Design and evaluation of a laser ion source for TITAN to measure 222Rn daughter product abundances

This research focuses on developing and implementing a Laser Ion Source (LIS) at TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) facility to achieve high-precision isotope abundance ratio mea-surements across diverse materials. The project aims to quantify long-lived daughter products of 222Rn, including 210Pb, 210Po, and 210Bi. Given the low abundance of these isobaric species in biological matri-ces, the instrumentation demands exceptional sensitivity and resolving power, which a Multiple-Reflection Time-of-Flight Mass-Spectrometer meets the requirement for this purpose. A key aspect of this work involves designing LIS ion optics for efficient ion production and transmission. The design process addresses several challenges, such as ion beam collimation, steering, filtering, and raster scanning. Quadrupole bender and space charge effects cause beam expansion and off-axis deflection, necessi-tating the use of Pierce electrodes, steering elements, and Einzel lenses to maintain beam confinement along the central axis. The extremely low abundance of radon daughter products in biological matrices (approxi-mately 10 ions of interest among 1014 total ions) requires selective filtering of unwanted species prior to mass analysis while adhering to RFQ acceptance limits. Another challenge involves maintaining consistent ion transmission efficiency during sample raster scanning, as the relative position of ablated ions to extraction electrodes changes. This issue was addressed through dynamic voltage tuning of steering elements based on laser position. Following simulation-based optimization, the system components were assembled and tested at the University of Calgary using a low-resolution time-of-flight setup. This preliminary testing phase al-lowed for validation and refinement of the design before final implementation at TITAN, ensuring optimal performance for high-precision isotopic analysis. Preliminary testing involved ion production on pure metal targets, automation of the LIS system using LabVIEW programming, and time-of-flight mass scans for three distinct masses. Ions were produced from aluminum, titanium, and copper targets to evaluate their time-of-flight peak parameters such as center and full width at half maximum. The center of the peaks for Al, Ti, and Cu was determined to be 247 μs, 249 μs, and 254 μs, respectively. Additionally, the full width at half maximum (FWHM) values for Al, Ti, and Cu were measured as 7 μs, 12 μs, and 10 μs, respectively. The system is working as designed and will be installed on TITAN.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Discipline thesis:degree_discipline

Physics & Astronomy

Grantor

Science

Year dc:date.issued

2025

Author dc:creator

• Ashrafkhani Limoudehi, Behnam

Advisors dc:contributor.advisor

• Wieser, Michael
• Thompson, Robert

Committee members dc:contributor.committeemember

• Friesen, Timothy
• Kwiatkowski, Ania
• Shi, Yujun
• Mueller, Peter

• Laser Ion Source (LIS)
• Time-of-flight mass spectrometry
• Isotope abundance ratio measurements
• Radon daughter products
• Ion optics design

Statement dc:rights

• Unless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/48732

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/121142