220 likes | 332 Views
Midterm Accelerator Test Facility development goals and new experimental possibilities. Vitaly Yakimenko April 5, 2007. ATF development plan (Experimental program support). Support for current exponential program: Efficient staff allocation
E N D
Midterm Accelerator Test Facility development goals and new experimental possibilities Vitaly Yakimenko April 5, 2007
ATF development plan (Experimental program support) Support for current exponential program: • Efficient staff allocation • 2.5 FTE to support accelerator operations, development • 4 FTE to support laser systems operations, high voltage experimental systems and optical diagnostics, limited laser development and upgrades. • 4 FTE facility support and maintenance (electrical, mechanical, computer control) • 1.5 FTE administrative, safety • Additional R&D (laser cavity, OSC) will be covered by temporary people and additional funding (LDRD, ILC, …) • Spare, interchangeable components • Reliability upgrades/fault proved components • Training/safety, simplified/standardized Experimental Safety Reviews • Scheduling based on goals instead of the fixed time • Remote experiments…
ATF development plan (Diagnostics) • Beam quality • Photocathode laser beam shaping • Beam based alignment (Gun- Faraday cup) • Beams diagnostics • Routine daily emittance/pulse length characterization • Each shot CO2 energy and pulse structure characterization • Beam structures • ~100 bunches, 24 ns spacing train was operated in the past • IFEL micro bunching at 10 micron was used in many experiments: (STELA, HGHG, PASER, …) • 3-4 bunches spaced by 360-720 picoseconds were used for dielectric Wakefield experiments • Beam break up during compression was used for two beam PWFA • We will place additional effort to ease multibunch operation and its diagnostics
ATF development plan (program) • X-band technology • Linac • Compensated energy spread after compression • Increase in top beam energy • Detailed longitudinal tomography • Possibility for high gradient/high brightness beam experiments • X-band waveguide-wiggler • Deflection cavity • Laser only experiments (EUV, Ion beam generation, …) • New experimental area, transport line • Facility research complimentary to the main program • ILC positron source (High rep. rate CO2 cavity) • OSC test • Electron beam energy upgrade
ATF development plan (laser) (Goals in this presentation, techniques in next) • New photoinjector/CO2 slicing laser • Reliable technology • Shorter CO2 beams • 3 dimensional profile control on the cathode • Single pulse CO2 power increase • Study of the short pulse CO2 limit (1 ps @ 10 atm, 100 fs with isotopes) • Higher energy extraction 30J • Higher repetition rate, improved stability/predictability • Laser cavity operations • ~100KW average power laser beam optimized for Compton interaction (100-1000 times better than alternatives) • Sustained circulation of the 1J, 5ps laser pulse for few microseconds
Modulator construction (03/2007) Low level RF (4/2007) Klystron repair and delivery (4/2007) Klystron test (5/2007) Linac section installation (8/2007) Plasma Wakefield Acceleration experiments and VISA would be the main beneficiary of this upgrade X-bend installation timeline
X-bend installation • Energy chirp compensation in compressed beam • Increase in beam energy available to experiments • New capability for measurement and manipulation of longitudinal phase space Summary of beam parameters with and without x-bend section in the H line.
ATF Energy upgrade • Energy upgrade to 1.5 GeV can be realized by adding recirculation loops • Benefits are: • Multiple energies would be available • New experimental floor • No interference with existing operations • Relatively inexpensive… • Space is available • User input is being investigated… • Cost of the upgrade was estimated at $3M • Considerable man-power is needed to study and generate scientific case for AARD
Single pulse CO2 power increase • Two directions: Pulse length and energy • 30-50 J can be extracted from current amplifier with new windows • ~1 picosecond should be achievable with new slicing laser • Isotope mixtures can allow for 100fs beam amplification • Combination of multiple effects needs careful studies: • Power broadening of the amplification bands • Pulse shortening due to media saturation • Nonlinear dispersion in windows • … • “Dream beam” or “bubble” accelerator with 10 micron laser • High charge • Compton based X-ray source could have 1027 (s mm2 mrad2 0.1%)-1 • High gradients for acceleration based on nonlinear effects • High energy/extreme brightness of ion beams • 30J x 100fs : 0.3 Petawatt laser beam at 10 micron is stronger that any today laser for experiments based on pondormotive potential.
New prospects for laser-driven ion sources Electron interacting with a strong EM wave acquires energy where - dimensionless laser strength parameter. Thus, CO2 laser (=10 m) produces 100 times higher particle yield per 1 Joule to compare with presently used solid state lasers (1 m) provided that a threshold condition is reached.
Non scaling FFAG test with ion or/and electron beams(Thanks to S. Berg) • FFAGs are useful when rapid acceleration is needed • The have advantages over cyclotrons because • They can have smaller apertures • They can more easily reach relativistic energies • Beam resonances prevent ordinary accelerators from having large energy spreads • FFAGs have several methods for dealing with the fact that circulation time of the beam depends on energy
Conditions for Bubble formation(Thanks to A. Pukhov) Laser power threshold: cavity trapped e- Accelerated charge scales as: laser Final energy : Bubble can be formed in a finite window of plasma densities: 10 micron laser unlikely to offer record gradient in this application, but might solve problems for practical applications: higher charge, more stable, better controlled final energy.
