Paul L. Hartman

The Formation and Maintenance of Electron and Ion Beams

The radial potential distribution in an ionic beam of circular cross section is calculated and the maximum beam current which can be obtained in a beam of given radius and boundary conditions is computed. In the case of ions the maximum beam currents may be quite small. The ions in such beams have a considerable velocity distribution which in turn leads to a greater beam divergence than former calculations indicate. In Section 3 a method is worked out for holding the beam together during the initial accelerations. A disadvantage of cylindrical lenses is pointed out in this connection. The use of electrostatic lenses for holding together a beam composed of high energy particles is discussed in some detail. Calculations show the special arrangements of the lenses necessary for producing convergence of the beam. A few other arrangements to prevent divergence which were tried experimentally are described.

Improvements in a Source for Use in the Vacuum Ultraviolet

An improved version of a low-pressure hot cathode discharge lamp for use in the vacuum ultraviolet is described. It has been used with hydrogen, helium, argon, and nitrogen to furnish line radiation from below 500 A to about 1650 A and continuum radiation from hydrogen from 1650 A to 3500 A. The lamp operates at low voltages, is reliable, and simple to rejuvenate when the output becomes low. Figures are given on its output as seen through a specific monochromator.

Reflectivity of Silver Chloride in the Ultraviolet

The reflectivity of silver chloride was measured at room temperature and at temperatures near those of liquid nitrogen and liquid helium over the wavelength range 2150–3750 A. The reflectivity-transmission cryostat used in making these measurements is described. The results at room temperature show the presence of a reflectivity peak around 2600 A, which is in the vicinity of the first absorption peak. The reflectivity peak sharpens and shifts to shorter wavelengths, attaining a value of nearly 40% at 2300 A when close to liquid helium temperature.

Vacuum Ultraviolet Monochromator

A new focusing vacuum monochromator is described which incorporates features making available a simple and flexible double monochromator with a single control. The focusing is provided with a linear motion coupled to a nearly balanced linkage system which, coupled to the grating, satisfies the conditions of the Rowland mount. Entrance and exit slits, variable in width, are offset to either side of the plane of the Rowland circle, which is of one‐meter diameter. Transparent window valves allow isolating the lamp and detector chamber from the monochromator, maintaining vacuum while making visual or near uv checks through the instrument. A filter wheel is built in to obviate some of the difficulty with scattered radiation when the instrument is used singly. Two units have been built and mounted as to allow changeover to the double system. The latter has yet to be tried but, used individually, they make nice instruments.

Hydrogen Lamp of Good Intensity and Reliability for the Vacuum Ultraviolet

A reliable, easily constructed, hydrogen discharge lamp has been developed and used extensively during the past several years as a light source for optical experiments in the vacuum ultraviolet, viz., between 900 and 1800 A. The lamp is a rather intense source of radiation consisting of the many lined molecular spectrum of hydrogen.

An Investigation of the Linear Accelerator

A treatment of the acceleration of particles by the linear resonance accelerator is given, including the calculation of the velocity distribution of particles emergent from the device and a method for improving the yield and the velocity distribution. Calculated curves showing these features are shown. The mass selection properties of the device are also considered. Focusing is considered briefly and a discussion of the characteristics of a quarter wave‐length line as applied to a resonance accelerator is included. The experimental features of a linear accelerator as built up are described. Probable particle energies to be expected from any future device of the kind are indicated.

Notes on UHV beryllium windows

Techniques are described for making large ultrahigh vacuum beryllium windows for use in synchrotron radiation installations. Procedures are given for affecting both hard brazed seals and demountable seals involving either lead or copper gaskets. Brazed seals can be made to either stainless steel or copper. Possible alternative methods are suggested.

Lyman‐α radiation from Cs‐H+ and Na‐H+ charge transfer processes with a plasma gun

Lyman‐α radiation due to near‐resonant preferred charge transfer in the systems Cs‐H+ and Na‐H+ was observed for proton fluxes of up to 3×1021 cm−2 sec−1 and alkali densities of up to 1014 cm−3. These results with a plasma gun provide a significant first step towards vuv lasing with such systems.