Abstract

Recently, pulsed laser processing of Cu samples has been demonstrated to produce rough surfaces whose structuring at the nanoscale ensures an impressive reduction of the secondary electron yield. This feature has an undoubted appealing for applications in future high energy particle accelerators. However, the effective application of such laser treated surfaces in this context requires a rigorous evaluation of their vacuum behavior, especially when used at cryogenic temperatures. To this aim, here, we compare thermal programmed desorption between 20 and 70 K by dosing Ar multilayers of different thicknesses on a laser treated copper substrate and on its flat counterpart. Our results highlight that the spongelike structural features confer to the laser treated sample's non-negligible effects due to the gas-substrate interaction. This results in a much vaster and higher desorption temperature range with respect to what is observed from the flat substrates. This evidence could render it very difficult to find temperature intervals for which detrimental vacuum transients could be avoided in the cryogenic beam pipes. On these bases, although the electron cloud mitigation efficiency has been settled, before definitely including porous surfaces in any cryogenic machine design, all the consequences of having a rough rather than a flat wall should be carefully evaluated.

Highlights

  • Secondary Electron Yield (SEY) is defined as the ratio of the number of electrons leaving the sample surface (Iout) to the number of incident electrons (Ip)

  • Some Electron-cloud effects (ECEs) mitigation strategies have the objective of reducing such SEY,[5,13,14,15,16] and surface geometrical modification has been proved to be quite effective for this purpose

  • The appealing and advantageous results of laser processing have brought in a short time laser treated copper (LASE-Cu) surfaces to be proposed for use in future accelerator technology

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Summary

Introduction

Secondary Electron Yield (SEY) is defined as the ratio of the number of electrons leaving the sample surface (Iout) to the number of incident electrons (Ip). This results in a much vaster and higher desorption temperature range with respect to what is observed from the flat substrates.

Results
Conclusion

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