| Autor: |
Michal Haubner, Vincent Baglin, Bernard Henrist |
| Rok vydání: |
2022 |
| Předmět: |
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| Zdroj: |
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 531:34-43 |
| ISSN: |
0168-583X |
| Popis: |
CERN’s Large Hadron Collider cryomagnets embed a 1.9 K UHV chamber lined with a 5–20 K beam-screen (BS) that intercepts the synchrotron radiation and electron cloud (EC). The low–energy EC irradiates the BS and desorbs gas, creating a dynamic vacuum effect. A novel setup controllably reproduces this by irradiating an unbaked as-received BS copper sample at 15 K with 0–1.4 keV electrons, representing a slice of the EC spectrum. This collector-based setup is qualified using a HOPG reference for secondary electron yield (SEY) and $^{15}$N$_2$ as a tracer in low-energy electron stimulated desorption (ESD) measurements. Measurement at 15 K revealed sub-10 eV ESD thresholds and a maximum around 300 eV of 0.18 H2/e$^-$ and 0.13 CO/e$^-$. Irradiation with 300 eV and 1 keV electrons at ∼ 8.10$^{-4}$ C.mm$^{-2}$ conditioned ESD and SEY alike. Similar dose at 17 eV only caused minor SEY reduction and no ESD decline. The as-received H2 and CO2 yields at 300 eV decreased 5-150x between 15 and 265 K, respectively. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect