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Tissue Equivalent Proportional Counter (TEPC)
02.20.09
Scientists and payload developers can get more information on International Space Station research facilities by contacting the ISS Payloads Office or at 281-244-6187.

Overview | Description | Applications | Operations | Results | Publications | Images

Facility/Payload Overview

Brief Facility Summary

The Tissue Equivalent Proportional Counter (TEPC) is a microdosimetric instrument that measures radiation dose and dose equivalent in complex radiation fields (fields containing a mixture of particle types).

Facility Manager(s)

  • Fadi M. Riman, Engineering and Science Contract Group, Houston, TX

    • Co-Facility Manager(s)

    Information Pending

    Facility Developer

    Battelle Pacific Northwest National Laboratory, Richland, WA

    Sponsoring Agency

    National Aeronautics and Space Administration (NASA)

    Expeditions Assigned

    |2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|

    Previous ISS Missions

    The ISS TEPC is a fifth generation detector system which has been used on Mir and several Space Shuttle Missions.

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    Facility/Payload Description

    Facility Summary

    • The Tissue Equivalent Proportional Counter (TEPC) consists of a spectrometer and cylindrical detector with which to measure external radiation doses.

    Description

    The Tissue Equivalent Proportional Counter (TEPC) is a gas proportional counter used to characterize the radiation environment. The purpose of the TEPC is to collect a record of the International Space Station (ISS) environment to construct exposure history records for the crew. TEPC will also provide near real-time measurements to ground personnel during radiation events and make survey measurements in different parts of the ISS for shield verifications.

    TEPC collects data as a function of time to measure the dose and estimate the dose equivalent by making spectral measurements of the lineal energy loss of the radiation as it passes through the detector volume. The omni-directional detector is surrounded by a tissue equivalent plastic and the internal gas (propane) provides an energy deposition response similar to human tissue. The detector gas is at a very low pressure such that the mass of the gas is approximately that of a cell. The 512 channel spectrometer stores the lineal energy data in energy bins ranging from approximately 25 keV/micron through channels exceeding 1000 keV/micron. The crew is able to read the current level through an electronic display and has the capability to telemeter data to the ground every 10 seconds. TEPC is a portable piece of equipment, integrated with numerous ports in various modules to support the survey function of the equipment.

    TEPC is an automatic microdosimetry system. Each TEPC consists of two main components, the spectrometer unit and the detector unit. The spectrometer unit contains a powerful computer that allows real-time analysis of the data and provides calculations of total dose, total dose equivalent and incremental dose, as a function of linear energy transfer (LET) and time, for penetrating radiation in space. The detector unit is attached directly to the multi-channel analyzer (MCA) card in the spectrometer.

    Different size detectors can be attached to the TEPC depending on the desired task. The radiation data that is measured can be stored inside the spectrometer unit for later analysis or communicated via RS-232 to a host computer. The TEPC is calibrated in terms of lineal energy, by exposing it to fission neutrons and 137Cesium sources.

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    Operations

    Facility Operations

    When TEPC is powered on, it is either in standby or acquire mode. Standby can only be achieved by 1553b command. It is use to put the unit in a Mode that will support the data download protocol of the command and data handling (C and DH) system and support unit commanding. It also will store the current file to memory. In Acquire the unit is collecting data.

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    Results/More Information

    The TEPC was launched to ISS during Expedition 2 in 2001; it failed on orbit, and was powered off on 10/12/2006. The TEPC was returned on STS-117/13A, a new TEPC was delivered to the ISS on STS-118/13A.1. The new TEPC has several improvements; the toxicity level 4 battery has been removed; new software version was implemented and the detector characterization exceeds any other TEPC detector that has flown.

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    Availability

  • On-Board ISS

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    Related Web Sites

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    Publications

    Results Publications

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      Related Publications

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        Images

        imageNASA Image: ISS015E12110 - View of the Tissue Equivalent Proportional Counter (TEPC) Radiation Detector (gold cylinder) and the TEPC Spectrometer (gold box) in the U.S. Laboratory, Destiny during Expedition 15. The TEPC monitors radiation doses at the cellular level.
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        Information Provided and Updated by the ISS Program Scientist's Office
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