Long-range propagation of ultrafast ionizing laser pulses in a resonant nonlinear medium

Demeter, G.; Moody, J. T.; Kedves, M. Á.; Ráczkevi, B.; Aladi, M.; Bachmann, A.-M.; Batsch, F.; Braunmüller, F.; Djotyan, G. P.; Fedosseev, V. N.; Friebel, Florence; Gessner, Spencer; Guran, E.; Hüther, M.; Lee, V.; Martyanov, M.; Muggli, P.; Öz, E.; Panuganti, H.; Verra, L.; Porta, G. Zevi Della

doi:10.1103/physreva.104.033506

Cited by 9 publications

(17 citation statements)

References 37 publications

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“…2). The spectrum also had significant intensity at the 795 nm D 1 resonance line (5s 2 S 1/2 → 5p 2 P 1/2 transition) and the 776 nm transitions to higher lying excited states (5p 2 P 3/2 → 5d 2 D 3/2 and 5d 2 D 5/2 ), similarly to our previous experiments [9]. In the other half of the measurements, spectral shaping was used to obtain laser pulses with the central wavelength shifted away from these resonances.…”

Section: Experiments a Laser Propagation Experiments Apparatussupporting

confidence: 89%

“…These single-photon resonances also have a major impact on the propagation of the ionizing laser pulse -a question studied only very recently in the context of ultra-short pulse propagation [8]. It has been suggested [9], that the single-photon resonances give rise to a strong but saturable nonlinearity which can be very advantageous for the propagation of the ionizing pulse. In particular, theoretical indication was that the plasma column becomes longer and more sharply bounded with the use of a resonant ionizing pulse.…”

Section: Introductionmentioning

confidence: 99%

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Generation of 10-m-lengthscale plasma columns by resonant and off-resonant laser pulses

Demeter¹,

Moody²,

Kedves³

et al. 2023

Preprint

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Creating extended, highly homogeneous plasma columns like that required by plasma wakefield accelerators can be a challenge. We study the propagation of ultra-short, TW power ionizing laser pulses in a 10-meter-long rubidium vapor and the plasma columns they create. We perform experiments and numerical simulations for pulses with 780 nm central wavelength, which is resonant with the D2 transition from the ground state of rubidium atoms, as well as for pulses with 810 nm central wavelength, some distance from resonances. We measure transmitted energy and transverse width of the pulse and use schlieren imaging to probe the plasma column in the vapor close to the end of the vapor source. We find, that resonant pulses are more confined in a transverse direction by the interaction than off-resonant pulses are and that the plasma channels they create are more sharply bounded. Off-resonant pulses leave a wider layer of partially ionized atoms and thus lose more energy per unit propagation distance. Using experimental data, we estimate the energy required to generate a 20-meter-long plasma column and conclude that resonant pulses are much more suitable for creating a long, homogeneous plasma.

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Section: Experiments a Laser Propagation Experiments Apparatussupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Generation of 10-m-lengthscale plasma columns by resonant and off-resonant laser pulses

Demeter¹,

Moody²,

Kedves³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…The proton bunch propagates in a plasma created by a relativistic ionisation front (RIF). The RIF is the result of the propagation of a short and intense laser pulse in a rubidium vapour [24][25][26][27]. When the RIF is placed within the proton bunch, the part of the bunch behind the RIF travelling in plasma is transformed into a train of microbunches.…”

Section: Summary Of Experimental Results From Awake Runmentioning

confidence: 99%

The AWAKE Run 2 programme and beyond

Gschwendtner¹,

Lotov²,

Muggli³

et al. 2022

Preprint

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Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. Use of high energy protons to drive wakefields in plasma has been demonstrated during Run 1 of the AWAKE programme at CERN. Protons of energy 400 GeV drove wakefields that accelerated electrons to 2 GeV in under 10 m of plasma. The AWAKE collaboration is now embarking on Run 2 with the main aims to demonstrate stable accelerating gradients of 0.5-1 GV/m, preserve emittance of the electron bunches during acceleration and develop plasma sources scalable to 100s of metres and beyond. By the end of Run 2, the AWAKE scheme should be able to provide electron beams for particle physics experiments and several possible experiments have already been evaluated. This article summarises the programme of AWAKE Run 2 and how it will be achieved as well as the possible application of the AWAKE scheme to novel particle physics experiments.

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“…This is can be fulfilled by carefully tailoring rubidium vapor density in the chamber and achieving single-electron ionization of the atoms with a probability very close to unity [30]. The propagation of the ultra-short, TW ionizing pulse along the vapor source is itself a complex nonlinear process [26], especially because it is resonant with the rubidium D 2 transition line [27,28]. Validating the quality of the plasma can be done near the downstream end of the vapor source, where a pair of observation ports on opposite sides of the chamber allow the passage of a probe beam transverse to the plasma channel axis.…”

Section: Schlieren Imaging Of a Plasma Channel Cross-section A Measur...mentioning

confidence: 99%

“…At the heart of the novel accelerator device, a 10-meter-long plasma channel achieves the modulation of the energetic proton bunch and the acceleration of witness electron bunches in the emerging wakefields. Created via photoionization using a terawatt laser system in a rubidium vapor source chamber [24,25], plasma channel generation is in itself a complex problem of laser beam propagation/filamentation [26][27][28]. Optical diagnostic tools monitoring the plasma channel can thus have a significant role in optimizing, improving the accelerator device and understanding wakefield physics.…”

Section: Introductionmentioning

confidence: 99%

Machine learning methods for Schlieren imaging of a plasma channel in tenuous atomic vapor

Bíró¹,

Pocsai²,

Barna³

et al. 2022

Preprint

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We investigate the usage of a Schlieren imaging setup to measure the geometrical dimensions of a plasma channel in atomic vapor. Near resonant probe light is used to image the plasma channel in a tenuous vapor and machine learning techniques are tested for extracting quantitative information from the images. By building a database of simulated signals with a range of plasma parameters for training Deep Neural Networks, we demonstrate that they can extract from the Schlieren images reliably and with high accuracy the location, the radius and the maximum ionization fraction of the plasma channel as well as the width of the transition region between the core of the plasma channel and the unionized vapor. We test several different neural network architectures with supervised learning and show that the parameter estimations supplied by the networks are resilient with respect to slight changes of the experimental parameters that may occur in the course of a measurement.

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Long-range propagation of ultrafast ionizing laser pulses in a resonant nonlinear medium

Cited by 9 publications

References 37 publications

Generation of 10-m-lengthscale plasma columns by resonant and off-resonant laser pulses

Generation of 10-m-lengthscale plasma columns by resonant and off-resonant laser pulses

The AWAKE Run 2 programme and beyond

Machine learning methods for Schlieren imaging of a plasma channel in tenuous atomic vapor

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