Determination of electron-impact transfer rate coefficients between argon 1s<sub>2</sub>and 1s<sub>3</sub>states by laser pump–probe technique

Carbone, E.; Hübner, S Simon; Mullen, van der Jjam Joost; Kroesen, Gmw Gerrit; Sadeghi, N.

doi:10.1088/0022-3727/46/41/415202

Cited by 18 publications

(27 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lifetime of the Ar p effective level has been taken directly from the literature (Wiese & Martin, 1980), as well as for the Ar Ã 2 excimer state (Neeser et al, 1997). However, for the Ar s states the mixture between resonant and metastable states at high pressure requires taking into account the exchange between levels due to electron collisions (Carbone et al, 2013) (1997) photons (Mills & Hieftje, 1984). These effects can be approximated by a longer effective lifetime of the Ar s level block, which in our case is of the order of microseconds.…”

Section: Fluid Modelmentioning

confidence: 99%

Hybrid modelling of a high-power X-ray attenuator plasma

Ortega

Lacoste

Minea

2018

J Synchrotron Radiat

View full text Add to dashboard Cite

X-ray gas attenuators act as stress-free high-pass filters for synchrotron and free-electron laser beamlines to reduce the heat load in downstream optical elements without affecting other properties of the X-ray beam. The absorption of the X-ray beam triggers a cascade of processes that ionize and heat up the gas locally, changing its density and therefore the X-ray absorption. Aiming to understand and predict the behaviour of the gas attenuator in terms of efficiency versus gas pressure, a hybrid model has been developed, combining three approaches: an analytical description of the X-ray absorption; Monte Carlo for the electron thermalization; and a fluid treatment for the electron diffusion, recombination and excited-states relaxation. The model was applied to an argon-filled attenuator prototype built and tested at the European Synchrotron Radiation Facility, at a pressure of 200 mbar and assuming stationary conditions. The results of the model showed that the electron population thermalizes within a few nanoseconds after the X-ray pulse arrival and it occurs just around the X-ray beam path, recombining in the bulk of the gas rather than diffusing to the attenuator walls. The gas temperature along the beam path reached 850 K for 770 W of incident power and 182 W m of absorbed power. Around 70% of the absorbed power is released as visible and UV radiation rather than as heat to the gas. Comparison of the power absorption with the experiment showed an overall agreement both with the plasma radial profile and power absorption trend, the latter within an error smaller than 20%. This model can be used for the design and operation of synchrotron gas attenuators and as a base for a time-dependent model for free-electron laser attenuators.

show abstract

Section: Fluid Modelmentioning

confidence: 99%

Hybrid modelling of a high-power X-ray attenuator plasma

Ortega

Lacoste

Minea

2018

J Synchrotron Radiat

View full text Add to dashboard Cite

show abstract

“…From the absorption profile one can obtain the density of atoms in the lower state of the line and the temperature of the gas. This method has been used in the study of a variety of plasma sources, like surfatron launchers Carbone et al, 2013), microwave discharges (Latrasse et al, 2007), inductively coupled plasmas (de Regt et al, 1996;Jonkers et al, 1999) or dielectric barrier discharges (Leiweke & Ganguly, 2013). In our case, we used a single laser source tuned to the 1s 5 !…”

Section: Tunable Laser Absorption Spectroscopymentioning

confidence: 99%

Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

Ortega¹,

Lacoste²,

Béchu³

et al. 2017

J Synchrotron Radiat

View full text Add to dashboard Cite

X-ray gas attenuators are used in high-energy synchrotron beamlines as high-pass filters to reduce the incident power on downstream optical elements. The absorption of the X-ray beam ionizes and heats up the gas, creating plasma around the beam path and hence temperature and density gradients between the center and the walls of the attenuator vessel. The objective of this work is to demonstrate experimentally the generation of plasma by the X-ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X-ray power absorption. The gases used in this study were argon and krypton between 13 and 530 mbar. The distribution of the 2p excited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X-ray transmission. The results showed a plasma confined around the X-ray beam path, its size determined mainly by the spatial dimensions of the X-ray beam and not by the absorbed power or the gas pressure. In addition, the X-ray absorption showed a hot central region at a temperature varying between 400 and 1100 K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X-ray beam plays an essential role in the X-ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.

show abstract

“…Chemical and biological reactions, on the level of atoms and molecules, recently became one of the most thoroughly studied physical phenomena [1][2][3][4][5][6][7]. One of the well−known ways to investigate them is the pump−and−probe technique [1][2][3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…One of the well−known ways to investigate them is the pump−and−probe technique [1][2][3][4][5][6][7][8][9]. This technique had not been used so widely in this field before different lasers generating short pulses of elec− tromagnetic radiations were developed [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier (MOPA) laser system

Młyńczak

Sawicz-Kryniger

Fry

et al. 2014

Opto-Electronics Review

View full text Add to dashboard Cite

The Linac coherent light source (LCLS) at the SLAC National Accelerator Laboratory (SLAC) is the world’s first hard X-ray free electron laser (XFEL) and is capable of producing high-energy, femtosecond duration X-ray pulses. A common technique to study fast timescale physical phenomena, various “pump/probe” techniques are used. In these techniques there are two lasers, one optical and one X-ray, that work as a pump and as a probe to study dynamic processes in atoms and molecules. In order to resolve phenomena that occur on femtosecond timescales, it is imperative to have very precise timing between the optical lasers and X-rays (on the order of ∼20 fs or better). The lasers are synchronized to the same RF source that drives the accelerator and produces the X-ray laser. However, elements in the lasers cause some drift and time jitter, thereby de-synchronizing the system. This paper considers cross-correlation technique as a way to quantify the drift and jitter caused by the regenerative amplifier of the ultrafast optical laser.

show abstract

Determination of electron-impact transfer rate coefficients between argon 1s₂and 1s₃states by laser pump–probe technique

Cited by 18 publications

References 27 publications

Hybrid modelling of a high-power X-ray attenuator plasma

Hybrid modelling of a high-power X-ray attenuator plasma

Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier (MOPA) laser system

Contact Info

Product

Resources

About

Determination of electron-impact transfer rate coefficients between argon 1s2and 1s3states by laser pump–probe technique

Cited by 18 publications

References 27 publications

Hybrid modelling of a high-power X-ray attenuator plasma

Hybrid modelling of a high-power X-ray attenuator plasma

Characterization of X-ray gas attenuator plasmas by optical emission and tunable laser absorption spectroscopies

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier (MOPA) laser system

Contact Info

Product

Resources

About

Determination of electron-impact transfer rate coefficients between argon 1s₂and 1s₃states by laser pump–probe technique