Tapering Enhanced Stimulated Superradiant Amplification Experimental Program — Fermilab (FERMILAB-SLIDES-21-0147-AD)
Summary
A Fermilab slide presentation (FERMILAB-SLIDES-21-0147-AD) on the Tapering Enhanced Stimulated Superradiant Amplification experimental program, presented by P. Musumeci on behalf of the TESSA collaboration. The outline covers the TESSA roadmap, the single-pass TESSA‐FAST experimental plans, and a long term program that includes a TESSA oscillator, an ICS-based gamma ray source, and polarized positron production. The slides state that the TESSATRON measured a record 10 % efficiency. The listed goals of TESSA‐FAST include the first experimental measurements of the spectral and transverse profile of the amplified radiation and a demonstration of record single pass energy extraction. The conclusions state that a formal proposal to the FAST/IOTA facility is to be submitted soon.
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“Tapering Enhanced Stimulated Superradiant Amplification Experimental Program — Fermilab (FERMILAB-SLIDES-21-0147-AD).”
Original at www.osti.gov. Archived at Pandemic Darlings, https://pandemicdarlings.com/source-documents/2021-us-bureau-of-labor-statistics-2021b-us-department-of-the-treasury-2021a-federal-reserve-board-2021-and-hale-et-al/
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Fermilab
Tapering Enhanced Stimulated Superradiant Amplification
experimental program
FERMILAB-SLIDES-21-0147-AD
This manuscript has been authored by Fermi Forward Discovery Group, LLC
under Contract No. 89243024CSC000002 with the U.S. Department of Energy,
Office of Science, Office of High Energy Physics.
Tapering Enhanced Stimulated
Superradiant Amplification
experimental program
P. Musumeci
on behalf of TESSA collaboration
TESSA‐FAST collaboration
J. Duris, N. Sudar, Y. Park, A. Fisher, P. Denham Graduate Students (UCLA)
A. Zholents, J. Byrd, A. Lumpkin (Argonne National Laboratory)
A. Murokh, T. Hodgetts, R. Agustsson (Radiabeam Technologies)
S. Webb, C. Hall (Radiasoft)
A. Gover (Tel Aviv University)
S. Nagaitsev, D. Broemmelsiek, A. Valishev, G. Stancari (FNAL)
Funding agencies : DOE SBIR/STTR program, DOE BES (SCGSR + UCLA)
Outline
• Electron beam‐based high efficiency radiation sources
• TESSA roadmap
• Near term proposal.
• Single‐pass TESSA – FAST experimental plans
• Long term program.
• TESSA oscillator.
• ICS‐based gamma ray source
• Polarized positron production
How to efficiently extract energy from relativistic e‐beams?
Single molecule imaging EUV lithography
High energy lasers High power THz sources
High efficiency enables high average and peak power light sources
Unique characteristics of ponderomotive interaction in magnetic undulator
Particle acceleration ‐ Radiation generation
In an FEL energy in the e‐beam is In an IFEL the electron beam absorbs
transferred to a radiation field energy from a radiation field.
High intensity
laser
𝜆 1 𝐾
𝜆
2𝛾
• “Without radiation there is no acceleration” – R. Palmer
• “To be efficient an accelerator must be able to operate in reverse”
• IFEL/FEL is a particularly advantageous interaction scheme in this regard
• Vacuum‐based accelerator. No mechanism for energy loss. Efficient energy exchange
• Tunability. Resonance can be adjusted using undulator parameters and beam energy
(from FIR to X‐rays)
• Plane wave or far field accelerator: minimal 3D effects. Transverse beam cross‐
section can be mm‐size for m‐scale radiation wavelength.
