FLS2023 - Table of Session: TU1C (Working Group C: Compact Light Sources)

Paper	Title	Page
TU1C1	An Efficient Optimisation of a Burst Mode-Operated Fabry-Perot Cavity for Compton Light Sources	46
	V. Mușat, E. Granados, A. Latina CERN, Meyrin, Switzerland E. Cormier CELIA, Talence, France G. Santarelli ILE, Palaiseau Cedex, France
	The burst mode operation of a Fabry-Perot cavity (FPC) allows for the generation of a high-intensity photon beam in inverse Compton scattering (ICS) sources. The geometry and burst mode parameters of the FPC can be optimised to maximise the scattered photon flux. A novel optimisation method is presented, significantly improving processing speed and accuracy. The FPC’s dimensions, mirror requirements, and effective energy can be obtained from the electron beam parameters at the interaction point. A multi-objective optimization algorithm was used to derive the geometrical parameters of the FPC; this brought orders of magnitude increase in computation speed if compared to the nominal Monte Carlo-based approaches. The burst mode parameters of the FPC were obtained by maximizing the effective energy of the laser pulse in the FPC. The impact of optical losses and thermal lensing on the FPC parameters is addressed. Preliminary parameters of an ICS source implementing this novel optimisation are presented. The source could reach high-performance photon beams for high-energy applications.
	Slides TU1C1 [1.776 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C1
About •	Received ※ 22 August 2023 — Revised ※ 24 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TU1C2	Evolution of the Inverse Compton Scattering X-ray Source of the ELSA Accelerator	50
	A. Pires, R. Rosch, J. Touguet CEA, Arpajon, France N. Delerue Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France V. Le Flanchec CEA/DAM/DIF, Arpajon, France
	The Inverse Compton Scattering (ICS) X-ray source of ELSA accelerator at CEA-DAM, presents an efficient approach for generating X-rays with a compact linac. The source consists of a 30 MeV, 15 ps rms, up to 3 nC electron beam; and a table-top Nd:YAG laser. X-rays are produced in the 10-80 keV range, higher X-ray energies achieved with frequency doubling of the laser. The yield is increased by a factor of 8 thanks to an optical mirror system developed at CEA, folding the laser beam path and accumulating successive laser pulses. We present a new version of the device, with improvement of mechanical constraints management, adjunction of motorized mirrors, and a new imaging system. A Chirped Pulse Amplification (CPA) system was also designed, enabling higher amplification levels without exceeding laser damage threshold. The uniqueness of this CPA system lies in its use of a short wavelength bandwidth, ±250 pm after Self-Phase Modulation (SPM) broadening, and a line density of 1850 lines/mm for the gratings of the compressor. The pulse is stretched with a chirped fiber Bragg grating (CFBG) before amplification in Nd:YAG amplifiers, and compressed by a double pass grating compressor.
	Slides TU1C2 [7.085 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C2
About •	Received ※ 25 August 2023 — Revised ※ 25 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TU1C3	A Compton Light Source Based on Counter Propagating Direct Laser Acceleration Channels
	T. Meir, I. Cohen, L. Perelmutter, I. Pomerantzpresenter Tel Aviv University, Tel-Aviv, Israel A.V. Arefiev, K. Tangtartharakul UCSD, La Jolla, California, USA T. Cohen Soreq NRC, Yavne, Israel
	For the past two decades, intense lasers have supported new schemes for generating high-energy particle beams in university-scale laboratories. With the direct laser acceleration (DLA) method, the leading part of the laser pulse ionizes the target material and forms a positively charged ion plasma channel into which electrons are injected and accelerated. A striking feature of DLA is the extremely high conversion efficiency from laser energy to MeV electrons, with reported values as high as 23%, which makes this mechanism ideal for generating large numbers of photo-nuclear reactions. DLA is well understood and reproduced in numeric simulations. However, the electron energies obtained with the highest laser intensities available nowadays, fail to meet numerical predictions. In an experimental campaign, followed by a numerical investigation, we revealed that at these higher laser intensities, the leading edge of the laser pulse may deplete the target material of its ionization electrons prematurely. We demonstrated that for efficient DLA to prevail, a target material of sufficiently high atomic number is required to maintain the injection of ionization electrons at the peak intensity of the pulse when the DLA channel is already formed. I will present a numerical study on employing this new understanding for realizing a high brightness Compton light source in two counter-propagating DLA channels. Our 3D particle-in-cell results indicate small cone-angle photon emission in the multi 10s of keV spectral range, with few-fs duration and micron-scale source size.
	Slides TU1C3 [6.684 MB]
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TU1C4	The CXFEL Project at Arizona State University	54
	W.S. Graves ASU, Tempe, USA
	Funding: This work supported by National Science Foundation awards 2153503, 1935994, and 1632780. The CXFEL Project encompasses the Compact X-ray Light Source (CXLS) that is now commissioning in the hard x-ray energy range 4-20 keV, and the Compact X-ray Free-Electron Laser (CXFEL) designed to lase in the soft x-ray range 300 ¿ 2500 eV. CXFEL has recently completed a 3-year design phase and just received NSF funding for construction over the next 5 years. These instruments are housed in separate purpose-built laboratories and rely on inverse Compton scattering of bright electron beams on powerful lasers to produce femtosecond pulses of x-rays from very compact linacs approximately 1 m in length. Both instruments use recently developed X-band distributed-coupling, room-temperature, standing-wave linacs and photoinjectors operating at 1 kHz repetition rates and 9300 MHz RF frequency. They rely on recently developed Yb-based lasers operating at high peak and average power to produce fs pulses of 1030 nm light at 1 kHz repetition rate with pulse energy up to 400 mJ. We present the current commissioning performance and status of CXLS. We also review the design and initial construction activities of the large collaborative effort to develop the fully coherent CXFEL.
	Slides TU1C4 [7.974 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C4
About •	Received ※ 30 August 2023 — Revised ※ 31 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

