The Accelerator Test Facility and Optical Stochastic Cooling

R&D

HEPAP AARD Sub panelVitaly Yakimenko

Brookhaven National Laboratory

February 15, 2006

BNL Accelerator Test Facility -

ATF

The ATF is a proposal-driven, advisory committee reviewed USER FACILITY for long-term R&D into the Physics of Beams.

The ATF serves the whole community: National Labs, universities, industry and international collaborations.

ATF contributes to Education in Beam Physics. (~2 PhD / year)

In-house R&D on photoinjectors, lasers, diagnostics, computer control and more (~3 Phys. Rev. X / year)

Support from HEP and BES.

The ATF features: High brightness electron

gun 75 Mev Linac High power lasers beam-

synchronized at the picosec level (TW level CO2 laser)

4 beam lines + controls

Main facility results/directions:

1. High brightness injectors: 2. Electron beam diagnostics3. Development of a picoseconds

Terawatt CO2 laser4. Generation of the short bunches on all

scales5. Experimental demonstration of various

advanced acceleration techniques6. Free Electron Laser experiments

Facility (concept, developments and name are copied) 24 PhD students graduated

Why we need better emittance

ICAIFEL

ThomsonX-ray source

HGHG

1995 1998 2001 2004

STELLA

5 m

2 m

1 m

0.5 m

VISA

Dielectric WFA

Smith Purcell

experiment

First 1.6 cell gun

Microbunching

Mg cathode Mg cathode

Gun IV

SASE @1m

Plasma WFA

Design of the 1.6 cell gun is adopted in more then a dozen facilities

To match FEL or accelerating optical and electron beams; or to transport through small (high frequency) accelerating channel

ATF Terawatt CO2 Laser Story (past and present)

InverseCherenkovaccelerator IFEL

accelerator

ThomsonX-ray source

HGHG

1995 2000 2005 2010

STELLA

EUV source

Ion andProtonsource

ResonantPWA

SeededLWFA

LACARAPASER

3 TW

300 GW

30 GW

3 GW

Nonlinear Thomsonscattering

Near-term plan (2-3 year scale)• Multi-bunch plasma wake field acceleration

experiments to demonstrate a high transformer ratio and a mono-energetic accelerated e-beam.

• Generation of ion, neutron, and proton beams with MeV energies from a foil and gas jet with a multi-Terawatt CO2 laser.

• Upgrade of the CO2 laser to the 20TW level and experimental studies of advanced accelerators and radiation sources in a strong-field relativistic regime.

• Operation and characterization of a visible SASE FEL in the amplifier regime.

• Continued improvement of electron beam brightness utilizing a photoinjector laser upgrade, advances in beam diagnostics and beam compression.

ATF Budget Analysis: FY03/07 ($K)PROJECT FY03 FY04 FY05 FY06(cur) FY07(proj)ATF Ops $1,680$1,800$1,800$1800 $1,990ATF Equ $200 $200 $200 $200 $220ATF (BES) $500 $500 $500 $500 $500

Totals: $2,380$2,500$2,500$2,500 $2,710

ATF is supported by•LDRD at different levels from its formation (currently 120K$/year) •HEP DOE from 1991 (directly)•BES DOE from 1991 (indirectly) from 2002 (directly)

ATF continues to be staffed at the critically low level: Recent reduction in the scientific personnel by 2 has negatively affected facility efficiency.

Increase in staff is needed to improve support of experiments, increase run time and make users programs more efficient.

ATF Org. chartDOE BES

B. Gibbs, ALD –(Contact)

S. DawsonChair, Physics Department

V. YakimenkoDirector ATF, Accelerator

External program committeeS. Chattopadhyay, Chair

M. WoodleEngineer Mechanical

M. MontemagnoEngineer Electrical

I. Pogorelsky, Physicist, Laser

I. PavlishinEngineer,

Laser

D. DavisTechnician

Mech./Laser

M. BabzienEngineer,

Laser

K. KuscheEngineer,

Safety

DOE HE,S. Aronson, ALD – (Contact)

R. MaloneSr. Tech. Architect

Computer Control

K. BergesenSoftware designer

A. Karostoshevsky,Mechanical designer

K. TuohyGroup Secretary

D. StolyarovResearch Associate,

Laser

T. CorwinTechnician

Electr./Mech.

