -MPY-


Why superconducting cavities1
Why Superconducting Cavities?

  • SC cavities offer

    • a surface resistance which is six orders of magnitude lower than normal conductors (NC)

    • high efficiency

      • even when cooling is included

    • low frequency, large aperture

      • smaller wake-field effects

    • high accelerating gradients

      • Theoretical limit for the between 45-55 MV/m depending on the cavity geometry

Lutz Lilje DESY -MPY-


Enter superconductivity pure elements

Superconductor (Blue) / Superconductor under pressure (Light Blue)

From: SUPERCONDUCTING MATERIALS – A TOPICAL OVERVIEW, R. Hott et al. FZK

Enter Superconductivity: Pure Elements

Lutz Lilje DESY -MPY-


Enter superconductivity pure elements1

Superconductor (Blue) / Superconductor under pressure (Light Blue)

From: SUPERCONDUCTING MATERIALS – A TOPICAL OVERVIEW, R. Hott et al. FZK

Enter Superconductivity: Pure Elements

Lutz Lilje DESY -MPY-


Critical magnetic field for the rf case
Critical magnetic field for the RF case

  • RF field at 1,3 GHz is ‘ON’ for less than 10-9 s

  • If there are no nucleation centers (surface defects...) the penetration of the magnetic field can be delayed. Superheating!

Superheating fields:

Niobium properties:

 Theoretical accelerating field limits

What is really the fundamental limit for RF cavities?

}

Lutz Lilje DESY -MPY-


Rf superconductivity
RF superconductivity

  • The superconducting Cooper pairs have inertia.

  • Therefore the unpaired normalconducting ‘feel’ also a part of the electromagnetic RF fields.

     Superconductors have for temperatures T>0 K a surface resistance!

Lutz Lilje DESY -MPY-


Electric conductivity and surface resistance
Electric conductivity and Surface resistance

Surface resistance in two-fluid model (analogous to skin depth):

  • Resistance depends

    • strongly on the temperature, we need 2 K

    • quadratically on frequency: Limit for 3 GHz would be 30 MV/m.

    • on the mean free path, what purity do we need?

Surface resistance for superconductors in BCS theory:

Effective penetration depth:

Lutz Lilje DESY -MPY-


Surface resistance r s

Geometry factor:

G = 270 Ohm

Surface resistance:

Surface resistance Rs

RBCS(T)

700 nOhm @ 4,2K

RRES

~10 nOhm @ 2K

Lutz Lilje DESY -MPY-


Flux penetration into a superconductor
Flux penetration into a superconductor

Electron holography is used to make magnetic fluxons visible (Tonomura et al.)

Fluxons stick to defects !

This is good for magnets, but bad for cavities.

Lutz Lilje DESY -MPY-


Surface resistance and accelerating gradient
Surface resistance and accelerating gradient

  • One usually measures the Q(Eacc) curve:

    • Q0~(1/ Rsurf)

    • Quality factor will tell you how much you have to pay for the cooling power

    • Depends on the accelerating gradient e.g. field emission

    • Helps to understand the loss mechanisms especially is supported by temperature mapping

Lutz Lilje DESY -MPY-


Surface resistance and accelerating gradient1
Surface resistance and accelerating gradient

Test temperature: 1,6 K

Test temperature: 2K

XFEL

ILC

One-cell cavities

Lutz Lilje DESY -MPY-


Outline2
Outline

  • Superconducting Radiofrequency Accelerating Sturctures (‘SCRF Cavities‘)

    • History

    • Properties

    • Technology

      • Limitations and Remedies

  • Example for Accelerator Systems

    • XFEL and ILC

Lutz Lilje DESY -MPY-


Temperature mapping system
Temperature Mapping System

  • Example of a Temperature mapping:

  • the picture shows a Mercator projection of a single-cell cavity

  • strong localised heating spot on the equator

  • another band of heating around the equator in the high magnetic field (high current) region

Lutz Lilje DESY -MPY-


Example of a material defect
Example Of A Material Defect

Defect found with X-ray technique: Tantalum

Heating on the outside surface measured with carbon resistors

Lutz Lilje DESY -MPY-


Quality control of nb for cavities
Quality Control Of Nb For Cavities

  • Eddy current scanning of all sheets

    • measures change of electric resistance

    • 0.5mm depth, 40 μm defect dia. sensitivity

    • rejection rate of sheets about 5 %

  • SQUID scanning under development

  • Some special investigations are possible on demand

    • x-ray radiography (defect visualization)

    • x-ray fluorescence (defect element determination)

    • neutron activation (Ta distribution)

