Henry. S. McKown

Differential Lead Retention in Zircons: Implications for Nuclear Waste Containment

An innovative ultrasensitive technique was used for lead isotopic analysis of individual zircons extracted from granite core samples at depths of 960, 2170, 2900, 3930, and 4310 meters. The results show that lead, a relatively mobile element compared to the nuclear waste-related actinides uranium and thorium, has been highly retained at elevated temperatures (105� to 313�C) under conditions relevant to the burial of synthetic rock waste containers in deep granite holes.

A new three-stage mass spectrometer for high abundance sensitivity measurements

Abstract A three-stage mass spectrometer has been constructed consisting of two magnetic stages of 30-cm radius followed by an electrostatic analyzer with a radius of 43.25 cm. The instrument gives an abundance sensitivity of better than 1 × 107 and is used primarily for the isotopic analysis of uranium.

Improved Performance of a Tandem Quadrupole/Time-of-Flight Mass Spectrometer

Abstract This paper describes the use of a time-of-flight mass spectrometer as the second stage of a MS/MS instrument. This system has been improved by the addition of a newly designed data acquisition system. The performance of this instrument will be discussed along with other modifications that are in progress to give further improvements.

Positron ionization mass spectrometry. I : Instrumentation

Abstract Initial studies have been performed to investigate the use of positrons to ionize polyatomic molecules for mass spectrometric analysis. A positron beam facility has been constructed which converts forward-scattered gamma radiation from a 150-MeV accelerator into positrons of a selected energy by means of a tungsten metal moderator. The positrons are transported by solenoidal magnetic fields into the ionization volume of a time-of-flight mass spectrometer where they interact with molecules of a target gas. The initial mass spectral results are apparently due to positron impact ionization and compare directly with electron impact ionization data acquired with the same apparatus. Further studies will seek to extend the energy range of the positrons into the region below the ionization energy of the target molecules, where other mechanisms of ionization are likely.

A new ion source for thermal emission mass spectrometry

Abstract An ion source with circularly-symmetric lens elements has been designed and evaluated using a single-filament, thermal-ionization mass spectrometer. Both uranium and plutonium samples have been analyzed. The new fource yields better ion transmission and improved results in comparison to the Nier-type source previously used.

A new high-resolution mass spectrometer with partial second-order double focusing☆

Abstract A high-resolution mass spectrometer of new design has been built to fulfill a variety of needs. It has partial second-order double focusing with a sector magnet of 30.5 cm radius and an electrostatic analyzer of 43.25 cm radius. The highest resolution obtained to date is 9000 with 0.0025 cm slits in the ion source. The instrument has been used for both organic and inorganic applications.

Prediction and Identification of Multiple-Photon Resonant Ionization Processes

Many single-color, multiple-photon transitions leading to ionization are observed for lanthanide and actinide elements in experiments using resonance ionization mass spectrometry (RIMS). It is desirable both to identify the energy levels involved in observed transitions and to be able to predict in advance their location. A computer code, ETRANS, has been written to perform these functions. Examples of both types of operation are given.

A thermal ion source for quadrupole mass spectrometers

Abstract A new ion source has been designed and tested for performing thermal ionization isotopic analyses with a quadrupole mass spectrometer. Significantly improved performance in comparison to the commercial source was obtained.

Data Acquisition and Processing for High-Resolution Mass Spectrometry Using a Small Nondedicated Computer Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.

ABSTRACT A system has been developed to process data generated by a high-resolution mass spectrometer using a small computer. The computer is dedicated to the instrument only during data acquisition and is otherwise available for a variety of computational tasks in a general mass spectrometry laboratory. The programs include those to acquire the data directly from the mass spectrometer and store them on the computer disk storage device (written in assembly language); those to reduce the data on the disk to a table of exact masses and intensities, including deconvolution of multiplets (written in FORTRAN IV); and those to determine possible empirical formulas and fragmentation sequences for a given series of exact masses (also in FORTRAN IV). All observed PFK peaks are used as reference masses in an advancing subregion techinque that gives improved mass measuring accuracy.