The spatial and temperature structure of vacuum spark plasmas

The spatial and temperature structures of the X-ray emitting components of low-inductance vacuum-spark plasmas are investigated. The plasmas produced by low-inductance vacuum sparks show striking resemblances to solar-flare plasmas. High-resolution photographs show that the spark plasmas are composed of hot (about 30 million K) compact sources (less than 20 microns) and cooler (about 10 million K) larger sources (of the order of 100 microns). Both types of sources may be produced by the same plasma at different times. The differences between the solar flare iron-line spectrum near 1.9 A and the spark iron-line spectrum are discussed and interpreted.