20th Advanced Accelerator Concepts Workshop

6 Nov 2022, 15:00 → 11 Nov 2022, 17:10 America/New_York

Hyatt Regency Long Island

Mark Palmer (Brookhaven National Laboratory) , Navid Vafaei-Najafabadi (Stony Brook University)

The AAC’22 workshop is the 20th in a series of by-invitation biennial fora for intensive discussions on long-term research in advanced accelerator physics and technology. This research supports the development of capabilities for the basic sciences, from photon science to high energy physics, as well as the development of compact accelerators for industrial, medical and security applications.

AAC'22 will be organized into eight working groups covering the following topical areas:

1. Laser-Plasma Wakefield Acceleration 
2. Computation for Accelerator Physics
3. Laser and High-Gradient Structure-Based Acceleration
4. Beam-Driven Acceleration
5. Beam Sources, Monitoring, and Control
6. Laser-Plasma Acceleration of Ions
7. Radiation Generation and Advanced Concepts
8. Advanced Laser and Beam Technology and Facilities

Conference Home:  https://www.aac2022.org/

 

Sunday, 6 November

18:00 → 19:30 Welcome Reception

Monday, 7 November

10:20 → 10:40 Coffee Break

12:10 → 13:30 Lunch

15:00 → 15:30 Coffee Break

Tuesday, 8 November

10:00 → 10:30 Coffee Break

12:00 → 13:20 Lunch

15:00 → 15:30 Coffee Break/Exhibits

Wednesday, 9 November

10:00 → 10:30 Coffee Break/Exhibits

12:00 → 13:20 Lunch

Thursday, 10 November

10:00 → 10:30 Coffee Break/Exhibits

12:00 → 13:20 Lunch

13:30 → 15:00 WGs 7+8 Joint Session: Session 1 of 1

Joint session between Working Groups 7 & 8:
WG7 - Radiation Generation and Advanced Concepts
WG8 - Advanced Laser and Beam Technology and Facilities

Conveners: John Palastro (University of Rochester, Laboratory for Laser Energetics) , Julia Mikhailova, Mr Marcus Babzien (BNL) , Stephen Milton

13:30 HIGHLY-EFFICIENT 20-MW L-BAND MULTI-BEAM KLYSTRON

A new concept for a high-power L-band RF amplifier is described, namely a Two-Stage Multi Beam Klystron (TS-MBK) operating with 12 hollow beamlets. This configuration allows for a remarkably high RF electronic efficiency of up to 90%, with a compact electro-mechanical layout. We present a conceptual design for a 1.0 GHz, 20 MW peak-power TS-MBK; its predicted performance was determined using particle-in-cell computer simulations. The tube’s efficiency—about 20% higher than conventional MBK’s—is due to good bunching of its 12, 30-kV, 12-A, 2.31-µK perveance hollow beamlets; followed by 150 kV post-acceleration that results in 0.157-µK, 180 kV beamlets with a total power of 26 MW that drive the output cavity. It is notable that the required modulator for this tube needs to provide pulses of only 30 kV, since post-acceleration can be achieved using a compact and much lower cost dc power supply. Further, the post-acceleration electric field prevents electrons reflected in the collector from returning towards the cathode. One application for this tube could be as the RF source for the 3-TeV CLIC drive beam, for which about 1230, 1.0 GHz tubes supplying a total average power of 184 MW are required. Another application could be to supply the high peak and high average power to drive the emerging compact and efficient electron cyclotron resonance accelerator eCRA, producing beams for environmental remediation and replacement of radioactive sources for sterilization. The optimal operating frequency for eCRA could be about 1000 MHz, but the TS-MBK design presented here can be scaled to other L-band frequencies. The high efficiency of our TS-MBK for these applications would result in significant operating cost savings and significant reduction in waste heat from the beam collector.

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*Sponsored in part by DOE Phase I SBIR grant DE-SC0022580, effective September 29, 2022.

Speaker: Dr Jay Hirshfield (Omega-P R&D, Inc.)

20-MW TS-MBK AAC2022.pptx

20-MW TS-MBK AAC2022.pptx

13:50 ELECTRON CYCLOTRON RESONANCE ACCELERATOR eCRA

Solutions of the single-particle equations of motion for electrons in the fields of an idealized TE111 microwave cavity in an external magnetic field near cyclotron resonance show acceleration rates that substantially exceed the limits for the CARA interaction. We have dubbed this new accelerator “eCRA.” Here, results are presented for realistic TE111 eCRA cavity geometry and finite space-charge beams that confirm the idealized solutions. The new features include cavity openings for RF inputs, beam injection, and pumping; RF input couplings that maximize efficiency; a thin window for exit of the accelerated beam; realistic magnetic field profiles; finite diameter multi-Ampere beams; and transient beam dynamics to model pulsed operation. One simulated eCRA example is for a copper cavity with Q0 of about 19,000, and a filling time of 85 ns due to strong external coupling. With RF input power at each of the two ports of 12.5 MW, an 8.0-A, 100 keV beam was shown to be accelerated to 2.2 MeV, giving a pulsed beam power of 17.6 MW and efficiency of 67%. Many applications are recognized for MW-class eCRA beams with energies in the range 1-10 MeV. Our first proof-of-principle demonstration of eCRA is to produce beams to generate intense X-ray fluxes to enable the replacement of radioactive sources now widely used for sterilization of medical supplies and foodstuffs. This demonstration will be based on use of available S-band components, although the optimal operating frequency for eCRA could be about 1000 MHz. In any case, the possibility of MW-level average power eCRA beams—even with predicted efficiencies >80%--will depend upon the availability of the required RF sources to drive eCRA. One candidate for this role is the 20-MW peak power two-stage multi-beam 1000 MHz klystron reported elsewhere in this Workshop.

