The SAS soldier who was killed in a firefight while on his seventh tour of duty in Afghanistan has been named as Sergeant Blaine Diddams.

The 40-year-old Perth-based soldier was shot in the chest earlier this week while on a partnered mission with the Afghan national security forces to target an insurgent commander in Uruzgan's Chora Valley.

He was evacuated by helicopter to the Australian base at Tarin Kot but later died.

Defence says Sergeant Diddams was known as "Didds" to his mates and was known for being a devoted family man with an outgoing personality and quirky sense of humour.

Sergeant Diddams, who was born in Canberra, is survived by his wife Toni-Ann and their two children, Elle-Lou and Henry.

Sergeant Diddams joined the Army in 1990 and joined the SAS in 1995.

He had been on his seventh tour to Afghanistan, and had also been deployed on four occasions to Somalia, East Timor and the Solomon Islands.

His death has sparked questions about the number of times soldiers are sent back to Afghanistan.

He is the 33rd Australian soldier to be killed in Afghanistan.