High quality ultrafast transmission electron microscopy using resonant microwave cavities

Ultrashort, low-emittance electron pulses can be created at a high repetition rate by using a TM$_{110}$ deflection cavity to sweep a continuous beam across an aperture. These pulses can be used for time-resolved electron microscopy with atomic spatial and temporal resolution at relatively large average currents. In order to demonstrate this, a cavity has been inserted in a transmission electron microscope, and picosecond pulses have been created. No significant increase of either emittance or energy spread has been measured for these pulses. At a peak current of $814\pm2$ pA, the root-mean-square transverse normalized emittance of the electron pulses is $\varepsilon_{n,x}=(2.7\pm0.1)\cdot 10^{-12}$ m rad in the direction parallel to the streak of the cavity, and $\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad in the perpendicular direction for pulses with a pulse length of 1.1-1.3 ps. Under the same conditions, the emittance of the continuous beam is $\varepsilon_{n,x}=\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad. Furthermore, for both the pulsed and the continuous beam a full width at half maximum energy spread of $0.95\pm0.05$ eV has been measured

Harbour Light. Port and transport related EU policy and regulations: The professionals' guide

Document type: Boo

On reductions of some KdV-type systems and their link to the quartic He'non-Heiles Hamiltonian

A few 2+1-dimensional equations belonging to the KP and modified KP hierarchies are shown to be sufficient to provide a unified picture of all the integrable cases of the cubic and quartic H\'enon-Heiles Hamiltonians.Comment: 12 pages, 3 figures, NATO ARW, 15-19 september 2002, Elb

An analysis of the morphology and submarine landslide potential of the upper and middle continental slope offshore Fraser Island, Queensland, Australia

This study presents an investigation into the geomorphological, sedimentological and geotechnical properties of submarine landslides present on the continental slope offshore Fraser Island. An extensive range of previously undiscovered features including marginal plateaus, linear rills, ridges and gullies, canyon systems, as well as slides and slumps were identified. Gravity cores (5.65 m and 3.64 m long) taken in the ‘Upper Slope Slide’ (25 km2 in area, 200-300 m thick), and the ‘Middle Slope Slide’ (11 km2 in area, 100-150 m thick) indicate the slide scars contain drapes of Pleistocene to Recent hemipelagic mud. Shorter gravity cores (1.33 m and 0.43 m long) taken adjacent to both slides terminated in stiff muds of upper Pliocene to lower Pleistocene age (Upper Slope Slide), and upper Miocene to lower Pliocene age (Middle Slope Slide). This unique pattern shows that the sediment is being accumulated and protected inside the slide hollows, while being actively removed from the exposed adjacent slopes, most likely by abrasion. Biostratigraphic ages determined for the basal material demonstrate that the seafloor surfaces at both sites are effectively erosional unconformities. The basal, stiff sediments on the upper slope was deposited between 2 and 2.5 Ma BP; this material was scoured and then buried beneath a 1 m thick sediment drape at 0.45 Ma BP. Sediments exposed on the seafloor adjacent to the Middle Slope Slide were dated at around 6-8.5 Ma BP. This indicates that the smooth upper continental slope developed its morphology by the late-mid Pleistocene, while the middle slope is a Post-Pliocene feature. It is thought that Pliocene-Pleistocene geological events including fluctuations in the intensity of surface and abyssal ocean currents are responsible for re-sculpting the continental slope’s morphology and have a) increased abrasion and erosion of the middle and upper slope; while b) suppressed sediment delivery

Continuous method for manufacturing grain-oriented magnetostrictive bodies

The invention comprises a continuous casting and crystallization method formanufacturing grain-oriented magnetostrictive bodies. A magnetostrictive alloy is melted in a crucible having a bottom outlet. The melt is discharged through the bottom of the crucible and deposited in an elongated mold. Heat is removed from the deposited melt through the lower end portion of the mold to progressively solidify the melt. The solid-liquid interface of the melt moves directionally upwardly from the bottom to the top of the mold, to produce the axial grain orientation

Theory and particle tracking simulations of a resonant radiofrequency deflection cavity in TM110_{110} mode for ultrafast electron microscopy

We present a theoretical description of resonant radiofrequency (RF) deflecting cavities in TM$_{110}$ mode as dynamic optical elements for ultrafast electron microscopy. We first derive the optical transfer matrix of an ideal pillbox cavity and use a Courant-Snyder formalism to calculate the 6D phase space propagation of a Gaussian electron distribution through the cavity. We derive closed, analytic expressions for the increase in transverse emittance and energy spread of the electron distribution. We demonstrate that for the special case of a beam focused in the center of the cavity, the low emittance and low energy spread of a high quality beam can be maintained, which allows high-repetition rate, ultrafast electron microscopy with 100 fs temporal resolution combined with the atomic resolution of a high-end TEM. This is confirmed by charged particle tracking simulations using a realistic cavity geometry, including fringe fields at the cavity entrance and exit apertures

Method of increasing magnetostrictive response of rare earth-iron alloy rods

This invention comprises a method of increasing the magnetostrictive response of rare earth iron (RFe) magnetostrictive alloy rods by a thermal-magnetic treatment. The rod is heated to a temperature above its Curie temperature, viz. from 400 rod is at that temperature, a magnetic field is directionally applied and maintained while the rod is cooled, at least below its Curie temperature

Dual mode microwave deflection cavities for ultrafast electron microscopy

This paper presents the experimental realization of an ultrafast electron microscope operating at a repetition rate of 75 MHz based on a single compact resonant microwave cavity operating in dual mode. This elliptical cavity supports two orthogonal TM$_{110}$ modes with different resonance frequencies that are driven independently. The microwave signals used to drive the two cavity modes are generated from higher harmonics of the same Ti:Sapphire laser oscillator. Therefore the modes are accurately phase-locked, resulting in periodic transverse deflection of electrons described by a Lissajous pattern. By sending the periodically deflected beam through an aperture, ultrashort electron pulses are created at a repetition rate of 75 MHz. Electron pulses with $\tau=(750\pm10)$ fs pulse duration are created with only $(2.4\pm0.1)$ W of microwave input power; with normalized rms emittances of $\epsilon_{n,x}=(2.1\pm0.2)$ pm rad and $\epsilon_{n,y}=(1.3\pm0.2)$ pm rad for a peak current of $I_p=(0.4\pm0.1)$ nA. This corresponds to an rms normalized peak brightness of $B_{np,\textrm{rms}}=(7\pm1)\times10^6$ A/m$^2$ sr V, equal to previous measurements for the continuous beam. In addition, the FWHM energy spread of $\Delta U = (0.90\pm0.05)$ eV is also unaffected by the dual mode cavity. This allows for ultrafast pump-probe experiments at the same spatial resolution of the original TEM in which a 75 MHz Ti:Sapphire oscillator can be used for exciting the sample. Moreover, the dual mode cavity can be used as a streak camera or time-of-flight EELS detector with a dynamic range $>10^4$