S TA N F O R D L I N E A R AC C E L E R ATO R C E N T E R Presented at Lepton Photon 2001, Rome, Italy

World-wide high-energy physics research will require a TeV-scale linear e+e– collider. Physics in such a TeV-scale center-of-mass-energy linear e+e– collider would complement the LHC now under construction at CERN. SLAC, FNAL, LBNL and LLNL in the United States have formed a collaboration to perform R&D toward the development of a 1-TeV-scale next-generation linear electron-positron collider. The R&D effort is supported on the international front through the SLAC-KEK research collaboration in which LLNL and LBNL also participate and collaborations with institutions in North America and Europe. Experience in building and operating the Stanford Linear Collider (SLC) forms a solid basis for the development process. New technologies, especially final beam size attainment, X-band structures, and improved rf delivery systems have been integrated into full-scale test facilities. The Next Linear Collider Test Accelerator and ASSET facility at SLAC, together with the Accelerator Test Facility at KEK provide the opportunities to validate new technology development needed to ensure the technological success of such a linear collider.

RF POWER DELIVERY AND DISTRIBUTIONRF POWER DELIVERY AND DISTRIBUTION

The technology for the NLC is based on warm copper structures, 75 MW X-band klystrons driven in groups of 8 by solid-state modulators, and permanent magnet arrays to focus the beams.

The goal of the NLC is to reach center-of-mass energies of 500 GeV to 1 TeV and above, an order of magnitude higher than achieved by SLC. Four major components make up the rf system: modulators, klystrons, pulse compression systems and accelerator structures. For NLC the modulator is an IGBT-switched induction design, a development of LLNL, Bechtel-Nevada and SLAC, using state-of-the-art solid-state technology. The klystrons are 75 MW PPM focus with a 3 µs flattop, structures are X-band, warm copper that are damped and detuned at an unloaded gradient of 70 MV/m, and rf pulse compression is achieved with a DLDS two-mode system. Components are undergoing tests at NLCTA and ASSET.

New collimation schemes are under study. Among these are consumable collimators with jaws that can be moved to a new position after damage, and repairable collimators that use jaws of liquid metal or similar technology that can be repaired continuously during operation. Although more speculative than consumable collimators, the initial prototype tests are very promising.

Permanent magnets have the advantage of requiring no operating power, and they may be less expensive than the electromagnets originally used in the NLC design. Work on these is a joint Fermilab-SLAC-LBNL program. A photograph of an experimental quadrupole is shown. Initial magnet tests have been encouraging.

NLCNLCU.S. Next Linear Collider Collaboration

LAWRENCE BERKELEYNATIONAL LABORATORYFERMI NATIONAL LABORATORY LAWRENCE LIVERMORE NATIONAL LABORATORY

~100 m

Electron Main Linac250-500 GeV (X)

Positron Main Linac250-500 GeV (X)

5 km

e+ Target

2 GeV (L)Pre-DampingRing (UHF)

DampingRing

(UHF)

DampingRing

(UHF)

2 GeV (S)

136 MeV (L)

6 GeV (S)

~100 m 0.6 GeV (X)

0.6 GeV (X)

Pre-Linac 6 GeV (S)

Pre-Linac6 GeV (S)

136 MeV (L)

6-20018602A85

e–

e–

Low EnergyIR (90-500 GeV) High Energy IR

(250 GeV to multi-TeV)

FinalFocus

FinalFocus

~20 m

~20 m

Dump

Dump

Compressor

Compressor

30 km

Compressor

Compressor

e+

e+

e–

Injector Systemfor 1.5 TeV

Bypass Lines50, 150, 250 GeV

Length for500 GeV/Beam

DampingManifold

Beam

To Manifold RFBPM Electronics

6-20018602A86

2

4

6

8

10

30

100 1000Energy (GeV)

Lum

inos

ity (

1033

cm

–2 s

ec –

1 )

LEIR

HEIR

6-20018602A95

This layout view shows the next-generation linear collider with a high-energy interaction region at cms values over 1 TeV and a low-energy interaction region at cms levels to ~500 GeV.

The graph shows luminosity vs energy for the high and low energy Interaction Regions.

(8)

TE01 / TE12

TE01 / TE12

TE01 / TE12

(1)

. . .

(3)

. . .

(4)

. . .

(2)

. . .

(5)

. . .

(7)

. . . . . .

(6)

. . .

TE01

TE01

TE01

TE01

Beam DirectionAccelerator Structures

Extractor

Tap-Offs

ConverterTaper

Low-Loss Circular Delay Line

Klystron8-PackTE11/TE12

Converter

Solid StateModulator

8-WayCombiner/Launcher

6-20018602A77

6-20018602A33

3 µsec

1100 Amps

75 kV

1) 10 kV/Div. 500 nSec2) 200 A/Div. 500 nSec

FromKlystrons

To Delay Lines

Local Feed

Dual-ModedTransfer Lines

6-20018602A75

COLLIMATION AND FINAL FOCUSCOLLIMATION AND FINAL FOCUS

PERMANENT MAGNETSPERMANENT MAGNETS

Consumable Collimator

Repairable Collimator

Repairable Collimator

Damaged Area

DamagedArea

HeatCool Cool

MoltenMetal

Beam FinishingRoller

New Surface

Low MeltingEutectic

MainRoller

Consumable Collimator

http://www-project.slac.stanford.edu/lc/nlc.html