preparing-an-isotopically-pure-229th-ion-beam-for-studies-of-229mth

Preparing an Isotopically Pure <sup>229</sup>Th Ion Beam for Studies of <sup>229m</sup>Th

A methodology is described to generate an isotopically pure 229Th ion beam in the 2+ and 3+ charge states. This ion beam enables one to investigate the ...

Ludwig-Maximilians-Universität München

Proton ranges in water between 145 MeV to 227 MeV initial energy have been measured at a clinical superconducting synchrocyclotron using the acoustic signal induced by the ion dose deposition (ionoacoustic effect). Detection of ultrasound waves was performed by a very sensitive hydrophone and signals were stored in a digital oscilloscope triggered by secondary prompt gammas. The ionoacoustic range measurements were compared to existing range data from a calibrated range detector setup on-site and agreement of better than 1 mm was found at a Bragg peak dose of about 10 Gy for 220 MeV initial proton energy, compatible with the experimental errors. Ionoacoustics has thus the potential to measure the Bragg peak position with submillimeter accuracy during proton therapy, possibly correlated with ultrasound tissue imaging.

Submillimeter ionoacoustic range determination for protons in water at a clinical synchrocyclotron.

Direct laser excitation of the lowest known nuclear excited state in ^{229}Th has been a long-standing objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer's excitation energy compared to the presently adopted value of (7.8±0.5)  eV. Here we present a direct laser excitation scheme for ^{229m}Th, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than 10^{4} and a total measurement time of less than three days for laser scanning appear to be achievable.

A Laser Excitation Scheme for ^{229m}Th.

The isotope Th is the only nucleus known to possess an excited state Th in the energy range of a few electronvolts-a transition energy typical for electrons in the valence shell of atoms, but about four orders of magnitude lower than typical nuclear excitation energies. Of the many applications that have been proposed for this nuclear system, which is accessible by optical methods, the most promising is a highly precise nuclear clock that outperforms existing atomic timekeepers. Here we present the laser spectroscopic investigation of the hyperfine structure of the doubly charged Th ion and the determination of the fundamental nuclear properties of the isomer, namely, its magnetic dipole and electric quadrupole moments, as well as its nuclear charge radius. Following the recent direct detection of this long-sought isomer, we provide detailed insight into its nuclear structure and present a method for its non-destructive optical detection.

Article	Year
Submillimeter ionoacoustic range determination for protons in water at a clinical synchrocyclotron. Physics in medicine and biology\| PubMed ID: 28742053	2017
A Laser Excitation Scheme for ^{229m}Th. Physical review letters\| PubMed ID: 29341722	2017
Laser spectroscopic characterization of the nuclear-clock isomer Th. Nature\| PubMed ID: 29670266	2018

Peter G. Thirolf

Biography

JoVE Journal Publications

Other Publications