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

13:30 → 15:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 1: Join WG4 for SWFA talks

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

13:30 SWFA in WG4 Session

WG3 participants: Please join WG4 session for SWFA talks

15:00 → 15:30 Coffee Break

15:30 → 17:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 2: Structures I

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

15:30 High Power Test Results of X-Band Dielectric Disk Accelerating Structures

As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, several single cell X-band dielectric disk loaded accelerators (DDA) have been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>100 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. Low loss ceramics with ε$_{r}$ ≈ 50 were selected based on simulation studies to optimize the RF-to-beam efficiency. One brazed and one clamped structure have been tested at high power, with the clamped structure reaching >100 MV/m accelerating gradient. The results of the high power tests will be presented.

Speaker: Ben Freemire (Euclid Beamlabs)

DDA_AAC2022_Freemire.pdf

16:00 Simulation Results of a Clamped Multicell Dielectric Disk Accelerating Structure

A method of decreasing the required footprint of linear electron accelerators and to improve their energy efficiency is utilizing short RF pulses (~9 ns) with Dielectric Disk Accelerators (DDA). A DDA is an accelerating structure that utilizes dielectric disks in its design to improve the shunt impedance. Two DDA structures have been designed and tested at the Argonne Wakefield Accelerator. A single cell clamped DDA structure recently achieved an accelerating gradient of 102 MV/m. A multicell clamped DDA structure has been designed and is currently being fabricated. Simulation results for this new structure show a 108 MV/m accelerating gradient with 400 MW of input power with a high shunt impedance and group velocity. Engineering designs have been improved from the single cell structure to ensure consistent clamping over the entire structure.

Speaker: Sarah Weatherly (Illinois Institute of Technology, Argonne National Laboratory)

AAC Presentation.pptx

16:30 Cryogenic Dielectric Accelerating Structures

Shunt impedance is one of the most important parameters characterizing particle acceleration efficiency. It is known that RF losses are reduced at cryogenic temperatures. For example, a record high shunt impedance of 350 MΩ/m was demonstrated recently for all metal X-band accelerating structure, which is more than 2 times higher than that at room temperature. Here we present a novel hybrid dielectric structure which can achieve even higher shunt impedance due to the fact that losses in dielectric materials reduced much more than in pure copper.

Speaker: Chunguang Jing

Cold Dielectric structures.pdf

Tuesday, 8 November

10:00 → 10:30 Coffee Break

12:00 → 13:20 Lunch

15:00 → 15:30 Coffee Break/Exhibits

15:30 → 17:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 4: Structures II

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

15:30 Evaluation of DLC (diamond-like carbon) Coating on Multipactor Suppression

Multipactor discharges in dielectric accelerating structures are a major limitation on the performance of this otherwise very promising technology for future high energy physics machines and other applications. Multipactor occurs when the Secondary Emission Yield (SEY) of the dielectric material used in accelerating structures is significantly higher than 1. In this work, we evaluated the effect of SEY reduction by means of amorphous Carbon (a-C) and Diamond-Like Carbon (DLC) coatings for different dielectric materials. We also report on the testing results for a DLC coated low energy dielectric accelerator.

Speaker: Chunguang Jing

Multipactor suppression.pdf

16:00 Short Pulse High Gradient Accelerating Structures

RF breakdown and pulse heating are the greatest obstacles to increasing the accelerating gradient. Numerous experiments have shown that the RF breakdown and pulse heating thresholds depend on the exposure time of the structure to the RF fields. The idea described here is to accelerate particles by short (nanosecond or subnanosecond) duration wakefields in a structure assembled of individually fed cells. Because there are no high-power efficient sources of such radiation, we focus on wakefield structures where witness bunches are accelerated by radiation generated by drive bunches. One of successful wakefield experiments has been carried out at Argonne Wakefield Accelerator facility. About 400 MV/m gradient was obtained at X-band photoinjector powered by 9 ns RF pulses. To substantially enhance the efficiency of short pulse structures we propose using of a periodic pulsed regime. In this regime the repetition rate of the excited RF pulses is equal to the repetition rate of the drive bunches and equal to the repetition rate of the witness bunches. In the optimal stationary conditions, the pulsed accelerating field is inversely proportional to losses of the structure. On the other hand, it was shown experimentally that at 45 K accelerating structures can sustain 25% higher gradient and have almost twice higher shunt impedance in comparison with structures at room temperature. The synergetic effect of short pulse technology and cryogenic technology would allow reaching world record gradients as well as high efficiency due to a higher wall conductance.

