CERN SPS electron cloud heat load measurements and simulations

A calorimeter, WAMPAC, operating at room temperature has been designed and installed into the SPS to measure directly the electron cloud induced heat load due to the Large Hadron Collider (LHC)-type proton beam. Theoretical behavior, calibrations, measurement protocols, preliminary results, and simulation benchmarking are presented. Scaling of the results to the LHC indicated a linear heating power in a LHC dipole of about $500\mathrm{mW}{\mathrm{m}}^{-1}$ for $5\times {10}^{10}\mathrm{\text{protons}}/{\mathrm{\text{bunch}}}^{-1}$ for a copper surface which is not fully conditioned (maximum of secondary electron yield $\sim 1.9$).

Figure 1

Ideal measurement cycle.

Figure 2

Schematic of the WAMPAC calorimeter.

Figure 3

Typical in situ calibration cycle. The relative temperature increase corresponds to $0.1\mathrm{W}/\mathrm{m}$. The average of the measured slopes is $2.7\mathrm{K}{\mathrm{W}}^{-1}{\mathrm{h}}^{-1}$.

Figure 4

Relative temperature and pressure observations when a LHC-type beam of three consecutive batches of 72 bunches with $5\times {10}^{10}\mathrm{\text{protons}}/{\mathrm{\text{bunch}}}^{-1}$ was circulating in the SPS.

Figure 5

Detail of the relative temperature increase observed during electron cloud activity of Fig. 4.

Figure 6

Average $⟨\mathrm{SEY}⟩$ and average electron energy versus the radial position perpendicular to the field lines.

Figure 7

Electron density in WAMPAC computed for a maximum SEY of 1.9.