An Efficient Optimisation of a Burst Mode-Operated Fabry-Perot Cavity for Compton Light Sources

46

V. Mușat, E. Granados, A. Latina
CERN, Meyrin, Switzerland
E. Cormier
CELIA, Talence, France
G. Santarelli
ILE, Palaiseau Cedex, France

The burst mode operation of a Fabry-Perot cavity (FPC) allows for the generation of a high-intensity photon beam in inverse Compton scattering (ICS) sources. The geometry and burst mode parameters of the FPC can be optimised to maximise the scattered photon flux. A novel optimisation method is presented, significantly improving processing speed and accuracy. The FPC’s dimensions, mirror requirements, and effective energy can be obtained from the electron beam parameters at the interaction point. A multi-objective optimization algorithm was used to derive the geometrical parameters of the FPC; this brought orders of magnitude increase in computation speed if compared to the nominal Monte Carlo-based approaches. The burst mode parameters of the FPC were obtained by maximizing the effective energy of the laser pulse in the FPC. The impact of optical losses and thermal lensing on the FPC parameters is addressed. Preliminary parameters of an ICS source implementing this novel optimisation are presented. The source could reach high-performance photon beams for high-energy applications.

Slides TU1C1 [1.776 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C1

About •

Received ※ 22 August 2023 — Revised ※ 24 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TU1C2

Evolution of the Inverse Compton Scattering X-ray Source of the ELSA Accelerator

50

A. Pires, R. Rosch, J. Touguet
CEA, Arpajon, France
N. Delerue
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
V. Le Flanchec
CEA/DAM/DIF, Arpajon, France