Compton back scattering – compact sub 100 fs x ray sourse 0.5 ps 50J “Dream beam” accelerator 5ps 50J
Polarized Positrons Source (PPS for ILC) Conventional Non-Polarized Positrons: In the proposal • Polarized g-ray beam is generated in Compton backscattering inside optical cavity of CO2 laser beam and 6 GeV e-beam produced by linac. • The required intensities of polarized positrons are obtained due to 10 times increase of the “drive” e-beam charge (compared to non polarized case) and 5 to 10 consecutive IPs. • Laser system relies on commercially available lasers but need R&D on a new mode of operation. • 5ps, 10J CO2 laser is operated at BNL/ATF. g to e+ conv. target 6GeV 1A e- beam 60MeV g beam 30MeV e+ beam 5-ps, 1-J CO2 laser ~2 m
Kerr generator Laser cavity system 8 x 200ps CO2 oscillator 1x150ns Ge optical switch 8 x 5ps 1mJ 8 pulses, 5ps, 10mJ (YAG laser) Regenerative amplifier PC TFP TFP 8x5ps 10mJ PC amplifier 8x300mJ BS 8x30mJ 8x 30mJ 5ps amplifier amplifier 8 x 1J 5ps 8 x 1J 24ns ring cavities (8 pulses x 3ns spacing) 1J / pulse sustained for 8.5 ms amplifier amplifier IP#1 IP#10
Has a potential to increase average intra-cavity power ~100 times at 10.6 microns. Purpose of the test: Demonstration of 100-pulse train inside regenerative amplifier that incorporates Compton interaction point. Demonstration of linear-to-circular polarization inversion inside the laser cavity. Test of the high power injection scheme LDRD – cavity tests 3% over 1 ms
“~100 times increase of the average intra-cavity power at 10 mm” • The required laser train format / repetition rate /average acting power at each IP: 100 pulses x 150Hz x 1J = 15 kW. • Efficient interaction with electron beam requires short (~5ps) and powerful (~1-2J) laser beam. • Such high-pressure laser does not exist. Non-destructive feature of Compton scattering allows putting interaction point inside laser cavity. • We can keep and repetitively utilize a circulating laser pulse inside a cavity until nominal laser power is spent into mirror/windows losses. • Assuming available 0.5 kW CO2 laser and 3% round-trip loss, 1-J pulse is maintained over 15,000 round trips/interactions (100 pulses x 150 Hz). Thus, 0.5 kW laser effectively acts as a 15 kW laser. • Equivalent solid state ( 1mm) laser producing the same number of gamma photons should be 150 kW average power with ~10J, 5ps beam. • Applications: • Compact femtoseconds x-ray source • X-ray source for RIA • Gamma collider laser • …
Compact femtoseconds x-ray source • 50-100 MeV photo injector/LINAC combination producing train of 500 bunches (0.8 nC, 100fs, ~2 mm) at 150Hz. • CO2 laser cavity / few cavities (2J, 5ps, 500 turns) • Head on Compton interaction • X-ray energies 6-24 keV • Peak brightness: 5x1024(s mm2 mrad2 0.1%)-1 • Average brightness: 108 (s mm2 mrad2 0.1%)-1 • ~10M$, 100 m2 / 5 beam lines Real CCD images Nonlinear and linear x-rays
Potential for generating exotic beams of nuclei(Thanks to V. Litvinenko) • Idea came from SPIRAL II Project (electron option) to use 45 MeV electron beam to generated 10-20 MeV Bremmstrahlung -rays and use Giant Dipole Resonance (GDR) for photofission of 238U into rare (neutron reach) nuclei http://ganinfo.in2p3.fr/research/developments/ spiral2/index.html • Because of the hard-edge in the energy spectrum, an ERL-based Compton -ray beam with high average power average is a better choice for such source • BNL is developing both high-current high-energy ERLs and high power C02 lasers - the key ingredients of such source • 3 GeV, 20 mA ERL (20 nC/bunch, 1 MHz rep-rate) in combination with four CO2 lasers (2J/pulse, Rayleigh range of 0.2 cm, 500 Hz rep-rate x 500 reflections) will provide 90 kW (i.e. 4x1016/sec) of -rays within the 10-20 MeV range of GDR • This -ray beam has very small divergence ~ 150 rad, and can be used to for photofission of 238U to generate ~1016/sec nuclei, including exotic CO2 lasers -ray beam
OSC test at NSLS (VUV ring)(Thanks to S. Kramer, A. Zholents) Practical Layout • 1st stage: lattice control (time of flight) test • studies of mirror less FEL • 2nd stage: cooling rate measurement … • Busy ring but Wigglers are already installed! • Linear optics are very appropriate • Hardware needed: • ~6 Power supplies • Vacuum port, 2-3 windows • Additional nonlinear correction? • Optical parametric amplifier at ~1.5 micron Electrical Cabinets Jogged Optical Path (25 M) Electron Beam Path Le = 51/2 = 25.5 M
Conclusion • Staff problems will be addressed in 2008 to improve user support. • Quality of the beam will be improved with beam based alignment, better diagnostics, shaped laser and possibly new gun. • X-band power should become available for experiments in 2007. High gradient, new beam diagnostic will studied. • High brightness, short beam structure with bunch spacing from femtosecons to nanoseconds is important part of program at ATF. • CO2 laser development will be directed towards tens of terawatt, sub-picosecond, stable and well diagnosed system. • Additional sources of funding would be needed to investigate high rep. rate and cavity mode of operations.
Studies for TeV-LC • Photoinjector • CO2 laser/Compton based positron source • Diagnostics (cavity based BPM, Tomography, …) • Beam handling (IFEL “heating” before compression) • Laser converter for Photon collider • Many studies for high gradient …