Radiation Dose Monitoring
Systematic dose monitoring provides the dose distribution profiles around the APS storage ring and identification of regions where the probability for damage is highest. Until recently, dose monitoring at the APS has been performed with thermoluminescent dosimeters and radiachromic films. In 2002, a new high-dose dosimetry technique has been added, i.e., alanine electron paramagnetic resonance (EPR) dosimetry.
Alanine is an amino acid in which disrupted molecular bonding due to ionizing radiation gives rise to free radicals. The radical concentration is a function of the absorbed dose and is then analyzed by EPR. This technique exhibits equivalent response for photons and electrons and an energy-independent response for photon energies above approximately 100 keV; however, dose underestimation occurs for photon energies below that value. Absorbed doses up to ~20 Mrad can be measured with this technique. The EPR spectrometer is an e-scan Bruker analyzer that is suitable for both pellet and film alanine dosimetry and capable of providing dose measurements from 1 krad to 20 Mrad. The dosimeters used currently at the APS are alanine films.
Dose measurements on the IDs are performed on the upstream (US) and the downstream (DS) ends of the devices. In addition, dose monitoring along the length of the damaged IDs is being performed to allow comparisons between absorbed dose and demagnetization profiles. The dosimeters are being replaced at the end of each run (i.e., approximately at three-month or four-month time intervals).
In addition to the IDs, other critical components around the accelerator (such as CCD cameras, encoders, motors and cables) are also being monitored. Integrated doses on these components provide information on their lifetime in the APS radiation environment.
Absorbed dose profiles on the IDs in the APS storage ring per run. Please note - The absorbed doses presented here refer only to those recorded on the two ends of each device in the storage ring [(i.e., upstream (US) and Downstream (DS)]. Higher doses that those US and DS have been recorded along the length of a few IDs in the storage ring. Such dose maxima ultimately have the potential to determine the severity of the demagnetization.
Run 2002-2
Run 2002-3
Run 2003-1
Alanine Dosimetry - absorbed dose profiles on the IDs in the APS storage ring per run.
Updated: October 6, 2010