atf experiments igor pogorelsky. the bnl accelerator test facility proposal-driven, advisory...
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ATF Experiments
Igor Pogorelsky
The BNL Accelerator Test Facility
e-
Nd:YAG LASER
LASERCO
2
35
81.6 MHz
LINAC
x
RF GUN
Proposal-driven, advisory committee reviewed USER’S FACILITY for R&D in Accelerator and Beam Physics.
High-brightness e beams synchronized to high-power lasers.
The purpose: developing long-term approach to new methods of acceleration, generation of radiation and associated subjects.
Serving National Labs, universities and industry.
ATF Experiment ATF Experiment HallHall
Our Core Capabilities
• High brightness laser cathode e-gun
(1 nC, 1 mm mrad , 10 ps)
• 70 MeV linac (120 MeV, 300 fs upgrade planned)
• 30 GW 150 ps CO2 laser (soon 3 terawatt, 10 ps)
• Fully instrumented experiment hall with 3 beam lines
• >1000 hours beam time delivered annually
• Nonlinear-Compton Scattering• Smith-Purcell Radiation• Photocathode R&D • Beam Position Monitors for Linear Colliders• Stimulated Dielectric Wakefield Accelerator
• Staged Electron Laser Accelerator (STELLA)• Compton Scattering of ps Electron and CO2 Beams
• Ultra-fast Optical Detection of Charged particles
• Laser Driven Cyclotron Autoresonance Accelerator (LACARA)
• A SASE-Free Electron Laser Experiment, (VISA)
• Electron Beam Compression Based Physics at the ATF
• Structure-based Laser Driven Acceleration in a Vacuum
• Optical Diffraction-Transition Radiation Interferometry Diagnostics
• Particle Acceleration by Stimulated Emission of Radiation
14 currently active experiments:
Illustrated by Thompson scattering experiment – presently the brightest Thomson x-ray source.
Benefits of using long-wavelength (=10m) CO2 laser:
• Combines advantages of high-quality conventional RF accelerators and high-gradient optical accelerators with =~1 m
•favorable phasing
•structure scaling.
Illustrated by STELLA - the first two-stage laser accelerator
• Ponderomotive potential that controls x-ray production, plasma wake generation and other strong-field phenomenais proportional to 2.
Optic al delay
High-Pressure CO2 Amplifiers
ATF CO2 Laser System
Bandwidth-limited amplification of picosecond CO2 laser pulses
/2
-0.4 -0.2 0.0 0.2 0.4
E/E
-0.010
-0.005
0.000
0.005
0.010
Simulations of electron beam bunching
initial uniform energy distribution bunching after drift
sinusoidal energy modulation after buncher
/2
-0.4 -0.2 0.0 0.2 0.4
E/E
-0.010
-0.005
0.000
0.005
0.010
/2
-0.4 -0.2 0.0 0.2 0.4
E/E
-0.010
-0.005
0.000
0.005
0.010
50% of electrons within FWHM=0.63 m
/2
-0.4 -0.2 0.0 0.2 0.4
Num
ber
of E
lect
rons
0
50
100
150
200
250
300
350
400
STELLA - Staged Electron Laser Acceleration
CO2 laser beam
ELECTRONSPECTROMETER
IFELACCELERATOR IFEL
BUNCHER
46 MeV 0.5 nC 2 mm mrad 3.5 ps
0.6 GW, 180 ps
Steeringcoil
BPM
BPM
BPM
BPM
Focusingquadrupoles
Steeringcoil
Focusingquadrupoles
Inverse Free Electron Laser (IFEL) Physics
Use periodic magnet array (wiggler/undulator) to cause electron trajectory tooscillate while traveling through array
Net energy exchange between electronsand laser beam possible if resonancecondition is satisfied
where L = laser wavelengthw = wiggler wavelength = Lorentz factorK = eBow/2mcBo = peak magnetic field
Higher energy exchange possibleusing tapered wiggler/undulator
22
21
2
w
L
K
S
S
S
S
S
S
N
NN
N
N
N
ELECTRONBEAM
UNDULATORMAGNET ARRAY
LASERBEAM
STELLA - Staged Electron Laser Acceleration
CO2 laser beam
ELECTRONSPECTROMETER
IFELACCELERATOR IFEL
BUNCHER
46 MeV 0.5 nC 2 mm mrad 3.5 ps
0.6 GW, 180 ps
Steeringcoil
BPM
BPM
BPM
BPM
Focusingquadrupoles
Steeringcoil
Focusingquadrupoles
STELLA IICO2 LASER BEAM CONVEX MIRROR
VACUUMPIPE
PARABOLICMIRROR WITH
CENTRAL HOLE
E-BEAM
E-BEAMFOCUSING
LENSES
E-BEAMFOCUSING
LENSES
DIPOLEMAGNET
SPECTROMETERVIDEO CAMERA
= QUADRUPOLE MAGNET
BUNCHER(IFEL1)
ACCELERATOR(IFEL2)
CHICANETAPERED
UNDULATORARRAY
VACUUMCHAMBER
LENS
WINDOW
Energy Shift (MeV)
-4 -3 -2 -1 0 1 2 3 4 5 6 7 8
Nu
mb
er
of E
lectr
on
s
0
100
200
300
400
500
Energy Shift (%)
-8 -6 -4 -2 0 2 4 6 8 10 12 14 16
ATF Thomson Scattering Experiment
Results from Thomson Scattering Experiment
0
5 106
1 107
1.5 107
0 2 4 6 8 10Energy (keV)
• Signal on detector is equivalent to 2.5x107 photons/pulse.
