Bob Siemann, SLAC High Energy Physics Advisory Panel October 30, - - PowerPoint PPT Presentation

Bob Siemann, SLAC

High Energy Physics Advisory Panel October 30, 2000

• 1. Introduction
• 2. Advanced Accelerator Research at SLAC
• 3. Two-Beam Linear Collider

Concept, Research, and Future

• 4. Plasma Wakefield Experiments

Wakefield Accel., e+ & e- Dynamics, Center for Advanced Accelerator and Beam Physics

High Energy Physics Energy Frontier

The Livingston curve is the context

1,000 TeV 10,000 TeV 100,000 TeV 1,000,000 TeV 100 TeV 10 TeV 1 TeV 100 GeV 10 GeV 1 GeV 100 MeV 10 MeV 1 MeV 1930 1950 1970 Year of Commissioning 1990 2010

Particle Energy

Proton Storage Rings Colliders Proton Synchrotrons Electron Linacs Synchrocyclotrons Proton Linacs Cyclotrons Electron Synchrotrons Sector-Focused Cyclotrons Electrostatic Generators Rectifier Generators Betatrons Electron Positron Storage Ring Colliders Electron Proton Colliders Linear Colliders

A “Livingston plot” showing the evolution

• f accelerator laboratory energy from 1930

until 2005. Energy of colliders is plotted in terms of the laboratory energy of particles colliding with a proton at rest to reach the same center of mass energy.

SC RF or High Power RF, Linear Collider TeV Linear Collider Digital Signal Processing, Storage Ring PEP-II, KEK-B, DAPHNE SC RF, Storage Ring CESR, LEP SC Magnets, Storage Ring Tevatron, HERA, LHC Technology & Topology Accelerator

Today’s High Energy Physics Program

Exponential growth of ECM through accelerator physics and technology innovation has lead to

Many of the discoveries central to

• ur understanding of particle physics

Multi-TeV collisions

Advanced Accelerator Research at SLAC

Accelerator research and development has always been a major component of the SLAC program Advanced accelerator research at SLAC

High power microwave sources, components and linear accelerators Storage rings –SPEAR was not the first storage ring, but it was the

critical step in the evolution of the storage ring topology that is central to almost all of today’s experiments

Linear colliders – The SLC was the first and only operating linear collider.

It was an essential first step towards high energy e+e- collisions.

On the “R” side of R&D Research into “advanced” technologies and concepts that could provide

the next innovations needed by particle physics

“Advanced”

In many cases one is applying or extending physics and technology that

is its own discipline to acceleration – ex. plasma physics, digital signal processing

This interdisciplinary attracts a broad range of scientists that extends well

beyond classical accelerator physics

Advanced Accelerator Research at SLAC

Advanced accelerator R&D activities

3D electromagnetic calculations Final focus designs using a low

energy beam as a lens

High frequency RF High power RF pulse compression Laser driven structures Plasma acceleration Plasma focusing Pulsed heating as a gradient limit Two-beam acceleration

crossed laser beams electron beam

LEAP acceleration cell: Two Gaussian beams of 850 nm laser light cross at 1.4o to form the acceleration field. Electrons are injected between the prisms into the crossed laser field. Mm-wave sheet- beam klystron: Prototype fabricated by LIGA (deep X-ray lithography). The center of this 3.5” dia wafer is a 92 GHz, 1 MW klystron circuit. The surrounding features are for quality control and non-contact measure- ments. First

• bser-

vation

• f

focusing of e+: Measurement of plasma focusing

• f a 30 GeV

positron beam. 1.5×1010 e+ per pulse.

Two-Beam Linear Collider

• Offers high-gradient acceleration which scales to multi-

TeV energy and higher frequency.

• Basic idea is a transformer: Decelerate high-current, low-

energy beam, accelerate low-current, high-energy beam.

– Efficiently accelerate a low-energy, high-current beam. – Compress energy by multi-turn stacking in a ring. – Distribute beam pulses to high-gradient accelerator. – Decelerate Drive Beam and Accelerate Main Beam.

• Net effect: Map energy from a long-pulse accelerator to

different locations along the high-gradient linac. Allows the use of low-frequency, conventional RF technology for Drive Beam acceleration.

The Two-Beam Transformer Concept

Accelerator Structure Accelerator Structure Accelerator Structure Accelerator Structure

F Quad BPM

760 MW 760 MW

D Quad BPM

B P M Q u a d

MAIN LINAC

Two-Beam Module Layout

Two Beam Acceleration (TBA)

Drive Beam Deceleration (190 A, 1.3 GeV - 1.5 MV/m) Main Beam Acceleration (0.8 A, 8 GeV + 93 MV/m) DRIVE LINAC

Decelerator Structure Decelerator Structure

Schematic Layout of a Two-Beam Linear Collider

• The total pulse length of the Drive Beam Accelerator is set equal to the

twice the total length of the high gradient linac.

• The first half of the drive beam pulse is used for positrons while the

second half is used for the electrons.

• The configuration above uses recirculation to use fewer drive beam RF

sources but with longer length.

3-2000 8534A01

Combiner Rings IP Drive Beam Linac 350 MeV Decelerator Loop Decelerator Loop 3p/2 Arc 3p/2 Arc Injection Transport Drive Beam Recirculation Loop e– Main Linac 3p/2 Arc 2 GeV 2 GeV 4 GeV Damping Ring Injector Linac Scavenger Loop e+ e–

Issues and Studies

• Gradient and choice of RF frequency (SLAC/NLC).
• Efficient Drive-Beam Acceleration (CTF3).
• Drive-beam combiner/energy compression (CTF3).
• Deceleration and RF power production (CTF2, CTF3).
• Compatibility as an upgrade to conventional approach (SLAC)
• Energy Reach (SLAC)

– To upgrade energy, increase length of linac and drive-beam transport. – Drive Beam complex is the same, except for longer pulse length.

• Some of these issues can be addressed in a test facility.
• CERN is planning a test facility, CTF3, which will convert the

present LEP injector to a two-beam test facility.

Conversion of LPI to Two-Beam Test at CERN

• SLAC will contribute electron gun and injector design.

Energy Compression by interleaving bunches in a combiner ring

• The injection region uses matched RF deflectors to

interleave four bunches at the quarter points of the cycle

Intensity Initial pulse train 1 2 3 4 Final pulse train

• Extraordinarily high fields developed in beam

plasma interactions

• Many questions related to the applicability of

plasmas to high energy accelerators and colliders

• P. Catravas, S. Chattopadhyay, E. Esarey, W. Leemans

Lawrence Berkeley Laboratory

• R. Assmann, F.-J. Decker, R. Iverson, M. J. Hogan, R.H. Siemann, D. Walz, D. Whittum

Stanford Linear Accelerator Center

• B. Blue, C. E. Clayton, R. Hemker, C. Joshi, K. A. Marsh, W. B. Mori, S. Wang

University of California Los Angeles

• T. Katsouleas, S. Lee, P. Muggli

University of Southern California

• E-157: First experiment to study Plasma Wakefield

Acceleration (PWFA) of electrons over meter scale distances

• Physics for positron beam drivers qualitatively

different (suck-in vs. blow-out)

• E-162

Li Plasma 193 nm Ionization Laser

1.4 m

σ = 0.7 mm E = 30 GeV Streak Camera 2 × 1010 e- 12 m 0.1 - 4×1014 cm-3

Cherenkov Radiator

OTR Radiators

E-157 PWFA

UCLA

• 0.3
• 0.2
• 0.1

0.1 0.2 0.3

• 8
• 4

4 8

05190cec+m2.txt 8:26:53 PM 6/21/00

impulse model BPM data

θ (mrad) φ (mrad)

plasma gas beam Blowout region Ion channel

laser θ

φ

• 1. Electron Beam Refraction

at the Gas–Plasma Boundary

50 100 150 200 250 300

• 2

2 4 6 8 10 12

σX DS OTR (µm) K*L∝ne

1/2

σ0 uv Pellicle=43 µm εN=9×10-5 (m rad) β0=1.15m

• 2. Transverse Wakefields

and Mismatched Beam

• Betatron Oscillations

Energy or Spot Size [a.u.]

• 10
• 5

5 10

• 100
• 50

50 100 150 200 Mean Energy Change [MeV] TextEnd Time Relative to the Center of the Bunch [ps] Energy difference with respecct to plasma OFF run TA06010ce.mat

TA06010ca.mat

Slice energy (MeV) Slice time (ps)

Head Tail

~ E(t) x(t)

Time [a.u.]

• 3. Longitudinal Wakefields
• Core De-acceleration and

Tail Acceleration

Three Highlights!

Impulse Model Data

E-157 PWFA

UCLA

• Run 1: A First Look at Positron Propagation in Long Homogeneous and Hollow Plasmas.
• Use working E-157 apparatus
• Positrons in homogeneous and hollow plasmas
• Transverse dynamics (time integrated & time resolved) in the “suck-in” regime
• Run 2: High Resolution Energy Gain Measurements of Positrons
• Move to new location in FFTB to build true imaging spectrometer
• Positrons in homogeneous and hollow plasmas
• Detailed structure of longitudinal wakes (acceleration)
• Run 3: High Resolution Energy Gain Measurements of Electrons
• Electrons in homogeneous and hollow plasmas
• Matched beam propagation in a long plasma
• Higher resolution acceleration measurements

Experimental Program E-162 e+ & e- Dynamics in PWFA

UCLA

UCLA, USC, Stanford Pre-proposal to NSF for a Physics Frontiers Center

Principal Investigators

• R. Byer, Stanford Applied Physics
• C. Joshi, UCLA Electrical Engineering
• T. Katsouleas, USC Electrical Engineering
• W. Mori, UCLA Physics & Electrical Engineering
• J. Rosenzweig, UCLA Physics
• R. Siemann, SLAC & Stanford Applied Physics

The Center

PI’s with diverse experience in plasmas, lasers, particle sources, RF,

computer simulation & classical accelerator physics. Committed to making the Center a major part of their research activities.

SLAC would host the Center and make unique facilities including the FFTB

and NLCTA available. This leverages the investment in the Center.

Center for Advanced Accelerator and Beam Physics

UCLA

• Based on the NLCTA (NLC Test Accelerator) -

300 MeV, 11.4 GHz linac with a ~ 200 nsec long beam with X-band bunches

• Low Energy Hall for experiments with ~50 MeV

beam available most of the time

• High Energy Hall for experiments with ~300

MeV beam that would have to be scheduled together with NLC RF development

• New injector - A single bunch, RF gun
• Two laser rooms for RF gun laser and

experimental laser

The Center’s Program

Begin with plasma acceleration experiments at the FFTB & high brightness

electron source physics.

In parallel, add experimental halls and lasers to the NLCTA complex. The

resultant ORION facility would be designed for rapid turn-around of experiments through shared diagnostics, layout, etc.

ORION would support a wide-ranging program in plasma, laser driven, RF

acceleration.

Computer modeling is an integral part of the Center

ORION

Center for Advanced Accelerator and Beam Physics

UCLA