John N. McMahon was identified incorrectly Monday as director of the foreign assessment division of the CIA. He held this post from April, 1981, until Jan. 4, 1982, when he was appointed executive director of the agency.

John N. McMahon, a 31-year-veteran of the Central Intelligence Agency, will be named today as deputy director to succeed Adm. Bobby Ray Inman, who is retiring, administration sources said yesterday.

The selection of McMahon, who now heads the CIA's foreign assessment division, is expected to mollify members of the Senate Intelligence Committee, who have been openly skeptical about the expertise of CIA Director William J. Casey.

Reflecting these concerns, Sen. Richard G. Lugar (R-Ind.), a key committee member, said last week that Inman's abrupt announcement of resignation had created "a rather traumatic situation" in the agency.

Lugar called a press conference to express his reservations about Casey and urged the administration to consult with the Senate committee before it selected a successor to Inman. The Indiana senator said that he was trying "to send some signals" to the White House.

These signals were heard by President Reagan and top aides, led by national security adviser William P. Clark. Administration sources said that McMahon, who also has Casey's confidence, was a unanimous choice in the administration, especially after senators, including Lugar and Henry M. Jackson (D-Wash.), passed the word that the choice was fully acceptable to them.

Jackson, without mentioning McMahon's name, said yesterday on "Face the Nation" (CBS, WDVM) that the appointment would be popular with Congress.

"I think he is a first-rate professional and will help the morale within the professional service because he has been selected out of the professional service," Jackson said.

McMahon, 52, a graduate of Holy Cross, joined the CIA in 1951 and has a wide range of experience in administrative, operational, scientific and technical positions in the agency. Midway in the Carter administration, he was appointed deputy director for operations, making him chief of CIA covert activities.

Last April, Casey named a political crony, Max Hugel, as deputy director for operations and McMahon took over as the director of the agency's National Foreign Assessment Center, an important position in which he was responsible for the production of finished intelligence.

On July 14, Hugel was forced to resign in the wake of reports that he had engaged in questionable stock market dealings. Ever since, some members of the Senate Intelligence Committee, led by Chairman Barry Goldwater (R-Ariz.), have been openly questioning Casey's judgment and abilities.

McMahon has the reputation in the CIA as being an extremely competent technician. Nonetheless, he will have big shoes to fill in his new assignment.

Inman, also well qualified technically, enjoyed an unusual measure of bipartisan confidence in Congress, and is given credit both in the CIA and outside of it for helping to restore the image of an agency that was badly damaged by the disclosures of the Vietnam and Watergate years. Before joining the CIA, Inman was director of the National Security Agency.

Inman's presence in the No. 2 spot throughout the Reagan administration helped to quiet persistent congressional concerns about Casey. Unless McMahon can take over this role, there is likely to be renewed demand from senators knowledgeable in intelligence matters that Reagan find himself a new CIA director.