Integrable Optics Test Accelerator Sergei Nagaitsev Fermilab April 3, 2013

Integrable Optics Test Accelerator

Sergei NagaitsevFermilab

April 3, 2013

Background and History• In 2006, Fermilab was asked to lead the US ILC/SRF R&D Program

we felt that the most effective way to do that was to learn by doing

• Construction of Test Facility began in 2006 as part of ILC/SRF R&D and later American Recovery and Reinvestment Act (ARRA)

2S. Nagaitsev, PASI 2nd annual meeting, Apr. 3-5, 2013

• It was recognized early in the planning process that an electron beam meeting the ILC performance parameters was itself a power resource of interest to the wider Advanced Accelerator R&D (AARD) community

• The Facility was motivated by the goal of building, testing and operating a complete ILC RF unit to:

Develop and demonstrate industrial and laboratory capability for producing state-of-the-art SCL components, assemble into a fully functioning system (photo-injector, bunch compressor, three 1.3 GHz ILC CMs, beamlines to dumps)

To carry out full beam-based system tests with high-gradient cryomodules and demonstrate ILC beam quality

Background and History• In planning the construction we therefore wanted to ensure that the

facility offered something of enduring value when it was completed. Hence, the investment in establishing a flexible facility that would readily

support an AARD user program.• For those reasons the ARRA-funded facility construction

incorporated space for additional ILC cryomodules to increase the beam energy to 1.5 GeV, space for multiple high-energy beamlines, space for a small circular ring for the exploration of advanced concepts, capability of transporting laser light into and out of the accelerator enclosure, an adequately-sized control room

• To date, an investment of $74M has been made, including $18M of ARRA funding, representing ~80% completion of the facility

• In June 2012, anticipating the completion of the ILC R&D Program, Fermilab was directed to prepare a proposal for the AARD program.

Proposal submitted to the DOE in Feb 2013

3 S. Nagaitsev, PASI 2nd annual meeting, Apr. 3-5, 2013

Our Proposal


http://apc.fnal.gov/programs2/ASTA_TEMP/index.shtml

We proposed to establish a proposal-driven Accelerator R&D User Facility at Fermilab’s Advanced Superconducting Test Accelerator (ASTA)

To do that requires:1. Supporting the completion of ASTA in a phased approach:

Build out the linear accelerator to ~800 MeV with three Cryomodules • associated beam transport lines, dumps and support systems

Construct the Integrable Optics Test Accelerator (IOTA)• A small, flexible storage ring to investigate beam dynamics of importance to

intensity frontier rings In further phases

• Add proton capability to IOTA (by reusing existing HINS equipment)• Increase peak current of compressed electron bunches by installation of 3.9

GHz system

2. Supporting the Operation of an Accelerator R&D User Program Support staff required to operate a 9 month/year proposal-driven

Accelerator R&D program


Substantial Investments Have Already Been Made At ASTA

6 Tunnel extension: $4.5M

Beam Dumps: $2MMagnets and Power Supplies: $4M

S. Nagaitsev, PASI 2nd annual meeting, Apr. 3-5, 2013RF Power

Systems: $8MCryomodules: $15M


New Muon LabCMTF

New Muon Lab – home of ASTA, CMTF – home of PXIE

S. Nagaitsev, PASI 2nd annual meeting, Apr. 3-5, 20138

Facilities

ASTA : Schematically (at the end of Stage IV)


ASTA : Upstream part

• Shows 3 SCRF CMs (1st CM – at Stage I.2, 2 more – Stage II)


242‘ (74 m)

42‘ (13 m)

ASTA : Downstream part

• proton RFQ not pictured (Stage III)


230‘ (70 m)

76‘ (23 m)

Experimental Areas 1 & 2Parameter Value Range Unit Comments

Energy Exp A 1 50 5-50 MeV maximum determined by booster cavity gradients

Energy Exp A 2 820 50-820 MeV 1500 MeV with 6 cryomodules

Bunch charge 3.2 0.02-20 nC maximum determined by cathode QE and laser power

Bunch spacing 333 10-∞ ns laser power

Bunch train T 1 1 bunch ms maximum limited by modulator and klystron power

Train rep rate 5 0.1-5 Hz minimum may be determined by egun T-regulation and stability considerations

Emittance rms norm 5 <1 … >100 π m maximum limited by aperture and beam losses

Bunch length rms 1 0.01-10 ps min obtained with Ti:Sa laser; maximumobtained with laser pulse stacking

Peak current 3 >9 kA 3 kA with low energy bunch compressor; 9 kA possible with 3.9 GHz linearizing cavity


* 3.2nC × 3000 bunches × 5 Hz × 0.82 GeV = 40 kW

Experimental Area 3: IOTA

Parameter Value UnitCircumference 38.7 mBending dipole field 0.7 TRF voltage 50 kV

Electron beam energy 150 MeVNumber of electrons 2 109

Transv. emittance r.m.s. norm 2 π m

Proton beam energy 2.5 MeVProton beam momentum 70 MeV/cNumber of protons 8 1010

Transv. emittance r.m.s. norm 0.1-0.2 π m


ASTA Science ThrustsIntensity Frontier of Particle Physics• Nonlinear, integrable optics• Space-charge compensation