• Low energy x-rays are blocked by Be window and air. 15% of total generated photons reach the detector.
• 1.7x108 photons/pulse produced at the interaction point.
• Since pulse duration of the x-ray signal is equal to the electron bunch length (3.5 ps), estimated peak x-ray intensity is 5x1019
photons/second.
e- beam5.8 GeV
CO2 laser ( =10.6 m, E=0.117 eV )
e-
e+
-rayEmax = 60MeV
e-e+ pair creation
Thin conversion
Collision point (CP)
Electronbeam
Laserbeam
f = 90 mm
The total number of -rays generated in 200 collision points is photons/bunch. W target of 1.75 mm thickness generates polarized positrons/bunch.
11103.8 10109.6
f f fe b ea m-
ta rg ettu n g sten t = 1 . 7 5 m m
-ra y s
6 1 m : A co llis io n reg io n 2 0 m
B e n d
e beam
-
e -e +
= 3 . 0 m m = 4 . 0 m me /e+ -
Proposed polarized positron source
for Japan Linear Collider
From Free Space …
Laser pulse duration shall match theinteraction length that is defined byRayleigh distance in free space. ….to Plasma ChannelWe brake the laser pulse duration constraint by extending the interaction length in a plasma channel.
20w
QEN bLx
crit
e
nn 1
r
ne
optical guide
Main capillaryT
rigg
er
Triggerpulse
CH
2
CH2
- H.V.
Electrodes
Plasma channel formation in the capillary discharge
0 00 0 0 0.. . . .21 3 4 5r, mm
0
2
4
6
8
Ne,
1017
cm-3
0
2
4
6
8
100 ns
200 ns
300 ns
500 ns
50 ns
laser beam atthe focal point
17 mm downstream from the focus in the free space
at the exit from the 17 mm plasma discharge
Channeling of CO2 laser in capillary discharge
HV DC /Pulseg e ne ra to r
C a p illa ry
Pa ra b o licm irro r
C O La se r
SRSp ulse r
IR c a m e ra
20 kV D C
Pre trig g e rp u lse
M a in trig g e rp u lse
2
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Image above: Plasma wakefields were generated at the Accelerator Test Facility by a relativistic electron bunch interacting with a plasma in a capillary tube. Details ... The Physics Department carries out research in experimental and theoretical high
energy, nuclear and condensed matter physics Samuel Aronson, ChairHoward Gordon, Associate Chair Peter Johnson, Acting Associate ChairOrganizational Chart Last update on: by S. Parrish.
Anouncements/Meetings
LoopFest IIBrookhaven National LabMay 14 - 16, 2003 CIPANP 20038th Conference on the Intersections of Particles and Nuclear PhysicsGrand Hyatt Hotel - NYCMay 19 - 24, 2003 Series of Colloquia on Astrophysics and Cosmology(MS Word FIle) Physics 2002 APS Fellows(MS Word File) APS Fellowship Program RHIC Detector Advisory Committee
Pla sm a so urc e
Sp e c tro m e te r
Ele c tro n e ne rg y
Fo c usingq ua d rup o le s
Lina c Pho to -inje c to r
Plasma Wakefield Generation and Probing
45 MeV 1 nC electron beam excites plasma wave that produces electron acceleration and focusing.
• Nonlinear-Compton Scattering• Smith-Purcell Radiation• Photocathode R&D • Beam Position Monitors for Linear Colliders• Stimulated Dielectric Wakefield Accelerator
• Staged Electron Laser Accelerator (STELLA)• Compton Scattering of ps Electron and CO2 Beams
• Ultra-fast Optical Detection of Charged particles
• Laser Driven Cyclotron Autoresonance Accelerator (LACARA)
• A SASE-Free Electron Laser Experiment, (VISA)
• Electron Beam Compression Based Physics at the ATF
• Structure-based Laser Driven Acceleration in a Vacuum
• Optical Diffraction-Transition Radiation Interferometry Diagnostics
• Particle Acceleration by Stimulated Emission of Radiation
12 more currently active experiments: