The alpha particle emitter Radium-223 dichloride (223RaCl2) has recently been approved for treatment of late-stage bone metastatic prostate cancer. There is considerable interest in studying this new agent outside of the clinical setting, however the supply of 223Ra is limited and expensive. We have engineered a 223Ra microgenerator using traces of 227Ac previously generated from cyclotron-produced 225Ac. Radiochemically pure 223RaCl2 was made, characterized, evaluated in vivo, and the source was recovered in high yield for regeneration of the microgenerator.

Currently there is a significant amount of interest in standoff radiation detection. One of the biggest challenges is to separate small radiation signals from large varying background radiation. Many systems have been developed to address this problem that rely on coded-aperture and/or Compton imaging. These imaging systems tend to be large, heavy, complex, and therefore expensive. In this paper we report on the development of a self-occluding directional gamma radiation sensor that is relatively small (<40 kg), inexpensive, and simple in design. Laboratory and field measurements suggest that these sensors will work as well as the gamma imaging systems for many radiation detection applications at a fraction of the cost, weight, and complexity. An azimuth can be resolved with a standard deviation of 7° in 10 seconds for a source yielding 45 CPS at the detector in a 300 CPS background radiation field. This paper describes the selfoccluding quad NaI directional gamma radiation detector, the impact of gamma energy and distance on angular precision and accuracy, and potential applications.

No abstract

Detecting energetic particles is a useful approach in studying space plasmas. Of specific interest are energetic neutral atoms (ENA) because their trajectories are unaffected by electric or magnetic fields. Imaging the ENA flux allows for the mapping of remote plasmas. In order to detect such particles, solid-state detectors are advantageous due to their lightweight and low power. However in the sensing environment the photon flux is usually several orders of magnitude higher than the ENA flux. Thus, in order to detect the energetic particles the photon flux must be blocked. Therefore, thin metal or carbon film filters that allow the transmission of ENAs while attenuating the photon signal are used. Here we report tests of low-density mats of carbon nanotubes (CNTs) as a filter medium. For a given mass per unit area (the parameter which sets the particle transmission energy threshold), CNTs are expected to absorb photons significantly better than thin films. The CNTs were grown by a water assisted chemical vapor deposition technique and pulled from their substrate to generate a CNT sheet covering an aperture. In order to test the performance of the CNT sheet as a filter, the transmissions of light and alpha particles were measured. We were able to achieve filter performance that resulted in alpha particle energy loss of only 5 keV with an optical density of 0.5.