Lutz Lilje DESY -MPY-


Eddy current scanning
Eddy Current Scanning

  • Large tantalum inclusions (~200 mm) and places with irregular patterns from surface preparation (grinding)

Grinding mark

Lutz Lilje DESY -MPY-


Result of eddy current scanning a Nb disc, dia. 265 mm

Real and imaginary part

of conductivity at defect,

typical Fe signal

Global view, rolling marks

and defect areas can be seen

Lutz Lilje DESY -MPY-


Principal arrangement of SQUID scanning

Measured response from the back side of the sheet

Nb test sheet with .1mm Ta inclusions

Lutz Lilje DESY -MPY-


High resolution optical inspection
High-Resolution Optical Inspection

  • New development by japanese colleagues to reduce reflections

    • Improved lighting technique using flat electro-luminescense strips

    • Damping of vibrations

  • Resolution down to a few micrometer!

Lutz Lilje DESY -MPY-


Courtesy Kyoto University / KEK

Lutz Lilje DESY -MPY-


AC80: cat’s eye

@cell#5_equator

100μm

Courtesy Kyoto University / KEK

1mm

Lutz Lilje DESY -MPY-


Electron effects field emission
Electron Effects:Field Emission

  • Emission of e- from cavity surface in presence of high surface E-fields

  • Emitted e- impacts elsewhere on cavity surface, heating the surface and increase Rs

  • Limits the achievable Eacc in cavity

  • Primary limitation over past 5-10 years

    • Strongly related to the cavity handling

    • Very clean surface preparation and handling are needed

      • This is by no means trivial!

        • Especially for multi-cell cavities

      • On-going effort needed in quality control

Lutz Lilje DESY -MPY-


Field emission
Field Emission

Pictures taken from: H. Padamsee, Supercond. Sci. Technol., 14 (2001), R28 –R51

Particle causing field emission

Temperature map of a field emitter

Simulation of electron trajectories in a cavity

Lutz Lilje DESY -MPY-


Cleanroom Technology for SC Cavities

  • the small surface resistance of the superconducting necessitates avoidance of NC contaminations larger than a few mm

    • detailed material specification and quality control need to be done

    • tight specification for fabrication e.g. welds have to be implemented

    • clean room technology is a must (e.g. QC with particle counts, monitoring of water quality, documentation of processes)

The inter-cavity connection is done in class 10 cleanrooms

Lutz Lilje DESY -MPY-


State of the art multi cell accelerating structures for xfel and ilc
State-of-the-Art:Multi-cell Accelerating structures for XFEL and ILC

XFEL

ILC

Lutz Lilje DESY -MPY-


Outline3
Outline

  • Superconducting Radiofrequency Accelerating Sturctures (‘SCRF Cavities‘)

    • History

    • Properties

    • Technology

      • Limitations and Remedies

  • Example for Accelerator Systems

    • XFEL and ILC

Lutz Lilje DESY -MPY-


Properties of xfel radiation
Properties of XFEL radiation

  • X-ray FEL radiation (0.2 - 14.4 keV)

    • ultrashort pulse duration <100 fs (rms)

    • extreme pulse intensities 1012-1014 ph

    • coherent radiation x109

    • average brilliance x104

  • Spontaneous radiation (20-100 keV)

    • ultrashort pulse duration <100 fs (rms)

    • high brilliance

spontaneous

radiation




After construction computer simulation
… after construction (computer simulation)

Building Phase 1


Xfel international project organization

  • XFEL Steering Committee ISC(Chair: J. Wood, UK)

  • Representatives of all countries intending to contribute to the XFEL facility

  • 13 countries have signed MoU (project preparation phase) in 2004

  • Nomination of European Project Team (Leader: Massimo Altarelli)

WG on Scientific and Technical issues STI(chair: F. Sette, ESRF)

WG on Administrative and Funding issuesAFI(chair: H.F. Wagner, Germany)

XFEL International Project Organization

Bi-lateral negotiations between Germany and signature countries on funding contributions are ongoing


Xfel principle schedule
XFEL Principle Schedule

2012/13

2014/15

2004

2006

preparation

construction

beam operation

2009: LCLS start operation (SLAC)

SASE1

SASE2+3,

project

start

spont. rad

industrialization of all Linac sub-systems

production

commissioning

acceptance test and installation

FLASH FLASH FLASH operation experience XFEL XFEL XFEL


Xfel tunnel
XFEL Tunnel

The XFEL tunnel layout was developed in several iterations.

A mockup is currently under construction.

Installation procedures

are under

study.


