Speaker
Description
The Korean light source, which is a 4th-generation storage ring, has been planned and launched since July 2021. The electron beam is accelerated to 200 MeV in the linac, then injected into the booster ring, reaching 4 GeV before being injected into the storage ring. The stored current is 400 mA and the 2 mA electron beam is injected into the storage ring every 2 min. The storage ring has 28 symmetrical cells with a beam emittance of 62 pm·rad. The storage ring circumference is 799.297 m, and both the storage ring and booster ring are located in the same tunnel.
The storage ring utilizes a Multi-Bend Achromat (MBA) lattice design. Along the storage ring, magnets generate synchrotron radiation that penetrates or is scattered from the storage ring vacuum chamber and impinges on nearby materials such as cables and water hoses. These scattered photons deposit energy in the surrounding materials. This energy deposition consequently causes material damage. The vacuum group identified critical radiation-exposed locations at CN05, CN06, CN10, and CN12. To assess radiation damage risk, a detailed geometric model of the storage ring cell was simulated using FLUKA 4-5.0 (CERN version) [1]. Synchrotron radiation spectra generated by the storage ring magnets were calculated using the SPECTRA [2] code and subsequently transported through the detailed geometric model in FLUKA. Two representative materials with contrasting radiation resistance, polytetrafluoroethylene (PTFE), known as Teflon (low resistance), and epoxy (high resistance), were evaluated. Deposited energy and estimated material lifetimes were determined. The lowest radiation resistance thresholds of 0.3 and 100 kGy [3] were selected for Teflon and epoxy, respectively, as a conservative approach.
Results demonstrate that epoxy exhibits sufficient radiation resistance for all considered critical locations throughout the facility lifetime. In contrast, Teflon is predicted to suffer significant radiation damage, e.g., around CN06, with an estimated operational lifetime of only 5 months. This estimation is very conservative. However, protective measures are recommended: either replacing Teflon with a more radiation-resistant polymer such as polyetheretherketone (PEEK) or installing lead shielding to mitigate photon exposure to Teflon components.
These results demonstrate the necessity of radiation damage estimation for the materials around the storage ring [4].
References
[1] C. Ahdida et al., New capabilities of the FLUKA multi-purpose code, Front. Phys. 9 (2022).
[2] T. Tanaka and H. Kitamura, SPECTRA: a synchrotron radiation calculation code, J. Synchrotron Radiat. 8 (2001).
[3] H. Schönbacher et al., Compilation of Radiation Damage Test Data: Part II, 2nd edition: Thermoset and Thermoplastic Resins, Composite Materials, CERN 98-01 (1998).
[4] P. Berkvens et al., The ESRF Extremely Brilliant Source (EBS), the 11th International Workshop on Radiation Safety at Synchrotron Radiation Sources (RADSYNCH 2023), Grenoble, France (2023).
| Topics | T6. Radiation damage to materials |
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