F. G. Serpa

Non-kinetic Damage on Insulating Materials by Highly Charged Ion Bombardment

Abstract We have measured the damage caused by the impact of low velocity, highly charged ions on insulating surfaces. Atomic force microscopy allows us to observe directly the surface topography with nanometer resolution. Using constant velocity (100 keV) Xe q + ions (25 ⩽ q ⩽ 50) impinging on mica, we observe damage caused by single ion impacts. Impact sites typically are circular hillocks. Within the range and accuracy of the data, the height and volume of the damaged regions are well approximated by a linear function of ion potential energy.

Lifetime measurements in the ground configuration of and using an electron beam ion trap

We have measured the radiative lifetimes for the level of and the level of . These measurements were performed by monitoring the temporal behaviour of their associated radiative decays during magnetic trapping mode in an electron beam ion trap (EBIT). Our lifetime results, 8.7(5) ms for and 5.7(5) ms for , are compared with theory.

The use of a Spherically Curved Crystal Spectrometer for X-ray Measurements on Electron Beam Ion Trap

Spherically curved crystal spectrometers are demonstrated for use on an Electron Beam Ion Trap (EBIT) for the first time. Such spectrometers are characterized by high light collection efficiency and relative insensitivity to source position, simultaneously, giving them an advantage that no X-ray spectrometer previously used on an EBIT has had. One of the spectrometer crystals tested is composed of mica, giving it the additional advantage that it can be used with reasonable efficiency up to very high order, allowing spectra to span a broad wavelength range from 0.5 Angstroms to 20 Angstroms. Spectra from Ne-like barium and He-like argon are presented.

Absolute Calibration of an X-ray Spectrometer on the NIST Electron-Beam Ion Trap: Control, Design and Systematics

The course of Electron-Beam Ion Trap (EBIT) experiments depends more and more on precision measurement. To design and test a system of absolute spectroscopy to 10-20 parts per million for such a source is a challenging task. Other design criteria include good efficiency in the 3-10 keV energy range, ability to focus a line source and high vacuum compatibility. Some difficulties are discussed. The use of a non-scanning Johann focussing spectrometer and its consequent calibration is discussed. The spectrometer has been used in a series of experiments on the NIST EBIT. The detector location is shown (both experimentally and by modelling) to provide a major systematic contribution, which can however be controlled to a suitable tolerance. Future directions are indicated.

Progress Towards Absolute X-Ray Spectroscopy on the NIST Electron-Beam Ion Trap: Current Status and Results

Recent observation of Hydrogen-like ions of Vanadium at the NIST Electron-Beam Ion Trap and measurements of Helium-like resonance line are presented. One particular feature of the current series of experiments is the possibility of absolute calibration in a near Doppler-free environment. The current approach to the possible measurement of QED effects in such a system is reviewed. There is great potential for precision measurements in the near future.

Fabry-Perot spectroscopy of a visible magnetic dipole transition in Ba34+

Abstract We are using Fabry-Perot interferometry to study visible lines from highly-charged ions created and trapped within an electron beam ion trap (EBIT). The 3d 4 5 D 2 – 5 D 3 titanium-like barium (Ba 34+ ) line at 3932(2) A was recently measured in Ref. [1] (C.A. Morgan et al., Phys. Rev. Lett. 74 (1995) 1716) using a grating monochromator. We present preliminary Fabry-Perot spectra of this line with significantly improved resolution. The Doppler-broadened 1 A line width is consistent with an expected ion temperature of less than 1 keV. We discuss the possibility of resolving Zeeman splittings, and of using these visible lines as a diagnostic in high temperature, low density plasmas, like those that exist in tokamaks and the EBIT itself.

Absolute Test of Quantum Electrodynamics for Helium-Like Vanadium

Absolute measurements of the energies of helium-like vanadium resonances on an electron beam ion trap (EBIT) are reported. The results agree with recent theoretical calculations and the experimental precision (27–40 ppm) lies at the same level as the current uncertainty in theory (0.1 eV). The measurements represent a 5.7%–8% determination of the quantum electrodynamics (QED) contribution to the transition energies and are the most precise measurements of the helium-like resonances in the Z = 19–31 range. These are the first precision X-ray measurements on the National Institute of Standards and Technology EBIT and strongly commend the EBIT as a new spectroscopic source for QED investigations.