A radiation concentrator, giving good concentration ratio when employed as a solar collector, incorporating a primary reflector (1) consisting of a pair of confocal uneven parabolic reflectors (5a and 5b) arranged on either side of an axis (103), a receiver (3) placed at the common focus (4) of the uneven parabolic reflectors, a pair of secondary reflectors (2) placed above the receiver (3) engulfing it. The uneven parabolic reflectors have their common focus (4) at the axis (103) and are rotated around the focus, in opposite direction, through an angle (157) that is 1/4 th of the angle subtended by the radiation source. The receiver (3) is configured to absorb the upper half of the reflected radiation and the secondary reflectors (2) are configured to re-reflect the lower half of the reflected radiation to the receiver (3).