Lessons from IFEL research
• Rubicon IFEL experiment demonstrated high
quality acceleration of 50 MeV e‐beam at BNL
ATF
• Strongly tapered helical undulator
• Prebuncher to maximize fraction of particles
captured in laser accelerator
100 MeV/m
• Monochromatic output < 2 % energy spread 11 periods
0.5 m undulator
• Stability <1.5% energy jitter 300 GW CO2 laser
• Emittance preservation
Laser off energy spectrum
IFEL output energy spectrum
NOCIBUR IFEL deceleration experiment
• Use RUBICON IFEL set up in reverse at BNL ATF
• Retune tapering profile for 0.54 m long helical undulator for high gradient deceleration
• Demonstrated >30% conversion efficiency from a relativistic electron beam
• Maximized capture with prebuncher modulator + chicane
• Up to 45% of 100 pC beam captured and decelerated
Prebuncher Undulator
Resonant energy
Undulator parameters
Tapering Enhanced Stimulated Superradiant Amplification
• Reversing the laser‐acceleration process, we can extract a large fraction of the energy from an
electron beam provided:
• A high current, microbunched input e‐beam
• An intense input seed
• High gain regime: strong tapering matches decelerating gradient to growing radiation field amplitude
IFEL deceleration
J. Duris et al. New Journal of Physics, 17 (2015)
Tapered FEL
• 𝜌 is the dimensionless FEL parameter, for short
wavelength typically ~ 0.1% or less
• High gain FEL
• Exponential growth (LG~ 1/𝜌)
• Saturation (Ps~ 𝜌Pb)
• 1981 KMR seminal paper on undulator tapering
• Hamiltonian model
• Concept of resonant phase
• Instabilities
• Old and renewed interest
Orzechowski et al., PRL 57, 2172 (1986).
• ELF. Waveguide FEL @35 GHz
• Paladin experiment at 10 um
• Nocibur / TESSA
• Self‐seeded cases for TW X‐FEL
Demonstrated 34 % efficiency
in a waveguide @ 35 GHz
TESSA examples & roadmap
Low gain regime High gain regime Optical cavity Applications
TESSA‐FAST EUV lithography
Obtain first measurements of LCLS2‐like injector
spectral and spatial properties 4 kA @ 1 GeV = 4 TW
of amplified radiation TESSO @MHz‐reprate 10‐20 kW
Nocibur of EUV radiation power
No intense input seed Duris et al. NJP 2015
available
Optical cavity and
recirculating scheme Laser ablation propulsion
Igniter pulse / RAFEL SRF accelerator driver
1 m MW‐average power laser
configuration
Proof‐of‐principle test with TW‐peak power
Simulation benchmark. Atmospheric transparency
High energy high brightness window. Phipps et al. JOSAB 2018
35 % efficiency @10 um
beamline
Deceleration from 65 ‐ >
35 MeV TESSATRON at Pegasus High flux Polarized Gamma‐Ray source
10 % efficiency Inverse Compton Scattering
Sudar et al. PRL 2016 THz range High rep‐rate IFEL acceleration to boost photon
J. Duris et al. PRAB 2018 energy
Zero‐slippage
waveguide FEL A. Murokh et al. Snowmass LOI
Prebunched e‐ CPPWG
beam Undulator
Magnets
In operation at UCLA Pegasus !!!
TESSATRON
• Strongly tapered helical Theseus undulator installed at UCLA Pegasus (5‐8 MeV
beamline)
• Zero‐slippage FEL physics. Use of waveguide to match e‐beam and radiation
group‐velocity + satisfy FEL resonant condition E‐beam spectrum
• Measured record 10 % efficiency
TESSA‐FAST project
• UCLA – RadiaBeam – ANL – FNAL – collaboration
• Main scientific goals: Beam Energy 220 MeV
• First experimental measurements of spectral and Peak current 0.6 kA
transverse profile characteristics of the radiation Emittance 3 um
amplified in the TESSA regime of operation. Charge 1 nC
• Demonstration of single pass record high energy Energy spread 0.1 %
extraction efficiency from a relativistic electron beam in
the VIS region Undulator length 4 x 0.96 m
• Open the path to MHz‐rep rate Tapering Enhanced Radiation wavelength 515 nm
Oscillator multi‐kW high power lasers Seed power 1 GW
• Enable high rep‐rate Inverse Compton Scattering based Interaction geometry Helical
polarized gamma‐ray sources for nuclear
physics/polarized positron production
Motivations for TESSA at FAST
• UCLA workshop on High Efficiency FELs. W. Fawley : “Before big $$$ are spent on a TW‐class x‐ray
FEL undulator, we need systematic, well diagnosed experimental studies of best tapering
strategies”
• Experiment originally designed for 340 MeV in LEA tunnel at APS linac, tuned for 266 nm
wavelength. Not a good match due to APS‐U schedule
• Scarcity of available high brightness beam facilities in the 200‐400 MeV range. Leverage
availability (time and space) of FAST linac
• Extend TESSA to SRF‐linac is a stepping stone towards high average power radiation sources.