Speaker: Sergey Kuzikov (Euclid Techlabs, LLC)

AAC2022 Short Pulse Structures.pptx

Short Pulse Accelerating Structures

16:30 Modulation of dense electron beams in nanostructures: A simulation study in preparation of the FACET-II E-336 experiment

Fields arising during the propagation of highly intense electron beams in structured targets of nanometer scale such as carbon-nanotubes can contain accelerating gradients of up to 10 TV/m with similarly strong focusing fields. Studies of beam-nanotarget interaction are therefore of interest as they may lead to an acceleration method with extremely high single-stage energy gains for electron or muon beams. The FACET-II E-336 experiment at the SLAC National Accelerator Laboratory aims to take advantage of the extreme beam densities available with the FACET-II electron beams to study its interaction with a grid of nanotube material. A simulation study with the Particle-In-Cell code CALDER was performed in preparation of the experimental campaign, illuminating transverse dynamics, such as magnetic trapping of beam particles in the tubes or deflection of the beam as a consequence of nanotube tilt. Additionally, the simulations indicate that nanotubes can act as an effective seed for beam-plasma instabilities. We will present the scientific goals of the project, report on simulations results and discuss how the observations can be translated into accessible observables.

Speaker: Alexander Knetsch

AAC2022_E336_Knetsch.pdf

Wednesday, 9 November

10:00 → 10:30 Coffee Break/Exhibits

12:00 → 13:20 Lunch

13:30 → 15:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 5: Laser / THz

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

13:30 THz generation fro 3-D printed structures in accelerators

The presentation will discuss advancements and new concepts on the topic of THz generation by 3-d printed structures in relativistic electron beams. A new concept has been developed that would greatly increase the efficiency of THz light generation, as well as allow for greater possibilities for control of the properties of the so generated Thz light. Wavelength, collimation and possibly pulse duration of the THz pulse could all be parameters that can be selected with the choice of a proper 3-D structure. This new concept would be more synchronized with the FEL beam than laser-based THz sources, and would take up less space and would be less expensive than THz undulators. The manufacture of the structures would be significantly simpler as well.

Speaker: Pavle Juranic (Paul Scherrer Institut)

THzGeneration_AAC2022.pptx

14:00 ACHIP experiments at the ARES linac

ARES is a linear particle accelerator at Deutsches Elektronen-Synchrotron DESY capable of producing high-quality, low-emittance electron beams dedicated to accelerator research and development. As an introduction we will present the achieved and projected performance of the ARES linac. An overview of the research activities on ultra-short electron bunch diagnostic methods, electron imaging and beam manipulation will be given.
The focus of this contribution will be the dielectric laser acceleration (DLA) campaign in the framework of the Accelerator on aCHip International Program (ACHIP) funded by Gordon and Betty Moore Foundation at ARES. We are employing a 2.05um wavelength Ho:YLF laser amplifier system to drive fused silica microstructures with the same periodicity manufactured by our collaborators at Stanford University. The goal of the experimental campaign is the improvement of transmitted charge compared to previous experiments while maintaining the acceleration gradient in the GV/m regime. Also, the ARES linac is foreseen to produce electron bunches exhibiting bunch lengths of less than 2fs, short enough to fit an acceleration bucket at the aforementioned wavelength, which corresponds to 6.8fs period. The arrival time jitter of the electrons at the interaction point will be larger than the laser period. To mitigate this a micro-bunching scheme was developed to synchronize a micro-bunch train with the DLA interaction. We will present the status and the recent achievements of the ACHIP DLA campaign.

Speaker: Willi Kuropka (Deutsches Elektronen-Synchrotron DESY)

WG3_presentation_WK_AAC22_187.pdf

WG3_presentation_WK_AAC22_187_summary.pdf

14:30 Energy Modulation in a Commercial Dual Grating Dielectric Structure

We present the latest experimental results using a dual grating dielectric laser accelerator (DLA) to modulate 6 MeV electrons. The structure is composed of two commercially available gratings, mounted independently with variable gap size controlled by 3 piezo motors. A 780 nm laser is used to drive the 800 nm periodic structure with gap size on the order of 1 um. These gratings are 4 mm long, enabling future long interaction experiments.

Speaker: Sophie Crisp (UCLA)

AAC2022_Upload.pptx

Thursday, 10 November

08:30 → 10:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 6

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

08:30 Update on the status of the C-band high gradient program at LANL

This talk will report on the status C-band high gradient research program at Los Alamos National Laboratory (LANL). The program is being built around two test facilities: C-band Engineering Research Facility in New Mexico (CERF-NM), and Cathodes And Radio-frequency Interactions in Extremes (CARIE). Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a high gradient test stand powered by a 50 MW, 5.712 GHz Canon klystron. The test stand is capable of conditioning accelerating cavities for operation at surface electric fields in excess of 300 MV/m. CERF-NM is the first high gradient C-band test facility in the United States. CERF-NM was fully commissioned in 2021. In the last year, multiple C-band high gradient cavities and components were tested at CERF-NM. Currently we work to implement several updates to the test stand including the ability to autonomously operate at high gradient for the round-the-clock high gradient conditioning. Adding capability to operate at cryogenic temperatures is considered. The construction of CARIE began in October of 2022. CARIE will house a cryo-cooled copper RF photoinjector with a high quantum-efficiency cathode and produce an ultra-bright 250 pC electron beam accelerated to the energy of 10 MeV. The status of the facility and initial beam physics simulations of the beamline will be presented.

Speaker: Evgenya Simakov (LANL)

AACSimakov.pdf

AACSimakov.pptx

09:00 New, High Efficiency RF Sources

Several new, high efficiency, RF sources are available or in development at frequencies from 325 MHz to 1.3 GHz and higher. If successfully developed, these new devices will represent lower cost alternatives to conventional RF sources. The primary focus is RF power production at higher efficiency and lower cost than currently available from conventional vacuum electron devices and solid-state sources. All devices are predicted to achieve more than 80% efficiency and provide lower acquisition and/or operating costs. A magnetron system with phase and amplitude control was successfully tested, producing 100kW at more than 80% efficiency. This system was developed for superconducting accelerators requiring fast feedback control of the RF power. The cost is estimated at $1 per watt. A multiple beam power grid tube was recently completed, providing sufficient beam power to generate 200 kW of RF power from 325 to 500 MHz at an estimated cost of 50 cents per watt. This device, if successfully tested, will provide a dramatically more compact and lower cost alternative to solid state systems now being used in this frequency and power range. Simulations predict 150 MHz of mechanical tuning range, and RF power generation up to 1 GHz may be feasible. Final assembly is in progress on a 100 kW CW, 1.3 GHz klystron simulated to achieve 80% efficiency using a COM-based RF circuit. Seal-in should be completed by the end of October, and the tube will be baked when a station is available. Testing is scheduled for January 2023. A 700 MHz, multiple beam inductive output tube is being developed with an estimated efficiency exceeding 80%. This tube will use moly grids to avoid the availability, cost, and yield issues associated with pyrolytic graphite grids. A new input coupler is dramatically simpler and more compact than previous versions, reducing both the cost and the size of the tube. Parts procurement is in progress, and testing is scheduled for spring 2023. These new sources could significantly impact the cost of new accelerator and colliders systems, particularly those requiring many RF source or operating at high duty.

Speaker: R Lawrence Ives (Calabazas Creek Research, Inc.)

