Abstract
Nanocrystalline diamond (NCD) foils have been in use at the Spallation Neutron Source as primary stripper foils for charge exchange injection since the machine's inception. NCD's low atomic number leads to reduced beam scattering while still being easy to handle, as opposed to even lighter elements. NCD foils also have the benefit of being free-standing, and rigid when grown under the right conditions to minimize residual stresses. This study overviews a method to mimic the Spallation Neutron Source (SNS) beam and characterize thermally driven failure of NCD foils. To do this, a foil test stand was developed with in situ diagnostics that tracks signs of foil sublimation and thinning. The foil test stand's electron beam is equated to the SNS beamline by comparing peak deposited energy densities for both beams. Post-mortem testing is also conducted to help elucidate changes the NCD foils undergo during exposure to the beam. A COMSOL simulation was also developed as a method to assess potential future changes to the NCD film and predict how changes to beam conditions will effect foil temperatures. This method allows for examination of the NCD foil's thermal limits and can be used to assess future changes to SNS stripper foils.
Original language | English |
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Article number | 166226 |
Journal | Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment |
Volume | 1027 |
DOIs | |
State | Published - Mar 11 2022 |
Funding
This work was supported by the DOE office of Science User Facilities . LS, LW, and NE are supported through funding for the Spallation Neutron Source. SNS is managed by UT-Battelle, LLC, under contract DE- AC05-00OR22725 for the U.S. Department of Energy . Foil synthesis, certain post-mortem testing, and modeling were conducted at the Center for Nanophase Materials Sciences, which is also a DOE Office of Science User Facility. Additionally, the authors would like to thank Jeff Holmes for simulations of the SNS beam/foil interaction, and Willem Blokland for operational data from the SNS foil pyrometer.
Keywords
- Charge exchange injection
- Electron beam mimic
- Foil failure
- Nanocrystalline diamond
- Stripper Foil
- Sublimation