• Enable very high flux ICS‐based polarized gamma‐ray source. Nuclear physics / Polarized Positron
Production
• Convergence of interests from University‐National Laboratory‐Industry.
TESSA‐FAST experiment setup
40.625 MHz Amplitude Magma system
515 nm seed
RF 650 MHz
Matching quads + diagnostics
D600 Injection chicane
Prebuncher Theseus undulators
Bunching chicane
From FAST linac
D600 dipole
Requires installation of TESSA beamline components including : Also needs:
o Seed laser system (at company, waiting to be shipped) Beamline supports
o Prebuncher (in hand, tuned) Power supplies
o Injection and Bunching chicane (in hand, ready to be shipped) Vacuum pump and controllers
o 4 undulator sections (2 ready, 2 to be built using latest round of SBIR funding) Control system integration
o 3 break sections (1 prototype built)
o Matching quadrupoles (missing)
o Radiation and beam long. phase space diagnostics (partially developed in collaboration with ANL)
TESSA simulations
Injection Chicane
D600 MQ1 Prebuncher Chicane
Theseus 1 Theseus 2 Theseus 3 Theseus 4
Prebuncher
Matching quads
Time‐independent simulations
• ~9 % power efficiency Beam Energy 220 MeV
• Doublet permanent magnet quadrupole (112 T/m) channel Peak current 0.6 kA
• 75 um average rms size in undulators Emittance 3 um
• 13 GW output power
Charge 1 nC
Energy spread 0.1 %
Undulator length 4 x 0.96 m
Radiation wavelength 515 nm
Seed power 1 GW
Interaction geometry Helical
Theseus: Tapered HElical SEgmented Undulator System
• 2 orthogonal Halbach arrays with constant Undulator period 3.2 cm
period and adjustable gap Peak field 0.75 T
• Improved design from Rubicon undulator
• 1 m long sections K_max 2.3
• Completed prebuncher (8 periods) and two Resonant energy @ 515 nm 220 MeV
undulator sections ( 28 periods) Gap (min/max) 5.5 mm / 7.5 mm
• Entrance and exit sections add ~ 1 period per
section to FEL interaction (GPTFEL)
• Measurements, tuning and fiducialization
ongoing
Prebuncher
THESEUS I THESEUS II
Hall probe scans Pulse wire
3D mini Hall probe (Senis‐GMW) Final trajectory adjustment
1 m translation stage Entrance and exit magnet tuning
Mounting system for centering Hall probe in Trajectory axis references to alignment
undulator (u‐beam+carriage) monument on undulator body to < 40 um
Need to keep/register the probe on the Consider checking trajectory after shipping?
undulator axis within 200 um and 2 degrees.
Linear system allows Matlab optimization for
magnet insertion
Tol=+/- 0.2%
Prebuncher chicane 3 magnet bunching chicane parameters
Dipole Strength 0.078T, 0.16 T (center)
Bend Angle .009 rad, .018rad (center)
FROM injection chicane To THESEUS Magnetic Length 146mm
Physical Chicane Length 410 mm
Prebuncher to Theseus I 1.368 m
entrance length
Microbunching R56 < 18 um
diagnostics chamber
Field and e‐beam Trajectory
Same dipole as
injection chicane
Old Neptune
chicane.
Thanks to Jamie
Roseznweig
Microbunching Diagnostics Chamber
‐ 2 stations in storage at ANL from A. Lumpkin
‐ FEL light and COTRI station with L=6.3 cm between foils.
‐ 50 um foil to block laser and preserve microbunching
Old setup
THESEUS Break Section Design
o One of the most critical section of the experiment
o 162.6 mm long
o Physics requirement: minimize inter‐undulator
distance where radiation is quickly diffracting and
losing intensity.