Speaker: Dr Jay Hirshfield (Particle Accelerator Research Foundation and Omega-R&D, Inc.)

eCRA presentation AAC2022.pptx

14:10 9.3 microns: Toward next-generation CO₂ laser for particle accelerators

The ATF's long-wave infrared (LWIR) laser produces optical pulses that enable substantially different acceleration regimes compared to near-infrared lasers. A 2 ps pulse duration and 5 TW peak power at 9.2 μm are presently the best demonstrated performance of this laser. This is achieved via chirped-pulse amplification of a microjoule seed pulse in a series of two high-pressure, mixed-isotope CO₂ laser amplifiers operating at the 9R branch of the CO₂ gain spectrum.
Combining the spectral bandwidth of the 9R and 9P branches will reduce the pulse duration to 500 fs while preserving the pulse energy, thus increasing the peak power by a factor of four. The central wavelength of such a laser would be 9.3 μm. One prerequisite for the proposed laser’s development is the increase in the energy of a seed laser to a millijoule level. Several schemes for generating high-energy LWIR seed pulses are currently being investigated. Nonlinear post-compression in bulk materials demonstrated recently in the sub-TW LWIR regime has the potential to further reduce the pulse duration to a few optical cycles (one cycle at 9.3 μm is 31 fs).
Achieving reliable 24/7 operation at a high repetition rate for future accelerators requires a quantum leap in the technology for pumping the high-pressure-gas active medium. In this regime, optical pumping at 4.3 or 2.8 μm is a promising alternative to electric discharge pumping. A kilojoule of optical energy must be deposited in the active medium of the CO₂ amplifier within a microsecond for multi-terawatt LWIR operation. Emerging mid-infrared sources, such as Fe:ZnSe laser and GaSb laser diodes, may help to overcome this challenge in the foreseeable future.

Speaker: Mikhail Polyanskiy (Brookhaven National Laboratory)

Polyanskiy - CO2 laser - final.pptx

14:30 FULFILLING THE MISSION OF BROOKHAVEN ATF AS A DOE’S FLAGSHIP USER FACILITY IN ACCELERATOR STEWARDSHIP

Over last three decades, BNL Accelerator Test Facility (ATF) pioneered the concept of a proposal-based user facility for lasers and electron beam-driven advanced accelerator research (AAR). This has made ATF, operating as an Office of Science National User Facility and a flagship DOE facility in Accelerator R&D Stewardship, an internationally recognized destination for researchers who benefit from access to unique experimental capabilities not otherwise available to individual institutions and businesses. The high-peak-power long-wave infrared (LWIR) laser is a unique tool available at ATF for experimental study of wavelength scaling of strong-field phenomena and testing of laser driven acceleration regimes that are more difficult to achieve at shorter wavelengths. Other ATF capabilities include high-brightness electron linac and a facility for ultra-fast electron diffraction and microscopy experiments. ATF pursues an ambitious upgrade plan for its lasers and electron beam infrastructure. The scope of the ATF upgrade is designed to enable advances in three key areas:
Laser R&D program: CO2 laser power upgrade to 20 TW peak power with pulse-width <500 fs will enable a world-leading program in AAR. Completing in-vacuum NIR and LWIR laser beam transport to ensure the best beam quality delivered to user experiments.
Electron Beam: Continue to move towards providing more highly compressed beams (~10 fs bunch) together with exploiting and expanding short bunch diagnostic capabilities.
UED/UEM: Improve system performance with wavelength-flexible OPA pump laser; Apply AI/ML techniques to both beam line tuning and real-time structural analysis.
A combination of these upgrades will pave the way for a range of scientific initiatives – from ion acceleration, which is relevant for future radiotherapy methodologies, to novel opportunities for investigating LWFA of electrons. This includes integrated multi-beam research in laser wakefield accelerators, such as the two-color ionization injection, with the promise of an all-optical scheme for generating collider-quality electrons beams.
This will ensure that the ATF user community will continue successful R&D in accelerator technology and conducting experiments at the forefront of AAR, which are key elements of the Accelerator Stewardship mission.

Speaker: Igor Pogorelsky (BNL)

WG8 talk.pptx

15:00 → 18:00 Afternoon at Leisure

Friday, 11 November

10:00 → 10:30 Coffee Break

12:00 → 13:00 Lunch

14:40 → 15:00 Coffee Break