Direct stop contribution at late time

As we mentioned, the fusion yields in the upstream layers were measured with a time cut of s, while the downstream measurements were done mainly with s. The proton contributions at these two time ranges, as well as those from different sources (e.g., direct vs. cycling), need to be considered separately.

We first investigate the protons from direct muon stops in a D₂ layer at late time. This is important for the measurements using thick downstream layers, from which the DS direct proton contribution cannot be subtracted by using the standard background runs which had no downstream layer.

In order to estimate this contribution, we looked at the yield of protons coming from the 14 T$\cdot l$ upstream deuterium layer when only a very thin downstream layer was present. Given in Table 8.10 is the yield in the peak at 3 MeV ( 2960<E<3040 ch) with time cut of 1<t<6 $\mu$s for two different series of runs. The counts just above and below the peak in the energy spectra (with the same total bin width), were subtracted to account for the background.

 

Table 8.10: Y_p-late ^dir, the proton yield in late time (1<t<6 $\mu$s).

Target			Yield/GMU ( )
US	DS	ID	Si1	Si2
SET114T$\cdot l$ D2	3T$\cdot l$ D2	II-9	1.77(45)	1.81(48)
SET214T$\cdot l$ D2	3T$\cdot l$ D2	II-14	1.36(74)	1.79(79)

 

As we will see later cycling from the US layer contributes very little at this late time, and assuming cycling from DS is negligible since the layer is very thin, we obtain Y_p-late ^dir, the proton yield from direct stops in 17 T$\cdot l$(14 US + 3 DS) of deuterium layers in the time region of 1<t<6$\mu$s. Averaging the above values, we have protons per GMU. Our downstream thicknesses ranged from 6 T$\cdot l$ to 23 T$\cdot l$, hence this yield was scaled proportionally to the thickness in order to give the direct stop contribution at late time.