Free-electron lasers: reliability, performance, and beam delivery

Edwards, Glenn S.; Evertson, D.W.; Gabella, W.; Grant, R. S.; King, T.L.; Kozub, John A.; Mendenhall, Marcus H.; Shen, Jin; Shores, Richard E.; Storms, S.; Traeger, Robert H.

doi:10.1109/2944.577303

Cited by 57 publications

(24 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…21 The beam comes in a train macropulses, each consisting of approximately 14,000 one-ps micropulses with 350 ps separation. A macropulse extends for about 5 μs with a repetition rate of 30 Hz.…”

Section: Methodsmentioning

confidence: 99%

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

et al. 2011

View full text Add to dashboard Cite

We report wavelength-and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt Free Electron Laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multi-photon absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two-and three-photon absorption coefficients (β and γ) as fitting parameters.Using newly measured values of the low-intensity FCA cross-sections, we find a best fit to the data at 2.8 µm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free carrier cross-sections and beam diameter. Receipt

show abstract

Section: Methodsmentioning

confidence: 99%

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The phase-space acceptance of this accelerator produces a train of micropulses, which are ∼0.7-1 ps long and separated by approximately 350 ps. 78 This train of ∼3 × 10 4 micropulses extends for about a 4 µs macropulse at a repetition rate of up to 30 Hz. Figure 5 shows a schematic of the temporal pulse structure of the Vanderbilt FEL.…”

Section: W M Keck Fel At Vanderbilt Universitymentioning

confidence: 99%

Mechanisms of Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation

Torres

Johnson

Haglund

et al. 2011

Critical Reviews in Solid State and Materials Sciences

View full text Add to dashboard Cite

For the last decade, a variant of pulsed laser ablation, Resonant-Infrared Matrix-Assisted Pulsed Laser Evaporation (RIR-MAPLE), has been studied as a deposition technique for organic and polymeric materials. RIR-MAPLE minimizes photochemical damage from direct interaction with the intense laser beam by encapsulating the polymer in a high infrared-absorption solvent matrix. This review critically examines the thermally-induced ablation mechanisms resulting from irradiation of cryogenic solvent matrices by a tunable free electron laser (FEL). A semi-empirical model is used to calculate temperatures as a function of time in the focal volume and determine heating rates for different resonant modes in two model solvents, based on the thermodynamics and kinetics of the phase transitions induced in the solvent matrices.Three principal ablation mechanisms are discussed, namely normal vaporization at the surface, normal boiling, and phase explosion. Normal vaporization is a highly inefficient polymer deposition mechanism as it relies on collective collisions with evaporating solvent molecules. Diffusion length calculations for heterogeneously nucleated vapor bubbles show that normal boiling is kinetically limited. During high-power pulsed-FEL irradiation, phase explosion is shown to be the most significant contribution to polymer deposition in RIR-MAPLE. Phase explosion occurs when the target is rapidly heated (10 8 to 10 10 K/s) and the solvent matrix approaches its critical temperature. Spontaneous density stratification (spinodal decay) within the condensed metastable phase leads to rapid homogeneous nucleation of vapor bubbles. As these vapor bubbles interconnect, large pressures build up within the condensed phase, leading to target explosions and recoil-induced ejections of polymer to a near substrate. Phase explosion is a temperature (fluence) threshold-limited process, while surface evaporation can occur even at very low fluences.

show abstract

“…In particular, in these survival studies of FEL incisions of the cortex, the collateral thermal injury as measured by histology was approximately one cell width deep (∼ 10 μm) to the laser incision and typically undetectable (<∼ 1 μm) on the sides of the incision without any additional sloughing off of tissue peripheral to the laser cavity as is the case with 3.0 micron tissue ablation. In parallel with these animal studies: the Mark-III FEL was upgraded to meet the performance and reliability standards of a medical laser; a set of surgical suites was constructed in the Vanderbilt FEL Center; and a beam delivery system was developed to transport the infrared beam from the FEL vault in the basement to the operating room on the fourth floor, culminating in a hand-held surgical tool that delivered the beam to the tissue surface [15]. While infrared fiber technology available at that time was a limiting factor, this limitation was overcome either by a modified articulated arm for human neurosurgery or by hollow-glass waveguide technology for human ophthalmic surgery [15,16].…”

Section: Fel Tissue Ablation and Surgical Applicationsmentioning

confidence: 99%

“…In parallel with these animal studies: the Mark-III FEL was upgraded to meet the performance and reliability standards of a medical laser; a set of surgical suites was constructed in the Vanderbilt FEL Center; and a beam delivery system was developed to transport the infrared beam from the FEL vault in the basement to the operating room on the fourth floor, culminating in a hand-held surgical tool that delivered the beam to the tissue surface [15]. While infrared fiber technology available at that time was a limiting factor, this limitation was overcome either by a modified articulated arm for human neurosurgery or by hollow-glass waveguide technology for human ophthalmic surgery [15,16]. Then a protocol for human FEL neurosurgery (essentially ablate a tissue volume the size of sugar cube from the surface of a golf-ball sized tumor) was granted an Investigational Device Exemption by the FDA and the protocol was approved by the State of Tennessee and by Vanderbilt University's Investigational Review Board.…”

Section: Fel Tissue Ablation and Surgical Applicationsmentioning

confidence: 99%

Mechanisms for soft‐tissue ablation and the development of alternative medical lasers based on investigations with mid‐infrared free‐electron lasers

Edwards

2009

Laser & Photonics Reviews

Self Cite

View full text Add to dashboard Cite

Experimental evidence indicating the potential biomedical advantages of using a Mark-III Free-Electron Laser (FEL) for the ablation of soft tissue were first reported in 1994. Research progress since that time is reviewed, including: 1) successful human surgery using the Mark-III FEL; 2) advances in understanding the physical mechanism for infrared tissue ablation and how these mechanistic features correlate with the preferential ablative properties; 3) the pursuit of table-top, nanosecondpulsed laser technology that mimics the preferential ablation properties of the Mark-III FEL with the aim of improving clinical acceptance of mid-infrared laser ablation of soft tissue; and 4) current research challenges.Ablation cavity in rat brain cortex due to irradiation with a Mark-III FEL tuned to a wavelength of 6.45 microns. One hundred macropulses (20 mJ each) at a macropulse repetition rate of 4 Hz were focused to a spot with a diameter of ∼ 100 microns on the tissue surface. The section was stained with H&E. A) Full view of ablation cavity, where the original magnification was x100. Total incision depth was 3.060 mm. B) Ablation cavity with an additional magnification of x17. Coagulation heat necrosis was not measurable (<∼ 1 μm) on the sides throughout the ablation cavity and limited to ∼ 4 μm at the deep (bottom most) aspect. Fold is a mounting artifact. Adapted by permission from MacMillan Publishers Ltd [1].

show abstract

Free-electron lasers: reliability, performance, and beam delivery

Cited by 57 publications

References 27 publications

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

Mechanisms of Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation

Mechanisms for soft‐tissue ablation and the development of alternative medical lasers based on investigations with mid‐infrared free‐electron lasers

Contact Info

Product

Resources

About