The stripping foil test stand in the Linac4 transfer line

Abstract

The 160 MeV H− beam from the Linac4 linear accelerator at CERN will be injected into the Proton Synchrotron Booster with a new H− charge-exchange injection system. It will include a stripping foil, to convert H− into protons by stripping off the electrons. To gain experience with these very fragile foils, prior to the installation in the PSB, and test different foil materials and thicknesses, lifetimes of the foils, the foil changing mechanism and interlocking functions, a stripping foil test stand will be installed in the Linac4 transfer line in 2015. This paper describes the mechanical design of the system and discusses the test possibilities and parameters.

Installation and commissioning of the stripping foil system in the new CERN PS booster 160 MeV H− injection region

“…The stripping foil handling and exchange mechanism, presented in detail in [11,12], consists of a stainlesssteel belt, rotating over two pulleys, to which a maximum of six foil holders can be attached by use of quick disconnect sliders (Fig. 2).…”

“…In 2018/2019 foils of different manufactures have been qualified regarding gluing & manipulation and stripping efficiency & lifetime in a test stand [11] installed in the L4 transfer line [14,15], described in more detail in § 6. The selected stripping foils for PSB beam commissioning are shown in Table 1.…”

“…The choice of 200 µg/cm 2 stripping foil is based on providing sufficient stripping efficiency, while minimizing the emittance blow-up, and hence the degradation of the beam brightness, induced by foil scattering [6]. The foils installed in the PSB were qualified by single foil passages in the L4 test stand [11], verification of the predicted scattering properties was thus not possible.…”

Measurements with the stripping foil test stand in the Linac4 Transfer Line

“…The design of the stripping foil handling and exchange mechanism, so-called TKSTR, of which an illustration is given in Figure 1, was extensively presented in [8,9]. Based on commercially available components [10], the unit for the L4 test stand is identical as the mechanism intended to be installed in the PSB.…”

“…In 2016 beam commissioning of L4 took place in steps of increasing energy to reach 160 MeV [7] and L4 is now performing operational reliability runs. A stripping foil test stand is installed in the L4 transfer line including the identical foil handling and exchange mechanism that will be used in the future PSB H − charge-exchange injection system [8]. This will allow to gain experience using these fragile foils, test different foil materials and thicknesses, evaluate the lifetime of the foils and foil holders and test the foil changing mechanism as well as the interlocking functions prior to the final installation in the PSB in 2019.…”