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 → 15:10 WG5: Beam Sources, Monitoring, and Control: Session 1

Conveners: Dr Samuel Barber (Lawrence Berkeley National Laboratory) , Yine Sun (Argonne National Laboratory)

13:30 Low-emittance high-energy muon source based on plasma wakefield acceleration

Plasma wakefield acceleration (PWA) channels are characterized by very high accelerating gradients and very strong focusing fields. We propose to employ these properties for effective production of low emittance high energy muon beams, consider muon beam dynamics in the PWFA cell and analyze various options and potential of the PWA-based muon sources.

Speaker: Vladimir Shiltsev (Fermilab)

MuonPWA_ShiltsevAAC_v1.pdf

MuonPWA_ShiltsevAAC_v1.pptx

13:50 Beam shaping using an ultra-high vacuum multileaf collimator and emittance exchange beamline

We report the development of a multileaf collimator (MLC) for charged particle beams, based on independently actuated tungsten strips which can selectively scatter unwanted particles. The MLC is used in conjunction with an emittance exchange beamline to rapidly generate highly variable longitudinal bunch profiles. The developed MLC consists of 40 independent leaves that are 2 mm wide and can move up to 10 mm, and operates in an ultra high vacuum environment, enabled by novel features such as magnetically coupled actuation. An experiment at the Argonne Wakefield Accelerator, which previously used inflexible, laser-cut masks for beam shaping before an emittance exchange beamline, was conducted to test functionality. The experiment demonstrated myriad transverse mask silhouettes, as measured on a scintillator downstream of the MLC and the corresponding longitudinal profiles after emittance exchange, as measured using a transverse deflecting cavity. Rapidly changing between mask shapes enables expeditious execution of various experiments without the downtime associated with traditional methods. The many degrees of freedom of the MLC can enable optimization of experimental figures of merit using feed-forward control and advanced machine learning methods.

Speaker: Nathan Majernik

Majernik - MLC talk.pdf

14:10 Stabilization and manipulation of laser-driven plasma acceleration with a weak auxiliary laser pulse

We show that uncontrolled phase fluctuations within an outer annulus of the near-field profile of a laser-wakefield drive pulse are primarily responsible for shot-to-shot fluctuations in the energy, charge, and pointing of wakefield-accelerated electrons. When a mask removes this unstable annulus, RMS fluctuations decrease by more than half without compromising average electron energy substantially. When light from the removed annulus is re-shaped into a co-polarized pulse that peaks on axis and co-propagates at controlled delays -120 < ∆t < 120 fs with respect to the 10× more intense drive pulse, fluctuations in electron and betatron x-ray properties reappear, peaking in amplitude when the weak pulse overlaps either the drive pulse (∆t = 0) or accelerating electrons and the tail of the drive pulse (∆t ≈ 30 fs). In the latter case, a net increase in average electron energy is observed. The results suggest the possibility of precisely and widely tuning the properties of laser-wakefield-accelerated electrons using a comparatively weak auxiliary pulse with a stable, independently controlled carrier envelope phase.

Speaker: Michael Downer (The University of Texas at Austin)

Downer_WG5_Monday.pptx

14:30 Online Correction Of Laser Focal Position Via Deployable Machine Learning Models

Ultrafast lasers play an increasingly critical role in the generation, manipulation, and acceleration of electron beams. Laser plasma accelerators enable order of magnitude improvements in accelerating gradient and promise compact tunable GeV electron beam sources, while novel photocathode systems permit fundamental advances in electron beam manipulation for accelerator and radiation applications. Advances in fast feedback systems are required to stabilize laser performance at kHz repetition rate operation against environmental fluctuations. A field programmable gate array (FPGA) based digital control system, coupled with responsive optics, can provide rapid and precise stabilization of ultrafast lasers. Here we report on an effort to develop, test, and deploy these systems across a range of beamlines operating at >1 Hz repetition rate, including 1 kHz systems. Our initial efforts demonstrate the calibration of a fast, non-destructive focal position diagnostic in concert with a deployable correction scheme. The resulting prototype shows diagnostic responsiveness into the 100s of Hz.

Speaker: Nathan Cook (RadiaSoft LLC)

Cook_AAC2022_onlinecorrection.pdf

14:50 A Compact Source of Positron Beams with Small Thermal Emittance

We investigate electrostatic traps as a novel source of positron beams for accelerator physics applications. The electrostatic trap is a simple device that accumulates and cools positrons produced by a radioactive source. Using well-established techniques, the positron beam is cooled down to or below room temperature. The thermal beam emittance is an order of magnitude smaller than beams produced by rf photocathodes [1]. The compact positron source can be built and operated at a fraction of the cost of traditional target-based positron sources. Despite these advantages, there are several features of electrostatic trap-based beams which limit their use to specialized applications. In this work, we study the features of positron beams from electrostatic traps. The positron bunch is first accelerated and compressed by an electrostatic buncher before being injected into an rf-cavity for further acceleration. We model the acceleration of the positron bunch up to an energy of 17.57 MeV with a transverse thermal emittance of 0.45 $\mu$m-rad, and bunch length of 0.21 mm. The beamline used in our model is about 1.5 meters long, which is comparable to an rf photocathode source, and far more compact than traditional target-based positron sources.

[1] B. J. Claessens, S. B. Van Der Geer, G. Taban, E. J. Vredenbregt, and O. J. Luiten, “Ultracold electron source,” Physical Review Letters, vol. 95, no. 16, pp. 1–4, 2005.

Speaker: Rafi Hessami (SLAC National Accelerator Laboratory)

AAC_2022_talk_positron_source.pptx

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 WG5: Beam Sources, Monitoring, and Control: Session 8

Conveners: Dr Samuel Barber (Lawrence Berkeley National Laboratory) , Yine Sun (Argonne National Laboratory)

13:30 Plasma-photonic diagnostic of plasma-based accelerators.

Reliable and versatile diagnostic methods are essential for modern accelerator facilities to successfully experiment with energetic particle bunches. Conventionally, an expansive network of tools is implemented in and around interaction points for optimization of experimental conditions; this is true for plasma-based accelerator experiments, with added restrictions to intercepting diagnostics due to the volatile plasma and increasingly intense fields of particle bunches. Here, we present a novel diagnostic that utilizes the afterglow light emitted from the plasma after interacting with an electron beam, demonstrate its utility to provide spatio-temporal synchronization between electron beam and plasma generating laser pulse, and discuss how it can be used for optimization of many plasma-based accelerator experimental parameters.

Speaker: Andrew Sutherland (University of Strathclyde)

13:50 Single-shot, transverse self-wakefield reconstruction from screen images

A method to reconstruct the transverse self-wakefields acting on a beam, based only on screen images, is introduced. By employing derivative-free optimization, the relatively high-dimensional parameter space can be efficiently explored to determine the multipole components up to the desired order. This technique complements simulations, which are able to directly infer the wakefield composition. It is applied to representative simulation results as a benchmark and also applied to experimental data on skew wake observations from dielectric slab structures.

Speaker: Nathan Majernik

Majernik - Wakefield reconstruction.pdf

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