Calmat SBL-4 400/2000W PAR64 Actinic Lamp
In the early 1970s Thorn became one of the first companies to introduce metal halide lamps for photochemical reactions, following the research led by Eric Beeson. Previously such actinic radiation had been produced by mercury lamps which offered high output, but their radiation was inconveniently concentrated in narrow spectral lines at 365 and 401nm. Alternatively carbon arcs were used, whose electrodes could be doped with metallic additives to produce broad UV-A and deep blue wavelengths ideally suited to diazo photopolymer materials, but were unstable and needed constant attention. Metal halide lamps allowed the introduction these species into an arc tube, solving both problems to create actinic radiation sources of both long life and high performance.

One of the first lamps was Thorn's Gallium Halide 1200W MBIL, introduced around 1970 for Agfa-Gevaert colour proofing units. In 1972 Thorn added the innovative Graph-X lamp, featuring a sealead beam reflector. The textured glass lens produced an elliptical beam of good uniformity, and its superior optical efficiency allowed that small lamp to match systems of 3-4x higher power. The nitrogen atmosphere in the reflector also extended life.

A drawback of all printing lamps at that time was the quantity of heat in the beam. For Thorn's customer Calmat of Holland, a dichroic reflector version was developed to radiate only the actinic radiation, allowing infrared and other visible wavelengths to escape from the rear. The cool operation of the first SBL2 lamp allowed operation up to 1200W, and added a feature of instant restrike by employing the G38 HR base. The lamp on this page is the still more powerful SBL4 lamp, which can be operated at up to 2kW.
Manufacturer: GE Lighting Ltd. Lamp 98-9835
Lamp Power: 400 - 2000 Watts
Lamp Current: ~4.4 Amps @ 400W ~16 Amps @ 1900W
Lamp Voltage: ~105 Volts @ 400W ~130 Volts @ 1900W
Cap Type: G38 Hot Restrike Mogul Bi-Post
Bulb Type: PAR-203 PAR-64 in eighths/inch
Bulb Finish: Dichroic Reflector Borosilicate
Electrodes: Backwound coils Thoriated tungsten
Arc Length: 25mm 1 inch
Atmosphere: Inner: Hg, (Fe,Ga)Ix | ArKr85 Outer: Nitrogen
Beam Angle: approx 50° x 30° to 50% peak intensity
Luminous Flux: N/A
Luminous Efficacy: N/A
Colour Temperature & CRI: CCT: N/A CRI: N/A
Chromaticity Co-ordinates: CCx: 0.240 CCy: 0.215
Lifetime: 1000h @ 400W 100h @ 2000W
Warm-up & Re-strike Time: 1 minute Instantaneous
Burning Position: Semi-universal Arctube axis horizontal
Overall Length: 175mm 6⅞ inch
Factory: Leicester England
Date of Manufacture: 1995 March Date Code: 63
Original Value: Approx £120 (1998)
 
References: 1) Thorn Lighting Comprehensive Catalogue, UK, 1984/85, p.233
2) Thorn Datasheet 2000W Photoprinting Metal Halide Lamp, 1986, UK
3) Photometric Measurement