The Hilger & Watts microfocus X-ray diffraction instrument has been redesigned to provide a tube allowing up to three times the target loading of previous tubes. The line focus, 6 mm × 100 μ, increases the target loading to 50 kv dc, 10 ma. To accomplish this, a new high-power transformer is provided with a special demountable tube and anode assembly with suitable cooling provided. The original 40 μ and 100 μ tubes are interchangeable with the new tube. Considerable gains in performance with photographic methods are indicated, but more notable is the increase in resolution when the microfocus unit is used as a source of X-ray for a diffractometer. The diffractometer can now be operated under the same conditions as those required for a conventional tube but with the much higher resolution.