[Sangetsu]

If you want to spell your name in katakana or hiragana characters, it's quite easy: ジェンセン　or じぇんせん. If you want your name in kanji, it's a bit more difficult, as there are many characters which the sounds in your name, but which have very different meanings. You would have to decide which characters you like depending on their meaning. The second half of your name could mean anything from "1000" to "train line", depending on the characters you pick.