R. PalmerATF Program Director

Story of one short experiment …Beam break up was noticed during beam compression studies by UCLA.

Beam before final compression Beam after final compression

EE~100 fs ~1 ps

Time resolved optical spectrum of the plasma emission was measured to characterize plasma #31 density USC & ATF

ne [

cm-3.]

time delay [ns]1

10

100

1000

10000

100000

0 100 200 300

Filter cutoff [microns]Filter cutoff [m]

CTR

[a.u

.]

CTR spectrum was measured by S. Banna #30 using UCLA bolometer #26 and THz filters from STI #32 to characterize beam

Beam was sent through plasma channel ATF & STI #32 in the first PWF double beam experiment

E

Experiments are very sophisticated and very efficient sharing of the resources between experimental groups is essential

Basic idea of OSCStochastic Cooling Optical Stochastic Cooling

2d sn eN3

is

l

NN

20 ideald dn nIn practice In practice time is amplifier limited

~ 12 m => power limited cooling time~1 hr with 16 W; bandwidth limited ~11 sec!

~ 5 cm => ideal bandwidth limited cooling time~2.5 hrs.

sample length ~10 cm

sample length ~50 m

5 main components of OSC

• Pair (per ring) of super conductive wigglers

• Optical amplifier (Optical Parametric Amplifier (OPA):

• Pump source for OPA • Lattice modification• Diagnostics

3 cm length crystal → intensity gain 3 105

Optical Parametric Amplifier OPA

Parametric process is photon interaction in which one high frequency photon is annihilated and two lower frequency photons are created, i.e.: (pump) =(signal) +(idler) where photon energy is conserved. In addition, photon momentum is conserved by the wave vectors: k(pump) =k(signal) +k(idler) .

OPA test at ATF• Basic parameters of the crystal• Bandwidth of the amplifier• Phase fidelity

Future development ATF ?• acquire X-band technology (extreme

beam compression, diagnostics, testing of X-band devices, high gradient…)

• Polarized Positron Source (PPS) with linac and CO2 laser R&D for ILC

• upgrade of CO2 system to 300TW level and high field experiments

• energy upgrade to 1GeV with energy recirculator (PWFA experiments, PPP)

Electron cooler in RHIC IP12

Number of particles in the ion bunch (as a result of “burn-off”,

recombination, cooling, IBS)

Integrated luminosityis about the same as without suppressionof recombinationdue to reductionin cooling force

<L>=7e27 <L>=6e27

<L>=6e27

Recombination: OFF Recombination: ONWigglers: OFF

Recombination: ONWigglers: ON

Average store Luminosity withoutCooling 6e26

20 MeV High Current High Brightness R&D ERL : layout in 912

Ampere Class Cryomodule

“Single mode cavity”:HOM (R/Q)Q~2*103 Ohms monopoles, ~2*105 Ohms/m dipole modes.BBU threshold current > 2 amperes

SRF Gun – critical element

CathodeisolationValves

Cathodeinstallationassembly

Beam lineisolation valve

Top cover withfacilities feedthru

Cavityassembly

InternalHelium dewar

Adjustable supports

Magnetic andthermalshielding

HOM Ferrite

Vacuum vesselPowercouplers

InsulatingVacuum Port

Gain in Emission mode:polycrystalline electronic grade, Ip=100nA, 300K

0

10

20

30

40

50

60

0 1 2 3 4 5 6

MV/m

Em

issi

on

gai

n

2keV 3keV 4keV 5keV

Gain of 50, still increasing W/ field, further investigation underway

Gain in Emission mode From Hydrogenated samples

Natural Diamond-Ip=100nA,T=300K

0

5

10

15

20

25

30

35

0 0.5 1 1.5 2

Field in MV/m

Gain

2keV 3keV 4keV 5keV