Density-dependent response of an ultracold plasma to few-cycle radio-frequency pulses

Wilson, Truman; Chen, Wei‐Ting; Roberts, Jacob

doi:10.1103/physreva.87.013410

Cited by 19 publications

(21 citation statements)

References 27 publications

(54 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…34. The twocycles of rf drive a collective oscillation in the electron component of the UCP whose resonant frequency is dependent on the plasma frequency associated with the peak density.…”

Section: Measuring the Effect Of Electron Evaporation On Ucp Evolutionmentioning

confidence: 99%

“…36 We measured the initial peak density of the UCP using the 2-cycle rf sweep technique described in Ref. 34 in order to link the value of the initial characteristic size of the ion distribution, r, to the value of f. For a given value of the electric field, F, we can calculate the number of ions required to produce a potential well depth, D, for each of the data points in Fig. 1.…”

Section: Number and Electric Field Calibrationmentioning

confidence: 99%

“…In this region, we have a set of cylindrically symmetric electrodes and a magnetic coil which are described in detail in Ref. 34.…”

Section: Apparatusmentioning

confidence: 99%

See 2 more Smart Citations

Influence of electron evaporative cooling on ultracold plasma expansion

2013

Self Cite

View full text Add to dashboard Cite

The expansion of ultracold neutral plasmas (UCP) is driven primarily by the thermal pressure of the electron component and is therefore sensitive to the electron temperature. For typical UCP spatial extents, evaporative cooling has a significant influence on the UCP expansion rate at lower densities (less than 10 8 /cm 3 ). We studied the effect of electron evaporation in this density range. Owing to the low density, the effects of three-body recombination were negligible. We modeled the expansion by taking into account the change in electron temperature owing to evaporation as well as adiabatic expansion and found good agreement with our data. We also developed a simple model for initial evaporation over a range of ultracold plasma densities, sizes, and electron temperatures to determine over what parameter range electron evaporation is expected to have a significant effect. We also report on a signal calibration technique, which relates the signal at our detector to the total number of ions and electrons in the ultracold plasma. V C 2013 AIP Publishing LLC. INTRODUCTIONThe creation of ultracold neutral plasmas (UCP) 1 has opened a new avenue into studies of the physics of strongly coupled plasmas 2-12 through control of the initial energies of the ions and electrons in the system. Based solely on the initial temperature of the ultracold atoms and the ability to impart little energy during the photoionization process, the ions and electrons in UCPs can be created at relatively low energies, producing plasmas that would have both components in the strongly coupled regime. However, studies have shown that effects such as disorder induced heating, 7,10,13-17 three-body recombination, 14,18,20,21 threshold lowering, 22,23 and Debye screening 6,12 can limit the amount of strongcoupling that is realized in UCP systems. These heating effects increase with the UCP density, though and this suggests that studying UCPs at low density would likely lead to lower electron temperatures, and in the case of electrons, more strongly coupled UCPs (the ions would have lower temperatures but the same strong-coupling owing to self-scaling effects). The effects of electron evaporation also increase with decreasing density, further lowering the electron temperature. This increase in the influence of evaporative cooling with decreasing UCP density is the subject of this work.The early time electron temperature in UCPs is typically experimentally determined from measurements of the UCP expansion, 14 although a direct measurement of this temperature has been reported in Ref. 24 and the electron temperature has been inferred from three-body recombination rates in Ref. 21. The finite temperature of electrons will make the electron density slightly lower than the ion density, creating an internal electric field which will drive the ions to expand. The expansion is typically modelled by a self-similar expansion obtained from the solution to collisionless Vlasov equations, which are applicable through a formal equivalence owing to the spheri...

show abstract

“…34. The twocycles of rf drive a collective oscillation in the electron component of the UCP whose resonant frequency is dependent on the plasma frequency associated with the peak density.…”

Section: Measuring the Effect Of Electron Evaporation On Ucp Evolutionmentioning

confidence: 99%

Section: Number and Electric Field Calibrationmentioning

confidence: 99%

See 1 more Smart Citation

Influence of electron evaporative cooling on ultracold plasma expansion

2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…This truncation point is labeled as R 0 . We set R 0 equal to 6σ 0 in our computations, which is reasonable based on typical extraction fields applied in UCP experiments 10,20 . To compute the electron distribution, the technique outlined in 19 is followed.…”

Section: Ucp Expansion and Electron Temperature Modelmentioning

confidence: 99%

Ultracold plasma expansion as a function of charge neutrality

Witte

Roberts

2014

Physics of Plasmas

Self Cite

View full text Add to dashboard Cite

Ultracold plasmas (UCPs) are created under conditions of near but not perfect neutrality. In the limit of zero electron temperature, electron screening results in non-neutrality manifesting itself as an interior region of the UCP with both electrons and ions and an exterior region composed primarily of ions. The interior region is the region of the most scientific interest for 2-component ultracold plasma physics. This work presents a theoretical model through which the time evolution of non-neutral UCPs is calculated. Despite Debye screening lengths much smaller than the characteristic plasma spatial size, model calculations predict that the expansion rate and the electron temperature of the UCP interior is sensitive to the neutrality of the UCP. The predicted UCP dependence on neutrality has implications for the correct measurement of several UCP properties, such as electron temperature, and a proper understanding of evaporative cooling of the electrons in the UCP.

show abstract

“…It is also possible to create strongly coupled ultracold plasmas by ionizing atoms in a gas jet (Heilmann et al, 2012;Morrison et al, 2008;Sadeghi et al, 2014). These plasmas are diagnosed using three-body recombination (Bannasch and Pohl, 2011;Bergeson and Robicheaux, 2008;Fletcher et al, 2007;Killian et al, 2001;Pohl et al, 2008;Sadeghi et al, 2011), thermalization rates Castro et al, 2010;Lyon and Bergeson, 2011;McQuillen et al, 2011), electron evaporation or rf absorption (Bergeson and Spencer, 2003;Killian et al, 2001;Lu et al, 2011;Roberts et al, 2004;Rolston, 2010, 2012;Wilson et al, 2013), charged particle imaging and detection (Morrison et al, 2008;Zhang et al, 2008), and optical fluorescence (Cummings et al, 2005;Laha et al, 2007;Lyon and Bergeson, 2011) and absorption Killian, 2007;Simien et al, 2004). Theoretical calculations and simulations ( Jin-Xing et al, 2011;Kuzmin and O'Neil, 2002b;Mendonca and Shukla, 2011;Murillo, 2006;Park et al, 2010;Pohl et al, 2004;Robicheaux and Hanson, 2002;Shukla and Avinash, 2011) give great insights into the properties of these plasmas.…”

Section: Introductionmentioning

confidence: 97%