Abstract
The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory's (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.
Highlights
High-performance targets under consideration to intercept multi-MW proton beams of a number of new particle accelerator initiatives depend almost entirely on the ability of the selected materials to withstand both the induced thermomechanical shock and simultaneously resist accumulated dose-induced damage
Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain their integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes
The post-irradiation analysis of the proton-irradiated materials consisted of two parts, namely the macroscopic assessment and the microscopic evaluation based on x-ray diffraction techniques at the Brookhaven National Laboratory (BNL) synchrotron light sources NSLS and NSLS II
Summary
High-performance targets under consideration to intercept multi-MW proton beams of a number of new particle accelerator initiatives depend almost entirely on the ability of the selected materials to withstand both the induced thermomechanical shock and simultaneously resist accumulated dose-induced damage. The latter manifests itself as radiation-induced change in the physiomechanical properties. Several materials known as superalloys in the mid-Z range have been considered as pion yielding targets for the desired pion spectrum or as parts of the target critical infrastructure in high power accelerator initiatives such as the Neutrino Factory, the T2 K experiment, etc These include Inconel-718, super-Invar, the gum multifunctional alloys and the titanium alloy Ti-6Al-4V. For the refractory metal tungsten, correlation of macroscopic and microstructural data revealed that radiationinduced phase changes may be responsible for the dramatically brittle behavior following irradiation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
