Neal Zapp

Preparing for the first Medipix detectors in space

Current plans call for two separate missions to deploy Medipix2-Technology-based detectors in space for the first time. NASA is planning to deploy 5 or more Radiation Environment Monitor (REM) units, each of which will contain a Medipix2 TimePix-based detector assembly, on the International Space Station (ISS) during the spring of 2012 as part of a Station Detailed Test Objective (SDTO). These units will be mounted on a single 8-layer printed circuit board containing a USB-based interface. The entire unit will have the form of a typical USB flash-memory device, and the USB interface will provide interactive control and data readout as well as the operating power. Each of the units will be separately plugged into one of the 21 Lenovo® T-61B laptops that are currently onboard the ISS. The purpose of this test is to acquire initial on-orbit data to allow feedback into the design of the next generation of Medipix device, which is intended to support the development of a portable, standalone, wireless and battery-powered personal space radiation dosimeter. The second mission, LUCID (Langton Ultimate Cosmic ray Intensity Detector) is part of a UK outreach project being conducted by the Simon Langton School for Boys in Canterbury, UK. A small instrument containing 5 detector assemblies, also containing the TimePix versions of the Medipix2 technology will be deployed on the upcoming UK TechDemoSat 1 mission, also planned for launch in 2012. These deployments have many similar embedded control software and ground-based analysis software requirements.

A comparison of quality factors and weighting factors for characterizing astronaut radiation exposures

Radiation exposures are typically characterized by two quantities. The first is the absorbed dose, or the energy deposited per unit mass for specific types of radiation passing through specified materials. The same amount of energy deposited in material by two different types of radiation, however, can result in two different levels of risk. Because of this, for the purpose of radiation protection operations, absorbed dose is modified by a second factor intended to normalize the risk associated with a given exposure. We present here an inter-comparison of methods for this modification. First is the radiation quality factor (Q), as defined by ICRP publication 60. This quantity is related functionally to the unrestricted linear energy transfer (LET) of a given radiation, and is multiplied by the absorbed dose to derive the dose equivalent (H). The second method for modifying absorbed dose is the radiation weighting factor, also given in ICRP-60, or as modified in NCRP report 115. To implement the weighting factor, the absorbed dose resulting from incidence of a particular radiation is multiplied by a factor assigned to that type of radiation, giving the equivalent dose. We compare calculations done based on identical fields of radiation representative of that encountered by the MIR space station, applying each of these two methods.

Space Applications of the FLUKA Monte‐Carlo Code: Lunar and Planetary Exploration

NASA has recognized the need for making additional heavy‐ion collision measurements at the U.S. Brookhaven National Laboratory in order to support further improvement of several particle physics transport‐code models for space exploration applications. FLUKA has been identified as one of these codes and we will review the nature and status of this investigation as it relates to high‐energy heavy‐ion physics.