Distribution of workload
Distribution of Workload

  • Accelerator technology was and is a collaborative effort

    • Build on TESLA Collaboration

    • Some R&D support for from EU FP6 programs

      • E.g. CARE, EUROFEL, EUROTeV

  • Common In-Kind Proposal for XFEL cold linac by several labs


Accelerator technology collaborative effort
Accelerator Technology:Collaborative Effort

Length quantized n/2 (possibility of ERL)

Industrial study module assembly (M6 done, M8 autumn 2007)

Superferric magnet (CIEMAT)

BPM (Saclay)

2 more cryostats (TTF3/INFN) delivered

Integrated HOM absorber

TTF3-type coupler

Industrialization launched (Orsay)

Tuner w/piezo (Saclay)

LLRF development (collab. Warsaw/Lodz)


Xfel accelerator module cryomodule
XFEL Accelerator Module (Cryomodule)

2 K return

70 K shield

2.2 K forward

magnet current feedthrough

5 K forward

80 K return

40 K forward

8 K return

4 K shield

RF main coupler

2 K 2-phase

cavity



Outline4
Outline

  • Superconducting Radiofrequency Accelerating Sturctures (‘SCRF Cavities‘)

    • History

    • Properties

    • Technology

      • Limitations and Remedies

  • Example for Accelerator Systems

    • XFEL and ILC

Lutz Lilje DESY -MPY-


Ilc layout1
ILC Layout

e+ production

e- e+ damping rings

e- source+ pre-acceleration

e+ pre-acceleration

target

e- transport line

e+ transport line

undulator

2-stage bunch compression

e+ main linac

e- main linac

2-stage bunch compression

e- beam dump

e+ beam dump

IP and 2 moveable detectors

Total length: ~31 km

Global Design Effort


Main linac layout
Main Linac Layout

  • Length ~11 km x 2

  • Average gradient 31.5 MV/m

  • 2 tunnels diameter 4.5 m

Penetrations:

Cable & Plumbing

Waveguide

LLRF, Controls,

Protection Racks

Charger

Main Modulator

HV Pulse Transformer

Horizontal Klystron

LCW Chiller

AC Switchgear

Waveguide Distribution

System

Dwg: J. Liebfritz

Global Design Effort


State of the art multi cell accelerating structures for xfel and ilc1
State-of-the-Art:Multi-cell Accelerating structures for XFEL and ILC

XFEL

ILC

Lutz Lilje DESY -MPY-


Alternative developments for ilc
Alternative Developments for ILC

  • Cost reduction is a strong driving force for ILC

    • ~16000 cavities

  • New Material

    • Large-grain niobium Material

    • Less fabrication steps than standard material

  • New Shapes

    • ‘Low-loss‘ and ‘Re-entrant‘

    • Could reduce power dissipation at cryogenic temperatures

Global Design Effort


Large grain material jlab
Large Grain Material (JLab)

Global Design Effort


Xfel large grain multi cell with ep
XFEL: Large Grain Multi-cell with EP

Large-grain niobium material with etch (BCP) and electropolishing (EP)

Behaviour similar to DESY observations on single-cells

Global Design Effort


Alternative cavity shapes
Alternative Cavity Shapes

Global Design Effort


K. Saito et al.

Global Design Effort


60mm aperture re entrant cavity best eacc 59 mv m cornell kek collaboration
60mm-Aperture Re-Entrant CavityBest Eacc = 59 MV/mCornell-KEK Collaboration

H. Padamsee et al. WEPMS009

Global Design Effort


Summary and outlook
Summary and Outlook

  • Superconducting accelerating structures have become a standard tool in particle accelerators

    • High efficiency and high accelerating gradients are available

  • Technology for superconducting cavities is challenging

    • High gradients necessitate very small level of contamination

    • Quality control is key to good performance

  • XFEL will be an important stepping stone for ILC

    • Technology is fully transferable

    • Industrialization experience is very valuable

  • ILC Gradients have been achieved in several multi-cell cavities already

Lutz Lilje DESY -MPY-


Backup
Backup

Lutz Lilje DESY -MPY-


Xfel accelerator module cryomodule1
XFEL Accelerator Module (Cryomodule)

module to module connection

cold mass with cavities, magnet / BPM, HOM abs. beam pipe, valve

module end group

manual valve

beam position monitor

magnet package


Main linac rf unit overview
Main Linac RF Unit Overview

  • Bouncer type modulator

  • Multibeam klystron (10 MW, 1.6 ms)

  • 3 Cryostats (9+8+9 = 26 cavities)

  • 1 Quadrupole at the center

Global Design Effort


ad