14

Energy Frontier of Particle Physics• Optical Stochastic Cooling• Advanced phase-space

manipulation• Flat beam-driven DWFA in slabs

Superconducting Accelerators for Science• Beam-based system tests with

high-gradient cryomodules• Long-range wakes• Ultra-stable operation of SCLs

Novel Radiation Sources• High-brightness x-ray channeling• Inverse Compton Gamma Ray

source

Stewardship and Applications• Generation and Manipulation

Ultra-Low Emittance Beams for Future Hard X-ray FELs

• XUV FEL Oscillator


Intensity Frontier• Proposal: Experimental demonstration of integrable

optics lattice at IOTA FNAL, SNS, JINR, Budker INP, BNL, JAI, U. of Colorado, U. of

Chicago

• Proposal: Space Charge Compensation in High Intensity Circular Accelerators

FNAL, support from CERN, BNL

• Experiments require the IOTA Ring Difficult to implement needed linear optics in existing facilities Lack of ring facilities in the US


A roadmap for high-intensity rings

1. Increase dynamic aperture of rings with strong sextupoles and octupoles

Single particle dynamics Also, addressed by the light-source community

2. Develop the theoretical basis of beam instabilities with strong space charge

3. Develop highly-nonlinear focusing lattices with reduced chaos

4. Reduce chaos in beam-beam effects

5. Ultimately, develop accelerators for super-high beam intensity

Self-consistent or compensated space-charge Strong non-linearity (for Landau damping) to suppress

instabilities Stable particle motion at large amplitudes


Addressed

by ASTA

Being

addressed

now


Integrable Optics at IOTA

• Main goals for studies with a pencil electron beam: Demonstrate a large tune spread of ~1 (with 4 lenses) without degradation of

dynamic aperture ( minimum 0.25 ) Quantify effects of a non-ideal lens and develop a practical lens (m- or e-lens)


ASTA : Downstream part (now)

beam dump

IOTA


Integrable Optics: Motivation• The main feature of all present accelerators – linear

focusing lattice: particles have nearly identical betatron frequencies (tunes) by design.

Hamiltonian has explicit time dependence All nonlinearities (both magnet imperfections and specially

introduced) are perturbations and make single particle motion unstable (non-integrable) due to resonant conditions

Stability depends on initial conditions

Regular trajectories for small amplitudes

Resonant islands (for larger amplitudes)

Chaos and loss of stability (for large amplitudes)


Does Focusing Need to be Linear?

• Are there “magic” nonlinearities with zero resonance strength?

• The answer is – yes (we call them “integrable”)• Search for a lattice design that is strongly nonlinear yet

stable Orlov (1963) -- attempt failed (non-integrable) McMillan (1967) – first successfull 1-D example Perevedentsev, Danilov (1990 - 1995) – several 1D, 2D examples Cary and colleagues (1994) – approximate integrability

• Our goal (with IOTA) is to create practical nonlinear accelerator focusing systems with a large frequency spread and stable particle motion.

Danilov, Nagaitsev, Phys. Rev. ST Accel. Beams 13, 084002 (2010)


Nonlinear Lenses

• “Integrable Optics” solutions: Make motion regular, limited and long-

term stable (usually involves additional “integrals of motion”)

• Can be Laplacian (with special magnets, no extra charge density involved)

• Or non-Laplacian (with externally created charge –e.g. special e-lens

or beam-beam

E(r) ~r/(1+r^2)

• Both types will be tested in IOTA


Concept: 2-m long

nonlinear magnet


A single nonlinear lens• A single 2-m long nonlinear lens creates a tune spread of ~0.25.

FMA, fractional tunes

Small amplitudes

(0.91, 0.59)

Large amplitudes

0.5 1.0

0.5

1.0

νx

νy


Sys

tem

: lin

ear

FO

FO

; 100

A;

linea

r K

V w

/ mis

mat

ch

Res

ult:

qui

ckly

dri

ves

test

-par

ticle

s in

to th

e ha

lo

500 passes; beam core (red contours) is mismatched; halo (blue dots) has 100x lower density

Space Charge Effects in Linear Optics LatticeTech-X simulationsdQ_sc ~ 0.7


Sys

tem

: oc

tupo

les;

100

A;

gene

raliz

ed K

V w

/ mis

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Res

ult:

non

linea

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cohe

renc

e su

ppre

sses

hal

o

500 passes; beam core (red contours) is mismatched; halo (blue dots) has 100x lower density

Integrable Optics Lattice with Space ChargedQ_sc ~ 0.7 Tech-X simulations


Space Charge CompensationBringing Protons to IOTA

• Allows tests of Integrable Optics with protons and realistic Space-Charge beam dynamics studies

• Allows Space-charge compensation experiments

~ 1 per one-turn injectionSCQ

2.5 MeV RFQ HINS


Space Charge Forces & Compensation

24

n

totpfSC

NrB

B=EZ, beam

direction

r, across the beam


Space-Charge Compensation in Circular Accelerators

• Goal: • Experimental demonstration of the space-charge

compensation technique with electron columns/electron lenses at dQ_sc >1

• Why ASTA: • Need 2.5 MeV high-current protons and IOTA – flexible

lattice storage ring

• Relevant accelerators: • All current and future high intensity proton rings (Booster,

MI, all LHC injectors, MC rings, etc)

Summary• ASTA offers:

A broad range in beam energies (50-800 MeV) High-repetition rate and the highest power beams available High beam quality and beam stability The brightest beams available Advanced phase-space manipulations (FB, EEX) Linacs and ring (IOTA), electrons and protons, lasers

• IOTA scientific goals are well aligned with Fermilab goals and investments in Intensity and Energy Frontiers

• ASTA is a great opportunity for collaboration, for post-docs and graduate students


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Integrable Optics Test Accelerator Sergei Nagaitsev Fermilab April 3, 2013