CCR RF Sources AAC2022.pdf

CCR RF Sources AAC2022.pptx

09:30 RF Cavity Needs for Future Muon Accelerators

The future of high energy colliders beyond the high luminosity upgrade to the LHC is presently unclear. Physics and economics arguments are being made for hadrons vs. leptons and circular vs. linear machines. A muon collider is now being considered in Europe as a potential Future Circular Collider at CERN. Among the technological challenges inherent to a muon accelerator are beam cooling and acceleration. The RF cavity requirements for each differ, and were studied under the US Muon Accelerator Program, which concluded in 2017. Renewed interest in muon accelerators has warranted the results of this R&D program be revisited. This presentation will review the designs and progress made on cooling channels and acceleration schemes, the logical next steps for each, and how these pertain to advanced accelerator concepts.

Speaker: Ben Freemire (Euclid Beamlabs)

MuonColliderRF_AAC2022_Freemire.pdf

10:00 → 10:30 Coffee Break/Exhibits

10:30 → 12:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 7: Proton / Other

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

10:30 High-Gradient 3 GeV Booster for Enhanced Proton Radiography at LANSCE

Increasing the proton beam energy from the present 800 MeV to 3 GeV will improve the resolution of the Proton Radiography Facility at the Los Alamos Neutron Science Center (LANSCE) by a factor of 10. It will bridge the gap between the existing facilities, which covers large length scales for thick objects, and future high-brightness light sources, which can provide the finest resolution. Proton radiography requires a sequence of short beam pulses (~ 20 x 80 ns) separated by intervals of variable duration, from about 200 ns to 1-2 μs. To achieve the required parameters, the high-gradient 3-GeV booster is proposed. Utilization of buncher-accelerator-debuncher scheme allows us to combine high-gradient acceleration with a significant reduction of beam momentum spread. Paper discusses details of linac design and expected beam parameters.

Speaker: Yuri Batygin (Los Alamos National Laboratory)

AAC22_talk.pptx

11:00 High-Gradient Accelerating Structures for 3-GeV Proton Radiography Booster

Increasing energy of proton beam at the Los Alamos Neutron Science Center (LANSCE) from 800 MeV to 3 GeV will improve radiography resolution ~10 times. This energy boost can be achieved with a compact cost-effective linac based on normal conducting high-gradient (HG) RF accelerating structures. Such an unusual proton booster is feasible for proton radiography (pRad), which operates with short beam pulses at very low duty. The pRad booster starts with a short L-band section to capture and compress the 800-MeV proton beam from the existing linac. The main HG linac is based on S- and C-band cavities. An L-band de-buncher at the booster end reduces the beam energy spread. We present details of development of proton HG structures with distributed RF coupling for the booster. Operating such structures at liquid-nitrogen temperatures will significantly reduce the required peak RF power. A short test structure was fabricated and is being tested at the LANL C-band RF Test Stand.

Speaker: Sergey Kurennoy (Los Alamos National Laboratory)

AAC2022_Kurennoy.pdf

AAC2022_Kurennoy.pptx

11:30 Plasmonic Wakes in a Semi-conductor

The possibility of exciting wakefields in a semi-conducting structure is discussed. The fundamental limitation of short mean free paths of electrons in the semi-conductor can be overcome above a threshold beam or laser driver intensity when the electrons are driven to sufficient velocities that their Coulomb collision cross-section drops precipitously. The wakes differ from those in either a plasma, non-conducting dielectric or metallic structure. The nature of those differences and their potential advantages for plasmonic wakes as novel particle accelerator structures are described.

Speaker: Tom Katsouleas (U of Ct)

12:00 → 13:20 Lunch

13:30 → 15:00 WG3: Laser and High-Gradient Structure-Based Acceleration: Session 8: Preparation of WG3 Summary Presentation

Conveners: Sergey Belomestnykh (Fermilab) , Xueying Lu (NIU / ANL)

13:30 Preparation of WG3 Summary presentation

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