USY: Upstream Yield

The time cut of 0.02<t<0.4 was used for the US measurements to select the fusion events in the upstream layer. The first 20 ns was avoided due to the prompt beam muon background, while the long time was excluded to remove the fusion events in the downstream layer.

For these measurements, we had two main choices of background run in most cases: BG1, a pure H₂ target, and BG2, a standard emission target with 20 T$\cdot l$ D₂ DS (see Table 8.2). Fortunately, thanks to a good signal-to-background ratio and the high yielding US fusion, the effect of background choice is small.

Examples of the US fusion data with the background are illustrated in Figs. 8.7 and 8.8 for 3 T$\cdot l$ and 14 T$\cdot l$ cases, respectively. Notice the differences in the peak width and the extent of the lower energy tail, both due to $\alpha$ particle energy loss in the D₂ layer.

To determine the $\alpha$ yield, we typically used at least two different energy cuts. The energy cut efficiency corrections were done using a dedicated Monte Carlo code, which will be discussed later. Si yield for the US fusion measurements with different backgrounds are given in Table 8.4. When the effects due to different background subtractions are larger than the statistical errors, we considered the former as a measure of the systematic uncertainty. These cases are indicated with ^* in the table. Runs with target ID=II-2, II-3, and II-4, were performed consecutively in identical conditions (except US thickness), hence the relative yields are more reliable than other separate runs.

 

Table 8.4: Si yield per GMU for the US fusion measurements with different background subtraction and energy cuts. A time cut of s was applied to select the US events. The error values with ^* include systematic effects due to the different background subtraction. Tritium concentration of c_t=0.1% was used, unless otherwise stated.

US	ID	E cut	BG	Yield (10-4/GMU)			BG avg.
(DS)		( ch)		Si1	Si2	Si avg.
3 T$\cdot l$	II-2	2.7; 3.7	BG1	0.580(15)	0.572(15)	0.576(11)	0.577(9)
(20)			BG2	0.582(15)	0.575(16)	0.579(11)
		3.1; 3.7	BG1	0.537(13)	0.541(13)	0.539(9)	0.541(8)
			BG2	0.543(13)	0.545(14)	0.544(10)
6 T$\cdot l$	II-3	2.0; 3.7	BG1	1.64(2)	1.67(2)	1.66(2)	1.658(14)
(20)			BG2	1.64(2)	1.68(2)	1.66(2)
		2.7; 3.7	BG2	1.55(2)	1.60(2)	1.68(1)	1.628(48)*
			BG2	1.55(2)	1.61(2)	1.58(2)
14 T$\cdot l$	II-4	1.0; 3.7	BG1	4.26(4)	4.27(4)	4.27(3)	4.273(24)
(20)			BG2	4.28(4)	4.28(4)	4.28(3)
		2.0; 3.7	BG1	3.97(4)	3.99(4)	3.98(3)	3.980(22)
			BG2	3.97(4)	3.99(4)	3.98(3)
14 T$\cdot l$	II-7	1.0; 3.7	BG1	4.24(3)	4.41(3)	4.33(2)	4.343(19)
(0)			BG3	4.24(3)	4.48(3)	4.36(2)
		2.0; 3.7	BG1	4.01(3)	4.15(3)	4.08(2)	4.098(17)
			BG3	4.02(3)	4.21(3)	4.12(2)
14 T$\cdot l$	II-13	1.0; 3.7	BG1	4.55(2)	4.54(2)	4.55(2)	4.580(35)*
(0)			BG3	4.58(2)	4.65(3)	4.62(2)
ct=.2%		2.0; 3.7	BG1	4.28(2)	4.28(2)	4.28(1)	4.300(20)*
			BG3	4.30(2)	4.34(2)	4.32(1)
20 T$\cdot l$	II-16	1.0; 3.7	BG1	4.41(3)	4.54(3)	4.48(2)	4.490(16)*
(0)			BG2	4.41(3)	4.60(3)	4.51(2)
ct=.05%		2.0; 3.7	BG1	3.99(2)	4.10(2)	4.05(2)	4.063(14)
			BG2	4.00(2)	4.16(2)	4.08(2)