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of 50 g, loose tetryl charges were detonated with one sap by means 
of equal lengths of primacord, Two gavges were employed, both in 
the intersection plane, The results on peak pressure, the only 
ones obtainable because of the interference of the primacord waves, 
are in agreement with those obtained with the larger charges, 
Results; Peak Pressure, Table I and Figs, 1, 3 and 4 summarize 
the peak pressure data, In perticular, Fig. 1 shows the results 
obtained in the intersection plane for the 1700 g. charges, corrections 
having been apvlied for systematic gauge differences and for the 
response time of the gauges (see below), It is seen that the initial 
shape of the curve follows the theory (H, Polocheck and R, J. Seegar:; 
Bureau of Ordnance, Explosives Research Report Nc, 14, 1944) but 
that the quantitative agreement is not perfect, 
It ig important to note that the correction for finite frequency 
response was made by extrapolating the pressure~time curve to zero 
time on a semi-log plot. Normally this plot 1s s atraight line for 
a time of the order of the time constants, indioating an initially 
exponential decay, In the region near the pressure maximum (c& = 62~72°) . 
the initial decay was nct exponential, and the sem&’-log plot showed 
& pronounced upward curvature in the initial portion, This causes 
the extrapoleted values in this region to be sonsiderably higher 
than the uncorrected values, In fact, the uncorrected peak preasures 
(Fig. 3) do not show a very pronounced maximum, Although the exact 
value of the correction for finite gauge size may not be obtained by 
this extrapolation procedure, there is no doubt that such a correction 
48 required and that it will be largest in the region indiceted, 
where the pressure is deoaying abnormally rapidly with time, 
The peak pressure curve obtained with 50 g, charges is shown 
in Fig, 4, If extrapolation had been possible, presumably the 
level of pressure, perticularly in the Mach region, would have 
been greeter, The maximum pressures occur at larger angles than 
for the 1700 g, charges, as would be expected from the larger 
i SgPASUE predicted for the lower pressure levels obtained from 
ed 
&. cherges,; 
The gauges G-2 and G-4 show a qualitatively different behavior 
from those in the intersection plane, For small angles (X~) 
G-2 and G-4 show two distinct peaks, corresponding to the waves from 
the two charges, G-A and G-B do not show two peaks because the 
waves arrive at the same time, At about a= 72°, G-2 begins to 
show only one peak, indicating that it has come within the Mach 
region, while G-4 does not show single peaks until a = 680,8°. As 
a rough estimate, a linear extrapolation to the interseqtion plane 
can be made, which indicates that the oritical angle for the onset 
of the Mach effect at this pressure (8900 psi) is of the order of 
63°, which is comparable with the theoretical value of 573°, 
The pressures measured outside the plane of intersection were 
the seme as those within for 80.8° end higher, At smaller angles 