The Inverse Compton Scattering (ICS) X-ray source of ELSA accelerator at CEA-DAM, presents an efficient approach for generating X-rays with a compact linac. The source consists of a 30 MeV, 15 ps rms, up to 3 nC electron beam; and a table-top Nd:YAG laser. X-rays are produced in the 10-80 keV range, higher X-ray energies achieved with frequency doubling of the laser. The yield is increased by a factor of 8 thanks to an optical mirror system developed at CEA, folding the laser beam path and accumulating successive laser pulses. We present a new version of the device, with improvement of mechanical constraints management, adjunction of motorized mirrors, and a new imaging system. A Chirped Pulse Amplification (CPA) system was also designed, enabling higher amplification levels without exceeding laser damage threshold. The uniqueness of this CPA system lies in its use of a short wavelength bandwidth, ±250 pm after Self-Phase Modulation (SPM) broadening, and a line density of 1850 lines/mm for the gratings of the compressor. The pulse is stretched with a chirped fiber Bragg grating (CFBG) before amplification in Nd:YAG amplifiers, and compressed by a double pass grating compressor.

Slides TU1C2 [7.085 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C2

About •

Received ※ 25 August 2023 — Revised ※ 25 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TU1C3

A Compton Light Source Based on Counter Propagating Direct Laser Acceleration Channels

T. Meir, I. Cohen, L. Perelmutter, I. Pomerantzpresenter
Tel Aviv University, Tel-Aviv, Israel
A.V. Arefiev, K. Tangtartharakul
UCSD, La Jolla, California, USA
T. Cohen
Soreq NRC, Yavne, Israel

For the past two decades, intense lasers have supported new schemes for generating high-energy particle beams in university-scale laboratories. With the direct laser acceleration (DLA) method, the leading part of the laser pulse ionizes the target material and forms a positively charged ion plasma channel into which electrons are injected and accelerated. A striking feature of DLA is the extremely high conversion efficiency from laser energy to MeV electrons, with reported values as high as 23%, which makes this mechanism ideal for generating large numbers of photo-nuclear reactions. DLA is well understood and reproduced in numeric simulations. However, the electron energies obtained with the highest laser intensities available nowadays, fail to meet numerical predictions. In an experimental campaign, followed by a numerical investigation, we revealed that at these higher laser intensities, the leading edge of the laser pulse may deplete the target material of its ionization electrons prematurely. We demonstrated that for efficient DLA to prevail, a target material of sufficiently high atomic number is required to maintain the injection of ionization electrons at the peak intensity of the pulse when the DLA channel is already formed. I will present a numerical study on employing this new understanding for realizing a high brightness Compton light source in two counter-propagating DLA channels. Our 3D particle-in-cell results indicate small cone-angle photon emission in the multi 10s of keV spectral range, with few-fs duration and micron-scale source size.

Slides TU1C3 [6.684 MB]

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TU1C4

The CXFEL Project at Arizona State University

54

W.S. Graves
ASU, Tempe, USA

Funding: This work supported by National Science Foundation awards 2153503, 1935994, and 1632780.
The CXFEL Project encompasses the Compact X-ray Light Source (CXLS) that is now commissioning in the hard x-ray energy range 4-20 keV, and the Compact X-ray Free-Electron Laser (CXFEL) designed to lase in the soft x-ray range 300 ¿ 2500 eV. CXFEL has recently completed a 3-year design phase and just received NSF funding for construction over the next 5 years. These instruments are housed in separate purpose-built laboratories and rely on inverse Compton scattering of bright electron beams on powerful lasers to produce femtosecond pulses of x-rays from very compact linacs approximately 1 m in length. Both instruments use recently developed X-band distributed-coupling, room-temperature, standing-wave linacs and photoinjectors operating at 1 kHz repetition rates and 9300 MHz RF frequency. They rely on recently developed Yb-based lasers operating at high peak and average power to produce fs pulses of 1030 nm light at 1 kHz repetition rate with pulse energy up to 400 mJ. We present the current commissioning performance and status of CXLS. We also review the design and initial construction activities of the large collaborative effort to develop the fully coherent CXFEL.

Slides TU1C4 [7.974 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU1C4

About •

Received ※ 30 August 2023 — Revised ※ 31 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)