o Quadrupole doublet to refocus beam
o Phase shifter design based on offset quadrupoles
+ electromagnetic dipole
o GPT model to evaluate dispersion effects
o Vacuum + diagnostics
*EMD design and position in the figure is not updated
Time‐dependent simulations
For equal bunch charges, a flatter current distribution yields higher energy efficiency due to slippage
Necessary to correct linac compression nonlinearity (no linearizer compared to advanced FEL beamlines) to better control
current distribution for four‐undulator setup
Longitudinal phase space from LINAC
TESSA Oscillator = TESSO
• Oscillator is needed whenever high intensity seed is not available J. Duris, P. Musumeci, N. Sudar, A. Murokh,
A. Gover. Tapering Enhanced Stimulated
• Solution: embed TESSA in optical resonator Superradiant Oscillator. Physical Review
Accelerators and Beams 21, 080705 (2018)
• Reach very high average power with high rep‐rate CW SRF accelerators
• Exploit 3 MHz (or 9 MHz if available) pulse train capability at FAST
• Oscillator start‐up : an open problem. Various possibilities.
• Igniter pulse 9 MHz 220 MeV 1.2 nC
• Control bunch parameters along train ‐> 12 kW average power
• Ramping of bunching chicane R56
Oscillator output
20 % efficiency would give
400 kW in pulse train
~50 % beamsplitter Igniter pulse 2.4 kW average power
9 MHz cavity 50 mJ per pulse – synch with e‐
beam
Oscillator transverse and longitudinal modes
• Lots of work to do: Optimize focusing optics. Optimize return fraction. Study stability to e‐beam current
fluctuations
• Modeling tools in hand. Use field propagator + GENESIS/GPTFEL to simulate multi‐pass in cavity
• Important connection with RAFEL and XFELO program at SLAC
• Longitudinal and transverse active cavity eigenmodes established after < 10 passes. Short pulse train
would be sufficient for first studies
• Cavity detuning/ spectral filtering is critical to select optimal lasing modes
Longitudinal TESSO cavity eigenmode
• Mirrors and stretcher optics may require cooling at
very high average powers
Transverse TESSO cavity eigenmode
ICS‐based Gamma‐ray production
For high flux gamma ray production via Compton the main Parameter Value
issue is the laser rate. His @ TUNL/Duke uses an FEL + E‐beam energy 220 MeV
storage ring to generate ~10^10 ph/sec
E‐beam charge 1.2 nC
Tunability (limited by optics) scales as 𝛾 Laser energy 50 mJ (20% efficiency)
Laser wavelength 515 nm
@ 9 MHz train / 5 Hz ‐> 5∙10^11 photons/sec – ps pulses
Gamma ray energy 1.8 MeV
Synchronization scheme. A possibility is two light pulses in a Gamma ray flux >10^7 per shot
2x longer cavity
Helical geometry ‐ > Circularly polarized gammas
50 mJ per pulse 9 MHz laser pulses synched with e‐beam
Gamma rays
Polarized positron production for e+/e‐ linear collider Case study for 40 MeV ph
• ILC/Higgs factory really benefits from polarized positron source
• Current scheme uses 200 m long undulator (K = 1) and 120 GeV beams to get the
required gamma ray flux (10^14 ph/sec) at 10 MeV.
• ICS‐based source considered, but laser‐power limited
• Murokh, Musumeci et al. Snowmass 21 LOI. Compact source proposed based on
IFEL acceleration + ICS + TESSA deceleration
• Optical energy recirculation
• Note: for ILC, with laser‐based Compton source it is hard to get close to 1 ph/e‐
so in order to get as many e+ as e‐, one would need to start with much higher e‐
current
Recirculating 515 nm cavity
Double Seed pulse
TW power. 515 nm
200 MeV
10 MeV gamma rays
IFEL acceleration to 500 MeV
Conclusions
• High gradient FEL interaction can achieve electrical‐to‐optical energy conversion
efficiency up to the tens of percent !
• BNL Nocibur experiment demonstrated 30 % energy extraction
• UCLA TESSATRON results shows 10 % efficiency and high gain in THz regime
• TESSA mechanism provides direct path to high peak power + high average power
radiation sources
• FAST is the only available high energy SRF accelerator beamline in US
• Leveraging significant investment in hardware from UCLA/RBT in the last 5 years
• Long range research program and various end‐applications
• TESSA‐FAST – First experiment targeting single pass high efficiency at 515 nm.
• TESSO – optical resonator cavity. build‐up. High average power lasing.
• Application developments (ICS‐based gamma ray source, SLAP, EUV‐lithography, TW‐XFEL)
• Formal proposal to FAST/IOTA facility to be submitted soon !!!
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