MOD: Moderation Yield

Similar to the US measurements, runs BG1 and BG2 were used for background subtraction for most runs. Because of the lower signal-to-background ratio, the choice of background had larger effects on the yield determination for the MOD measurements. Since B1 has no tritium or deuterium, it may underestimate the background, while unmoderated $\mu t$ emission from B2 may contribute to the over-subtraction of the background. Some events in B2 appear to come from $\mu t$ reaching Si detectors ($\mu$ capture on Si produces charged products), which have time structure similar to the real data with a characteristic time-of-flight. Table 8.5 gives the yield with different backgrounds. Similarly to the US measurements, the background subtraction effects are included in the error (noted with ^*), if it is larger than the statistical error. When one background run is clearly more applicable than the other, that alone was used for the yield determination, which was the case for 0 and 14 T$\cdot l$ measurements.

 

Table 8.5: Si yield per GMU for the MOD measurements (DS fusion with varying US moderator thickness) with different background subtractions and energy cuts. The error values with ^* include a systematic effect due to the different background subtraction. When one BG method is clearly more applicable than the other, we quote that value in the final column. Tritium concentration of c_t=0.1% was used.

US	T cut	E cut	BG	Yield (10-5/GMU)			BG avg.
(ID)	()	( ch)		Si1	Si2	Si avg.
0 T$\cdot l$	0.3; 6	1.0; 3.7	BG1	27.3(3)	26.6(3)	27.0(2)	25.35(20)
(II-1)			BG3	25.7(3)	25.0(3)	25.4(2)	(BG3 only)
		2.0; 3.7	BG1	25.4(2)	24.6(2)	25.0(2)	24.04(17)
			BG3	24.5(2)	23.6(2)	24.1(2)	(BG3 only)
3 T$\cdot l$	0.5; 6	1.0; 3.7	BG1	16.0(2)	16.5(2)	16.3(2)	15.38(88)*
(II-2)			BG3	14.3(2)	14.7(3)	14.5(2)
		2.0; 3.7	BG1	15.2(2)	15.6(2)	15.4(1)	14.90(50)*
			BG3	14.2(2)	14.6(2)	14.4(1)
6 T$\cdot l$	0.6; 6	1.0; 3.7	BG1	9.58(18)	9.84(18)	9.71(13)	8.82(90)*
(II-3)			BG3	7.82(19)	8.02(19)	7.92(13)
		2.0; 3.7	BG1	9.41(15)	9.38(15)	9.40(11)	8.88(52)*
			BG3	8.38(15)	8.34(16)	8.36(11)
14 T$\cdot l$	0.8; 6	1.0; 3.7	BG1	1.81(14)	2.16(14)	1.99(9)	1.93(11)
(II-4)			BG5	1.79(15)	2.07(15)	1.93(11)	BG5 only
		2.0; 3.7	BG1	1.92(9)	2.06(10)	1.99(7)	1.84(7)
			BG5	1.76(10)	1.91(10)	1.84(7)	BG5 only
14 T$\cdot l$1	0.8; 6	1.0; 3.7	BG5	3.17(16)	2.98(16)	3.08(11)	2.15(12)
(II-11)			BG6	2.29(16)	2.01(17)	2.15(12)	BG6 only
		2.0; 3.7	BG5	1.99(10)	1.89(10)	1.94(7)	1.86(7)
			BG6	1.96(10)	1.76(10)	1.86(7)	BG6 only

¹ With 500 T$\cdot l$ H₂ layer at DS under 20 T$\cdot l$ D₂ layer.