JP Sercel Associates (JPSA), of Hollis, N.J., announced that JSK Associates, a Santa Clara, Calif., distributor for the electronics manufacturing and assembly industry, will sell its line of ultraviolet (UV) laser processing systems and job shop services in California and Nevada. Jerry Karp will be the JSK sales representative. JPSA makes UV excimer and DPSS laser micro machining systems, UV and VUV laser beam delivery systems and provides UV laser materials processing development, optical damage testing and excimer laser refurbishment services.    . . .   Thomas O. Hunter was named president of Sandia Corp. and director of Sandia National Laboratories. Sandia is operated by Sandia Corp., a Lockheed Martin company, for the US Department of Energy's National Nuclear Security Administration. Hunter was formerly Sandia's senior vice president for defense programs, with oversight of the lab's nuclear weapons programs. He will replace C. Paul Robinson, who was president and labs director since August 1995. Robinson will leave Sandia April 29 to assist Lockheed Martin in preparing a bid to the Department of Energy to manage and operate Los Alamos National Laboratory. Joan Woodard will replace Hunter as head of Sandia's nuclear weapons program; she will remain Sandia's executive vice president and deputy director during the transition. Hunter said the core mission of Sandia, which has facilities in Albuquerque, N.M., and Livermore, Calif., will continue to be maintaining the nation's nuclear weapons stockpile and developing technology solutions for "the challenging problems that threaten peace and freedom at home and abroad."