## 3 LSC Test and Observation  
As an initial attempt to see the relationship between jet formation theory and the cutting performance per each segment, a series of field tests using flash X-ray was carried out. Multiple 18-in.- (or 457.2-mm-) long 2000 g/ft. commercially manufactured copper-lined LSCs (with a flat liner) were shot against an X-ray-transparent material of UHMW (ultra-high molecular weight polyethylene), density \(\rho=0.95\) g/cm\({}^{3}\), 24 \(\times\) 12 \(\times\) 5 in. (or 609 \(\times\) 305 \(\times\) 127 mm) block, and the penetration event was captured using a single 150 kV flash X-ray system located 4 feet (1219 mm) away (Figure 1). The geometrical specifications and the core charge properties of the 2000 g/ft LSCs are listed in Table 1[5]. Detailed dimensional specification of the LSC charge is listed in [5]. Because UHMW is transparent under the flash X-ray and the copper jets are not, the use of UHMW as a target material will reveal the penetration history during the jet-on-target. In order to improve the image quality and to prevent technical difficulties, multiple LSC shots with different exposure times were used to reveal the penetration time history in the target. It was assumed that the same sized LSCs would provide identical penetration or jet projection patterns. Previous field tests have shown that LSC detonation has quite reasonable consistency between shots (as long as the size of the LSC is identical), and this approach was determined to be reasonable. To capture the penetration time history in the UHMW target, the timing of the X-ray exposure is critical. Based on the calculated jet speed of the LSCs and an estimated penetration speed in the target, three exposure times of 75, 105, and 165 us after detonation were selected and three X-ray images were produced (Figure 2). Figure 1: Schematic diagram of the LSC test configuration. The three X-ray images show interesting patterns in jet during penetration. As in the X-ray images of [PERSON] and [PERSON], the LSC jet showed a well-organized pattern of particulation, depending on time after detonation (Figure 3). Based on the distribution density and formation of jet particles in the X-ray images, it was able to separate the jet segment groups into three categories: high-density regular jet (Jet Group A), low-density irregular jet (Jet Group B), and random jet particles (behind B, where large slug are included). A detailed description follows (Figure 3). In Jet Group A (high-density jet) all jet segments were close together and of uniform size/pattern distribution. Jet Group B showed a somewhat organized pattern, but the distance between the jet particles was larger than in Jet Group A and there were fewer jet particles. The size of each jet particle in B was much bigger than those in Jet Group A. Random jet particles followed behind Jet Group B, but there was no clear evidence that this group was well-organized, and the number of jet segments was not significant (bottom image in Figure 3). The penetration progressed in sequence: Jet Group A, Jet Group B, and then the random particles. Close observation of the images indicates that the interface between the jet (black dots and lines) and UHMW target (grey area) shows two distinct slope angles, depending on the speed of penetration, slow or fast (red-dotted slope lines in Figure 3). The fast cutting occurred in the very early stage of penetration (mainly Jet Group A), and the slow cutting occurred in the later stage (tail of Jet Group A, but principally Jet Group B, top and middle figures in Figure 3). Note that the slope lines indicate the speed of penetration, since the detonation front moved from left to right. In other words, the time history of the penetration is shown in a single X-ray image, from left to right. The disappearance of jet segments indicates the consumption of jet segments during penetration. By pinpointing the location of the jet segments' disappearance, the penetration depth of each jet group can be identified.