<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hi Chen,<div><br></div><div>I believe that the equation is correct, but the Figure 17.6 might be misleading. The text above Fig. 17.6 states that \phi is the <b>torsional </b>angle with the z-axis, not the angle between s1 and z. Hence, to my understanding, in order to derive s1z, one has to project into this angle (cos \phi), and then take into account the orientation of the elliptical target into the z axes (\theta - pi/2).</div><div><br></div><div>Hope this helps!</div><div><br></div><div>Fernando </div><div><div><br><blockquote type="cite"><div>On Nov 28, 2023, at 2:51 AM, cya_@nudt.edu.cn wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><div class="default-font-1701168762862" style="font-size: 14px; font-family: 宋体, arial, Verdana, sans-serif; caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div class="default-font-1697721404369" style="font-size: 14px; font-family: 宋体, arial, Verdana, sans-serif;"><p style="margin: 0px 0px 14px;"><span style="font-family: Arial;">Dear FLASH Users,</span></p><p style="margin: 0px 0px 14px;"><span style="font-family: Arial;">I have a question in Section 17.4.6.1 of the User's Guide, which is about the laser beam. The question is w</span><span style="font-family: Arial;">hy the local z-axis projection of s</span><sub style="font-family: Arial;">1<span class="Apple-converted-space"> </span></sub><span style="font-family: Arial;">is<span class="Apple-converted-space"> </span></span><em style="font-family: Arial;">l<sub>1</sub>cos(\phi)<sub>1</sub></em><span style="font-family: Arial;"></span><span style="font-family: Arial;"></span><em style="font-family: Arial;">cos(\theta - \pi /2)</em><span style="font-family: Arial;"><span class="Apple-converted-space"> </span>rather<span class="Apple-converted-space"> </span></span><span style="font-family: Arial;">than </span><em style="font-family: Arial;">l<sub>1</sub>cos(\phi)<sub>1</sub></em><sub style="font-family: Arial;"><span class="Apple-converted-space"> </span></sub><span style="font-family: Arial;">in equation 17.72.</span></p><p style="margin: 0px 0px 14px;"><span style="font-family: Arial;">Any possible suggestions would be great appreciated!</span></p><span style="font-family: Arial;">Best wishes, <br>Chen Yunan</span><br></div></div><span id="cid:03FF04A2-D987-4C88-84AF-482530E99009"><laserbeam.png></span><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">_______________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">flash-users mailing list</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="mailto:flash-users@flash.rochester.edu" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">flash-users@flash.rochester.edu</a><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;">For list info, including unsubscribe:</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="https://flash.rochester.edu/mailman/listinfo/flash-users" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">https://flash.rochester.edu/mailman/listinfo/flash-users</a></div></blockquote></div><br></div></body></html>